Contents 4 Issue (s), 61 Article (s)

Vol.19, Iss.9—Sep.1, 2021 • pp: 091202- Spec. pp:

Vol.19, Iss.8—Aug.1, 2021 • pp: 081101- Spec. pp:

Vol.19, Iss.7—Jul.1, 2021 • pp: 070501- Spec. pp:

Vol.19, Iss.6—Jun.1, 2021 • pp: 060002- Spec. pp:

Research ArticlesVol.19, Iss.9-Sep..1,2021
Infrared and Terahertz Photonics
Liquid crystal integrated metamaterial for multi-band terahertz linear polarization conversion
Shitong Xu, Fei Fan, Hongzhong Cao, Yinghua Wang, and Shengjiang Chang
Chinese Optics Letters
  • Publication Date: Sep. 10, 2021
  • Vol.19 Issue, 9 093701 (2021)
Instrumentation, Measurement, and Optical Sensing
Random Bragg-grating-based wavelength-tunable random fiber laser with a full-open cavity
Bing Lü, Wentao Zhang, Wenzhu Huang, and Fang Li
Chinese Optics Letters
  • Publication Date: Sep. 10, 2021
  • Vol.19 Issue, 9 091203 (2021)
Lasers, Optical Amplifiers, and Laser Optics
Stable noise-like pulse generation in all-PM mode-locked Tm-doped fiber laser based on NOLM
Meng Wang, Minqiu Liu, Yewang Chen, Deqin Ouyang, Junqing Zhao, Jihong Pei, and Shuangchen Ruan
Chinese Optics Letters
  • Publication Date: Sep. 10, 2021
  • Vol.19 Issue, 9 091402 (2021)
Lasers, Optical Amplifiers, and Laser Optics
Theoretical analysis of periodically poled LiNbO3 nonlinear mirror and its application in a passively mode-locked Nd:YSAG laser
Lina Zhao, Fangxin Cai, Luyang Tong, Ye Yuan, Wenyu Zhang, and Yangjian Cai
Chinese Optics Letters
  • Publication Date: Sep. 10, 2021
  • Vol.19 Issue, 9 091403 (2021)
Lasers, Optical Amplifiers, and Laser Optics
Enhanced optical absorption surface of titanium fabricated by a femtosecond laser assisted with airflow pressure
Xun Li, Ming Li, and Hongjun Liu
We propose an effective way to achieve an enhanced optical absorption surface of titanium alloy 7 (Ti7) fabricated by a femtosecond (fs) laser assisted with airflow pressure. The effect of laser scanning speed and laser power on the surfaces’ morphology and average reflectivity was studied. In order to further reduce the surface’s reflectivity, different airflow pressure was introduced during the fabrication of Ti7 by a fs laser. Furthermore, the average reflectivity of samples fabricated under different laser parameters assisted with airflow was presented. In addition, the high and low temperature tests of all samples were performed to test the stability performance of the hybrid micro/nanostructures in extreme environments. It is demonstrated that the airflow pressure has an important influence on the micro/nanostructures for light trapping, the average reflectivity of which could be as low as 2.31% over a broad band of 250–2300 nm before high and low temperature tests, and the reflection for specific wavelengths can go below 1.5%.
Chinese Optics Letters
  • Publication Date: Sep. 10, 2021
  • Vol.19 Issue, 9 091404 (2021)
Lasers, Optical Amplifiers, and Laser Optics
GSA and ESA dual-wavelength pumped 2.3 μm Tm:YLF laser on the 3H43H5 transition
Fei Wang, Haitao Huang, Haiwei Chen, Yushuo Bao, Zihan Li, and Deyuan Shen
The population trapping effect of the F34 level is an important factor limiting the power scaling of the 2.3 μm thulium (Tm) laser on the H34H35 transition. In this Letter, we demonstrate a novel scheme of ground state absorption (GSA) (H36H34) and excited state absorption (ESA) (F34H34) dual-wavelength pumped 2.3 μm Tm lasers. Introducing an ESA pumping process can accurately excite the Tm3+ ions accumulated in the F34 level to the H34 level, constructing a double populating mechanism for the upper laser level H34. A proof-of-principle experimental demonstration of the GSA (785 nm) and ESA (1470 nm) dual-wavelength pumped 2.3 μm Tm:LiYF4 (Tm:YLF) laser was realized. A maximum continuous-wave output power of 1.84 W at 2308 nm was achieved under 785 and 1470 nm dual-wavelength pumping, increased by 60% compared with the case of 785 nm single-wavelength pumping under the same resonator condition. Our work provides an efficient way to achieve higher output power from 2.3 μm Tm-doped lasers on the H34H35 transition.
Chinese Optics Letters
  • Publication Date: Sep. 10, 2021
  • Vol.19 Issue, 9 091405 (2021)
Optical Design and Fabrication
Micro-projection dynamic backlight for multi-view 3D display
Baichuan Zhao, Ruiying Huang, and Guojiao Lü
A micro-projection dynamic backlight for multi-view three-dimensional (3D) display is proposed. The proposed backlight includes a light emitting diodes (LEDs) array, a lenticular lens array, and a scattering film. The LED array, the lenticular lens, and the scattering film construct a micro-projection structure. In this structure, the LEDs in the array are divided into several groups. The light from each LED group can be projected to the scattering film by the lenticular lens and forms a series of bright stripes. The different LED groups have different horizontal positions, so these bright stripes corresponding to different LED groups also have different horizontal positions. Therefore, they can be used as a dynamic backlight. Because the distance between the LEDs array and the lenticular lens is much larger than the distance between the lenticular lens and the scattering films, the imaging progress will make the width of the bright stripes much smaller than that of the LEDs, and the pitch of the stripes is also decreased. According to the 3D display theory, the bright stripes with small width and pitch help to increase the number of views. Therefore, the proposed micro-projection dynamic backlight is very suitable for multi-view 3D display. An experimental prototype was developed, and the experimental results show that the micro-projection dynamic backlight can correctly complete the directional projection of the parallax images to form a 3D display.
Chinese Optics Letters
  • Publication Date: Sep. 10, 2021
  • Vol.19 Issue, 9 092201 (2021)
Ultrafast Optics and Attosecond/High-Field Physics
Generation of 601 fs pulse from an 8 kHz Nd:YVO4 picosecond laser by multi-pass-cell spectral broadening
Jiajun Song, Zhaohua Wang, Xianzhi Wang, Renchong Lü, Hao Teng, Jiangfeng Zhu, and Zhiyi Wei
Chinese Optics Letters
  • Publication Date: Sep. 10, 2021
  • Vol.19 Issue, 9 093201 (2021)
Visual Optics and Displays
High-speed playback of spatiotemporal division multiplexing holographic 3D video stored in a solid-state drive using a digital micromirror device
Kohei Suzuki, Minori Tao, Yuki Maeda, Hirotaka Nakayama, Ren Noguchi, Minoru Oikawa, Yuichiro Mori, Takashi Kakue, Tomoyoshi Shimobaba, Tomoyoshi Ito, and Naoki Takada
Chinese Optics Letters
  • Publication Date: Sep. 10, 2021
  • Vol.19 Issue, 9 093301 (2021)
Research ArticlesVol.19, Iss.8-Aug..1,2021
Imaging Systems and Image Processing
High-speed multimode fiber imaging system based on conditional generative adversarial network
Zhenming Yu, Zhenyu Ju, Xinlei Zhang, Ziyi Meng, Feifei Yin, and Kun Xu
Chinese Optics Letters
  • Publication Date: Aug. 10, 2021
  • Vol.19 Issue, 8 081101 (2021)
Integrated Optics
Near-infrared lasing and tunable upconversion from femtosecond laser inscribed Nd,Gd:CaF2 waveguides
Ruonan Li, Lifei Sun, Yangjian Cai, Yingying Ren, Hongliang Liu, Mark D. Mackenzie, and Ajoy K. Kar
