Abstract

Compact and efficient sources of high repetition rate, high peak power optical pulses are needed to replace the standard ultrashort optical pulse generation schemes due to their relatively large size and poor wall plug efficiency. In this paper, we present a new hybrid node-locked semiconductor laser system which is capable of producing optical pulses of 0.56 psec in duration with peak powers in excess of 38 watts. These optical pulses are both the shortest and most intense ever produced from an all semiconductor laser diode system. The optical pulses were generated by forming a hybrid mode-locked external cavity semiconductor laser, which incorporates a semiconductor traveling wave amplifier (TWA) as the gain medium, and a multiple quantum well (MQW) saturable absorber. Hybrid mode locking is achieved by actively mode locking the laser using current modulation techniques and tuning the laser operating wavelength to lie within the excitonic absorbtion region of the MQW saturable absorber. The generated optical pulses were compressed utilizing a grating pair compressor to remove the chirp which is impressed upon the optical pulse during the mode locking operation of the oscillator. The typical pulse duration generated directly from the oscillator is ~ 5 psec; the pulse durations obtained after compression were 0.56 psec. In order to achieve high peak output power, the resultant compressed pulses were reamplified in a semiconductor traveling wave amplifier. The resulting peak power obtained after amplification was 38 watts. In addition, we have measured the timing jitter of the laser system for pure passive mode locking and for hybrid mode-locked operation. We have observed that the hybrid mode-locked laser system has much less phase noise than the passively mode-locked laser.

© 1990 Optical Society of America