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2 Issue (s), 47 Article (s)
Vol.19, Iss.12—Dec.1, 2021 • pp: 120201- Spec. pp:
Vol.19, Iss.11—Nov.1, 2021 • pp: 110201- Spec. pp:
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ReviewsVol.19, Iss.12-Dec..1,2021
Nanophotonics, Metamaterials, and Plasmonics
Metallic nanoparticles/graphene-molecules hybrid system-based active biosensorWalid Aroua
The strong coupling between vibrational modes of molecules and surface plasmon resonance (SPR) modes in graphene makes them an ideal platform for biosensor techniques. In this paper, a new optical biosensor for molecule detection based on silver metallic nanoparticles (MNPs) and graphene/gold MNPs in a terahertz frequency range is achieved. It is established that the nonlinear electrical properties of graphene can play a major role in realizing a biosensor for molecule detection. The performance parameters of the proposed device are reported with respect to the chemical potential
Chinese Optics Letters
- Publication Date: Dec. 10, 2021
- Vol.19 Issue, 12 123603 (2021)
Research ArticlesVol.19, Iss.12-Dec..1,2021
Atomic and Molecular Optics
Uncertainty evaluation of the second-order Zeeman shift of a transportable 87Rb atomic fountain clockHenan Cheng, Siminda Deng, Zhen Zhang, Jingfeng Xiang, Jingwei Ji, Wei Ren, Tang Li, Qiuzhi Qu, Liang Liu, and Desheng Lü
In this article, taking advantage of the special magnetic shieldings and the optimal coil design of a transportable Rb atomic fountain clock, the intensity distribution in space and the fluctuations with time of the quantization magnetic field in the Ramsey region were measured using the atomic magneton-sensitive transition method. In an approximately 310 mm long Ramsey region, a peak-to-peak magnetic field intensity of a 0.74 nT deviation in space and a 0.06 nT fluctuation with time were obtained. These results correspond to a second-order Zeeman frequency shift of approximately
Chinese Optics Letters
- Publication Date: Dec. 10, 2021
- Vol.19 Issue, 12 120201 (2021)
Biophotonics
Recognizing local artifacts in two-photon imaging of dendrites beneath blood vessels in vivoCheng Jin, Ruheng Shi, Chi Liu, and Lingjie Kong
Localized wavefront aberrations would introduce artifacts in biomedical imaging, which, however, are often neglected, as their compensations are at the cost of the field-of-view. Here, we show rarely reported local artifacts in two-photon imaging of dendrites beneath blood vessels in a mouse brain in vivo and interpret the phenomena via numerical simulations. The artifacts of divided parallel structures are found to be induced by coma and astigmatism, resulting from sample tilting and the cylinder shape of vasculatures, respectively. Different from that in single-photon microscopy, such artifacts in nonlinear microscopy show unique characteristics and should be recognized for proper interpretation of the images.Localized wavefront aberrations would introduce artifacts in biomedical imaging, which, however, are often neglected, as their compensations are at the cost of the field-of-view. Here, we show rarely reported local artifacts in two-photon imaging of dendrites beneath blood vessels in a mouse brain in vivo and interpret the phenomena via numerical simulations. The artifacts of divided parallel structures are found to be induced by coma and astigmatism, resulting from sample tilting and the cylinder shape of vasculatures, respectively. Different from that in single-photon microscopy, such artifacts in nonlinear microscopy show unique characteristics and should be recognized for proper interpretation of the images.
Chinese Optics Letters
- Publication Date: Dec. 10, 2021
- Vol.19 Issue, 12 121701 (2021)
Biophotonics
Photoacoustic/ultrasound dual modality imaging aided by acoustic reflectorsGuangjie Zhang, Yu Sun, Xing Long, Rui Zhang, Meng Yang, and Changhui Li
Photoacoustic imaging (PAI) with a handheld linear ultrasound (US) probe is widely used owing to its convenient and inherent dual modality capability. However, the limited length of the linear probe makes PAI suffer from the limited view. In this study, we present a simple method to substantially increase the view angle aided by two US reflectors. Both phantom and
Chinese Optics Letters
- Publication Date: Dec. 10, 2021
- Vol.19 Issue, 12 121702 (2021)
Fiber Optics and Optical Communications
Robust integration of nitrogen-vacancy centers in nanodiamonds to optical fiber and its application in all-optical thermometryCe Bian, Minxuan Li, Wei Cao, Manli Hu, Zhiqin Chu, and Ruohui Wang
In this Letter, we developed a robust method for integrating nanodiamonds (NDs) to optical fiber. The NDs, containing nitrogen-vacancy (NV) centers, were uniformly mixed with UV adhesive before coating the end surface of a multimode fiber as a hemispherical film. The excitation and collection efficiency of NV fluorescence can be enhanced by increasing the thickness of UV adhesive film and additional aluminum film deposition. The fiber-based quantum sensor was also experimentally demonstrated for all-optical thermometry application. The variation of the refractive index of UV adhesive under different temperatures will also affect the NV collection efficiency by changing the light confinement. The demonstrated facile integration approach paves the way for developing fiber-based quantum thermometry and magnetometry.In this Letter, we developed a robust method for integrating nanodiamonds (NDs) to optical fiber. The NDs, containing nitrogen-vacancy (NV) centers, were uniformly mixed with UV adhesive before coating the end surface of a multimode fiber as a hemispherical film. The excitation and collection efficiency of NV fluorescence can be enhanced by increasing the thickness of UV adhesive film and additional aluminum film deposition. The fiber-based quantum sensor was also experimentally demonstrated for all-optical thermometry application. The variation of the refractive index of UV adhesive under different temperatures will also affect the NV collection efficiency by changing the light confinement. The demonstrated facile integration approach paves the way for developing fiber-based quantum thermometry and magnetometry.
Chinese Optics Letters
- Publication Date: Dec. 10, 2021
- Vol.19 Issue, 12 120601 (2021)
Imaging Systems and Image Processing
Fine edge detection in single-pixel imagingLiyu Zhou, Xianwei Huang, Qin Fu, Xuanpengfan Zou, Yanfeng Bai, and Xiquan Fu
Typical single-pixel imaging techniques for edge detection are mostly based on first-order differential edge detection operators. In this paper, we present a novel edge detection scheme combining Fourier single-pixel imaging with a second-order Laplacian of Gaussian (LoG) operator. This method utilizes the convolution results of an LoG operator and Fourier basis patterns as the modulated patterns to extract the edge detail of an unknown object without imaging it. The simulation and experimental results demonstrate that our scheme can ensure finer edge detail, especially under a noisy environment, and save half the processing time when compared with a traditional first-order Sobel operator.Typical single-pixel imaging techniques for edge detection are mostly based on first-order differential edge detection operators. In this paper, we present a novel edge detection scheme combining Fourier single-pixel imaging with a second-order Laplacian of Gaussian (LoG) operator. This method utilizes the convolution results of an LoG operator and Fourier basis patterns as the modulated patterns to extract the edge detail of an unknown object without imaging it. The simulation and experimental results demonstrate that our scheme can ensure finer edge detail, especially under a noisy environment, and save half the processing time when compared with a traditional first-order Sobel operator.
Chinese Optics Letters
- Publication Date: Dec. 10, 2021
- Vol.19 Issue, 12 121101 (2021)
Infrared and Terahertz Photonics
Continuous-wave terahertz diffraction tomography for measuring three-dimensional refractive index mapsDayong Wang, Xiaoyu Jin, Jie Zhao, Yunxin Wang, Lu Rong, and John J. Healy
Three-dimensional (3D) refractive index (RI) distribution is important to reveal the object’s inner structure. We implemented terahertz (THz) diffraction tomography with a continuous-wave single-frequency THz source for measuring 3D RI maps. The off-axis holographic interference configuration was employed to obtain the quantitative scattered field of the object under each rotation angle. The 3D reconstruction algorithm adopted the filtered backpropagation method, which can theoretically calculate the exact scattering potential from the measured scattered field. Based on the Rytov approximation, the 3D RI distribution of polystyrene foam spheres was achieved with high fidelity, which verified the feasibility of the proposed method.Three-dimensional (3D) refractive index (RI) distribution is important to reveal the object’s inner structure. We implemented terahertz (THz) diffraction tomography with a continuous-wave single-frequency THz source for measuring 3D RI maps. The off-axis holographic interference configuration was employed to obtain the quantitative scattered field of the object under each rotation angle. The 3D reconstruction algorithm adopted the filtered backpropagation method, which can theoretically calculate the exact scattering potential from the measured scattered field. Based on the Rytov approximation, the 3D RI distribution of polystyrene foam spheres was achieved with high fidelity, which verified the feasibility of the proposed method.
