Fabrication of side pump combiners when pumping with a laser diode and a fiber laser
Zhixian Li, Min Fu, Xiaofan Zhao, Hongye Li, Zilun Chen, Zefeng Wang, and Jinbao Chen
Side pumping combiners are widely used in fiber laser schemes for their high coupling efficiency, low insertion loss, and multi-point pumping capability. However, side pumping combiners perform differently in coupling efficiency when pumping with a laser diode (LD) and a high-brightness 1018 nm Yb-doped fiber laser (YDFL). In this paper, for the first time, to the best of our knowledge, we investigated the different parameters to fabricate the (2+1)×1 combiner with high coupling efficiency when pumping with an LD and a YDFL, respectively. After optimization, the maximum coupled pump power from one single-pump port of the combiner was 1200 W and 2730 W when pumping with a LD and a YDFL, respectively.Side pumping combiners are widely used in fiber laser schemes for their high coupling efficiency, low insertion loss, and multi-point pumping capability. However, side pumping combiners perform differently in coupling efficiency when pumping with a laser diode (LD) and a high-brightness 1018 nm Yb-doped fiber laser (YDFL). In this paper, for the first time, to the best of our knowledge, we investigated the different parameters to fabricate the
- Oct. 11, 2021
- Chinese Optics Letters
- Vol.20 Issue, 2 021401 (2022)
- DOI：10.3788/COL202220.021401
High-color-purity, high-brightness and angle-insensitive red structural color
Jintong Liu, Kun Feng, Yusi Wang, Qingyuan Li, Nan Chen, and Yikun Bu
We propose a simple five-layer structure for creating red structural color, which has high color purity and high brightness. The design is based on the superposition of a silver substrate and multilayer silicon material. Absorption at the shorter wavelengths of the structure is effectively guaranteed, and reflection at the longer wavelengths is well enhanced. The red structural color has a peak reflectivity of 91% and a colorimetric purity of 0.9. Moreover, the designed structure displays angle-invariant performance up to 60°. This kind of structure scheme is environmentally friendly with low fabrication cost, and it can play an important role in a variety of fields, such as color displays and image sensors.We propose a simple five-layer structure for creating red structural color, which has high color purity and high brightness. The design is based on the superposition of a silver substrate and multilayer silicon material. Absorption at the shorter wavelengths of the structure is effectively guaranteed, and reflection at the longer wavelengths is well enhanced. The red structural color has a peak reflectivity of 91% and a colorimetric purity of 0.9. Moreover, the designed structure displays angle-invariant performance up to 60°. This kind of structure scheme is environmentally friendly with low fabrication cost, and it can play an important role in a variety of fields, such as color displays and image sensors.
- Oct. 11, 2021
- Chinese Optics Letters
- Vol.20 Issue, 2 021601 (2022)
- DOI：10.3788/COL202220.021601
Terahertz out-of-plane coupler based on compact spot-size converter
Hongxiang Zhang, Changpei Liang, Jian Song, Chenzhong Fu, Xiaofei Zang, Lin Chen, and Jingya Xie
Low-loss dielectric terahertz (THz) chips are efficient platforms for diverse THz applications. One of the key elements in the chip is the coupler. Most of the available THz couplers are in-plane and couple the THz wave from the metal waveguide to the dielectric waveguide. However, out-of-plane couplers are more suitable for wafer-scale testing and tolerant of alignment variation. In this work, we propose an out-of-plane THz coupler for coupling the antenna to the dielectric waveguide. The device is constructed using a grating and a compact spot-size converter. As the conventional optical spot-size converters that apply directly to THz chips are too large, we have designed a compact spot-size converter based on a tapered waveguide with a lens. The total device is 2.9 cm long and can couple a 7 mm diameter THz beam to a 500 µm wide waveguide. The device can scan the THz beam, radiate the input rectangular waveguide mode to free space, and drive the rotation angle of the fan beam through the scanning frequency. We fabricated the device using a single lithography step on a silicon wafer. The out-of-plane coupling efficiency was found to be ∼5 dB at 194 GHz. The fan-beam steering range was found to be around 40° in the frequency range of 170–220 GHz. The proposed out-of-plane coupling technique may provide an effective way for THz wafer-scale testing with a higher degree of freedom for on-chip integration. Also, the proposed technique being non-mechanical, beam steering