Optical channel waveguides with depressed cladding configurations have been produced in Nd,Gd:CaF2 laser crystals by using ultrafast laser inscription. Waveguide properties are investigated in terms of guiding behaviors and localized laser-induced lattice damages. Under an optical pump of 808 nm light, continuous-wave waveguide lasing at 1.06 μm is achieved, with a single-mode operation and a minimum lasing threshold of 98.8 mW. Furthermore, the visible emissions of Nd3+ with short wavelengths ranging from 415 nm to 550 nm and long wavelengths from 550 nm to 625 nm are observed upon 808 nm laser excitation via the up-converted process. The intensity ratios of two wavelength ranges are proved to be tunable through changing the pumping polarizations.
Chinese Optics Letters
  • Publication Date: Aug. 10, 2021
  • Vol.19 Issue, 8 081301 (2021)
Lasers, Optical Amplifiers, and Laser Optics
Design of a single-mode directly modulated orbital angular momentum laser
Xiang Ma, Shuang Zheng, Jia Liu, Quanan Chen, Qiaoyin Lu, and Weihua Guo
We propose a design of single-mode orbital angular momentum (OAM) beam laser with high direct-modulation bandwidth. It is a microcylinder/microring cavity interacted with two types of second-order gratings: the complex top grating containing the real part and the imaginary part modulations and the side grating. The side grating etched on the periphery of the microcylinder/microring cavity can select a whispering gallery mode with a specific azimuthal mode number, while the complex top grating can scatter the lasing mode with travelling-wave pattern vertically. With the cooperation of the gratings, the laser works with a single mode and emits radially polarized OAM beams. With an asymmetrical pad metal on the top of the cavity, the OAM on-chip laser can firstly be directly modulated with electrical pumping. Due to the small active volume, the laser with low threshold current is predicted to have a high direct modulation bandwidth about 29 GHz with the bias current of ten times the threshold from the simulation. The semiconductor OAM laser can be rather easily realized at different wavelengths such as the O band, C band, and L band.
Chinese Optics Letters
  • Publication Date: Aug. 10, 2021
  • Vol.19 Issue, 8 081401 (2021)
Lasers, Optical Amplifiers, and Laser Optics
External focusing dependence of spatial distribution of air lasers during femtosecond laser filamentation in air
Jiayun Xue, Hui Gao, Nan Zhang, Lu Sun, Lie Lin, and Weiwei Liu
The spatial distribution of the forward-propagating amplified spontaneous emission (ASE) of nitrogen molecular ions during femtosecond laser filamentation in air is studied via numerical simulations. The results suggest that the divergence angle and signal intensity are extremely sensitive to the external focal length. Concurrently, we show that the optical Kerr effect plays a significant role in concentrating the directivity of ASE signals, particularly in cases of loose focusing. Furthermore, the simulations demonstrate that ASE signals are enhanced for a tight focus, although the corresponding filament length is shorter. The main physical mechanism underlying this process is the competition between the plasma defocusing and optical Kerr effects. The result is important for filamentation-based light detection and ranging applied to remote sensing.
Chinese Optics Letters
  • Publication Date: Aug. 10, 2021
  • Vol.19 Issue, 8 081402 (2021)
Lasers, Optical Amplifiers, and Laser Optics
Damage characteristics of dual-band high reflectors affected by nodule defects in the femtosecond regime
Bin Ma, Jiaqi Han, Jing Li, Ke Wang, Shuang Guan, Xinshang Niu, Haoran Li, Jinlong Zhang, Hongfei Jiao, Xinbin Cheng, and Zhanshan Wang
The influence of nodule defects on the characteristics of femtosecond laser-induced damage has not been fully investigated. In this study, two types of 800 nm/1064 nm dual-band HfO2/SiO2 high-reflection films with different configurations were analyzed. Combined with finite-difference time-domain electric field simulation and focused ion beam analysis, the initial state and growth process of femtosecond laser damage of nodules were explored. In particular, the sequence of blister damage determined by the film design and the inner damage caused by nodules were clarified. The rule of the laser-induced damage threshold of different size nodules was obtained. The difference in the damage behavior of nodules in the two types of films was elucidated.
Chinese Optics Letters
  • Publication Date: Aug. 10, 2021
  • Vol.19 Issue, 8 081403 (2021)
Lasers, Optical Amplifiers, and Laser Optics
Spectroscopic and laser properties of Er3+, Pr3+ co-doped LiYF4 crystal
Zhengda Sun, Feifei Wang, Haiping Xia, Hongkun Nie, Kejian Yang, Ruihua Wang, Jingliang He, and Baitao Zhang
In this paper, the absorption and fluorescence spectra of Er3+, Pr3+ co-doped LiYF4 (Er,Pr:YLF) crystal were measured and analyzed. The Pr3+ co-doping was proved to effectively enhance the Er3+:I411/2I413/2 mid-infrared transition at the 2.7 μm with 74.1% energy transfer efficiency from Er3+:I413/2 to Pr3+:F34. By using the Judd–Ofelt theory, the stimulated emission cross section was calculated to be 1.834×10-20 cm2 at 2685 nm and 1.359×10-20 cm2 at 2804.6 nm. Moreover, a diode-end-pumped Er,Pr:YLF laser operating at 2659 nm was realized for the first time, to the best of our knowledge. The maximum output power was determined to be 258 mW with a slope efficiency of 7.4%, and the corresponding beam quality factors Mx2=1.29 and My2=1.25. Our results suggest that Er,Pr:YLF should be a promising material for 2.7 μm laser generation.
Chinese Optics Letters
  • Publication Date: Aug. 10, 2021
  • Vol.19 Issue, 8 081404 (2021)
Microwave Photonics
Optimization of optical signal-to-distortion ratio in a channel-interleaved photonic ADC via a coherent multi-frequency RF driver
Junyan Li, Na Qian, Shiyu Hua, and Weiwen Zou
A microwave-chip-based coherent multi-frequency RF driver is developed for a channel-interleaved photonic analog-to-digital converter (PADC) system, which comprises a multi-class optical demultiplexer and supports a sampling speed of 40 GSa/s. The generated signals from the RF driver are adjustable in both amplitude and phase. We analyze the relationship between the characteristics of the generated RF driver signals and the demultiplexing performance in theory based on the optical signal-to-distortion ratio (OSDR). It is the most effective parameter to evaluate the performance of the demultiplexer in a PADC system without an electronic analog-to-digital converter. By precisely adjusting the amplitude and phase of signals, the OSDR is optimized. The results verify the compatibility between the RF driver and the PADC system.
Chinese Optics Letters
  • Publication Date: Aug. 10, 2021
  • Vol.19 Issue, 8 083901 (2021)
Nanophotonics, Metamaterials, and Plasmonics
Surface-plasmonic sensor using a columnar thin film in the grating-coupled configuration [Invited]
Kiran Mujeeb, Muhammad Faryad, Akhlesh Lakhtakia, and Julio V. Urbina
The excitation of a surface-plasmon-polariton (SPP) wave guided by a columnar thin film (CTF) deposited on a one-dimensional metallic surface-relief grating was investigated for sensing the refractive index of a fluid infiltrating that CTF. The Bruggemann homogenization formalism was used to determine the relative permittivity scalars of the CTF infiltrated by the fluid. The change in the refractive index of the fluid was sensed by determining the change in the incidence angle for which an SPP wave was excited on illumination by a p-polarized plane wave, when the plane of incidence was taken to coincide with the grating plane but not with the morphologically significant plane of the CTF. Multiple excitations of the same SPP wave were found to be possible, depending on the refractive index of the fluid, which can help increase the reliability of results by sensing the same fluid with more than one excitation of the SPP wave.
