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2019
Volume: 17 Issue 8
20 Article(s)
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Research Articles
Atomic and Molecular Physics
Optimization of temperature characteristics of a transportable 87Rb atomic fountain clock
Xinwen Wang, Kangkang Liu, Henan Cheng, Wei Ren, Jingfeng Xiang, Jingwei Ji, Xiangkai Peng, Zhen Zhang, Jianbo Zhao, Meifeng Ye, Lin Li, Tang Li, Bin Wang, Qiuzhi Qu, Liang Liu, and Desheng Lü
A high-performance transportable fountain clock is attractive for use in laboratories with high-precision time-frequency measurement requirements. This Letter reports the improvement of the stability of a transportable rubidium-87 fountain clock because of an optimization of temperature characteristics. This clock integrates its physical packaging, optical benches, microwave frequency synthesizers, and electronic controls onto an easily movable wheeled plate. Two optical benches with a high-vibration resistance are realized in this work. No additional adjustment is required after moving them several times. The Allan deviation of the fountain clock frequency was measured by comparing it with that of the hydrogen maser. The fountain clock got a short-term stability of 2.3×10 13 at 1 s and long-term stability on the order of 10 16 at 100,000 s.A high-performance transportable fountain clock is attractive for use in laboratories with high-precision time-frequency measurement requirements. This Letter reports the improvement of the stability of a transportable rubidium-87 fountain clock because of an optimization of temperature characteristics. This clock integrates its physical packaging, optical benches, microwave frequency synthesizers, and electronic controls onto an easily movable wheeled plate. Two optical benches with a high-vibration resistance are realized in this work. No additional adjustment is required after moving them several times. The Allan deviation of the fountain clock frequency was measured by comparing it with that of the hydrogen maser. The fountain clock got a short-term stability of
Chinese Optics Letters
- Publication Date: Aug. 10, 2019
- Vol. 17, Issue 8, 080201 (2019)
Diffraction and Gratings
Multi-band imaging and focusing of photonic crystal flat lens with scatterer-size gradient
Yuan Cen, Jianlan Xie, and Jianjun Liu
In this Letter, a photonic crystal (PC) flat lens with a scatterer-size gradient is proposed, which simultaneously achieves imaging of the point source and sub-wavelength focusing of the plane wave in the first, second, and fifth bands. The imaging of the point source breaks through the diffraction limit in the second and fifth bands. The PC flat lens with the scatterer-size gradient is expected to be used in a new multifunctional optical imaging and focusing device, which improves the application potential of a PC flat lens.In this Letter, a photonic crystal (PC) flat lens with a scatterer-size gradient is proposed, which simultaneously achieves imaging of the point source and sub-wavelength focusing of the plane wave in the first, second, and fifth bands. The imaging of the point source breaks through the diffraction limit in the second and fifth bands. The PC flat lens with the scatterer-size gradient is expected to be used in a new multifunctional optical imaging and focusing device, which improves the application potential of a PC flat lens..
Chinese Optics Letters
- Publication Date: Aug. 10, 2019
- Vol. 17, Issue 8, 080501 (2019)
Fiber Optics and Optical Communications
Vernier effect of fiber interferometer based on cascaded PANDA polarization maintaining fiber
Shun Liu, Ping Lu, Enci Chen, Wenjun Ni, Deming Liu, Jiangshan Zhang, and Zhenggang Lian
This Letter shows the Vernier effect based on two segments of PANDA polarization maintaining fiber (PMF), whose lengths are 28 and 23 cm, respectively. The two PMFs are spliced together, and the angle between the fast axes is set to 45°. This cascaded PMF is inserted in a Sagnac loop to form an interferometer that can generate the Vernier effect. The spectrum consists of finesse fringe and envelope and realizes simultaneous measurement of strain and temperature. The envelope can provide strain and temperature sensitivities of 58.0 pm/με and 1.05 nm/°C. The finesse fringe provides sensitivities of 5.9 pm/με and 1.36 nm/°C.This Letter shows the Vernier effect based on two segments of PANDA polarization maintaining fiber (PMF), whose lengths are 28 and 23 cm, respectively. The two PMFs are spliced together, and the angle between the fast axes is set to 45°. This cascaded PMF is inserted in a Sagnac loop to form an interferometer that can generate the Vernier effect. The spectrum consists of finesse fringe and envelope and realizes simultaneous measurement of strain and temperature. The envelope can provide strain and temperature sensitivities of 58.0 pm/με and 1.05 nm/°C. The finesse fringe provides sensitivities of 5.9 pm/με and 1.36 nm/°C..
