Microcavity Raman Laser-Based FMCW LiDAR with Enhanced Echo Sensitivity

Frequency-modulated continuous-wave laser detection and ranging (FMCW LiDAR) is a useful technology with various applications. However, numerous existing FMCW LiDAR systems are bulky, restricting their applicability in scenarios where minimizing the form factor is essential. Another major limitation is their echo-signal sensitivity. Considering that the detected targets are typically noncooperative, efficient detection of scattered light is imperative. Based on that, a microcavity Raman laser-based FMCW LiDAR is proposed combined with laser feedback technique. In the laser feedback regime, weak echo signals from targets participate in the stimulated radiation of the laser and are enhanced spontaneously when the measurement signal resonates with the laser relaxation oscillation. Without extra optical amplifiers, the laser cavity functions as an intrinsic amplifier and provides an improved signal-to-noise ratio of over 30 dB compared with conventional frequency swept interference methods. The response optical power limit can be down to 7.92 fW in the experiment. The standard deviation in 10 measurements is about 217 μm when targeting an aluminum block. By combining the proposed system with a 2-axis galvanometer scanner, 3D imaging of actual scenes can also be effectively reconstructed. This study illustrates a microcavity Raman laser-based device for conducting FMCW ranging measurements. It employs an extremely low-power near-infrared laser for detection, effectively addressing the issue of laser active detection equipment being easily detected.