using it, may therefore find applications in THz radar, communication, and sensing.Low-loss dielectric terahertz (THz) chips are efficient platforms for diverse THz applications. One of the key elements in the chip is the coupler. Most of the available THz couplers are in-plane and couple the THz wave from the metal waveguide to the dielectric waveguide. However, out-of-plane couplers are more suitable for wafer-scale testing and tolerant of alignment variation. In this work, we propose an out-of-plane THz coupler for coupling the antenna to the dielectric waveguide. The device is constructed using a grating and a compact spot-size converter. As the conventional optical spot-size converters that apply directly to THz chips are too large, we have designed a compact spot-size converter based on a tapered waveguide with a lens. The total device is 2.9 cm long and can couple a 7 mm diameter THz beam to a 500 µm wide waveguide. The device can scan the THz beam, radiate the input rectangular waveguide mode to free space, and drive the rotation angle of the fan beam through the scanning frequency. We fabricated the device using a single lithography step on a silicon wafer. The out-of-plane coupling efficiency was found to be ∼5 dB at 194 GHz. The fan-beam steering range was found to be around 40° in the frequency range of 170–220 GHz. The proposed out-of-plane coupling technique may provide an effective way for THz wafer-scale testing with a higher degree of freedom for on-chip integration. Also, the proposed technique being non-mechanical, beam steering using it, may therefore find applications in THz radar, communication, and sensing.
- Oct. 11, 2021
- Chinese Optics Letters
- Vol.20 Issue, 2 021301 (2022)
- DOI：10.3788/COL202220.021301
High performance optical sensor based on double compound symmetric gratings
Chaoying Shi, Xiuhong Liu, Jinhua Hu, Haiyan Han, and Jijun Zhao
A high performance optical sensor based on a double compound symmetric gratings (DCSGs) structure is designed. The reflection spectrum of the DCSG is investigated by utilizing a method that combines a theoretical model with the eigenmode information of the grating structure. The theoretical results, which are observed to agree well with those acquired by rigorous coupled-wave analysis, show that the linewidth of the reflection spectrum decreases upon the increasing distance between the grating strips. This research work will lay a foundation for studying high performance integrated optical sensors in miniature nanostructures.A high performance optical sensor based on a double compound symmetric gratings (DCSGs) structure is designed. The reflection spectrum of the DCSG is investigated by utilizing a method that combines a theoretical model with the eigenmode information of the grating structure. The theoretical results, which are observed to agree well with those acquired by rigorous coupled-wave analysis, show that the linewidth of the reflection spectrum decreases upon the increasing distance between the grating strips. This research work will lay a foundation for studying high performance integrated optical sensors in miniature nanostructures.
- Oct. 11, 2021
- Chinese Optics Letters
- Vol.20 Issue, 2 021201 (2022)
- DOI：10.3788/COL202220.021201
Development of single-resonant optical parametric oscillator with tunable output from 410 nm to 630 nm
Miao Wang, Jian Ma, Tingting Lu, Shanjiang Hu, Xiaolei Zhu, and Weibiao Chen
A single-resonant low-threshold type-I β-Ba2BO4 (BBO) optical parametric oscillator (OPO) with tunable output from 410 nm to 630 nm at 5 kHz repetition rate is reported. By taking the noncollinear phase matching method, low-threshold OPO operation could be obtained compared with the configuration of collinear phase matching, and the maximum optical–optical conversion efficiency of 11.8% was achieved at 500 nm wavelength when 0.4 mJ pump pulse energy was applied. When the noncollinearity angle was preset at 1.6°, 4.8°, and 6.3°, a continuously tuning output with a total spectral range of 220 nm was successfully obtained by adjusting the phase matching angle of the BBO crystal.A single-resonant low-threshold type-I
- Oct. 18, 2021
- Chinese Optics Letters
- Vol.20 Issue, 2 021403 (2022)
- DOI：10.3788/COL202220.021403
High-accuracy mode recognition method in orbital angular momentum optical communication system
Lin Zhao, Yuan Hao, Li Chen, Wenyi Liu, Meng Jin, Yi Wu, Jiamin Tao, Kaiqian Jie, and Hongzhan Liu