Chinese Optics Letters
- Publication Date: Aug. 10, 2019
- Vol. 17, Issue 8, 080601 (2019)
Demonstration of high-dimensional free-space data coding/decoding through multi-ring optical vortices
Shiyao Fu, Yanwang Zhai, Heng Zhou, Jianqiang Zhang, Ci Yin, and Chunqing Gao
Multi-ring optical vortices are a kind of structured beams that carry orbital angular momentum (OAM) and have concentrical doughnut intensity distributions. In this Letter, we present both theoretically and experimentally a scheme that employs the dimensions of both the OAM states and radial index of multi-ring optical vortices simultaneously to accomplish high-dimensional free-space data coding/decoding transmissions. Such a scheme can further improve the coding efficiency when limited OAM states are available. In the proof-of-concept experiment, 64-ary coding/decoding employing 16 OAM states and four radial indices are present. Also, the coding/decoding performance when facing various atmosphere turbulences is evaluated. Furthermore, a 64 × 64 gray image (totally, 32,768 bits) is also transmitted through multi-ring optical vortices coding in free-space successfully, showing good transmission performance.Multi-ring optical vortices are a kind of structured beams that carry orbital angular momentum (OAM) and have concentrical doughnut intensity distributions. In this Letter, we present both theoretically and experimentally a scheme that employs the dimensions of both the OAM states and radial index of multi-ring optical vortices simultaneously to accomplish high-dimensional free-space data coding/decoding transmissions. Such a scheme can further improve the coding efficiency when limited OAM states are available. In the proof-of-concept experiment, 64-ary coding/decoding employing 16 OAM states and four radial indices are present. Also, the coding/decoding performance when facing various atmosphere turbulences is evaluated. Furthermore, a 64 × 64 gray image (totally, 32,768 bits) is also transmitted through multi-ring optical vortices coding in free-space successfully, showing good transmission performance..
Chinese Optics Letters
- Publication Date: Aug. 10, 2019
- Vol. 17, Issue 8, 080602 (2019)
A Q-switched erbium-doped fiber laser based on ZrS2 as a saturable absorber
Ping Hu, Yan Huang, Fangfang Liu, Ying Liu, Liping Guo, Xiaolu Ge, and Xiaojuan Liu
A passively Q-switched erbium-doped fiber (EDF) laser is proposed and demonstrated utilizing a zirconium disulfide (ZrS2)-based saturable absorber (SA). ZrS2 nanosheets are prepared, whose modulation depth, saturation intensity, and nonsaturable absorbance are measured to be 14.7%, 0.34 MW/cm2, and 17.4%, respectively. Then, a Q-switched EDF laser is implemented by the ZrS2-SA. The pulse repetition rate varies from 40.65 to 87.1 kHz when the pump power changes from 55 to 345 mW. The shortest pulse width is 1.49 μs with pulse energy of 33.5 nJ. As far as we know, this is the shortest pulse width obtained by a ZrS2-SA so far.
