Microcavity Raman Laser-Based FMCW LiDAR with Enhanced Echo Sensitivity

Abstract

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.

Dynamic Measurement with High Precision Using Frequency Agile Spatial Encoding Integrated FMCW LiDAR

“…Therefore, achieving a high-precision and rapid measurement of equipment speed and displacement information is crucial. Typical applications include tracking the motion of cutting tools in high-precision machine tools, real-time monitoring of velocity and distance information during industrial robot operation, high-speed in situ measurement, and dynamic speed analysis of lithography machine processing platforms. − Frequency-modulated continuous-wave (FMCW) laser measurement technology is widely applied in various complex scenarios for precision measurements due to its characteristics of large time-bandwidth product, high measurement accuracy, and strong anti-interference capability. , The fundamental principle of FMCW laser measurement involves acquiring target measurement information through the beat frequency signal generated by interference between the laser echo signal and the local oscillator signal. Traditional static target ranging often assumes no relative motion between the laser detection system and the target. − In practical applications, targets often exhibit relative or high-speed motion.…”

“…Numerous researchers have reported several methods aimed at achieving efficient, structurally simple, and accurately measuring FMCW LiDAR dynamic measurement systems from perspectives including system architecture and detection signal processing methods. , Microcavity Raman LiDAR has a simple structure and high echo sensitivity. Nevertheless, achieving high-precision measurements of dynamic target velocities still requires resolution of short temporal intervals . One approach proposes a LiDAR system that independently measures the velocity and distance using complex optical fields.…”