Mode Control for High Performance Laser Diode Sources

We report on recent progress in the control of optical modes toward the improvement of commercial high-performance diode laser modules. Control of the transverse mode has allowed scaling of the optical mode volume, increasing the peak output power of diode laser emitters by a factor of two. Commercially-available single emitter diodes operating at 885 nm now exhibit >25 W peak (12 W rated) at >60% conversion efficiency. In microchannel-cooled bar format, these lasers operate >120 W at 62% conversion efficiency. Designs of similar performance operating at 976 nm have shown >37,000 equivalent device hours with no failures. Advances in the control of lateral modes have enabled unprecedented brightness scaling in a fiber-coupled package format. Leveraging scalable arrays of single emitters, the conductively-cooled nLIGHT Pearl TM package now delivers >80 W peak (50 W rated) at >53% conversion efficiency measured from a 200-μm core fiber output and >45 W peak (35 W rated) at >52% conversion efficiency measured from a 100-μm fiber output. nLIGHT has also expanded its product portfolio to include wavelength locking by means of external volume Bragg gratings. By controlling the longitudinal modes of the laser, this technique is demonstrated to produce a narrow, temperature-stabilized spectrum, with minimal performance degradation relative to similar free-running lasers.