Sapphire/Nd:YAG composite by pulsed electric current bonding for high-average-power lasers.

As a new bonding technique for high-power laser optics, pulsed electric current bonding (PECB) of sapphire and Nd:YAG ceramics was demonstrated. The optical properties of the composite were measured, and its microstructure at the interface and laser performance was analyzed. The optical transmittance was equal to the theoretical value, and the transmitted wavefront was λ/3 (λ=633  nm); both are appropriate values for laser applications. The microstructural analysis indicated an absence of scattering sources such as pores or non-contact points at the sapphire/Nd:YAG interface, and the distance of yttrium diffusion into the sapphire was theoretically expected to be less than 10 nm, much smaller than that of ceramic materials bonded by conventional thermal diffusion techniques. The laser performance of the composite material showed an 18% higher output power with almost the same threshold power and slope efficiency as a Nd:YAG ceramic due to the sapphire-conductive cooling effect. This new PECB technique for different transparent materials has the potential to bond large aperture optical materials over 100 mm in diameter and could be especially effective for fabricating active laser media for high-average-power lasers having both high-pulse energy and high repetition rates.