A passively
Chinese Optics Letters
- Publication Date: Aug. 10, 2019
- Vol. 17, Issue 8, 080603 (2019)
10 Gb/s two-dimensional free-space optical code division multiple access wiretap channel with spatial diversity
Jianhua Ji, Jianjia Zhang, Bing Wu, Ke Wang, and Ming Xu
We experimentally demonstrate a 10 Gb/s free-space optical wiretap channel based on a spatial-diversity scheme and optical code division multiple access. In weak and middle turbulence cases, the bit error rate of a legitimate user can be decreased, and physical layer security can be simultaneously enhanced.We experimentally demonstrate a 10 Gb/s free-space optical wiretap channel based on a spatial-diversity scheme and optical code division multiple access. In weak and middle turbulence cases, the bit error rate of a legitimate user can be decreased, and physical layer security can be simultaneously enhanced..
Chinese Optics Letters
- Publication Date: Aug. 10, 2019
- Vol. 17, Issue 8, 080604 (2019)
Hybrid OCS/OBS interconnect in intra-data-center network
Qian Kong, Yafeng Zhan, and Peng Wan
We report on a data center network (DCN) architecture based on hybrid optical circuit switching (OCS) and optical burst switching (OBS) interconnect for dynamic DCN connectivity provisioning. With the combination of the centralized and distributed control of the software-defined optical networks, the proposed interconnect can achieve unprecedented flexibility in dealing with both mice and elephant flow in the DCN. Numerical simulation is employed to investigate the performance of the proposed architecture. The results show that the OBS module has preferable performance in dealing with a larger burst packet, and the throughput is constrained by the capacity of the server random access memory module.We report on a data center network (DCN) architecture based on hybrid optical circuit switching (OCS) and optical burst switching (OBS) interconnect for dynamic DCN connectivity provisioning. With the combination of the centralized and distributed control of the software-defined optical networks, the proposed interconnect can achieve unprecedented flexibility in dealing with both mice and elephant flow in the DCN. Numerical simulation is employed to investigate the performance of the proposed architecture. The results show that the OBS module has preferable performance in dealing with a larger burst packet, and the throughput is constrained by the capacity of the server random access memory module..
Chinese Optics Letters
- Publication Date: Aug. 10, 2019
- Vol. 17, Issue 8, 080605 (2019)
Lasers and Laser Optics
Non-collinear phase-matching sum-frequency generation based on boundary total reflection in bulk KDP | Editors' Pick
Yan Guan, Fang Wang, Ying Yang, Deen Wang, Xin Zhang, Qiang Yuan, Wei Zhou, Dongxia Hu, Xuewei Deng, and Huaijin Ren
Collinear phase-matching of sum-frequency generation (SFG) has been studied thoroughly previously, while non-collinear schemes are sometimes more flexible in application. However, this phase-matching type is more difficult to meet and control. We employ a convenient method to obtain harmonic generation in bulk potassium dihydrogen phosphate (KDP), using an incident wave vector and a reflected wave vector to create a triangle phase-matching relationship. With a simple, flexible set-up, we can observe 351 nm SFG, and the conversion efficiency is up to ～3.6% per reflection. Furthermore, we believe this approach has potential application value and improvement space.Collinear phase-matching of sum-frequency generation (SFG) has been studied thoroughly previously, while non-collinear schemes are sometimes more flexible in application. However, this phase-matching type is more difficult to meet and control. We employ a convenient method to obtain harmonic generation in bulk potassium dihydrogen phosphate (KDP), using an incident wave vector and a reflected wave vector to create a triangle phase-matching relationship. With a simple, flexible set-up, we can observe 351 nm SFG, and the conversion efficiency is up to ～3.6% per reflection. Furthermore, we believe this approach has potential application value and improvement space..