Chinese Optics Letters
- Publication Date: Dec. 10, 2021
- Vol.19 Issue, 12 123701 (2021)
Integrated Optics
High-performance ultra-compact polarization splitter-rotators based on dual-etching and tapered asymmetrical directional couplerChangjian Xie, Xihua Zou, Fang Zou, and Yong Zhang
High-performance ultra-compact polarization splitter-rotators (PSRs) are designed and experimentally demonstrated, using dual etching and a tapered asymmetrical directional coupler. First, two novel PSRs are designed with nanowire and subwavelength grating cross-port waveguides and verified in simulations. Then, one of the two PSRs is fabricated. Experiment results reveal that the extinction ratio is higher than 28 dB or 32 dB at 1550 nm for the launched fundamental transverse magnetic or the transverse electric modes, while the corresponding insertion loss and polarization conversion loss are 0.33 dB and 0.18 dB, respectively.High-performance ultra-compact polarization splitter-rotators (PSRs) are designed and experimentally demonstrated, using dual etching and a tapered asymmetrical directional coupler. First, two novel PSRs are designed with nanowire and subwavelength grating cross-port waveguides and verified in simulations. Then, one of the two PSRs is fabricated. Experiment results reveal that the extinction ratio is higher than 28 dB or 32 dB at 1550 nm for the launched fundamental transverse magnetic or the transverse electric modes, while the corresponding insertion loss and polarization conversion loss are 0.33 dB and 0.18 dB, respectively.
Chinese Optics Letters
- Publication Date: Dec. 10, 2021
- Vol.19 Issue, 12 121301 (2021)
Lasers, Optical Amplifiers, and Laser Optics
Low-noise amplification of dissipative Kerr soliton microcomb lines via optical injection locking lasersQiang Zhang, Boyuan Liu, Qin Wen, Jinhui Qin, Yong Geng, Qiang Zhou, Guangwei Deng, Kun Qiu, and Heng Zhou
The dissipative Kerr soliton microcomb provides a promising laser source for wavelength-division multiplexing (WDM) communication systems thanks to its compatibility with chip integration. However, the soliton microcomb commonly suffers from a low-power level due to the intrinsically limited energy conversion efficiency from the continuous-wave pump laser to ultra-short solitary pulses. Here, we exploit laser injection locking to amplify and equalize dissipative Kerr soliton comb lines, superior gain factor larger than 30 dB, and optical-signal-to-noise-ratio (OSNR) as high as 60 dB obtained experimentally, providing a potential pathway to constitute a high-power chip-integrated WDM laser source for optical communications.The dissipative Kerr soliton microcomb provides a promising laser source for wavelength-division multiplexing (WDM) communication systems thanks to its compatibility with chip integration. However, the soliton microcomb commonly suffers from a low-power level due to the intrinsically limited energy conversion efficiency from the continuous-wave pump laser to ultra-short solitary pulses. Here, we exploit laser injection locking to amplify and equalize dissipative Kerr soliton comb lines, superior gain factor larger than 30 dB, and optical-signal-to-noise-ratio (OSNR) as high as 60 dB obtained experimentally, providing a potential pathway to constitute a high-power chip-integrated WDM laser source for optical communications.
Chinese Optics Letters
- Publication Date: Dec. 10, 2021
- Vol.19 Issue, 12 121401 (2021)
Lasers, Optical Amplifiers, and Laser Optics
Q-switched mode-locked multimode fiber laser based on a graphene-deposited multimode microfiberJia-Wen Wu, Yu-Xin Gao, Xu-Bin Lin, Jin-Gan Long, Hu Cui, Zhi-Chao Luo, Wen-Cheng Xu, and Ai-Ping Luo
We report Q-switched mode-locked (QML) pulses generation in an Yb-doped multimode fiber (MMF) laser by using a graphene-deposited multimode microfiber (GMM) for the first time, to the best of our knowledge. The single-wavelength QML operation with the central wavelength tunable from 1028.81 nm to 1039.20 nm and the dual-wavelength QML operation with the wavelength spacing tunable from 0.93 nm to 5.79 nm are achieved due to the multimode interference filtering effect induced by the few-mode fiber and MMF structure and the GMM in the cavity. Particularly, in the single-wavelength QML operation, the fifth harmonic is also realized owing to the high nonlinear effect of the GMM. The obtained results indicate that the QML pulses can be generated in the MMF laser, and such a flexible tunable laser has promising applications in optical sensing, measuring, and laser processing.We report Q-switched mode-locked (QML) pulses generation in an Yb-doped multimode fiber (MMF) laser by using a graphene-deposited multimode microfiber (GMM) for the first time, to the best of our knowledge. The single-wavelength QML operation with the central wavelength tunable from 1028.81 nm to 1039.20 nm and the dual-wavelength QML operation with the wavelength spacing tunable from 0.93 nm to 5.79 nm are achieved due to the multimode interference filtering effect induced by the few-mode fiber and MMF structure and the GMM in the cavity. Particularly, in the single-wavelength QML operation, the fifth harmonic is also realized owing to the high nonlinear effect of the GMM. The obtained results indicate that the QML pulses can be generated in the MMF laser, and such a flexible tunable laser has promising applications in optical sensing, measuring, and laser processing.
Chinese Optics Letters
- Publication Date: Dec. 10, 2021
- Vol.19 Issue, 12 121402 (2021)
Lasers, Optical Amplifiers, and Laser Optics
Non-mechanical beam scanner based on VCSEL integrated amplifier with resonant wavelength detuning designShanting Hu, Xiaodong Gu, Masanori Nakahama, and Fumio Koyama
We demonstrate the non-mechanical beam steering and amplifier operation of a vertical cavity surface emitting laser (VCSEL) integrated Bragg reflector waveguide amplifier with a cut-off wavelength detuning design, which enables unidirectional lateral coupling, continuous electrical beam steering, and diffraction-limited divergence angle. We present the modeling of the proposed structure for unidirectional coupling between a seed single-mode VCSEL and slow-light amplifier. We also present the detailed operating characteristics including the near-field and far-field patterns, light/current characteristics, and lasing spectrum. The experimental measurements exhibit a single-mode output of over 8 mW under CW operation, a continuous beam steering range of 16°, and beam divergence below 0.1° as an optical beam scanner. The integrated amplifier length is as small as 0.9 mm, and thus we could expect much higher powers and higher resolution points by increasing the amplifier lengths.We demonstrate the non-mechanical beam steering and amplifier operation of a vertical cavity surface emitting laser (VCSEL) integrated Bragg reflector waveguide amplifier with a cut-off wavelength detuning design, which enables unidirectional lateral coupling, continuous electrical beam steering, and diffraction-limited divergence angle. We present the modeling of the proposed structure for unidirectional coupling between a seed single-mode VCSEL and slow-light amplifier. We also present the detailed operating characteristics including the near-field and far-field patterns, light/current characteristics, and lasing spectrum. The experimental measurements exhibit a single-mode output of over 8 mW under CW operation, a continuous beam steering range of 16°, and beam divergence below 0.1° as an optical beam scanner. The integrated amplifier length is as small as 0.9 mm, and thus we could expect much higher powers and higher resolution points by increasing the amplifier lengths.
Chinese Optics Letters
- Publication Date: Dec. 10, 2021
- Vol.19 Issue, 12 121403 (2021)
Lasers, Optical Amplifiers, and Laser Optics
Reduced threshold current density of GaN-based green laser diode by applying polarization doping p-cladding layerLingrong Jiang, Jianping Liu, Lei Hu, Liqun Zhang, Aiqin Tian, Wei Xiong, Xiaoyu Ren, Siyi Huang, Wei Zhou, Masao Ikeda, and Hui Yang
Absorption induced by activated magnesium (Mg) in a p-type layer contributes considerable optical internal loss in GaN-based laser diodes (LDs). An LD structure with a distributed polarization doping (DPD) p-cladding layer (CL) without intentional Mg doping was designed and fabricated. The influence of the anti-waveguide structure on optical confinement was studied by optical simulation. The threshold current density, slope efficiency of LDs with DPD p-CL, and Mg-doped CL, respectively, were compared. It was found that LDs with DPD p-CL showed lower threshold current density but reduced slope efficiency, which were caused by decreasing internal loss and hole injection, respectively.Absorption induced by activated magnesium (Mg) in a p-type layer contributes considerable optical internal loss in GaN-based laser diodes (LDs). An LD structure with a distributed polarization doping (DPD) p-cladding layer (CL) without intentional Mg doping was designed and fabricated. The influence of the anti-waveguide structure on optical confinement was studied by optical simulation. The threshold current density, slope efficiency of LDs with DPD p-CL, and Mg-doped CL, respectively, were compared. It was found that LDs with DPD p-CL showed lower threshold current density but reduced slope efficiency, which were caused by decreasing internal loss and hole injection, respectively.
