In situ controlled growth of low-temperature GaAs and its application for mode-locking devices

We report on the potential of reflectance difference spectroscopy (RDS) in realizing high reproducibility, optimization of growth conditions, and in s itu control for growth of extremely thick high quality GaAs layers at low s ubstrate temperatures (LT). The amplitude of the observed anisotropy in the RDS caused by the linear electro-optic effect is directly related to the i ncorporated As antisite density. Therefore, in situ RDS allows a real time determination of nonstoichiometry and hence, of the electrical and optical properties of the layers. We show that extremely thick LT-GaAs layers (up t o 14 mu m) grown by molecular beam epitaxy (MBE) with optimized growth para meters can be successfully implemented as a material for obtaining self-sta rting mode-locking of a Nd:glass fiber laser.