Abstract

Reported is a technique called tangential phase-matching employed to increase conversion efficiency in Type-I sum-frequency generation (SFG) of 1064 nm Nd:YAG laser and its harmonic pumped 568.6nm Rhodamin dye laser radiation in beta barium borate (BBD)^[2] crystal using focused^[3] input beams. Tangential phase-matching is characterised by tangency of the wave-vector surface of input waves with that of generated one. The collinear tangential phase-matching commonly known as noncritical phase-matching (NCPM) is associated with some special feature no walk-off as it allows the use of long crystal to improve efficency without double refraction and also large angular tolerance. But this can be realised only at a wavelength as determined by crystal dispersion. The noncollinear tangential phasematching also have the same advantages. Such a situation on the other hand can be realised at any desirable wavelength. Though the generation is limited by the walk-off effect of the crystal, the conversion efficiency can be increased in noncollinear tangential phase-matching by focusing the beam over which large angular tolerance exists. An additional advantage of this situation is the automatic seperation of the generated beam from the input beams.

© 1992 IQEC