TUNABLE STABILIZED SINGLE-FREQUENCY GRINROD EXTERNAL COUPLED CAVITY SEMICONDUCTOR-LASERS

An amplitude coupling factor has been proposed to modify the mode-selection theory of the semiconductor laser with graded-index-rod external coupled cavity (GRECC) [4]. In this paper the computer simulation is carried out based on the modified theory. We find that the GRINROD external coupled cavity improves the side-mode suppression greatly, and any displacement of the GRINROD with respect to the laser chip degrades optical coupling, thus reducing sidemode suppression. Moreover, the tunable GRECC laser diode is presented in this paper. A tuning range of over 11 nm and side-mode suppression better than 35 dB have been obtained. Its long-term center frequency fluctuation and drift are less than 2 MHz by frequency locked to NH3 absorption lines. The demonstration of its use in an FSK heterodyne experimental transmission system indicates that the tunable GRECC laser diode is a promising light source for coherent optical-fiber communication. © 1990 IEEE