Highly Reliable, High Power Cryogenic Red Diode Lasers

The objective of this proposal is to eliminate the catastrophic optical damage that limits the peak operating power of cryogenically operated visible red (630-nm) laser diodes. The method to be applied is band gap disordering by Zn-diffusion. This will be the first time this technique has ever been applied to high power visible red laser diodes. It will also be the first application of band gap disordering in a system intended for cryogenic operation. nLight Photonics, through programs with Directed Energy Solutions, has pushed the absolute state of the art in red diode lasers operating at 665-nm (room temperature) and 630-nm (cryogenic temperatures). Peak powers of 90W and 50% electrical-to-optical efficiency have been achieved from a 1-cm wide bar of 1-mm cavity length. Individual emitters have achieved 6.3W peak power while operating at room temperature. Through these programs the limiting mechanism in achieving higher powers is no longer the thermal escape of carriers, but the catastrophic failure of the optical facets under the intense optical field power densities.