Chinese Optics Letters
- Publication Date: Aug. 10, 2019
- Vol. 17, Issue 8, 081401 (2019)
Effect of spatio-temporal coupling on ultrafast laser direct writing in glass
Qin Li, Wenbo Li, Wei Chu, Yuxiang Cao, Wencheng Zhang, Hongliang Ma, Zuanming Jin, and Ye Dai
Spatio-temporal coupling characteristics of ultrafast laser pulses are quantitatively tailored. An asymmetric microstructure is induced in the focal volume when the laser scans perpendicularly to the direction of the spatial chirp in fused silica. The tilted direction reverses when adding a Dove prism into the light path. The sign of the pulse front tilt can be turned from positive to negative by changing the group delay dispersion by steps. We reveal that the tilted direction of a microstructure depends on spatial chirp, and the interplay between spatio-temporal chirp leads to the change of tilted angles.Spatio-temporal coupling characteristics of ultrafast laser pulses are quantitatively tailored. An asymmetric microstructure is induced in the focal volume when the laser scans perpendicularly to the direction of the spatial chirp in fused silica. The tilted direction reverses when adding a Dove prism into the light path. The sign of the pulse front tilt can be turned from positive to negative by changing the group delay dispersion by steps. We reveal that the tilted direction of a microstructure depends on spatial chirp, and the interplay between spatio-temporal chirp leads to the change of tilted angles..
Chinese Optics Letters
- Publication Date: Aug. 10, 2019
- Vol. 17, Issue 8, 081402 (2019)
Vibration-insensitive fiber spool for laser stabilization
Junchao Huang, Lingke Wang, Yifei Duan, Yafeng Huang, Meifeng Ye, Lin Li, Liang Liu, and Tang Li
Excess frequency noise induced by mechanical vibration is the dominant noise source at low Fourier frequencies in fiber-delay-line stabilized lasers. To resolve this problem, a double-winding fiber spool is designed and implemented that has ultralow acceleration sensitivity in all spatial directions. By carefully choosing the optimal geometry parameters of the fiber spool, we achieve acceleration sensitivity of 8 × 10 11/g and 3 × 10 11/g (g denotes the gravitational acceleration) in axial and radial directions, respectively.Excess frequency noise induced by mechanical vibration is the dominant noise source at low Fourier frequencies in fiber-delay-line stabilized lasers. To resolve this problem, a double-winding fiber spool is designed and implemented that has ultralow acceleration sensitivity in all spatial directions. By carefully choosing the optimal geometry parameters of the fiber spool, we achieve acceleration sensitivity of 8 × 10 11/g and 3 × 10 11/g (g denotes the gravitational acceleration) in axial and radial directions, respectively..
Chinese Optics Letters
- Publication Date: Aug. 10, 2019
- Vol. 17, Issue 8, 081403 (2019)
1 kHz nanosecond-pulsed room temperature Fe:ZnSe laser gain-switched by a ZnGeP2 optical parametric oscillator
Yingyi Li, Ke Yang, Gaoyou Liu, Baoquan Yao, and Youlun Ju
We demonstrate a Fe:ZnSe laser gain-switched by a ZnGeP2 optical parametric oscillator (OPO) under the pulse repetition frequency of 1 kHz at room temperature. The 2.9 μm signal light of the OPO is employed as the pump for the Fe:ZnSe laser. The maximum output power of the Fe:ZnSe laser is 58 mW with the pulse duration of 2.7 ns under the incident pump power of 280 mW, corresponding to a peak pulse power of 21.5 kW and an optical-to-optical efficiency of 20.7%. The spectrum of the Fe:ZnSe laser has a range of 4030.2–4593.6 nm with a dip at 4187.1–4340.4 nm due to the absorption of CO2.We demonstrate a Fe:ZnSe laser gain-switched by a ZnGeP2 optical parametric oscillator (OPO) under the pulse repetition frequency of 1 kHz at room temperature. The 2.9 μm signal light of the OPO is employed as the pump for the Fe:ZnSe laser. The maximum output power of the Fe:ZnSe laser is 58 mW with the pulse duration of 2.7 ns under the incident pump power of 280 mW, corresponding to a peak pulse power of 21.5 kW and an optical-to-optical efficiency of 20.7%. The spectrum of the Fe:ZnSe laser has a range of 4030.2–4593.6 nm with a dip at 4187.1–4340.4 nm due to the absorption of CO2..
