MODE STABILIZATION METHOD FOR SUPERSTRUCTURE-GRATING DBR LASERS

A wavelength stabilization method for widely tunable superstructure-gr ating (SSG) distributed Bragg reflector (DBR) laser is described. The output characteristics under tuning are studied theoretically and expe rimentally. It is found that peak reflectivity states, in which the la sing mode is just aligned with the reflection peaks of both DBR's, are obtained at saddle points in the output characteristics while changin g the two SSG-DBR currents. Based on these results, a method for the B ragg frequency control of the two SSG-DBR's is proposed. The feedback control circuit keeps the lasing mode at a peak reflectivity state, an d it suppresses mode hopping. Additionally, the oscillation mode is lo cked to arbitrary reference wavelengths of an optical filter. Stabiliz ation at 200 GHz(1.6nm)-spaced 16 wavelengths was achieved within the wide tuning range of the SSG-DBR laser. Control was maintained under a laser temperature variation of +/-5 degrees C as a result of the Brag g frequency control of the two DBR's.