Abstract

Investigation of physics of ultra-fast phenomena in semiconductor lasers is important for high-speed modulation and short pulse generation. It has been recently demonstrated that quantum well (QW) lasers have the advantage to generate shorter light pulses, since the differential gain is enhanced by a factor of four compared to conventional double-hetero structure lasers [1]. In fact, an extremely narrow light pulse (<1.3psec) was successfully observed in a quantum well laser [2]. This is the shortest pulse so far achieved in the semiconductor lasers without external cavity. However, effects of QW structure-parameters, such as thickness and the number of QWs, on the picosecond pulse dynamics have not been discussed sufficiently. In this paper, we investigate short pulse generation in QW lasers with emphasis on dependence of pulse form on the QW structures. The results demonstrate that the pulse duration strongly depends on the QW structures: The QW laser having a smaller number of QWs generates broader light pulses, which results from in both reduced differential gain and higher quasi-Fermi-energy level of electrons E_Fc.

© 1989 Optical Society of America