Abstract

The recent demonstration of high-brightness light-emitting-diodes and laser diodes has established the III-V nitrides as key materials for optoelectronics operating in the green-ultraviolet (UV) wavelength range While the optical and electrical properties of the nitride materials were widely explored, their extraordinary nonlinear optical properties have recently attracted intensive studies Our recent investigations revealed their large close-resonant third order nonlinearities, including two photon absorption coefficient and nonlinear refractive index For second- order nonlinear process of second harmonic generation (SHG) in GaN, several research groups including Miragliotta et al. [1] have experimentally determined the second order susceptibility χ⁽²⁾ in bulk GaN and have found increased nonlinearities when a large DC electric field was applied to the surface of a GaN film It is well known that second order nonlinear effects can only be observed in noncentro-symmetric structures These were commonly realized by applying an external electric field or by using compositionally asymmetric coupled quantum wells In nitride-based quantum wells, the intrinsically present, piezoelectric field breaks the inversion symmetry automatically and makes the second-order nonlinearity possible Taking advantage of these properties, we have recently demonstrated the SHG microscopy of GaN for the piezoelectric field distribution mapping in nitride based materials, including bulk GaN and InGaN/GaN MQWs.

© 2000 IEEE