Chinese Optics Letters
- Publication Date: Dec. 10, 2021
- Vol.19 Issue, 12 121404 (2021)
Lasers, Optical Amplifiers, and Laser Optics
Long-term frequency-stabilized optical frequency comb based on a turnkey Ti:sapphire mode-locked laserGuang Yang, Haosen Shi, Yuan Yao, Hongfu Yu, Yanyi Jiang, Albrecht Bartels, and Longsheng Ma
We report a long-term frequency-stabilized optical frequency comb at 530–1100 nm based on a turnkey Ti:sapphire mode-locked laser. With the help of a digital controller, turnkey operation is realized for the Ti:sapphire mode-locked laser. Under optimized design of the laser cavity, the laser can be mode-locked over a month, limited by the observation time. The combination of a fast piezo and a slow one inside the Ti:sapphire mode-locked laser allows us to adjust the cavity length with moderate bandwidth and tuning range, enabling robust locking of the repetition rate (fr) to a hydrogen maser. By combining a fast analog feedback to pump current and a slow digital feedback to an intracavity wedge and the pump power of the Ti:sapphire mode-locked laser, the carrier envelope offset frequency (fceo) of the comb is stabilized. We extend the continuous frequency-stabilized time of the Ti:sapphire optical frequency comb to five days. The residual jitters of fr and fceo are 0.08 mHz and 2.5 mHz at 1 s averaging time, respectively, satisfying many applications demanding accuracy and short operation time for optical frequency combs.We report a long-term frequency-stabilized optical frequency comb at 530–1100 nm based on a turnkey Ti:sapphire mode-locked laser. With the help of a digital controller, turnkey operation is realized for the Ti:sapphire mode-locked laser. Under optimized design of the laser cavity, the laser can be mode-locked over a month, limited by the observation time. The combination of a fast piezo and a slow one inside the Ti:sapphire mode-locked laser allows us to adjust the cavity length with moderate bandwidth and tuning range, enabling robust locking of the repetition rate (fr) to a hydrogen maser. By combining a fast analog feedback to pump current and a slow digital feedback to an intracavity wedge and the pump power of the Ti:sapphire mode-locked laser, the carrier envelope offset frequency (fceo) of the comb is stabilized. We extend the continuous frequency-stabilized time of the Ti:sapphire optical frequency comb to five days. The residual jitters of fr and fceo are 0.08 mHz and 2.5 mHz at 1 s averaging time, respectively, satisfying many applications demanding accuracy and short operation time for optical frequency combs.
Chinese Optics Letters
- Publication Date: Dec. 10, 2021
- Vol.19 Issue, 12 121405 (2021)
Lasers, Optical Amplifiers, and Laser Optics
Influence of annealing temperature on the performance of TiO2/SiO2 nanolaminated filmsYun Cui, Yuanan Zhao, Ge Zhang, Meiping Zhu, Chen Song, Chunxian Tao, Tan Shu, and Jianda Shao
Different laminated structures of
Chinese Optics Letters
- Publication Date: Dec. 10, 2021
- Vol.19 Issue, 12 121406 (2021)
Light-Matter Interaction
High period frequency LIPSS emerging on 304 stainless steel under the irradiation of femtosecond laser double-pulse trainsYifei Li, Jie Hu, Wei Liu, Jiangang Yin, and Jiangang Lu
In this work, we used femtosecond laser double-pulse trains to produce laser-induced periodic surface structures (LIPSS) on 304 stainless steel. Surprisingly, a novel type of periodic structure was discovered, which, to the best of our knowledge, is the first in literature. We surmised that the cause for this novel LIPSS was related to the weak energy coupling of subpulses when the intrapulse delay was longer than the thermal relaxation time of stainless steel. Furthermore, we found that the fluence combination and arrival sequence of subpulses in a double-pulse train also influenced LIPSS morphology.In this work, we used femtosecond laser double-pulse trains to produce laser-induced periodic surface structures (LIPSS) on 304 stainless steel. Surprisingly, a novel type of periodic structure was discovered, which, to the best of our knowledge, is the first in literature. We surmised that the cause for this novel LIPSS was related to the weak energy coupling of subpulses when the intrapulse delay was longer than the thermal relaxation time of stainless steel. Furthermore, we found that the fluence combination and arrival sequence of subpulses in a double-pulse train also influenced LIPSS morphology.
Chinese Optics Letters
- Publication Date: Dec. 10, 2021
- Vol.19 Issue, 12 123801 (2021)
Nanophotonics, Metamaterials, and Plasmonics
Multifrequency superscattering pattern shapingYao Qin, Jinying Xu, Yineng Liu, and Huanyang Chen
Multifrequency superscattering is a phenomenon in which the scattering cross section from a subwavelength object simultaneously exceeds the single-channel limit at multiple frequency regimes. Here, we achieve simultaneously, within a graphene-coated subwavelength structure, multifrequency superscattering and superscattering shaping with different engineered scattering patterns. It is shown that multimode degenerate resonances at multiple frequency regimes appearing in a graphene composite structure due to the peculiar dispersion can be employed to resonantly overlap electric and magnetic multipoles of various orders, and, as a result, effective multifrequency superscattering with different engineered angular patterns can be obtained. Moreover, the phenomena of multifrequency superscattering have a high tolerance to material losses and some structural variations. Our work should anticipate extensive applications ranging from emission enhancing, energy harvesting, and antenna design with improved sensitivity and accuracy due to multifrequency operation.Multifrequency superscattering is a phenomenon in which the scattering cross section from a subwavelength object simultaneously exceeds the single-channel limit at multiple frequency regimes. Here, we achieve simultaneously, within a graphene-coated subwavelength structure, multifrequency superscattering and superscattering shaping with different engineered scattering patterns. It is shown that multimode degenerate resonances at multiple frequency regimes appearing in a graphene composite structure due to the peculiar dispersion can be employed to resonantly overlap electric and magnetic multipoles of various orders, and, as a result, effective multifrequency superscattering with different engineered angular patterns can be obtained. Moreover, the phenomena of multifrequency superscattering have a high tolerance to material losses and some structural variations. Our work should anticipate extensive applications ranging from emission enhancing, energy harvesting, and antenna design with improved sensitivity and accuracy due to multifrequency operation.
Chinese Optics Letters
- Publication Date: Dec. 10, 2021
- Vol.19 Issue, 12 123601 (2021)
Nanophotonics, Metamaterials, and Plasmonics
Strong coupling with absorption and emission features of Ag@Au hollow nanoshells interacting with J-aggregated dye moleculesTianchen Zhao, Qiang Ma, Yajie Bian, Yuyi Zhang, Yiting Liu, Xiaolei Zhang, Botao Wu, E Wu, Shitao Lou, and Qingyuan Jin
We investigate the strong coupling from 5,5’,6,6’-tetrachloro-1,1’-diethyl-3,3’-di(4-sulfobutyl)-benzimidazolocarbocyanine (TDBC) molecules near pure nano-triangular Ag prisms or Ag@Au hollow nanoshells. When TDBC molecules are deposited on pure Ag nanoprisms or Ag@Au hollow nanoshells with the plasmonic resonance peak, matching very closely with the absorption band of TDBC J-aggregates, obvious Rabi splitting can be observed due to the strong coupling regime. Meanwhile, the photoluminescence intensity decreased with the increasing of the temperature, verifying the decreasing plasmon–exciton coupling interaction in the higher temperature. Our experimental results are coincident with the simulation results calculated by finite-difference time-domain method.We investigate the strong coupling from 5,5’,6,6’-tetrachloro-1,1’-diethyl-3,3’-di(4-sulfobutyl)-benzimidazolocarbocyanine (TDBC) molecules near pure nano-triangular Ag prisms or Ag@Au hollow nanoshells. When TDBC molecules are deposited on pure Ag nanoprisms or Ag@Au hollow nanoshells with the plasmonic resonance peak, matching very closely with the absorption band of TDBC J-aggregates, obvious Rabi splitting can be observed due to the strong coupling regime. Meanwhile, the photoluminescence intensity decreased with the increasing of the temperature, verifying the decreasing plasmon–exciton coupling interaction in the higher temperature. Our experimental results are coincident with the simulation results calculated by finite-difference time-domain method.
