Heater-Tuned Single-Grating Distributed Bragg Reflector Lasers With a Thermal Confinement Waveguide Structure

To evaluate the effect of thermally isolated waveguide structure in a heater-based tunable distributed Bragg reflector (DBR) laser, the temperature distribution and thermo-optical characteristics are investigated at various heater powers. The reflection spectrum of the DBR is designed, and the tuning characteristics of the fabricated DBR laser are compared with simulation results. It is found that the waveguide temperature increases linearly with the heater power, whereas the effective refractive index increases nonlinearly, resulting in the corresponding nonlinear wavelength-tuning characteristics. In order to obtain efficient thermal tuning characteristics, a thermal isolation structure of the reverse-mesa waveguide is introduced. In this device, the temperature of the waveguide core increases steeply at low tuning power levels, resulting in highly efficient wavelength tuning properties. On the other hand, at high tuning power, the DBR reflection spectrum broadens and the side-mode suppression ratio (SMSR) performances degrades. These effects are found to be caused mainly by non-uniform temperature distribution along the longitudinal direction.