This project is aimed to develop gain-switched laser diodes with high-power optical pulses of sub-nanosecond duration for application in light detection and ranging (LiDAR). The design of gain-switched diode lasers is very different from high-power continuous-wave operated laser diodes. The threshold current is high to build up high-power optical pulses, and the pulse trailing should be suppressed to avoid erroneous and delayed detection of single-photon avalanche diodes. Moreover, the laser facets should keep high-peak-pulsed optical power from catastrophic optical mirror damage (COMD). Still another issue is laser emission characteristics on fiber coupling, beam collimation and two-dimensional scanning. Based on our experiences and achievements from industrial-academic-research cooperation in the past five years, this sub-project will conduct following research and development under the layout of main project. The first year will focus on design of asymmetric waveguide and simulation of pulse characteristics for 808-nm edge-emitting laser structure. The duration of optical pulses should be minimized and with suppressed pulse trailing. The second year will substantially increase COMD level by fabrication of window structure through quantum-well intermixing technique. The third year will extend lasing wavelength from 808 nm to 905nm. The width of stipe waveguide will be properly determined to suppress filamentation and high-order lateral modes, and the cavity length is optimized to have maximum power conversion efficiency. The fourth year will study the gainswitching characteristics of surface-emitting lasers. We propose novel photoniccrystal surface-emitting lasers to generate gain-switched optical pulses. High-peak-power pulsed laser diodes are key components for vehicle application of LiDAR. They also constitute costly expenses of LiDAR module. However, domestic research and development is not yet started because of technological complexity and academic advancement. With your respectful review and approval of project grants, more and more academic and industrial units will be urged for self-development and novel application of semiconductor lasers. It surely will enhance competitiveness of optical semiconductor industry in Taiwan.