Chinese Optics Letters
  • Publication Date: Aug. 10, 2021
  • Vol.19 Issue, 8 083601 (2021)
Nonlinear Optics
Real-time and ultrafast optical pulse quantization based on slicing the supercontinuum
Ya Guo, Qiang Cai, Zhiwei Jia, Bingjie Xu, Zhensen Gao, Qianwu Zhang, Ruonan Zhang, Adonis Bogris, K. Alan Shore, Yuncai Wang, and Pu Li
All-optical analog-to-digital conversion is a paramount issue in modern science. How to implement real-time and ultrafast quantization to optical pulses with different intensities in an all-optical domain is a central problem. Here, we report a real-time demonstration of an all-optical quantization scheme based on slicing the supercontinuum in a nonlinear fiber. In comparison with previous schemes through off-line analysis of the power of different optical spectral components in the supercontinuum, this, to the best of our knowledge, is the first demonstration of such functionality online in the time domain. Moreover, the extinction ratio among the quantized outputs can exceed 10 dB, which further confirms the feasibility of the proposed quantization scheme. The current 3 bit resolution in the proof-of-principle experiment is limited by the current experimental condition, but it can be expected to be greatly enhanced through improving both the spectral width of the generated supercontinuum and the number of filtering channels used.
Chinese Optics Letters
  • Publication Date: Aug. 10, 2021
  • Vol.19 Issue, 8 081901 (2021)
Nonlinear Optics
Mode-locked all-fiber laser with high stability based on cobalt oxyfluoride
Ximei Liu, Mengli Liu, Yaorong Wang, Kai Huang, Ming Lei, Wenjun Liu, and Zhiyi Wei
Recent years have witnessed the exploration of fiber laser technology focused on numerous pivotal optoelectronic applications from laser processing and remote sensing to optical communication. Here, using cobalt oxyfluoride (CoOF) as the nonlinear material, a 156 fs mode-locked fiber laser with strong stability is obtained. The rapid thermal annealing technique is used to fabricate the CoOF, which is subsequently transferred to the tapered region of the microfiber to form the effective pulse modulation device. CoOF interacts with the pulsed laser through the evanescent field to realize the intracavity pulse shaping, and then the stable mode-locked pulse is obtained. The mode-locked operation is maintained with the pulse duration of 156 fs and repetition rate of 49 MHz. In addition, the signal-to-noise ratio is about 90 dB. Those experimental results confirm the attractive nonlinear optical properties of CoOF and lay a foundation for the ultrafast application of low-dimensional transition metal oxides.
Chinese Optics Letters
  • Publication Date: Aug. 10, 2021
  • Vol.19 Issue, 8 081902 (2021)
Optical Design and Fabrication
Fabrication of microholes array on titanium foil by a femtosecond laser and a surface’s wettability switching
Cong Wang, Bo Liu, Zhi Luo, Kaiwen Ding, and Ji’an Duan
In this study, an effective method is proposed for controlling a titanium foil surface’s wettability. A microholes array series is fabricated on the surface of titanium foil by a femtosecond laser under different laser energy and pulse number. The changes of the titanium surface’s morphology are characterized. When placed in a darkroom with high-temperature treatment and immersed in alcohol under UV irradiation, respectively, the femtosecond laser treated surfaces display switchable wettability. It is demonstrated that the changing between Ti-OH and Ti-O prompts the transformation between superhydrophilic and superhydrophobic. Compared with existing reports, the switchable wetting cycle is shortened to 1.5 h. The functional surfaces with switchable wettability have potential applications in oil–water separation and water mist collection.
Chinese Optics Letters
  • Publication Date: Aug. 10, 2021
  • Vol.19 Issue, 8 082201 (2021)
Optical Materials
Tunable coherent perfect absorption in three-dimensional Dirac semimetal films
Jipeng Wu, Jie Tang, Rongzhou Zeng, Xiaoyu Dai, and Yuanjiang Xiang
Chinese Optics Letters
  • Publication Date: Aug. 10, 2021
  • Vol.19 Issue, 8 081601 (2021)
Optoelectronics
Optical tensor core architecture for neural network training based on dual-layer waveguide topology and homodyne detection
Shaofu Xu, and Weiwen Zou
Chinese Optics Letters
  • Publication Date: Aug. 10, 2021
  • Vol.19 Issue, 8 082501 (2021)
Optoelectronics
Ultra-low detection delay drift caused by the temperature variation in a Si-avalanche-photodiode-based single-photon detector
Yurong Wang, Linli Wang, Chenyi Wu, Zhaohui Li, Lei Yang, and Guang Wu
Chinese Optics Letters
  • Publication Date: Aug. 10, 2021
  • Vol.19 Issue, 8 082502 (2021)
Optoelectronics
Cascaded deep ultraviolet light-emitting diode via tunnel junction
Huabin Yu, Zhongjie Ren, Muhammad Hunain Memon, Shi Fang, Danhao Wang, Zhongling Liu, Haochen Zhang, Feng Wu, Jiangnan Dai, Changqing Chen, and Haiding Sun
Chinese Optics Letters
  • Publication Date: Aug. 10, 2021
  • Vol.19 Issue, 8 082503 (2021)
Physical Optics
Temporal Airy–Talbot effect in linear optical potentials
Tianwen Han, Hao Chen, Wenwan Li, Bing Wang, and Peixiang Lu
Chinese Optics Letters
  • Publication Date: Aug. 10, 2021
  • Vol.19 Issue, 8 082601 (2021)
Ultrafast Optics and Attosecond/High-Field Physics
Proposal for experimentally observing expectant ball lightning
Silin Guo, Zhongpeng Li, Chuliang Zhou, and Ye Tian
Chinese Optics Letters
  • Publication Date: Aug. 10, 2021
  • Vol.19 Issue, 8 083201 (2021)
Research ArticlesVol.19, Iss.7-Jul..1,2021
Biophotonics
Compact long-working-distance laser-diode-based photoacoustic microscopy with a reflective objective
Lijun Deng, Qi Chen, Yang Bai, Guodong Liu, Lüming Zeng, and Xuanrong Ji
Photoacoustic microscopy (PAM) has quickly developed into a noninvasive biomedical imaging technique to achieve detection, diagnosis, and monitoring. Compared with Q-switched neodymium-doped yttrium aluminum garnet or optical parametric oscillator lasers, a low-cost and small-size laser diode (LD) used as an alternative light source is conducive to achieving the miniaturization and integration for preclinical transformation. However, the LD’s low peak output power needs the high numerical aperture objective to attain tight focus, which limits the working distance (WD) of the system in only 2–3 mm, resulting in not achieving the backward coaxial confocal mode. Here, we present a compact visible LD-based PAM system with a reflective objective to achieve a 22 mm long WD and a 10 μm lateral resolution. Different depth subcutaneous microvascular networks in label-free mouse ears have successfully reappeared in vivo with a signal-to-noise ratio up to 14 dB by a confocal alignment. It will be a promising tool to develop into a handy tool for subcutaneous blood vessel imaging.
Chinese Optics Letters
  • Publication Date: Jul. 10, 2021
  • Vol.19 Issue, 7 071701 (2021)
Biophotonics
Nonlinear photoacoustic imaging dedicated to thermal-nonlinearity characterization
Yujiao Shi, and Zhenhui Zhang
