Experimental simulation of ranging action using Si photonic crystal modulator and optical antenna

Time of flight light detection and ranging (LiDAR) has been tested and used as a key device for auto-driving of vehicles. Frequency-modulated continuous-wave (FMCW) LiDAR potentially achieves a high sensitivity. In this study, we fabricated and tested two components of FMCW LiDAR based on Si photonics. The ranging action was also experimentally simulated. A Si photonic crystal slow light Mach-Zehnder modulator was driven by linearly frequency-chirped signals to generate quasi-frequency-modulated signal light. Then, the light was inserted into a fiber delay line of 20-320 m. Its output was irradiated to a photonic crystal slow beam steering device that acted as an optical antenna via a free-space transmission. The detected light was mixed with the reference light branched after the modulation in balanced photodiodes. A sufficiently sharp beat spectrum was observed, whose frequency well agreed with that expected for the delay line. The experimental simulation of the FMCW LiDAR, thus, was achieved.