Page 374 - Tunable Lasers Handbook

334 Norman P. Barnes

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40 42 44 46 48
Angle (degrees)
FIGURE 15 Phase-matching cume for LiNbO, for a 1.061-ym pump.

through 22). ZnGeP, could tune over this range with a variation of about 4", the
smallest angular range; CdSe would require about 14", the largest angular range.
AgGaS, does display an unusually flat tuning range about 4.2 ym. Besides this.
the tuning curves are in general similar, except for the direction of the curvature.
As such, selection of the best nonlinear crystal would probably be based on con-
siderations other than the phase matching curves.

9. PERFORMANCE

Optical parametric oscillators have developed from their initial stage where
they were little more than a curiosity. Initial performance was limited by lack of
high optical quality nonlinear crystals. nonlinear crystals with relatively small
nonlinear coefficients. and limited pump laser performance. In addition, optical
parametric oscillators were in competition with dye lasers in the visible and near
infrared. Pulsed dye lasers have an advantage because laser-pumped dye lasers do
not necessarily require high beam quality from the pump laser. In essence, dye
lasers can serve as an optical integrator, converting a fixed-wavelength pump laser
with relatively poor beam quality into a tunable laser with a better beam quality.
In the face of these difficulties, optical parametric oscillators enjoyed limited com-
mercial applications for a considerable time. However, several increases in optical
parametric oscillator technology have improved the viability of these devices.