A Pulsed Ultraviolet Laser Positioning System Based on 4H-SiC Four-Quadrant Photodetectors

In this work, a pulsed ultraviolet (UV) laser positioning system based on 4H-SiC four-quadrant photodetectors (4-QDs) is demonstrated and applied to the self-calibration of laser deflection angle. The 4H-SiC 4-QD with a photosensitive area of 8 mm in diameter exhibits high uniformity in performance across all quadrants, including a low dark current of ~7 pA and a peak responsivity of 0.12 A/W at 275 nm. Charge-sensitive amplifiers (CSAs) are developed for the linear amplification of the photocurrents. Based on a 266 nm pulsed laser, a 4-QD, CSAs and a displacement platform, the system exhibits excellent positioning performance over an area of <inline-formula> <tex-math notation="LaTeX">$600\times 600\mu $ </tex-math></inline-formula> m, with a mean absolute error of <inline-formula> <tex-math notation="LaTeX">$5.52\mu $ </tex-math></inline-formula> m. Finally, a prototype laser beam deflection angle self-calibration system based on the fabricated 4-QD is realized, achieving a calibration error below 0.0015° with a relative error below 0.5%.