Design of chirped-coupling sidewall Bragg gratings for narrow linewidth distributed feedback lasers

A chirped-coupling sidewall Bragg grating is proposed to mitigate the nonlinear effects that deteriorate the linewidth in DFB lasers operating at a high power and current regime. This novel grating geometry is analyzed and simulated to extract the optimal design parameters in terms of intra-cavity field distribution. Compared to lasers with uniform Bragg gratings, devices fabricated with a chirped-coupling grating are shown to operate in stable single mode operation over a wider current and power range and exhibit linewidth as narrow as 100 kHz.