Chinese Optics Letters
- Publication Date: Dec. 10, 2021
- Vol.19 Issue, 12 123602 (2021)
Optical Materials
Ultra-fast and low-cost fabrication of transparent paperLulin Wei, Jie Li, Haohao Wang, Shuhong Nie, Wenming Su, Dafang Huang, and Mingwei Zhu
Transparent paper is a kind of promising and environmentally friendly material. In this study, we show that transparent paper can be fabricated in an ultra-fast and low-cost way. This low-cost top-down method only takes three steps of cell separation, lignin removal, and cold pressing to obtain a high-quality transparent paper. The fabrication time is further reduced, and the resulted transparent paper shows high transparency up to 90.3%. The application as a substrate material for transparent and flexible electronic devices is demonstrated by emulating the printed circuit on the prepared transparent paper. This top-down method will greatly promote the market-oriented applications of transparent paper as an environment friendly material.Transparent paper is a kind of promising and environmentally friendly material. In this study, we show that transparent paper can be fabricated in an ultra-fast and low-cost way. This low-cost top-down method only takes three steps of cell separation, lignin removal, and cold pressing to obtain a high-quality transparent paper. The fabrication time is further reduced, and the resulted transparent paper shows high transparency up to 90.3%. The application as a substrate material for transparent and flexible electronic devices is demonstrated by emulating the printed circuit on the prepared transparent paper. This top-down method will greatly promote the market-oriented applications of transparent paper as an environment friendly material.
Chinese Optics Letters
- Publication Date: Dec. 10, 2021
- Vol.19 Issue, 12 121601 (2021)
Quantum Optics and Quantum Information
Population dynamics of ultra-cold atoms interacting with radiation fields in the presence of inter-atomic collisionsE. Ghasemian, and M. K. Tavassoly
We investigate the dynamics of a system that consists of ultra-cold three-level atoms interacting with radiation fields. We derive the analytical expressions for the population dynamics of the system, particularly, in the presence and absence of nonlinear collisions by considering the rotating wave approximation (RWA). We also reanalyze the dynamics of the system beyond RWA and obtain the state vector of the system to study and compare the time behavior of population inversion. Our results show that the system undergoes two pure quantum phenomena, i.e., the collapse–revival and macroscopic quantum self-trapping due to nonlinear collisional interactions. The occurrence of such phenomena strongly depends on the number of atoms in the system and also the ratio of interaction strengths in the considered system. Finally, we show that the result of the perturbed time evolution operator up to the second-order is in agreement with the numerical solution of the Schrödinger equation. The results presented in the paper may be useful for the design of devices that produce a coherent beam of bosonic atoms known as an atom laser.We investigate the dynamics of a system that consists of ultra-cold three-level atoms interacting with radiation fields. We derive the analytical expressions for the population dynamics of the system, particularly, in the presence and absence of nonlinear collisions by considering the rotating wave approximation (RWA). We also reanalyze the dynamics of the system beyond RWA and obtain the state vector of the system to study and compare the time behavior of population inversion. Our results show that the system undergoes two pure quantum phenomena, i.e., the collapse–revival and macroscopic quantum self-trapping due to nonlinear collisional interactions. The occurrence of such phenomena strongly depends on the number of atoms in the system and also the ratio of interaction strengths in the considered system. Finally, we show that the result of the perturbed time evolution operator up to the second-order is in agreement with the numerical solution of the Schrödinger equation. The results presented in the paper may be useful for the design of devices that produce a coherent beam of bosonic atoms known as an atom laser.
Chinese Optics Letters
- Publication Date: Dec. 10, 2021
- Vol.19 Issue, 12 122701 (2021)
Spectroscopy
Influence of a dielectric decoupling layer on the local electric field and molecular spectroscopy in plasmonic nanocavities: a numerical studyGong Chen, Jiazhe Zhu, and Xiaoguang Li
In this Letter, we use electromagnetic simulations to systematically investigate the influence of a thin dielectric layer on the local electric field and molecular spectroscopy in the plasmonic junction. It is found that both the intensity and spatial confinement of the electric field and molecular spectroscopy can be significantly enhanced by applying a dielectric layer with large dielectric constant. We also discuss the optimal dielectric layer thickness to obtain the largest quantum efficiency of a dipole emitter. These results may be instructive for further studies in molecular spectroscopy and optoelectronics in plasmonic junctions.In this Letter, we use electromagnetic simulations to systematically investigate the influence of a thin dielectric layer on the local electric field and molecular spectroscopy in the plasmonic junction. It is found that both the intensity and spatial confinement of the electric field and molecular spectroscopy can be significantly enhanced by applying a dielectric layer with large dielectric constant. We also discuss the optimal dielectric layer thickness to obtain the largest quantum efficiency of a dipole emitter. These results may be instructive for further studies in molecular spectroscopy and optoelectronics in plasmonic junctions.
Chinese Optics Letters
- Publication Date: Dec. 10, 2021
- Vol.19 Issue, 12 123001 (2021)
Ultrafast Optics and Attosecond/High-Field Physics
Time-energy analysis of the photoionization process in a double-XUV pulse combined with a few-cycle IR fieldYi Jia, Li Guo, Shilin Hu, Xinyan Jia, Daihe Fan, Ronghua Lu, Shensheng Han, and Jing Chen
We calculate the time-energy distribution (TED) and ionization time distribution (ITD) of photoelectrons emitted by a double-extreme-ultraviolet (XUV) pulse and a two-color XUV-IR pulse using the Wigner distribution-like function based on the strong field approximation. For a double-XUV pulse, besides two identical broad distributions generated by two XUV pulses, many interference fringes resulting from the interference between electrons generated, respectively, by two pulses appear in the TED. After adding an IR field, the TED intuitively exhibits the effect of the IR field on the electron dynamics. The ITDs during two XUV pulses are no longer the same and show the different changes for the different two-color fields, the origin of which is attributed to the change of the electric field induced by the IR field. Our analysis shows that the emission time of electrons ionized during two XUV pulses mainly depends on the electric field of the combined XUV pulse and IR pulse.We calculate the time-energy distribution (TED) and ionization time distribution (ITD) of photoelectrons emitted by a double-extreme-ultraviolet (XUV) pulse and a two-color XUV-IR pulse using the Wigner distribution-like function based on the strong field approximation. For a double-XUV pulse, besides two identical broad distributions generated by two XUV pulses, many interference fringes resulting from the interference between electrons generated, respectively, by two pulses appear in the TED. After adding an IR field, the TED intuitively exhibits the effect of the IR field on the electron dynamics. The ITDs during two XUV pulses are no longer the same and show the different changes for the different two-color fields, the origin of which is attributed to the change of the electric field induced by the IR field. Our analysis shows that the emission time of electrons ionized during two XUV pulses mainly depends on the electric field of the combined XUV pulse and IR pulse.
Chinese Optics Letters
- Publication Date: Dec. 10, 2021
- Vol.19 Issue, 12 123201 (2021)
Ultrafast Optics and Attosecond/High-Field Physics
Wave mixing and high-harmonic generation enhancement by a two-color field driven dielectric metasurface [Invited]Weifeng Yang, Yichong Lin, Xueyi Chen, Yuxuan Xu, Hongdan Zhang, Marcelo Ciappina, and Xiaohong Song
High-harmonic generation in metasurfaces, driven by strong laser fields, has been widely studied. Compared to plasma, all-dielectric nanoscale metasurfaces possess larger nonlinearity response and higher damage threshold. Additionally, it can strongly localize the driven field, greatly enhancing its peak amplitude. In this work, we adopt a Fano resonant micro-nano structure with transmission peaks at different wavelengths and explore its nonlinear response by both single and two-color pump fields. Compared to the high-order harmonics induced by the first resonant wavelength, the intensity of the high-harmonic radiation results is enhanced by one order of magnitude, when the metasurface is driven by various resonant and non-resonant wavelength combinations of a two-color field.High-harmonic generation in metasurfaces, driven by strong laser fields, has been widely studied. Compared to plasma, all-dielectric nanoscale metasurfaces possess larger nonlinearity response and higher damage threshold. Additionally, it can strongly localize the driven field, greatly enhancing its peak amplitude. In this work, we adopt a Fano resonant micro-nano structure with transmission peaks at different wavelengths and explore its nonlinear response by both single and two-color pump fields. Compared to the high-order harmonics induced by the first resonant wavelength, the intensity of the high-harmonic radiation results is enhanced by one order of magnitude, when the metasurface is driven by various resonant and non-resonant wavelength combinations of a two-color field.
