Semiconductor laser module

Abstract

A semiconductor laser module of an external-cavity type in which a GaAs/AlGaAs-based semiconductor laser having ripples in the gain-wavelength characteristic thereof and an optical transmission medium including a Bragg grating are optically coupled by an optical coupling member. A gain peak wavelength (&lgr;(Ith)) for the case where the modularized semiconductor laser is driven with a threshold current (Ith) is set on the shorter-wavelength side of the reflection center wavelength (&lgr;BG) of the Bragg grating, a gain peak wavelength (&lgr;(Iop)) of the semiconductor laser for a maximum operating current (Iop) is set on the longer-wavelength side of the gain peak wavelength (&lgr;(Ith)), a pulling wavelength width (&lgr;PULL) and a de-tuning width (&lgr;detun) of the semiconductor laser module are set so that the de-tuning width (&lgr;detun) is smaller than the pulling wavelength width (&lgr;PULL), the resulting difference (=&lgr;PULL−&lgr;detun) is greater than the full width at half maximum of the reflection spectrum of the Bragg grating, and the gain peak wavelength (&lgr;(Ith)) is on the longer-wavelength side of a limit value (&lgr;LIMIT).