Spectral and intensity noise characteristics of double external cavity semiconductor lasers

Abstract

Double external cavity configurations are encountered in many real situations, such as coupled-cavity lasers, optical fiber transmitter modules, and optoelectronic integrated circuits. This configuration has also been found to be useful in obtaining stable single longitudinal mode operation with narrow linewidth.1 Recently, we studied the static and dynamic properties of asymmetric external cavity lasers with tilt asymmetries, whose behavior is similar to that of a double external cavity system with lengths L and 2L.2 The primary purpose of this paper is to describe extension of our previous work to more general independent double external cavity systems, for which we determine characteristics such as optical mode spectra, intensity noise spectra, and laser linewidth. The feedback phase conditions for optimum system stability and various operating regimes are determined. The most notable advantage of using a double external cavity system is that the compound cavity mode spacing can be increased by adjusting the feedback phase, while maintaining narrower spectral linewidth than that obtained using each single cavity separately. Theoretical predictions based on an effective reflectivity model with two independent feedback terms agreed well with experiments.