Chinese Optics Letters
- Publication Date: Dec. 10, 2021
- Vol.19 Issue, 12 123202 (2021)
ReviewsVol.19, Iss.11-Nov..1,2021
Biophotonics
Review of photoacoustic imaging for microrobots tracking in vivo [Invited]On the CoverDengfeng Li, Yachao Zhang, Chao Liu, Jiangbo Chen, Dong Sun, and Lidai Wang
Microrobots-assisted drug delivery and surgery have been always in the spotlight and are highly anticipated to solve the challenges of cancer in situ treatment. These versatile small biomedical robots are expected to realize direct access to the tumor or disease site for precise treatment, which requires real-time and high-resolution in vivo tracking as feedback for the microrobots’ actuation and control. Among current biomedical imaging methods, photoacoustic imaging (PAI) is presenting its outstanding performances in the tracking of microrobots in the human body derived from its great advantages of excellent imaging resolution and contrast in deep tissue. In this review, we summarize the PAI techniques, imaging systems, and their biomedical applications in microrobots tracking in vitro and in vivo. From a robotic tracking perspective, we also provide some insight into the future of PAI technology in clinical applications.Microrobots-assisted drug delivery and surgery have been always in the spotlight and are highly anticipated to solve the challenges of cancer in situ treatment. These versatile small biomedical robots are expected to realize direct access to the tumor or disease site for precise treatment, which requires real-time and high-resolution in vivo tracking as feedback for the microrobots’ actuation and control. Among current biomedical imaging methods, photoacoustic imaging (PAI) is presenting its outstanding performances in the tracking of microrobots in the human body derived from its great advantages of excellent imaging resolution and contrast in deep tissue. In this review, we summarize the PAI techniques, imaging systems, and their biomedical applications in microrobots tracking in vitro and in vivo. From a robotic tracking perspective, we also provide some insight into the future of PAI technology in clinical applications.
Chinese Optics Letters
- Publication Date: Nov. 10, 2021
- Vol.19 Issue, 11 111701 (2021)
Nonlinear Optics
Performance comparison of lithium-niobate-based extremely high-field single-cycle terahertz sources [Invited]György Tóth, László Pálfalvi, Szabolcs Turnár, Zoltán Tibai, Gábor Almási, and János Hebling
Tilted-pulse-front-pumping (TPFP) lithium-niobate terahertz (THz) pulse sources are widely used in pump-probe and control experiments since they can generate broadband THz pulses with tens of microjoules of energy. However, the conventional TPFP setup suffers from limitations, hindering the generation of THz pulses with peak electric field strength over 1 MV/cm. Recently, a few setups were suggested to mitigate or even eliminate these limitations. In this paper, we shortly review the setups that are suitable for the generation of single-cycle THz pulses with up to a few tens of megavolts/centimeter focused electric field strength. The THz pulses available with the new layouts pave the way for previously unattainable applications that require extremely high electric field strength and pulse energy in the multi-millijoule range.Tilted-pulse-front-pumping (TPFP) lithium-niobate terahertz (THz) pulse sources are widely used in pump-probe and control experiments since they can generate broadband THz pulses with tens of microjoules of energy. However, the conventional TPFP setup suffers from limitations, hindering the generation of THz pulses with peak electric field strength over 1 MV/cm. Recently, a few setups were suggested to mitigate or even eliminate these limitations. In this paper, we shortly review the setups that are suitable for the generation of single-cycle THz pulses with up to a few tens of megavolts/centimeter focused electric field strength. The THz pulses available with the new layouts pave the way for previously unattainable applications that require extremely high electric field strength and pulse energy in the multi-millijoule range.
Chinese Optics Letters
- Publication Date: Nov. 10, 2021
- Vol.19 Issue, 11 111902 (2021)
Research ArticlesVol.19, Iss.11-Nov..1,2021
Atomic and Molecular Optics
Molecular orientation induced by HZhiwei Ge, Xuequn Hou, Yu Zhao, and Qingtian Meng
We take
Chinese Optics Letters
- Publication Date: Nov. 10, 2021
- Vol.19 Issue, 11 110201 (2021)
Diffraction, Gratings, and Holography
Real-time gradation-expressible amplitude-modulation-type electroholography based on binary-weighted computer-generated hologramRen Noguchi, Kohei Suzuki, Yoshiki Moriguchi, Minoru Oikawa, Yuichiro Mori, Takashi Kakue, Tomoyoshi Shimobaba, Tomoyoshi Ito, and Naoki Takada
In amplitude-modulation-type electroholography, the binary-weighted computer-generated hologram (BW-CGH) facilitates the gradation-expressible reconstruction of three-dimensional (3D) objects. To realize real-time gradation-expressible electroholography, we propose an efficient and high-speed method for calculating bit planes consisting of BW-CGHs. The proposed method is implemented on a multiple graphics processing unit (GPU) cluster system comprising 13 GPUs. The proposed BW-CGH method realizes eight-gradation-expressible electroholography at approximately the same calculation speed as that of conventional electroholography based on binary computer-generated holograms. Consequently, we were able to successfully reconstruct a real-time electroholographic 3D video comprising approximately 180,000 points expressed in eight gradations at 30 frames per second.In amplitude-modulation-type electroholography, the binary-weighted computer-generated hologram (BW-CGH) facilitates the gradation-expressible reconstruction of three-dimensional (3D) objects. To realize real-time gradation-expressible electroholography, we propose an efficient and high-speed method for calculating bit planes consisting of BW-CGHs. The proposed method is implemented on a multiple graphics processing unit (GPU) cluster system comprising 13 GPUs. The proposed BW-CGH method realizes eight-gradation-expressible electroholography at approximately the same calculation speed as that of conventional electroholography based on binary computer-generated holograms. Consequently, we were able to successfully reconstruct a real-time electroholographic 3D video comprising approximately 180,000 points expressed in eight gradations at 30 frames per second.
Chinese Optics Letters
- Publication Date: Nov. 10, 2021
- Vol.19 Issue, 11 110501 (2021)
Fiber Optics and Optical Communications
Compensation of turbulence-induced wavefront aberration with convolutional neural networks for FSO systemsMin’an Chen, Xianqing Jin, Shangbin Li, and Zhengyuan Xu
To reduce the atmospheric turbulence-induced power loss, an AlexNet-based convolutional neural network (CNN) for wavefront aberration compensation is experimentally investigated for free-space optical (FSO) communication systems with standard single mode fiber-pigtailed photodiodes. The wavefront aberration is statistically constructed to mimic the received light beams with the Zernike mode-based theory for the Kolmogorov turbulence. By analyzing impacts of CNN structures, quantization resolution/noise, and mode count on the power penalty, the AlexNet-based CNN with 8 bit resolution is identified for experimental study. Experimental results indicate that the average power penalty decreases to 1.8 dB from 12.4 dB in the strong turbulence.To reduce the atmospheric turbulence-induced power loss, an AlexNet-based convolutional neural network (CNN) for wavefront aberration compensation is experimentally investigated for free-space optical (FSO) communication systems with standard single mode fiber-pigtailed photodiodes. The wavefront aberration is statistically constructed to mimic the received light beams with the Zernike mode-based theory for the Kolmogorov turbulence. By analyzing impacts of CNN structures, quantization resolution/noise, and mode count on the power penalty, the AlexNet-based CNN with 8 bit resolution is identified for experimental study. Experimental results indicate that the average power penalty decreases to 1.8 dB from 12.4 dB in the strong turbulence.
Chinese Optics Letters
- Publication Date: Nov. 10, 2021
- Vol.19 Issue, 11 110601 (2021)
Fiber Optics and Optical Communications
Signal transmission of 4 GHz beyond the system bandwidth in UV-C LED communication based on temporal ghost imagingMengyin Jin, Zeyuan Qian, Xinwei Chen, Xugao Cui, Ke Jiang, Xiaojuan Sun, Dabing Li, and Pengfei Tian
Due to the bandwidth limitation of the ultraviolet-C (UV-C) optical communication system and strong channel attenuation, it is difficult to transmit high-frequency signals. In this paper, the temporal ghost imaging (TGI) algorithm was first applied to the UV-C communication experimentally, and we realized the transmission of a 4 GHz signal through 95.34 MHz system bandwidth. The study indicates that the TGI algorithm can significantly improve the signal-to-noise ratio (SNR) compared with the on–off keying method. Our research provides a new approach for alleviating transmission frequency limitation due to poor SNR and insufficient hardware bandwidth.Due to the bandwidth limitation of the ultraviolet-C (UV-C) optical communication system and strong channel attenuation, it is difficult to transmit high-frequency signals. In this paper, the temporal ghost imaging (TGI) algorithm was first applied to the UV-C communication experimentally, and we realized the transmission of a 4 GHz signal through 95.34 MHz system bandwidth. The study indicates that the TGI algorithm can significantly improve the signal-to-noise ratio (SNR) compared with the on–off keying method. Our research provides a new approach for alleviating transmission frequency limitation due to poor SNR and insufficient hardware bandwidth.