Chinese Optics Letters
- Publication Date: Aug. 10, 2019
- Vol. 17, Issue 8, 081404 (2019)
Ultrafast dynamics of three types of simultaneous shockwaves and filament attenuation in femtosecond laser multi-pulse ablation of PMMA
Guoyan Wang, Lan Jiang, Jingya Sun, Jie Hu, Qingsong Wang, Ming Li, and Yongfeng Lu
Cylindrical shockwaves inside polymethyl methacrylate (PMMA) generated simultaneously with two hemispherical shockwaves induced by a femtosecond Gaussian beam laser were investigated using an ultrafast pump–probe imaging technique. The evolutions of these three shockwaves with probe delay and incident pulse number have been systematically analyzed. The plasma intensity and filament length in the center of cylindrical shockwave both decayed with pulse number. Moreover, the self-focused filament moved downstream towards the output surface with an increased pulse number. The experimental results and mechanism illustrated that energy deposition was suppressed by a degraded nonlinear effect due to a pre-ablated structure in multi-pulse irradiation.Cylindrical shockwaves inside polymethyl methacrylate (PMMA) generated simultaneously with two hemispherical shockwaves induced by a femtosecond Gaussian beam laser were investigated using an ultrafast pump–probe imaging technique. The evolutions of these three shockwaves with probe delay and incident pulse number have been systematically analyzed. The plasma intensity and filament length in the center of cylindrical shockwave both decayed with pulse number. Moreover, the self-focused filament moved downstream towards the output surface with an increased pulse number. The experimental results and mechanism illustrated that energy deposition was suppressed by a degraded nonlinear effect due to a pre-ablated structure in multi-pulse irradiation..
Chinese Optics Letters
- Publication Date: Aug. 10, 2019
- Vol. 17, Issue 8, 081405 (2019)
Materials
Comparative study of coherent terahertz emission from Fe/Pt ferromagnetic heterostructures
Xiao-Peng He, Pan-Hui Huang, Xiao-Yu Yang, Zuan-Ming Jin, Shi-Tao Lou, Xiao-Lei Zhang, and Qing-Yuan Jin
The ultrafast spin dynamic of in-plane magnetized Fe/Pt films was investigated by terahertz emission spectroscopy. The amplitude of the emitted terahertz wave is proportional to the intensity of the exciting laser beams. Both the amplitude and polarity of the terahertz wave can be adjusted by modifying the external magnetic field. The dependency of the amplitude on external magnetic fields is coincident to the hysteresis loops of the sample. Also, the polarity of the terahertz wave is reversed, as the magnetization orientation is reversed. The super-diffusive transient spin current with an inverse spin Hall effect is attributed to the main mechanism of the terahertz emission.The ultrafast spin dynamic of in-plane magnetized Fe/Pt films was investigated by terahertz emission spectroscopy. The amplitude of the emitted terahertz wave is proportional to the intensity of the exciting laser beams. Both the amplitude and polarity of the terahertz wave can be adjusted by modifying the external magnetic field. The dependency of the amplitude on external magnetic fields is coincident to the hysteresis loops of the sample. Also, the polarity of the terahertz wave is reversed, as the magnetization orientation is reversed. The super-diffusive transient spin current with an inverse spin Hall effect is attributed to the main mechanism of the terahertz emission..
