Abstract

Based on the Nd: YVO₄ microchip laser frequency-shifted feedback system, we carry out the detection of ultra-weak light signals, and verify that the response limit of the proposed system can reach 0.5 photon per second (corresponding to 2.1 × 10⁻⁷ photon's energy per frequency modulation cycle of 0.42 μs), with approximately linear response to weak light. Then, the system is compared with the traditional Mach-Zehnder heterodyne interference system, the comparison results confirm the higher intensity response sensitivity of the laser feedback technology (about six orders of magnitude) when detecting both cooperative and non-cooperative targets. On this basis, a verification experiment is carried out on long-distance weak light imaging, and the “THU” pattern made of unpolished aluminum blocks is successfully reconstruct at 60 m distance (with an additional 10⁻⁷ attenuation provided by the neutral density filter added to the optical path). During the imaging process, the response energy as low as 2 × 10⁻⁵ photon is achieved in each frequency modulation cycle of 0.42 μs. The successful implementation of the laser frequency-shifted feedback detection enables an anti-disturbance and sensitive coherent method in weak light signals detection.

Common-path heterodyne self-mixing interferometry with polarization and frequency multiplexing

Shaohui Zhang, Shulian Zhang, Yidong Tan, and Liqun Sun
Opt. Lett. 41(20) 4827-4830 (2016)

Long-range vibration detection system using heterodyne interferometry

John R. Rzasa, Kyuman Cho, and Christopher C. Davis
Appl. Opt. 54(20) 6230-6236 (2015)

Coherent laser detection of the femtowatt-level frequency-shifted optical feedback based on a DFB fiber laser

Yuanyang Zhao, Desheng Zhu, Yourui Tu, Lingling Pi, Hongtao Li, Lin Xu, Zhijia Hu, Yuecheng Shen, Benli Yu, and Liang Lu
Opt. Lett. 46(6) 1229-1232 (2021)

Sensitivity enhancement in photothermal interferometry by balanced detection of the complex response to moving excitation

Jingtao Dong, Xinglong Xie, Lei Yang, Xianli Lang, Rongsheng Lu, Tengda Zhang, Lei Zhang, Sheng Zhou, and Jingsong Li
Opt. Lett. 46(12) 2976-2979 (2021)

Closed-loop phase-shifting homodyne interferometry using heterodyne phase detection

Youichi Bitou
Appl. Opt. 47(33) 6219-6225 (2008)