Chinese Optics Letters
- Publication Date: Nov. 10, 2021
- Vol.19 Issue, 11 110602 (2021)
Fiber Optics and Optical Communications
Gain and laser performance of heavily Er-doped silica fiber fabricated by MCVD combined with the sol-gel methodQiubai Yang, Yan Jiao, Chunlei Yu, Chongyun Shao, Fengguang Lou, Shikai Wang, Lei Zhang, Qiuhong Yang, and Lili Hu
In this work, a heavily Er-doped fiber with an 8 µm core diameter and a numerical aperture of 0.13 was prepared by the modified chemical vapor deposition (MCVD) technique combined with the sol-gel method. The background loss and absorption coefficient at 1530 nm were measured to be 20 dB/km and 128 dB/m, respectively. Thanks to the sol-gel method, the fiber showed a good doping homogeneity, which was confirmed through unsaturable absorption measurement. The net gains of three 25, 45, and 75-cm-long fibers were measured in the range of 1520 to 1600 nm, and the highest gain reached above 23 dB at both 1530 and 1560 nm in 25 and 75-cm-long fibers, respectively. The short-cavity laser performance was measured using centimeter-scale fibers. The maximum output power of 12 mW was demonstrated in a 6.5-cm-long active fiber with a slope efficiency of 20.4%. Overall, the prepared heavily Er-doped silica fiber is a promising item to be applied in a high-repetition-rate or single-frequency fiber laser.In this work, a heavily Er-doped fiber with an 8 µm core diameter and a numerical aperture of 0.13 was prepared by the modified chemical vapor deposition (MCVD) technique combined with the sol-gel method. The background loss and absorption coefficient at 1530 nm were measured to be 20 dB/km and 128 dB/m, respectively. Thanks to the sol-gel method, the fiber showed a good doping homogeneity, which was confirmed through unsaturable absorption measurement. The net gains of three 25, 45, and 75-cm-long fibers were measured in the range of 1520 to 1600 nm, and the highest gain reached above 23 dB at both 1530 and 1560 nm in 25 and 75-cm-long fibers, respectively. The short-cavity laser performance was measured using centimeter-scale fibers. The maximum output power of 12 mW was demonstrated in a 6.5-cm-long active fiber with a slope efficiency of 20.4%. Overall, the prepared heavily Er-doped silica fiber is a promising item to be applied in a high-repetition-rate or single-frequency fiber laser.
Chinese Optics Letters
- Publication Date: Nov. 10, 2021
- Vol.19 Issue, 11 110603 (2021)
Fiber Optics and Optical Communications
Multi-distributed probabilistically shaped PAM-4 system for intra-data-center networksMengli Liu, Mingyi Gao, and Junchi Ke
Probabilistically shaped (PS) pulse amplitude modulation (PAM) is a promising technique for intra-data-center networks due to its superior performance, for which a low-complexity and cost-effective distributed matching method is critical. In this work, we propose an energy-level-assigned method to yield PS-PAM-4 signals with various bit rates based on variable probabilistic distributions. We experimentally demonstrate the proposed method in a 25 Gbaud PS-PAM-4 transmission over a bandwidth of approximately 10 GHz. Compared to a uniform PAM-4 system, the proposed multi-distributed PS-PAM-4 system approaches the hard decision threshold at a wide range of received optical power for different applications.Probabilistically shaped (PS) pulse amplitude modulation (PAM) is a promising technique for intra-data-center networks due to its superior performance, for which a low-complexity and cost-effective distributed matching method is critical. In this work, we propose an energy-level-assigned method to yield PS-PAM-4 signals with various bit rates based on variable probabilistic distributions. We experimentally demonstrate the proposed method in a 25 Gbaud PS-PAM-4 transmission over a bandwidth of approximately 10 GHz. Compared to a uniform PAM-4 system, the proposed multi-distributed PS-PAM-4 system approaches the hard decision threshold at a wide range of received optical power for different applications.
Chinese Optics Letters
- Publication Date: Nov. 10, 2021
- Vol.19 Issue, 11 110604 (2021)
Imaging Systems and Image Processing
Polarization descattering imaging: a solution for nonuniform polarization characteristics of a target surfaceYi Wei, Pingli Han, Fei Liu, Jinpeng Liu, and Xiaopeng Shao
This paper presents a polarization descattering imaging method for underwater detection in which the targets have nonuniform polarization characteristics. The core of this method takes the nonuniform distribution of the polarization information of the target-reflected light into account and expands the application field of underwater polarization imaging. Independent component analysis was used to separate the target light and backscattered light. Theoretical analysis and proof-of-concept experiments were employed to demonstrate the effectiveness of the proposed method in estimating target information. The proposed method showed superiority in accurately estimating the target information compared with other polarization imaging methods.This paper presents a polarization descattering imaging method for underwater detection in which the targets have nonuniform polarization characteristics. The core of this method takes the nonuniform distribution of the polarization information of the target-reflected light into account and expands the application field of underwater polarization imaging. Independent component analysis was used to separate the target light and backscattered light. Theoretical analysis and proof-of-concept experiments were employed to demonstrate the effectiveness of the proposed method in estimating target information. The proposed method showed superiority in accurately estimating the target information compared with other polarization imaging methods.
Chinese Optics Letters
- Publication Date: Nov. 10, 2021
- Vol.19 Issue, 11 111101 (2021)
Lasers, Optical Amplifiers, and Laser Optics
Wideband chaos generation based on a dual-mode microsquare laser with optical feedbackChunguang Ma, Jiliang Wu, Jinlong Xiao, Yongtao Huang, Yali Li, Yuede Yang, and Yongzhen Huang
We propose and demonstrate the generation of wideband chaos based on a dual-mode microsquare semiconductor laser with optical feedback. By adjusting the dual-mode intensity ratio and the feedback strength, wideband chaos covering more than 50 GHz in the RF spectrum is achieved. The standard and effective bandwidths of the chaotic signal are 31.3 GHz and 30.7 GHz with the flatness of 8.3 dB and 6.1 dB, respectively.We propose and demonstrate the generation of wideband chaos based on a dual-mode microsquare semiconductor laser with optical feedback. By adjusting the dual-mode intensity ratio and the feedback strength, wideband chaos covering more than 50 GHz in the RF spectrum is achieved. The standard and effective bandwidths of the chaotic signal are 31.3 GHz and 30.7 GHz with the flatness of 8.3 dB and 6.1 dB, respectively.
Chinese Optics Letters
- Publication Date: Nov. 10, 2021
- Vol.19 Issue, 11 111401 (2021)
Lasers, Optical Amplifiers, and Laser Optics
Frequency-modulated continuous-wave dual-frequency LIDAR based on a monolithic integrated two-section DFB laserChangsheng Wang, Yunshan Zhang, Jilin Zheng, Jin Li, Zhenxing Sun, Jianqin Shi, Lianyan Li, Rulei Xiao, Tao Fang, and Xiangfei Chen
We demonstrate a high-resolution frequency-modulated continuous-wave dual-frequency LIDAR system based on a monolithic integrated two-section (TS) distributed feedback (DFB) laser. In order to achieve phase locking of the two lasers in the TS-DFB laser, the sideband optical injection locking technique is employed. A high-quality linear frequency-modulated signal is achieved from the TS-DFB laser. Utilizing the proposed LIDAR system, the distance and velocity of a target can be measured accurately. The maximum relative errors of distance and velocity measurement are 1.6% and 3.18%, respectively.We demonstrate a high-resolution frequency-modulated continuous-wave dual-frequency LIDAR system based on a monolithic integrated two-section (TS) distributed feedback (DFB) laser. In order to achieve phase locking of the two lasers in the TS-DFB laser, the sideband optical injection locking technique is employed. A high-quality linear frequency-modulated signal is achieved from the TS-DFB laser. Utilizing the proposed LIDAR system, the distance and velocity of a target can be measured accurately. The maximum relative errors of distance and velocity measurement are 1.6% and 3.18%, respectively.
