High-power picosecond laser diodes based on different methods of fast gain control for high-precision radar applications

摘要

Current-pumped picosecond-range laser diodes with a peak power significantly exceeding that achievable from gain-switched lasers are of major interest for a large variety of commercial applications. A group of phenomena have been explored in which the peak transient gain is efficiently controlled by a fast reduction in the pumping current. Common to all these phenomena is the fact that the peak powers of the emitted picosecond optical pulses (15-100 ps) exceed that obtainable from gain-switched laser diodes by at least an order of magnitude, although the physical reasons for the high gain and the design principles of the semiconductor structures are different. The main problem in the realization of these picosecond modes in low-cost practical systems is the high sensitivity of the operation regime to structural and circuit parameters. A related problem is the questionable reproducibility of the fabrication processes used so far. Proper development of reliable high-power picosecond transmitters will require the use of more advanced fabrication methods and further study of the effect of structural parameters on the properties of the picosecond lasing mode. In this paper we report on a record value for the power density of the picosecond lasing (50W / 30ps) obtained from a laser diode chip of width 20 μm and give a qualitative interpretation of the operating mode. Use of the MOCVD process for diode fabrication should allow reproducible technology for picosecond laser diodes to be developed.