Chinese Optics Letters
- Publication Date: Aug. 10, 2019
- Vol. 17, Issue 8, 081601 (2019)
Medical optics and biotechnology
Spectrophotometer with enhanced sensitivity for uric acid detection
Nurfatihah Che Abd Rashid, Nor Hafizah Ngajikin, Asrul Izam Azmi, Rashidah Arsat, Suhaila Isaak, Noran Azizan Cholan, and Nur Ellina Azmi
A spectrophotometer with an LED as the light source for uric acid detection is proposed in this work. The mechanism of uric acid detection is based on energy absorbed by sodium urate, which is a chemical product of uric acid and sodium hydroxide solution. For the performance validation, comparison between the spectrophotometer with an LED and halogen lamp is carried out. Measurement results suggest that the spectrophotometer system with LED light has better sensitivity than that with halogen light. At a 460 nm wavelength, the sensitivity for the spectrophotometer with an LED is 0.0046 dL/mg, which is 73% higher than that with halogen light that records 0.0012 dL/mg. This enhanced sensitivity is attributed to the higher luminous efficacy of the LED light beam. As a result, a larger amount of flux interacts with the sample, leading to the sensitivity enhancement. The spectrophotometer with an LED is also applied for the detection of uric acid in a real human urine sample. Based on the experimental data at a 460 nm wavelength, the method manages to achieve the sensitivity of 0.0016 dL/mg, accuracy of 96.01%, limit of detection of 4.79 mg/dL, and limit of quantification of 14.52 mg/dL. These findings show that the use of LED as the input light source is promising for the spectrophotometer.A spectrophotometer with an LED as the light source for uric acid detection is proposed in this work. The mechanism of uric acid detection is based on energy absorbed by sodium urate, which is a chemical product of uric acid and sodium hydroxide solution. For the performance validation, comparison between the spectrophotometer with an LED and halogen lamp is carried out. Measurement results suggest that the spectrophotometer system with LED light has better sensitivity than that with halogen light. At a 460 nm wavelength, the sensitivity for the spectrophotometer with an LED is 0.0046 dL/mg, which is 73% higher than that with halogen light that records 0.0012 dL/mg. This enhanced sensitivity is attributed to the higher luminous efficacy of the LED light beam. As a result, a larger amount of flux interacts with the sample, leading to the sensitivity enhancement. The spectrophotometer with an LED is also applied for the detection of uric acid in a real human urine sample. Based on the experimental data at a 460 nm wavelength, the method manages to achieve the sensitivity of 0.0016 dL/mg, accuracy of 96.01%, limit of detection of 4.79 mg/dL, and limit of quantification of 14.52 mg/dL. These findings show that the use of LED as the input light source is promising for the spectrophotometer..
Chinese Optics Letters
- Publication Date: Aug. 10, 2019
- Vol. 17, Issue 8, 081701 (2019)
Nonlinear Optics
Two-photon absorption towards pulse modulation in mechanically exfoliated and CVD monolayer cascaded MoS2 structures
Yafeng Xie, Saifeng Zhang, Xiaoyan Zhang, Ningning Dong, Ivan M. Kislyakov, Song Luo, Zhanghai Chen, Jean-Michel Nunzi, Long Zhang, and Jun Wang
Mechanical exfoliation (ME) and chemical vapor deposition (CVD) MoS2 monolayers have been extensively studied, but the large differences of nonlinear optical performance between them have never been clarified. Here, we prepared MoS2 monolayers using ME and CVD methods and investigated the two-photon absorption (TPA) response and its saturation. We found that the TPA coefficient of the ME monolayer was about (1.88 ± 0.21) × 103 cm/GW, nearly two times that of the CVD one at (1.04 ± 0.15) × 103 cm/GW. Furthermore, we simulated and compared the TPA-induced optical pulse modulation in multilayer cascaded structures, which is instructive and meaningful for the design of optical devices such as a beam shaper and optical limiter.Mechanical exfoliation (ME) and chemical vapor deposition (CVD) MoS2 monolayers have been extensively studied, but the large differences of nonlinear optical performance between them have never been clarified. Here, we prepared MoS2 monolayers using ME and CVD methods and investigated the two-photon absorption (TPA) response and its saturation. We found that the TPA coefficient of the ME monolayer was about (1.88 ± 0.21) × 103 cm/GW, nearly two times that of the CVD one at (1.04 ± 0.15) × 103 cm/GW. Furthermore, we simulated and compared the TPA-induced optical pulse modulation in multilayer cascaded structures, which is instructive and meaningful for the design of optical devices such as a beam shaper and optical limiter..
