Abstract

Nonlinear parametric processes, that now seem to be the most promising means for providing laser light beams with very large tuning ranges, have a critical limiting factor due to the phase matching requirement. Violation of this requirement is possible when the interaction length is limited to very "thin" crystals. The common method to solve this problem is by using the crystal birefringence. This allows a limited degree of wavelength tunability by changing the angle of the beam propagation in the crystal. Another solution is quasi-phasematching by "artificial" spatial modulation of the optical nonlinearity, or the refractive index also restricts the phase matching to a specific input wavelength. In recent works¹ we have demonstrated a new method for broadband second harmonic generation (SHG) by controllable spread spectrum quasi-phase matching. The broad spectrum of the domain grating period provided the broadband capability. We have also demonstrated second harmonic generation for prespecified discrete or continuous beam wavelengths by tailored quasi-phase matching.²

© 1994 IEEE