We proposed a nonlinear photoacoustic (PA) technique as a new imaging contrast mechanism for tissue thermal-nonlinearity characterization. When a sine-modulated Gaussian temperature field is introduced by a laser beam, in view of the temperature dependence of the thermal diffusivity, the nonlinear PA effect occurs, which leads to the production of second-harmonic PA (SHPA) signals. By extracting the fundamental frequency PA and SHPA signal amplitudes of samples through the lock-in technique, a parameter that only reflects nonlinear thermal-diffusivity characteristics of the sample then can be obtained. The feasibility of the technique for thermal-nonlinearity characterization has been studied on phantom samples. In vitro biological tissues have been studied by this method to demonstrate its medical imaging capability, prefiguring great potential of this new method in medical imaging applications.
Chinese Optics Letters
  • Publication Date: Jul. 10, 2021
  • Vol.19 Issue, 7 071702 (2021)
Diffraction, Gratings, and Holography
Aperture synthesis based solely on phase images in digital holography
Jun Long, Ping Cai, Chiyue Liu, Weijuan Qu, and Hao Yan
Aperture synthesis is an important approach to improve the lateral resolution of digital holography (DH) techniques. The limitation of the accuracy of registration positions between sub-holograms affects the quality of the synthesized image and even causes the failure of aperture synthesis. It is a major issue in aperture synthesis of DH. Currently intensity images are utilized to find the registration positions of sub-holograms in aperture synthesis. To improve the accuracy of registration positions, we proposed a method based on similarity calculations of the phase images between sub-holograms instead of intensity images. Furthermore, a quantitative indicator, degree of image distortion, was applied to evaluate the synthetic results. Experiments are performed and the results verify that the proposed phase-image-based method is better than the state-of-the-art intensity-image-based techniques in the estimation of registration positions and provides a better synthesized final three-dimensional shape image.
Chinese Optics Letters
  • Publication Date: Jul. 10, 2021
  • Vol.19 Issue, 7 070501 (2021)
Lasers, Optical Amplifiers, and Laser Optics
Experimental observation of transient mode-locking in the build-up stage of a soliton fiber laser
Yinqi Wang, Xiaoyue Wang, Junsong Peng, Ming Yan, Kun Huang, and Heping Zeng
Chinese Optics Letters
  • Publication Date: Jul. 10, 2021
  • Vol.19 Issue, 7 071401 (2021)
Lasers, Optical Amplifiers, and Laser Optics
High-repetition-rate 1.5 µm passively Q-switched Er:Yb:YAl3(BO3)4 microchip laser
Songqing Zha, Yujin Chen, Bingxuan Li, Yanfu Lin, Wenbin Liao, Yuqi Zou, Chenghui Huang, Zhanglang Lin, and Ge Zhang
Chinese Optics Letters
  • Publication Date: Jul. 10, 2021
  • Vol.19 Issue, 7 071402 (2021)
Lasers, Optical Amplifiers, and Laser Optics
Highly twisted M-line of a vortex beam due to the coupling of ultrahigh-order modes
Cheng Yin, Xuefen Kan, Kun Guo, Tao Wang, Jiangming Xu, Qingbang Han, Jian Wu, and Zhuangqi Cao
In modern optics, particular interest is devoted to the phase singularities that yield complicated and twisted phase structures by photons carrying optical angular momentum. In this paper, the traditional M-line method is applied to a vortex beam (VB) by a symmetric metal cladding waveguide chip, which can host numerous oscillating guided modes via free space coupling. These ultrahigh-order modes (UOMs) result in high angular resolution due to the high finesse of the resonant chip. Experiments show that the reflected pattern of a VB can be divided into a series of inner and outer rings, whilst both of them are highly distorted by the M-lines due to the UOMs’ leakage. Taking the distribution of the energy flux into account, a simple ray-optics-based model is proposed to simulate the reflected pattern by calculating the local incident angle over the cross section of the beam. The theoretical simulations fit well with the experimental results, and the proposed scheme may enable new applications in imaging and sensing of complicated phase structures.
Chinese Optics Letters
  • Publication Date: Jul. 10, 2021
  • Vol.19 Issue, 7 071403 (2021)
Microwave Photonics
RF self-interference cancellation by using photonic technology [Invited]Editors' Pick
Xiuyou Han, Xinxin Su, Shuanglin Fu, Yiying Gu, Zhenlin Wu, Xiaozhou Li, and Mingshan Zhao
Radio frequency (RF) self-interference is a key issue for the application of in-band full-duplex communication in beyond fifth generation and sixth generation communications. Compared with electronic technology, photonic technology has the advantages of wide bandwidth and high tuning precision, exhibiting great potential to realize high interference cancellation depth over broad band. In this paper, a comprehensive overview of photonic enabled RF self-interference cancellation (SIC) is presented. The operation principle of photonic RF SIC is introduced, and the advances in implementing photonic RF SIC according to the realization mechanism of phase reversal are summarized. For further realistic applications, the multipath RF SIC and the integrated photonic RF SIC are also surveyed. Finally, the challenges and opportunities of photonic RF SIC technology are discussed.
Chinese Optics Letters
  • Publication Date: Jul. 10, 2021
  • Vol.19 Issue, 7 073901 (2021)
Nanophotonics, Metamaterials, and Plasmonics
Ultrafast control of slow light in THz electromagnetically induced transparency metasurfaces
Yi Zhao, Qiuping Huang, Honglei Cai, Xiaoxia Lin, Hongchuan He, Hao Cheng, Tian Ma, and Yalin Lu
In this paper, we experimentally demonstrate ultrafast optical control of slow light in the terahertz (THz) range by combining the electromagnetically induced transparency (EIT) metasurfaces with the cut wire made of P+-implanted silicon with short carrier lifetime. Employing the optical-pump THz-probe spectroscopy, we observed that the device transited from a state with a slow light effect to a state without a slow light effect in an ultrafast time of 5 ps and recovered within 200 ps. A coupled oscillator model is utilized to explain the origin of controllability. The experimental results agree very well with the simulated and theoretical results. These EIT metasurfaces have the potential to be used as an ultrafast THz optical delay device.
Chinese Optics Letters
  • Publication Date: Jul. 10, 2021
  • Vol.19 Issue, 7 073602 (2021)
Nonlinear Optics
In-situ modal inspection based on transverse second harmonic generation in single CdS nanobelt
Chenguang Xin, Jie Qi, Rui Zhang, Li Jin, and Yanru Zhou
Chinese Optics Letters
  • Publication Date: Jul. 10, 2021
  • Vol.19 Issue, 7 071901 (2021)
Nonlinear Optics
Robust modal phase matching in subwavelength x-cut and z-cut lithium niobate thin-film waveguides
Lingzhi Peng, Lihong Hong, Baoqin Chen, Peng He, and Zhiyuan Li
We use the nonlinear coupled-mode theory to theoretically investigate second-harmonic generation (SHG) in subwavelength x-cut and z-cut lithium niobate (LN) thin-film waveguides and derive the analytical formula to calculate SHG efficiency in x-cut and z-cut LN thin-film waveguides explicitly. Under the scheme of optimal modal phase matching (MPM), two types of LN thin films can achieve highly efficient frequency doubling of a 1064 nm laser with a comparable conversion efficiency due to very consistent modal field distribution of the fundamental wave and second-harmonic wave with efficient overlap between them. Such a robust MPM for high-efficiency SHG in both the subwavelength x-cut and z-cut LN thin-film waveguides is further confirmed in a broad wavelength range, which might facilitate design and application of micro–nano nonlinear optical devices based on the subwavelength LN thin film.
