MECHANISM OF WAVELENGTH TUNING AND FREQUENCY-MODULATION IN 3-ELECTRODE DFB LASERS

The static and dynamic characteristics of three-electrode DFB lasers a re investigated, In wavelength tuning, the side sections determine the effective Bragg wavelength, while the center section acts as the acti ve phase shifter. A continuous tuning with a wide range of 5 mn is dem onstrated utilizing a requisite thermal contribution to the extension of the effective Bragg wavelength shift. The direction of the frequenc y shift in carrier-induced frequency modulation (FM) can be described by a single parameter - the phase shift in the center section, It is a lso pointed out that a wide FM bandwidth exceeding 10 GHz can be obtai ned for red-shifted cases, despite the modulation bandwidth of the car rier density being limited by the carrier lifetime. The interpretation presented in this paper makes the operating mechanism clearly underst andable for practical use.