Ultra-Narrow Bragg Grating for Active Semiconductor Laser Linewidth Reduction through Electrical Feedback

Abstract

A π-phase shifted Bragg grating is used as a frequency discriminator to reduce the frequency and phase noise of a semiconductor laser, and therefore its linewidth, using an electrical feedback loop on its injection current. The spectral notch at the center of the reflection peak of the grating was found to be 15 MHz FHWM, allowing for a laser linewidth reduction to 2 kHz over measurement times of 1 ms.