Chinese Optics Letters
  • Publication Date: Jul. 10, 2021
  • Vol.19 Issue, 7 071902 (2021)
Nonlinear Optics
Precise control of micro-rod resonator free spectral range via iterative laser annealing
Qin Wen, Wenwen Cui, Yong Geng, Heng Zhou, and Kun Qiu
Chinese Optics Letters
  • Publication Date: Jul. 10, 2021
  • Vol.19 Issue, 7 071903 (2021)
Optical Design and Fabrication
Self-aligned fiber-based dual-beam source for STED nanolithography
Jian Chen, Guoliang Chen, and Qiwen Zhan
A fiber-based source that can be exploited in a stimulated emission depletion (STED) inspired nanolithography setup is presented. Such a source maintains the excitation beam pulse, generates a ring-shaped depletion beam, and automatically realizes dual-beam coaxial alignment that is critical for two beam nanolithography. The mode conversion of the depletion beam is realized by using a customized vortex fiber, which converts the Gaussian beam into a donut-shaped azimuthally polarized beam. The pulse width and repetition frequency of the excitation beam remain unchanged, and its polarization states can be controlled. According to the simulated point spread function of each beam in the focal region, the full width at half-maximum of the effective spot size in STED nanofabrication could decrease to less than 28.6 nm.
Chinese Optics Letters
  • Publication Date: Jul. 10, 2021
  • Vol.19 Issue, 7 072201 (2021)
Quantum Optics and Quantum Information
Heterodyne detection enhanced by quantum correlation
Boya Xie, and Sheng Feng
Chinese Optics Letters
  • Publication Date: Jul. 10, 2021
  • Vol.19 Issue, 7 072701 (2021)
Ultrafast Optics and Attosecond/High-Field Physics
Scattering-amplitude phase in spiderlike photoelectron momentum distributions
Jiu Tang, Guizhong Zhang, Yufei He, Xin Ding, and Jianquan Yao
The spiderlike structures in the photoelectron momentum distributions of ionized electrons from the hydrogen atom are numerically simulated by using a semiclassical rescattering model (SRM) and solving the time-dependent Schr?dinger equation (TDSE), focusing on the role of the phase of the scattering amplitude. With the SRM, we find that the spiderlike legs shift to positions with smaller transverse momentum values while increasing the phase. The spiderlike patterns obtained by SRM and TDSE are in good agreement upon considering this phase. In addition, the time differences in electron ionization and rescattering calculated by SRM and the saddle-point equations are either in agreement or show very similar laws of variation, which further corroborates the significance of the phase of the scattering amplitude.
Chinese Optics Letters
  • Publication Date: Jul. 10, 2021
  • Vol.19 Issue, 7 073201 (2021)
X-Ray Optics
Efficient three-dimensional characterization of C/C composite reinforced with densely distributed fibers via X-ray phase-contrast microtomography
Ke Li, Yantao Gao, Haipeng Zhang, Guohao Du, Hefei Huang, Hongjie Xu, and Tiqiao Xiao
Carbon fiber (CF)/pyrolytic graphite (PG) composites are promising structural materials for molten salt reactors because of their superior performance. Due to the minor density difference between CF and PG, existing methods are impractical for efficient three-dimensional characterization of CF/PG composites. Therefore, in this study, a method based on in-line phase-contrast X-ray microtomography was developed to solve the aforementioned problem. Experimental results demonstrate that the method is suitable for comprehensive characterization of CF/PG composites. The relationship between the microporous defects and fiber orientations of such composites was also elucidated. The findings can be useful for improving the manufacturing process of CF/PG composites.
Chinese Optics Letters
  • Publication Date: Jul. 10, 2021
  • Vol.19 Issue, 7 073401 (2021)
Research ArticlesVol.19, Iss.6-Jun..1,2021
Special Issue on Lithium Niobate Based Photonic Devices
High-quality-factor optical microresonators fabricated on lithium niobate thin film with an electro-optical tuning range spanning over one free spectral range
Zhe Wang, Chaohua Wu, Zhiwei Fang, Min Wang, Jintian Lin, Rongbo Wu, Jianhao Zhang, Jianping Yu, Miao Wu, Wei Chu, Tao Lu, Gang Chen, and Ya Cheng
Chinese Optics Letters
  • Publication Date: Jun. 10, 2021
  • Vol.19 Issue, 6 060002 (2021)
Special Issue on Lithium Niobate Based Photonic Devices
Integrated thin film lithium niobate Fabry–Perot modulator [Invited]Editors' Pick
Mengyue Xu, Mingbo He, Yuntao Zhu, Lin Liu, Lifeng Chen, Siyuan Yu, and Xinlun Cai
Chinese Optics Letters
  • Publication Date: Jun. 10, 2021
  • Vol.19 Issue, 6 060003 (2021)
Special Issue on Lithium Niobate Based Photonic Devices
Efficient second harmonic generation in silicon covered lithium niobate waveguides
Bin Fang, Shenglun Gao, Zhizhang Wang, Shining Zhu, and Tao Li
Chinese Optics Letters
  • Publication Date: Jun. 10, 2021
  • Vol.19 Issue, 6 060004 (2021)
Special Issue on Lithium Niobate Based Photonic Devices
Directly generating vortex beams in the second harmonic by a spirally structured fundamental wave
Jun Li, Haigang Liu, Yan Li, Xianping Wang, Minghuang Sang, and Xianfeng Chen
Chinese Optics Letters
  • Publication Date: Jun. 10, 2021
  • Vol.19 Issue, 6 060005 (2021)
Special Issue on Lithium Niobate Based Photonic Devices
Polarization diversity two-dimensional grating coupler on x-cut lithium niobate on insulator
Renyou Ge, Hao Li, Ya Han, Lifeng Chen, Jian Xu, Meiyan Wu, Yongqing Li, Yannong Luo, and Xinlun Cai
We propose and demonstrate a polarization diversity two-dimensional grating coupler based on the lithium niobate on insulator platform, for the first time, to the best of our knowledge. The optimization design, performance characteristics, and fabrication tolerance of the two-dimensional grating coupler are thoroughly analyzed utilizing the three-dimensional finite-difference time-domain method. Experimentally, -7.2 dB of coupling efficiency is achieved with 1 dB bandwidth of 64 nm. The polarization-dependent loss is about 0.4 dB around 1550 nm. Our work provides new polarization multiplexing approaches for the lithium niobate on insulator platform, paving the way for critical applications such as high-speed polarization multiplexed electro-optical modulators.
Chinese Optics Letters
  • Publication Date: Jun. 10, 2021
  • Vol.19 Issue, 6 060006 (2021)
Special Issue on Lithium Niobate Based Photonic Devices
Locally periodically poled LNOI ridge waveguide for second harmonic generation [Invited]
Biao Mu, Xianfang Wu, Yunfei Niu, Yan Chen, Xinlun Cai, Yanxiao Gong, Zhenda Xie, Xiaopeng Hu, and Shining Zhu
Chinese Optics Letters
  • Publication Date: Jun. 10, 2021
  • Vol.19 Issue, 6 060007 (2021)
Special Issue on Lithium Niobate Based Photonic Devices
On-chip erbium-doped lithium niobate waveguide amplifiers [Invited]
Qiang Luo, Chen Yang, Zhenzhong Hao, Ru Zhang, Dahuai Zheng, Fang Bo, Yongfa Kong, Guoquan Zhang, and Jingjun Xu
Chinese Optics Letters
  • Publication Date: Jun. 10, 2021
  • Vol.19 Issue, 6 060008 (2021)
Special Issue on Lithium Niobate Based Photonic Devices
High-Q lithium niobate microring resonators using lift-off metallic masks [Invited]
Ke Zhang, Zhaoxi Chen, Hanke Feng, Wing-Han Wong, Edwin Yue-Bun Pun, and Cheng Wang