Chinese Optics Letters
- Publication Date: Aug. 10, 2019
- Vol. 17, Issue 8, 081901 (2019)
Interactive length of fundamental wave and second harmonic generated on the surface of anomalous dispersion medium
Xiaojing Wang, Huaijin Ren, Gang Wang, and Jun He
In this Letter, a new method is presented to calculate the interactive length between the fundamental wave and second harmonic generation (SHG) for the configuration of total internal reflection on the inner surface of a nonlinear crystal. Three independent experiments are designed to measure the bandwidths of this second harmonic wave. The theoretical expression of the intensity of SHG is obtained through a nonlinear coupled wave equation. The interactive length of this phase-matched SHG can be calculated mathematically by utilizing the measured bandwidths and the intensity equation. There is no existing method to obtain the interactive length either from theoretical calculations or by experimental measurement. This method can be applied to estimate the extremely short interactive volume in nonlinear processes.In this Letter, a new method is presented to calculate the interactive length between the fundamental wave and second harmonic generation (SHG) for the configuration of total internal reflection on the inner surface of a nonlinear crystal. Three independent experiments are designed to measure the bandwidths of this second harmonic wave. The theoretical expression of the intensity of SHG is obtained through a nonlinear coupled wave equation. The interactive length of this phase-matched SHG can be calculated mathematically by utilizing the measured bandwidths and the intensity equation. There is no existing method to obtain the interactive length either from theoretical calculations or by experimental measurement. This method can be applied to estimate the extremely short interactive volume in nonlinear processes..
Chinese Optics Letters
- Publication Date: Aug. 10, 2019
- Vol. 17, Issue 8, 081902 (2019)
Optical Design and Fabrication
Diffraction-limited microfocusing generated by polymer microlines separated by 1.12 μm
Azeddine Tellal, Omar Ziane, and Patrice L. Baldeck
The diffraction of a dielectric microline pair is optimized by numerical simulations to generate an efficient focusing pattern with a micron-scale footprint. Microlines separated by 1.12 μm are fabricated by two-photon polymerization on a glass substrate, and their diffraction pattern is characterized by three-dimensional wide-field transmission microscopy. A line pair, having a width W=0.40 μm and a height H=0.80 μm, leads to diffraction-limited focusing in the visible spectrum. Depending on wavelength, its focal length, lateral resolution, and depth of focus are in the ranges of 0.8–1.3 μm, 0.22–0.44 μm, and 1.7–2.13 μm, respectively. Such a microlens based on the diffraction of only two subwavelength scatterers could be used for the design of miniature optical sensors with micron and sub-micron pixels.The diffraction of a dielectric microline pair is optimized by numerical simulations to generate an efficient focusing pattern with a micron-scale footprint. Microlines separated by 1.12 μm are fabricated by two-photon polymerization on a glass substrate, and their diffraction pattern is characterized by three-dimensional wide-field transmission microscopy. A line pair, having a width W = 0.40 μm H = 0.80 μm
Chinese Optics Letters
- Publication Date: Aug. 10, 2019
- Vol. 17, Issue 8, 082201 (2019)
Optical devices
Angle tolerant transmissive color filters exploiting metasurface incorporating hydrogenated amorphous silicon nanopillars | Editors' Pick
Ishwor Koirala, Chul-Soon Park, Sang-Shin Lee, and Duk-Yong Choi
Angle tolerant transmissive subtractive color filters incorporating a metasurface exploiting hydrogenated amorphous silicon nanopillars (NPs) on a glass substrate were proposed and demonstrated. The achieved transmission efficiency ranged from 75% to 95% at off-resonance wavelengths. For an NP resonator, electric and magnetic-field distributions in conjunction with absorption cross-sections were investigated to confirm a resonant transmission dip, which is primarily governed by the absorption resulting from simultaneous excitation of magnetic and electric dipoles via Mie scattering. The proposed devices exhibit higher angular tolerance and lower crosstalk for the absorption spectra and, therefore, are applicable with photodetectors, image sensors, and imaging/display devices.Angle tolerant transmissive subtractive color filters incorporating a metasurface exploiting hydrogenated amorphous silicon nanopillars (NPs) on a glass substrate were proposed and demonstrated. The achieved transmission efficiency ranged from 75% to 95% at off-resonance wavelengths. For an NP resonator, electric and magnetic-field distributions in conjunction with absorption cross-sections were investigated to confirm a resonant transmission dip, which is primarily governed by the absorption resulting from simultaneous excitation of magnetic and electric dipoles via Mie scattering. The proposed devices exhibit higher angular tolerance and lower crosstalk for the absorption spectra and, therefore, are applicable with photodetectors, image sensors, and imaging/display devices..
