Photonics Research, Volume. 12, Issue 4, 663(2024)
Frequency-comb-linearized, widely tunable lasers for coherent ranging
Fig. 1. Applications and principle of widely tunable lasers. (a) Applications requiring linearly chirping lasers. OCT, optical coherence tomography; OFDR, optical frequency-domain reflectometry; LiDAR, light detection and ranging. (b) Principle of laser chirp linearization. An ideal laser chirps at a constant rate. However, in reality, the actual chirp rate varies. By beating the laser with its delayed part, the chirp nonlinearity in the optical domain is revealed in the radio frequency (RF) domain.
Fig. 2. Schematic and experimental setup of laser chirp characterization. (a) Experimental setup. BPF, band-pass filter; PC, polarization controller; BPD, balanced photodetector; LPF, low-pass filter; OSC, oscilloscope. (b) Illustration of the laser frequency beating with the OFC during laser chirping at a rate of
Fig. 3. Characterization of Toptica CTL laser’s chirp dynamics. (a) Normalized chirp rate
Fig. 4. Coherent LiDAR experiment. (a) Maps of measured relative distance of an engraved surface with pre-linearization and without linearization. The sample’s tilt angle of 11.6° is measured and subtracted. (b) Space spectra of the ranging profiles obtained with pre-linearization and without linearization. Fast Fourier transform is applied on the ranging profile of each case to retrieve the spectrum. The peaks correspond to the distance
Fig. 5. Comparison of three Toptica lasers’ chirp dynamics in the wide tuning mode. (a) Normalized chirp rate
Fig. 6. Characterization of chirp dynamics of a Santec laser in the wide tuning mode. (a) Normalized chirp rate
Fig. 7. Comparison of four Santec lasers’ chirp dynamics in the wide tuning mode. (a) Normalized chirp rate
Fig. 8. Characterization of chirp dynamics of a New Focus laser in the wide tuning mode. (a) Normalized chirp rate
Fig. 9. Characterization of chirp dynamics of an EXFO laser in the wide tuning mode. (a) Normalized chirp rate
Fig. 10. Characterization of chirp dynamics of an NKT laser in the fine tuning mode. (a) Normalized chirp rate
Fig. 11. Characterization of chirp dynamics of two NKT lasers in the fine tuning mode. (a) Normalized chirp rate
Fig. 12. Characterization of chirp dynamics of a Santec laser in the fine tuning mode. (a) Normalized chirp rate
Fig. 13. Characterization of chirp dynamics of four Santec lasers in the fine tuning mode. (a) Normalized chirp rate
Fig. 14. Characterization of chirp dynamics of a Toptica laser in the fine tuning mode. (a) Normalized chirp rate
Fig. 15. (a) Different drive signals. (b) Fourier transform of different drive signals.
Fig. 16. Characterization of chirp dynamics of three Toptica lasers in the fine tuning mode. (a) Normalized chirp rate
Fig. 17. Characterization of chirp dynamics of a New Focus laser in the fine tuning mode. (a) Normalized chirp rate
Fig. 18. Laser characterization for LiDAR demonstration. (a) Normalized chirp rate
Fig. 19. Setup for LiDAR demonstration and precision test. (a) Experimental setup. BPD, balanced photodetector; OSC, oscilloscope. (b) Histogram of deviation of ranging measurement. The long-term stability of pre-linearization is verified by a precision test. A mirror is fixed at a distance of 53.361 mm and measured 1128 times every 3 s. The standard deviation of the measured distance is 11 μm.
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Baoqi Shi, Yi-Han Luo, Wei Sun, Yue Hu, Jinbao Long, Xue Bai, Anting Wang, Junqiu Liu. Frequency-comb-linearized, widely tunable lasers for coherent ranging[J]. Photonics Research, 2024, 12(4): 663
Category: Spectroscopy
Received: Oct. 31, 2023
Accepted: Jan. 29, 2024
Published Online: Mar. 15, 2024
The Author Email: Junqiu Liu (liujq@iqasz.cn)