High-Q lithium niobate (LN) optical micro-resonators are an excellent platform for future applications in optical communications, nonlinear optics, and quantum optics. To date, high-Q factors are typically achieved in LN using either dielectric masks or femtosecond laser ablation, while the more standard and commonly available lift-off metallic masks are often believed to lead to rough sidewalls and lowered Q factors. Here, we show that LN microring resonators with strong light confinement and intrinsic Q factors over 1 million can be fabricated using optimized lift-off metallic masks and dry etching processes, corresponding to a waveguide propagation loss of 0.3 dB/cm. The entire process is fully compatible with wafer-scale production and could be transferred to other photonic materials.

Chinese Optics Letters
  • Publication Date: Jun. 10, 2021
  • Vol.19 Issue, 6 060010 (2021)
Special Issue on Lithium Niobate Based Photonic Devices
Nonlinear Talbot self-healing in periodically poled LiNbO3 crystal [Invited]On the Cover
Bingxia Wang, Shan Liu, Tianxiang Xu, Ruwei Zhao, Peixiang Lu, Wieslaw Krolikowski, and Yan Sheng

The nonlinear Talbot effect is a near-field nonlinear diffraction phenomenon in which the self-imaging of periodic objects is formed by the second harmonics of the incident laser beam. We demonstrate the first, to the best of our knowledge, example of nonlinear Talbot self-healing, i.e., the capability of creating defect-free images from faulty nonlinear optical structures. In particular, we employ the tightly focused femtosecond infrared optical pulses to fabricate LiNbO3 nonlinear photonic crystals and show that the defects in the form of the missing points of two-dimensional square and hexagonal periodic structures are restored in the second harmonic images at the first nonlinear Talbot plane. The observed nonlinear Talbot self-healing opens up new possibilities for defect-tolerant optical lithography and printing.

