Wavelength stabilization of high-power laser diodes using Bragg gratings inscribed in their highly multimode fiber pigtails

Abstract

Efficient wavelength stabilization of an off-the-shelf high-power laser diode operating at 976 nm is demonstrated by using a highly multimode fiber Bragg grating (FBG). This first-order grating is inscribed with 400 nm femtosecond pulses inside the 200 µm/0.22 NA pure silica core of the diode's fiber pigtail. The FBG reduces the wavelength thermal drift of the 70 W diode by a factor of 12 while also reducing its emission linewidth by a factor of 2.8. At maximum output power, a power penalty of only 6% is measured. This promising approach offers a robust and compact scheme to stabilize the spectrum of high-power laser diodes that are particularly useful for fiber-laser pumping.