Chinese Optics Letters
- Publication Date: Nov. 10, 2021
- Vol.19 Issue, 11 111402 (2021)
Lasers, Optical Amplifiers, and Laser Optics
Adjustable-free and movable Nd:YVO4 thin disk laser based on the telecentric cat’s eye cavityEditors' PickWei Wang, Yongxi Gao, Di Sun, Xiao Du, Jie Guo, and Xiaoyan Liang
In this paper, we propose and demonstrate an adjustable-free and movable
Chinese Optics Letters
- Publication Date: Nov. 10, 2021
- Vol.19 Issue, 11 111403 (2021)
Lasers, Optical Amplifiers, and Laser Optics
Simultaneous tailoring of longitudinal and transverse mode inside an Er:YAG laserRui Song, Xueting Liu, Shiyao Fu, and Chunqing Gao
In this paper, we demonstrate a scheme to tailor both longitudinal and transverse modes inside a laser cavity and constitute an eye-safe single longitudinal mode
Chinese Optics Letters
- Publication Date: Nov. 10, 2021
- Vol.19 Issue, 11 111404 (2021)
Lasers, Optical Amplifiers, and Laser Optics
Switchable single- and dual-wavelength femtosecond mode-locked Er-doped fiber laser based on carboxyl-functionalized graphene oxide saturable absorberQimeng Lin, Li Yan, Yuanqi Song, Xuzhuo Jia, Xiaoqiang Feng, Lei Hou, and Jintao Bai
In this Letter, we demonstrated the switchable single- and dual-wavelength femtosecond soliton generation in single-mode Er-doped fiber lasers with the usage of carboxyl-functionalized graphene oxide (GO-COOH) saturable absorbers (SAs) for the first time, to the best of our knowledge. The fiber laser generated a stable single-wavelength conventional soliton at 1560.1 nm with a pulse duration of 548.1 fs. The dual-wavelength solitons centered at 1531.9 nm and 1555.2 nm with a spacing of approximately 23 nm can be obtained by adjusting the pump power of the cavity. Our experimental results indicated the GO-COOH has great potential to be used in ultrafast fiber lasers as broadband SAs.In this Letter, we demonstrated the switchable single- and dual-wavelength femtosecond soliton generation in single-mode Er-doped fiber lasers with the usage of carboxyl-functionalized graphene oxide (GO-COOH) saturable absorbers (SAs) for the first time, to the best of our knowledge. The fiber laser generated a stable single-wavelength conventional soliton at 1560.1 nm with a pulse duration of 548.1 fs. The dual-wavelength solitons centered at 1531.9 nm and 1555.2 nm with a spacing of approximately 23 nm can be obtained by adjusting the pump power of the cavity. Our experimental results indicated the GO-COOH has great potential to be used in ultrafast fiber lasers as broadband SAs.
Chinese Optics Letters
- Publication Date: Nov. 10, 2021
- Vol.19 Issue, 11 111405 (2021)
Microwave Photonics
Linearized wideband and multi-carrier link based on TL-ANNEnji Liu, Zhenming Yu, Zhiquan Wan, Liang Shu, Kaixuan Sun, Lili Gui, and Kun Xu
The analog photonics link (APL) is widely used in microwave photonics. However, in wideband and multi-carrier systems, the third inter-modulation distortion (IMD3) and cross-modulation distortion (XMD) will jointly limit the spurious-free dynamic range (SFDR) of links. In this paper, we experimentally present a linearized wideband and multi-carrier APL, in which the IMD3 and XMD are mitigated simultaneously by using artificial neural networks with transfer learning (TL-ANN). In this experiment, with different artificial neural networks, which are trained with the knowledge obtained from the two- or three-sub-carrier system, the IMD3 and XMD are suppressed by 21.71 dB and 11.11 dB or 22.38 dB and 16.73 dB, and the SFDR is improved by 13.4 dB or 14.3 dB, respectively. Meanwhile, compared with previous studies, this method could reduce the training time and training epochs to 16% and 25%.The analog photonics link (APL) is widely used in microwave photonics. However, in wideband and multi-carrier systems, the third inter-modulation distortion (IMD3) and cross-modulation distortion (XMD) will jointly limit the spurious-free dynamic range (SFDR) of links. In this paper, we experimentally present a linearized wideband and multi-carrier APL, in which the IMD3 and XMD are mitigated simultaneously by using artificial neural networks with transfer learning (TL-ANN). In this experiment, with different artificial neural networks, which are trained with the knowledge obtained from the two- or three-sub-carrier system, the IMD3 and XMD are suppressed by 21.71 dB and 11.11 dB or 22.38 dB and 16.73 dB, and the SFDR is improved by 13.4 dB or 14.3 dB, respectively. Meanwhile, compared with previous studies, this method could reduce the training time and training epochs to 16% and 25%.
Chinese Optics Letters
- Publication Date: Nov. 10, 2021
- Vol.19 Issue, 11 113901 (2021)
Microwave Photonics
Chip-scale Brillouin instantaneous frequency measurement by use of one-shot frequency-to-power mapping based on lock-in amplificationYuqiu Xu, Yonglan Yang, Xing Li, Xin Wang, and Weiwen Zou
We demonstrate a chip-scale scheme of Brillouin instantaneous frequency measurement (IFM) in a CMOS-compatible doped silica waveguide chip. In the chip-scale Brillouin IFM scheme, the frequency-to-power mapping process is achieved by one-shot detection without additional time averaging and implemented by lock-in amplification, which successfully detects the Brillouin gain of the doped silica waveguide chip in the time domain. A Costas frequency modulated signal ranging from 8 GHz to 9 GHz is experimentally measured, and the frequency measurement errors are maintained within 58 MHz.We demonstrate a chip-scale scheme of Brillouin instantaneous frequency measurement (IFM) in a CMOS-compatible doped silica waveguide chip. In the chip-scale Brillouin IFM scheme, the frequency-to-power mapping process is achieved by one-shot detection without additional time averaging and implemented by lock-in amplification, which successfully detects the Brillouin gain of the doped silica waveguide chip in the time domain. A Costas frequency modulated signal ranging from 8 GHz to 9 GHz is experimentally measured, and the frequency measurement errors are maintained within 58 MHz.
Chinese Optics Letters
- Publication Date: Nov. 10, 2021
- Vol.19 Issue, 11 113902 (2021)
Nonlinear Optics
All-optical carrier recovery for self-homodyne detection via injection locked Brillouin laser in whispering-gallery-mode microcavityBoyuan Liu, Yong Geng, Qiang Zhang, Xinjie Han, Jing Xu, Heng Zhou, and Kun Qiu
We demonstrate comprehensive investigation of the injection locking dynamics of a backscattered Brillouin laser in silica whispering-gallery-mode microcavity. Via injection locking, the Brillouin laser acquires highly correlated phase with the seed laser, enabling ultra-narrow bandwidth, high gain, and coherent optical amplification. Also, for the first time, to the best of our knowledge, the injection locked Brillouin laser is utilized to implement all-optical carrier recovery from coherent optical data signals. We show that by using the injection locked Brillouin laser as a local oscillator for self-homodyne detection, high-quality data receiving can be realized, even without traditional electrical compensations for carrier frequency and phase drifts.We demonstrate comprehensive investigation of the injection locking dynamics of a backscattered Brillouin laser in silica whispering-gallery-mode microcavity. Via injection locking, the Brillouin laser acquires highly correlated phase with the seed laser, enabling ultra-narrow bandwidth, high gain, and coherent optical amplification. Also, for the first time, to the best of our knowledge, the injection locked Brillouin laser is utilized to implement all-optical carrier recovery from coherent optical data signals. We show that by using the injection locked Brillouin laser as a local oscillator for self-homodyne detection, high-quality data receiving can be realized, even without traditional electrical compensations for carrier frequency and phase drifts.
Chinese Optics Letters
- Publication Date: Nov. 10, 2021
- Vol.19 Issue, 11 111901 (2021)
Nonlinear Optics
Vector dynamics of ultrafast cylindrical vector beams in a mode-locked fiber laserJiazhu Wang, Liang Jin, Shangzhi Xie, Renyan Wang, He Zhang, Yingtian Xu, Xin Zhao, Yan Li, and Xiaohui Ma
The vector dynamics of solitons are crucial but easily neglected for realizing vortex solitons. In this Letter, we investigate the effect of vector dynamics on cylindrical vector beams (CVBs) implementation and propose a novel technical method to realize femtosecond CVBs based on vector-locked solitons, which are presented as group-velocity-locked vector solitons (GVLVSs) in the experiment. The outstanding vector properties of GVLVSs not only greatly improve the efficiency of solitons converted into CVBs and output power of CVBs (2.4 times and 4.1 times that of scalar solitons and vector change periodical solitons, with the purity of 97.2%), but also relax the obstacle of ultrafast CVBs from the fundamental frequency to the harmonic regime (up to 198 MHz) for the first time, to the best of our knowledge. This is the highest repetition rate reported for ultrafast CVBs based on passive mode-locking. The investigation of the influence of solitons vector dynamics evolution on the realization of CVBs provides guidance for the excellent performance of ultrafast CVBs.The vector dynamics of solitons are crucial but easily neglected for realizing vortex solitons. In this Letter, we investigate the effect of vector dynamics on cylindrical vector beams (CVBs) implementation and propose a novel technical method to realize femtosecond CVBs based on vector-locked solitons, which are presented as group-velocity-locked vector solitons (GVLVSs) in the experiment. The outstanding vector properties of GVLVSs not only greatly improve the efficiency of solitons converted into CVBs and output power of CVBs (2.4 times and 4.1 times that of scalar solitons and vector change periodical solitons, with the purity of 97.2%), but also relax the obstacle of ultrafast CVBs from the fundamental frequency to the harmonic regime (up to 198 MHz) for the first time, to the best of our knowledge. This is the highest repetition rate reported for ultrafast CVBs based on passive mode-locking. The investigation of the influence of solitons vector dynamics evolution on the realization of CVBs provides guidance for the excellent performance of ultrafast CVBs.
