Abstract

There are many mechanisms for generating transient optical phase gratings. Though particular advantage can be taken of semipermanent mechanisms such as photorefractive and photochromic effects, there are also uses for purely transient mechanisms such as those based on the third-order nonlinear susceptibility (c⁽³⁾ or n₂), population changes, or thermal (dn/dT) mechanisms. Transient grating mechanisms have the virtue of allowing real-time interaction of interfering waves as in phase conjugation, image amplification and manipulation, optical switching and modulation, nonlinear resonators, or neural networks. A new mechanism of transient optical phase grating formation, called the pyro-electro-optic effect, is proposed which combines the pyroelectric and electro-optic effects to convert spatial intensity variations into transient phase gratings. The pyro-electro-optic mechanism has a figure-of-merit that is proportional to the pyroelectric, electro-optic and absorption coefficients and inversely proportional to the specific heat. The grating response time is proportional to the specific heat and inversely proportional to the thermal conductivity. Diffraction efficiencies approaching unity are predicted in several readily available inorganic and organic electro-optic materials with modest pulse energies from Q-switched Nd:YAG lasers. Pyro-electro-optic gratings are also compared with third-order thermal (dn/dT), and photorefractive mechanisms.

© 1991 Optical Society of America