Vortex optical communication has been a hot research field in recent years. A key step is mode recognition in the orbital angular momentum (OAM) free-space optical (FSO) communication system. In this article, we propose an OAM mode recognition method based on image recognition technology, which uses the interferogram between the vortex beam and the Gaussian beam to identify the OAM mode. In order to resist the influence of atmospheric turbulence on the recognition accuracy, we added a Gaussian smoothing filter into the recognition process. Moreover, we used random phase screens to generate interferogram sets at distances of 1 km and 2 km. The verification result shows that the proposed scheme produces high identification accuracy for the distorted optical field. The average accuracy can reach 100% and 87.78% under the conditions of medium- and strong-turbulence levels, respectively. It is anticipated that these results might be helpful for improving the reliability of the OAM-FSO communication system in the future.Vortex optical communication has been a hot research field in recent years. A key step is mode recognition in the orbital angular momentum (OAM) free-space optical (FSO) communication system. In this article, we propose an OAM mode recognition method based on image recognition technology, which uses the interferogram between the vortex beam and the Gaussian beam to identify the OAM mode. In order to resist the influence of atmospheric turbulence on the recognition accuracy, we added a Gaussian smoothing filter into the recognition process. Moreover, we used random phase screens to generate interferogram sets at distances of 1 km and 2 km. The verification result shows that the proposed scheme produces high identification accuracy for the distorted optical field. The average accuracy can reach 100% and 87.78% under the conditions of medium- and strong-turbulence levels, respectively. It is anticipated that these results might be helpful for improving the reliability of the OAM-FSO communication system in the future.
- Oct. 11, 2021
- Chinese Optics Letters
- Vol.20 Issue, 2 020601 (2022)
- DOI：10.3788/COL202220.020601
Diode-pumped 13 W Yb:KGW femtosecond laser
Jinfang Yang, Zhaohua Wang, Jiajun Song, Xianzhi Wang, Renchong Lü, Jiangfeng Zhu, and Zhiyi Wei
We report on a high-power diode-pumped Yb:KG(WO4)2 (Yb:KGW) mode-locked laser with a semiconductor saturable absorber mirror (SESAM). For 32.7 W of incident pump power, we generate 261 fs pulses with the maximum average output power of up to 13.0 W and spectrum centered around 1039 nm at 68.4 MHz, corresponding to 190 nJ of single pulse energy and 0.72 MW of peak power. The optical-to-optical conversion efficiency is 39.8%, and the slope efficiency is 64.4%. The Yb:KGW laser exhibits a power stability better than 0.543% of the root-mean-square in 2 h.We report on a high-power diode-pumped
- Oct. 18, 2021
- Chinese Optics Letters
- Vol.20 Issue, 2 021404 (2022)
- DOI：10.3788/COL202220.021404
Rapid fabrication of microrings with complex cross section using annular vortex beams
Chenchu Zhang, Hanchang Ye, Rui Cao, Shengyun Ji, Heng Zhang, Linhan Zhao, Sizhu Wu, and Hua Zhai
A ring-shaped focus, such as a focused vortex beam, has played an important role in microfabrication and optical tweezers. The shape and diameter of the ring-shaped focus can be easily adjusted by the topological charge of the vortex. However, the flow energy is also related to the topological charge, making the individual control of diameter and flow energy of the vortex beam impossible. Meanwhile, the shape of the focus of the vortex beam remains in the hollow ring. Expanding the shape of focus of structural light broadens the applications of the vortex beam in the field of microfabrication. Here, we proposed a ring-shaped focus with controllable gaps by multiplexing the vortex beam and annular beam. The multiplexed beam has several advantages, such as the diameter and flow energy of the focal point can be individually controlled and are not affected by the zero-order beam, and the gap size and position are controllable.A ring-shaped focus, such as a focused vortex beam, has played an important role in microfabrication and optical tweezers. The shape and diameter of the ring-shaped focus can be easily adjusted by the topological charge of the vortex. However, the flow energy is also related to the topological charge, making the individual control of diameter and flow energy of the vortex beam impossible. Meanwhile, the shape of the focus of the vortex beam remains in the hollow ring. Expanding the shape of focus of structural light broadens the applications of the vortex beam in the field of microfabrication. Here, we proposed a ring-shaped focus with controllable gaps by multiplexing the vortex beam and annular beam. The multiplexed beam has several advantages, such as the diameter and flow energy of the focal point can be individually controlled and are not affected by the zero-order beam, and the gap size and position are controllable.
