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
  • Oct. 11, 2021
  • Chinese Optics Letters
  • Vol.20 Issue, 2 022601 (2022)
  • DOI:10.3788/COL202220.022601
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.
  • Oct. 18, 2021
  • Chinese Optics Letters
  • Vol.20 Issue, 2 023801 (2022)
  • DOI:10.3788/COL202220.023801
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.
  • Oct. 11, 2021
  • Chinese Optics Letters
  • Vol.20 Issue, 2 020601 (2022)
  • DOI:10.3788/COL202220.020601
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
  • Oct. 18, 2021
  • Chinese Optics Letters
  • Vol.20 Issue, 2 021403 (2022)
  • DOI:10.3788/COL202220.021403
High performance optical sensor based on double compound symmetric gratings
Chaoying Shi, Xiuhong Liu, Jinhua Hu, Haiyan Han, and Jijun Zhao
  • Oct. 11, 2021
  • Chinese Optics Letters
  • Vol.20 Issue, 2 021201 (2022)
  • DOI:10.3788/COL202220.021201
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.
  • Oct. 11, 2021
  • Chinese Optics Letters
  • Vol.20 Issue, 2 021301 (2022)
  • DOI:10.3788/COL202220.021301
High-color-purity, high-brightness and angle-insensitive red structural color
Jintong Liu, Kun Feng, Yusi Wang, Qingyuan Li, Nan Chen, and Yikun Bu
  • Oct. 11, 2021
  • Chinese Optics Letters
  • Vol.20 Issue, 2 021601 (2022)
  • DOI:10.3788/COL202220.021601