Chinese Optics Letters
- Publication Date: Nov. 10, 2021
- Vol.19 Issue, 11 111903 (2021)
Optical Design and Fabrication
Design of multi-passband polymer multilayer film and its application in photovoltaic agricultureMing Li, Yang Liu, Fangxin Zhang, Xinyu Zhang, Zhisen Zhang, Altyeb Ali Abaker Omer, Shutao Zhao, and Wen Liu
To solve the issue of the contradiction between photovoltaic power generation and plant photosynthesis for sunlight demand, we propose a design method of multi-passband polymer multilayer optical structure. Using polycarbonate (PC) and polymethyl methacrylate (PMMA), two polymer materials with different refractive indices, the passband position and passband bandwidth are calculated and adjusted by the transmission matrix method and TFCalc software. A 450 nm, 660 nm, and 730 nm three-passband filter was realized by superimposing stacks of different band positions. The feasibility of the photovoltaic agriculture was confirmed by the power generation efficiency and the actual plant growth.To solve the issue of the contradiction between photovoltaic power generation and plant photosynthesis for sunlight demand, we propose a design method of multi-passband polymer multilayer optical structure. Using polycarbonate (PC) and polymethyl methacrylate (PMMA), two polymer materials with different refractive indices, the passband position and passband bandwidth are calculated and adjusted by the transmission matrix method and TFCalc software. A 450 nm, 660 nm, and 730 nm three-passband filter was realized by superimposing stacks of different band positions. The feasibility of the photovoltaic agriculture was confirmed by the power generation efficiency and the actual plant growth.
Chinese Optics Letters
- Publication Date: Nov. 10, 2021
- Vol.19 Issue, 11 112201 (2021)
Optical Design and Fabrication
Optical design of a compact and high-transmittance compressive sensing imaging system enabled by freeform opticsDewen Cheng, Hailong Chen, Tong Yang, Jun Ke, Yang Li, and Yongtian Wang
Using compressive sensing for imaging has many applications, and it is an important branch of computational imaging. In this Letter, freeform surfaces are introduced in the hardware optical system design of a compressive sensing imager. The system works under the medium wave infrared band and realizes a
Chinese Optics Letters
- Publication Date: Nov. 10, 2021
- Vol.19 Issue, 11 112202 (2021)
Optical Materials
Mid-infrared flat-topped broadband chiral helix metamaterials based on indium tin oxide and their chiral propertiesWentao Zhang, Weijie Shi, Hui Guo, and Changchun Yan
We proposed a periodic mid-infrared broadband chiral structure. Its unit cell consists of four indium tin oxide (ITO) helix subunits with different radii. The simulation results show that the flat-topped broadband circular dichroism (CD) can be achieved in the mid-infrared band by optimizing the parameters of helix structures. The simulation results also show that compared with the metallic (Ag and Au) helix structures, the ITO helix structure proposed exhibits evidently better broadband CD and optical activity, which provides a new idea for the design of broadband polarization state control devices in the mid-infrared band.We proposed a periodic mid-infrared broadband chiral structure. Its unit cell consists of four indium tin oxide (ITO) helix subunits with different radii. The simulation results show that the flat-topped broadband circular dichroism (CD) can be achieved in the mid-infrared band by optimizing the parameters of helix structures. The simulation results also show that compared with the metallic (Ag and Au) helix structures, the ITO helix structure proposed exhibits evidently better broadband CD and optical activity, which provides a new idea for the design of broadband polarization state control devices in the mid-infrared band.
Chinese Optics Letters
- Publication Date: Nov. 10, 2021
- Vol.19 Issue, 11 111601 (2021)
Optical Materials
Field-induced transformation of ferroelectric domain states in KTN crystalQuanxin Yang, Xiaojin Li, Hongliang Liu, Yingying Ren, and Pengfei Wu
We report an interesting study of electric-field-induced transformation from a single domain ferroelectric state to the multiple domain ferroelectric state in a KTa1-xNbxO3 (KTN) crystal. Experimental results obtained using the confocal μ-Raman spectroscopy confirm the dynamic change of lattice structures induced by an external electric field. Furthermore, the dependence of relative permittivity on the applied voltage also indicates the transformation of ferroelectric states involving the processes of splintering, inversion, and re-formation of ferroelectric domains.We report an interesting study of electric-field-induced transformation from a single domain ferroelectric state to the multiple domain ferroelectric state in a KTa1-xNbxO3 (KTN) crystal. Experimental results obtained using the confocal μ-Raman spectroscopy confirm the dynamic change of lattice structures induced by an external electric field. Furthermore, the dependence of relative permittivity on the applied voltage also indicates the transformation of ferroelectric states involving the processes of splintering, inversion, and re-formation of ferroelectric domains.
Chinese Optics Letters
- Publication Date: Nov. 10, 2021
- Vol.19 Issue, 11 111602 (2021)
Physical Optics
Liquid crystal devices for vector vortex beams manipulation and quantum information applications [Invited]Zhi-Xiang Li, Ya-Ping Ruan, Peng Chen, Jie Tang, Wei Hu, Ke-Yu Xia, and Yan-Qing Lu
Vector vortex beams (VVBs) have attracted significant attention in both classical and quantum optics. Liquid crystal (LC), beyond its applications in information display, has emerged as a versatile tool for manipulating VVBs. In this review, we focus on the functions and applications of typical LC devices in recent studies on controlling the space-variant polarized vortex light. Manipulation of VVBs through patterned nematic LC optical elements, patterned cholesteric LC optical elements, self-assembled defects, and LC spatial light modulators is discussed separately. Moreover, LC-based novel optical applications in the field of quantum information are reviewed.Vector vortex beams (VVBs) have attracted significant attention in both classical and quantum optics. Liquid crystal (LC), beyond its applications in information display, has emerged as a versatile tool for manipulating VVBs. In this review, we focus on the functions and applications of typical LC devices in recent studies on controlling the space-variant polarized vortex light. Manipulation of VVBs through patterned nematic LC optical elements, patterned cholesteric LC optical elements, self-assembled defects, and LC spatial light modulators is discussed separately. Moreover, LC-based novel optical applications in the field of quantum information are reviewed.
Chinese Optics Letters
- Publication Date: Nov. 10, 2021
- Vol.19 Issue, 11 112601 (2021)
Quantum Optics and Quantum Information
Sequential 3 → 1 quantum random access code utilizing unsharp measurementsZhiguang Pang, Jiang Gao, Tianlei Hou, Min Wei, Jian Li, and Qin Wang
Quantum random access codes (QRACs) are important communication tasks that are usually implemented in prepare-and-measure scenarios. The receiver tries to retrieve one arbitrarily chosen bit of the original bit-string from the code qubit sent by the sender. In this Letter, we analyze in detail the sequential version of the
Chinese Optics Letters
- Publication Date: Nov. 10, 2021
- Vol.19 Issue, 11 112701 (2021)
Solar Energy and Photovoltaics
Incorporation of Ag into Cu(In,Ga)Se2 films in low-temperature processZhaojing Hu, Yunxiang Zhang, Shuping Lin, Shiqing Cheng, Zhichao He, Chaojie Wang, Zhiqiang Zhou, Fangfang Liu, Yun Sun, and Wei Liu
Chalcopyrite
Chinese Optics Letters
- Publication Date: Nov. 10, 2021
- Vol.19 Issue, 11 114001 (2021)
Lithium Niobate Based Photonic Devices (2021)
Submission Open:1 November 2020; Submission Deadline: 25 February 2021
Editor (s):
Broadband and lossless lithium niobate valley photonic crystal waveguide [Invited]Editors' Pick
Vol. 19, Issue 6, 060014 (2021)
Vol. 19, Issue 9, 091301 (2021)
Wideband thin-film lithium niobate modulator with low half-wave-voltage length product
Vol. 19, Issue 6, 060016 (2021)
Intelligent algorithms: new avenues for designing nanophotonic devices [Invited]On the Cover
Vol. 19, Issue 1, 011301 (2021)
Integrated thin film lithium niobate Fabry–Perot modulator [Invited]Editors' Pick
Vol. 19, Issue 6, 060003 (2021)
Topological photonic states in artificial microstructures [Invited]On the Cover
Vol. 19, Issue 5, 052602 (2021)
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