- Oct. 18, 2021
- Chinese Optics Letters
- Vol.20 Issue, 2 023801 (2022)
- DOI：10.3788/COL202220.023801
Nanoparticle trapping by counter-surface plasmon polariton lens
Jingjing Hong, Xingping Zhou, Rui Zhuang, Wei Peng, Jiawei Liu, Aiping Liu, and Qin Wang
A counter-surface plasmon polariton lens (CSPPL) is proposed to perform stable nanoparticle trapping by providing up to 120kbT optical potential depth. The optical potential depth is related to the incident angle and phase difference of the light incident on two gratings of CSPPL. The depth of optical potential can be manipulated with negligible displacement by the incident angle less than 20°. Both the depth and the center position of the optical potential well can be manipulated by the incident phase difference. The study of stable and manipulatable optical potential on the CSPPL promotes the integration of optical tweezers.A counter-surface plasmon polariton lens (CSPPL) is proposed to perform stable nanoparticle trapping by providing up to 120kbT optical potential depth. The optical potential depth is related to the incident angle and phase difference of the light incident on two gratings of CSPPL. The depth of optical potential can be manipulated with negligible displacement by the incident angle less than 20°. Both the depth and the center position of the optical potential well can be manipulated by the incident phase difference. The study of stable and manipulatable optical potential on the CSPPL promotes the integration of optical tweezers.
- Oct. 14, 2021
- Chinese Optics Letters
- Vol.20 Issue, 2 023601 (2022)
- DOI：10.3788/COL202220.023601
Depolarization index from Mueller matrix descatters imaging in turbid water
Fei Liu, Shichao Zhang, Pingli Han, Fangyi Chen, Lin Zhao, Yingying Fan, and Xiaopeng Shao
Polarization underwater imaging is of great potential to target detection in turbid water. Typical methods are challenged by the requirement on degrees of polarization (DoPs) of both target light and backscattering. A polarization descattering imaging method was developed using the Mueller matrix, which in turn derived a depolarization (Dep) index from the Mueller matrix to characterize scattering media by estimating the transmittance map by combining a developed optimal function. By quantifying light attenuation with the transmittance map, a clear vision of targets can be recovered. Only using the information of scattering media, the underwater vision under diverse water turbidity was enhanced by the results of experimental data.Polarization underwater imaging is of great potential to target detection in turbid water. Typical methods are challenged by the requirement on degrees of polarization (DoPs) of both target light and backscattering. A polarization descattering imaging method was developed using the Mueller matrix, which in turn derived a depolarization (Dep) index from the Mueller matrix to characterize scattering media by estimating the transmittance map by combining a developed optimal function. By quantifying light attenuation with the transmittance map, a clear vision of targets can be recovered. Only using the information of scattering media, the underwater vision under diverse water turbidity was enhanced by the results of experimental data.
- Oct. 11, 2021
- Chinese Optics Letters
- Vol.20 Issue, 2 022601 (2022)
- DOI：10.3788/COL202220.022601
Advanced Photonics, Vol. 3,Issue 2, 024003 (2021)
Advanced Photonics, Vol. 3,Issue 2, 026004 (2021)
Review of bio-optical imaging systems with a high space-bandwidth product
Advanced Photonics, Vol. 3,Issue 4, 044001 (2021)
Dual-Comb Nonlinear Spectroscopy
Laser & Optoelectronics Progress, Vol. 58,Issue 1, 0100001 (2021)
Three-Dimensional Measurement Method of Light Field Imaging Based on Deep Learning
Chinese Journal of Lasers, Vol. 47,Issue 12, 1204005 (2020)
Surface Plasmon Enhanced Silicon-Based Near-Infrared Photoconductive Detector
Chinese Journal of Lasers, Vol. 47,Issue 11, 1113002 (2020)
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