Effective bandwidth reduction for a high-power laser-diode array by an external-cavity technique

bandwidth of a high-power laser-diode array was effectively suppressed by use of an off-axis external-cavity technique. The external cavity consisted of a beam-transformation system and a pair of off-axis volume Bragg gratings. During operation at a drive current of 40 A, we reduced the bandwidth's full width at half-maximum from 3.3 to 0.24 nm (14-fold reduction) and achieved an output power of 20 W, or as much as 87% of the power radiated by a free-running laser-diode array without an external cavity.