Chinese Optics Letters
  • Publication Date: Jun. 10, 2021
  • Vol.19 Issue, 6 060011 (2021)
Special Issue on Lithium Niobate Based Photonic Devices
Recent progress of second harmonic generation based on thin film lithium niobate [Invited]
Yang Li, Zhijin Huang, Wentao Qiu, Jiangli Dong, Heyuan Guan, and Huihui Lu
Recently, nonlinear photonics has attracted considerable interest. Among the nonlinear effects, second harmonic generation (SHG) remains a hot research topic. The recent development of thin film lithium niobate (TFLN) technology has superior performances to the conventional counterparts. Herein, this review article reveals the recent progress of SHG based on TFLN and its integrated photonics. We mainly discuss and compare the different techniques of TFLN-based structures to boost the nonlinear performances assisted by localizing light in nanostructures and structured waveguides. Moreover, our conclusions and perspectives indicate that more efficient methods need to be further explored for higher SHG conversion efficiency on the TFLN platform.
Chinese Optics Letters
  • Publication Date: Jun. 10, 2021
  • Vol.19 Issue, 6 060012 (2021)
Special Issue on Lithium Niobate Based Photonic Devices
Surface lattice resonances in dielectric metasurfaces for enhanced light-matter interaction [Invited]
Yuechen Jia, Yingying Ren, Xingjuan Zhao, and Feng Chen

