Longitudinal mode control in GaAs lasers using a three-mirror active-passive cavity

Abstract

Integrated optics techniques have been used to form a three-mirror laser diode configured to form a long active cavity and a short passive cavity. The third mirror results from an abrupt etched step down to the waveguide layer of a large optical cavity heterostructure laser. We have observed predominantly single-frequency operation at current levels up to 1.5 times threshold. For certain ratios of passive-to-active cavity length, these devices operated multimode within a narrow frequency range, whereas diodes with different length ratios emit two modes widely separated in frequency.