All-prism achromatic phase matching for tunable second-harmonic generation

Achromatic phase matching (APM) involves dispersing the light entering a no nlinear optical crystal so that a wide range of wavelengths is simultaneous ly phase matched. We constructed an APM apparatus consisting of six prisms, the final dispersion angle of which was optimized to match to second order in wavelength the type I phase-matching angle of beta barium berate (BBO). With this apparatus, we doubled tunable fundamental light from 620 to 700 in in wavelength using a 4-mm-long BBO crystal. An analogous set of six pri sms after the BBO crystal, optimized to second order in second-harmonic wav elength, realigned the output second-harmonic beams. Computer simulations p redict that adjustment of a single prism can compensate annular misalignmen t of any or all the prisms before the crystal, and similarly for the prisms after the crystal. We demonstrated such compensation with the experimental device. The simulations also indicate that the phase-matching wavelength b and can be shifted and optimized for different crystal lengths. (C) 1999 Op tical Society of America.