Chinese Optics Letters
- Publication Date: Aug. 10, 2019
- Vol. 17, Issue 8, 082301 (2019)
Design of an all-optical logic sequence generator based on polarization holographic gratings | On the Cover
Renjie Xia, Changshun Wang, Tianyu Chen, Yujia Pan, Ziyao Lü, and Lili Sun
In this Letter, an all-optical logic sequence generator based on two different polarization holographic gratings has been proposed and demonstrated, which has one input port and four output ports. The polarization state of input light signal determines logic output signals. It can produce four kinds of logic sequence output signals: 1000, 0100, 0010, and 0001, corresponding to the input light signal of four different polarization states: the p-linear, s-linear, left-handed circular, and right-handed circular. The two polarization gratings have been fabricated, and the working principle of the logic sequence generator has been proved by diffraction pattern analysis of polarization gratings.In this Letter, an all-optical logic sequence generator based on two different polarization holographic gratings has been proposed and demonstrated, which has one input port and four output ports. The polarization state of input light signal determines logic output signals. It can produce four kinds of logic sequence output signals: 1000, 0100, 0010, and 0001, corresponding to the input light signal of four different polarization states: the p-linear, s-linear, left-handed circular, and right-handed circular. The two polarization gratings have been fabricated, and the working principle of the logic sequence generator has been proved by diffraction pattern analysis of polarization gratings..
Chinese Optics Letters
- Publication Date: Aug. 10, 2019
- Vol. 17, Issue 8, 082302 (2019)
Physical Optics
Multiple-fringe structure of attosecond transient absorption spectrum driven by mid-infrared laser
Jinxing Xue, Candong Liu, Zhinan Zeng, Ruxin Li, and Zhizhan Xu
We theoretically investigate the delay-dependent attosecond transient absorption spectra in the helium atom dressed by an infrared laser pulse in the wavelength range of 800–2400 nm. By numerically solving the three-dimensional time-dependent Schr dinger equation, we find that the absorption spectrogram exhibits a multiple-fringe structure for using the mid-infrared dressing pulse. The quantitative calculation of the transition matrix between different Floquet states provides direct evidence on the origin of the multiple-fringe structure. Our result shows that the wavelength of the dressing pulse is an important parameter and the unique feature of attosecond transient absorption spectroscopy can be induced in the mid-infrared regime.We theoretically investigate the delay-dependent attosecond transient absorption spectra in the helium atom dressed by an infrared laser pulse in the wavelength range of 800–2400 nm. By numerically solving the three-dimensional time-dependent Schr dinger equation, we find that the absorption spectrogram exhibits a multiple-fringe structure for using the mid-infrared dressing pulse. The quantitative calculation of the transition matrix between different Floquet states provides direct evidence on the origin of the multiple-fringe structure. Our result shows that the wavelength of the dressing pulse is an important parameter and the unique feature of attosecond transient absorption spectroscopy can be induced in the mid-infrared regime..
Chinese Optics Letters
- Publication Date: Aug. 10, 2019
- Vol. 17, Issue 8, 082601 (2019)
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