Lithium niobate (LiNbO3) is a versatile crystalline material for various photonic applications. With the recent advances in LiNbO3-on-insulator (LNOI) thin film technology, LiNbO3 has been regarded as one of the most promising platforms for multi-functional integrated photonics. In this work, we present the field enhancement due to collective resonances in arrayed LiNbO3 nanoantennas. These resonances arise from the enhanced radiative coupling of localized Mie resonances in the individual nanoparticles and Rayleigh anomalies due to in-plane diffraction orders of the lattice. We describe the pronounced differences in field enhancement and field distributions for electric and magnetic dipoles, offering valuable information for the design and optimization of high-quality-factor optical metasurfaces based on LiNbO3.

Chinese Optics Letters
  • Publication Date: Jun. 10, 2021
  • Vol.19 Issue, 6 060013 (2021)
Special Issue on Lithium Niobate Based Photonic Devices
Broadband and lossless lithium niobate valley photonic crystal waveguide [Invited]
Rui Ge, Xiongshuo Yan, Yuping Chen, and Xianfeng Chen

We investigate the influences of structure parameters and interface shapes on the bandwidth of the edge state of lithium niobate valley photonic crystals. By increasing the size difference of two air holes in the same unit cell, we find that the bandwidth of the lossless nontrivial edge state possesses a peak value of 0.0201(a/λ), which can be used to construct broadband valley photonic crystal waveguides. Mode field distributions verify that the waveguide is robust against sharp bends and exhibits chirality. When the unit cell is arranged in a bearded interface with the top and bottom components showing negative and positive valley Chern numbers, respectively, we find that the lithium niobate valley photonic crystal is more likely to exhibit a lossless edge state, which is difficult to be realized in valley waveguides with low refractive index materials. This work can provide guidance on the design of the high-performance topological waveguide.

Chinese Optics Letters
  • Publication Date: Jun. 10, 2021
  • Vol.19 Issue, 6 060014 (2021)
Special Issue on Lithium Niobate Based Photonic Devices
Effect of dimension variation for second-harmonic generation in lithium niobate on insulator waveguide [Invited]
Xiao-Hui Tian, Wei Zhou, Kun-Qian Ren, Chi Zhang, Xiaoyue Liu, Guang-Tai Xue, Jia-Chen Duan, Xinlun Cai, Xiaopeng Hu, Yan-Xiao Gong, Zhenda Xie, and Shi-Ning Zhu
Chinese Optics Letters
  • Publication Date: Jun. 10, 2021
  • Vol.19 Issue, 6 060015 (2021)
Special Issue on Lithium Niobate Based Photonic Devices
Hybrid mono-crystalline silicon and lithium niobate thin films [Invited]
Houbin Zhu, Qingyun Li, Huangpu Han, Zhenyu Li, Xiuquan Zhang, Honghu Zhang, and Hui Hu

The heterogeneous integration of silicon thin film and lithium niobate (LN) thin film combines both the advantages of the excellent electronics properties and mature micro-processing technology of Si and the excellent optical properties of LN, comprising a potentially promising material platform for photonic integrated circuits. Based on ion-implantation and wafer-bonding technologies, a 3 inch wafer-scale hybrid mono-crystalline Si/LN thin film was fabricated. A high-resolution transmission electron microscope was used to investigate the crystal-lattice arrangement of each layer and the interfaces. Only the H-atom-concentration distribution was investigated using secondary-ion mass spectroscopy. High-resolution X-ray-diffraction ω2θ scanning was used to study the lattice properties of the Si/LN thin films. Raman measurements were performed to investigate the bulk Si and the Si thin films. Si strip-loaded straight waveguides were fabricated, and the optical propagation loss of a 5-μm-width waveguide was 6 dB/cm for the quasi-TE mode at 1550 nm. The characterization results provide useful information regarding this hybrid material.

Chinese Optics Letters
  • Publication Date: Jun. 10, 2021
  • Vol.19 Issue, 6 060017 (2021)