Mechanism of wavelength tuning and frequency modulation in three-electrode DFB lasers

The static and dynamic characteristics of three-electrode DFB lasers are investigated. In wavelength tuning, the side sections determine the effective Bragg wavelength, while the center section acts as the active phase shifter. A continuous tuning with a wide range of 5 nm is demonstrated utilizing a requisite thermal contribution to the extension of the effective Bragg wavelength shift. The direction of the frequency shift in carrier-induced frequency modulation (FM) can be described by a single parameter-the phase shift in the center section. It is also pointed out that a wide FM bandwidth exceeding 10 GHz can be obtained for red-shifted cases, despite the modulation bandwidth of the carrier density being limited by the carrier lifetime. The interpretation presented in this paper makes the operating mechanism clearly understandable for practical use