Page 372 - Tunable Lasers Handbook

332 Norman P. Barnes

1.2 -
-

1.0 -
r
h -
a,
5 0.8 -
E
2 - 0.355pm Pump
.-
0
E
- 0.6 -
5
cn - KDP
C
-
a,
a,

t

I I I I I I I I
41 43 45 47 49
Angle (degrees)

FIGURE 1 2 Phase-matching curves for ADP and KDP for a 0.355-pm pump.

Tunable radiation in the near infrared can be obtained from an optical para-
metric oscillator using a 0.532-ym pump and a LiNbO, or BBO nonlinear crystal
(Figs. 14, 15, and 16). Operation at somewhat longer wavelengths than shown in
the figures may be possible, depending on the infrared absorption properties of
the particular nonlinear crystal. Because of absorption, calculations were not car-
ried out beyond 2.2 ym in BBO and 4.0 pm in LiNbO,. A device based on BBO
would be attractive because a single crystal could be used to tune over a very
large wavelength range. On the other hand, a device based on LiNbO, would be
attractive if a narrow spectral bandwidth device were desired.
A Nd:YAG laser can be used directly as a pump source for at least three dif-
ferent nonlinear crystals, LiNbO,, BBO, and AgGaS, (as shown in Figs. 15. 16,
and 17). In the first case, the range from about 1.4 im to beyond 4.0 ym could
be covered with a single LiNbO, crystal. BBO could not cover the same range
due to transparency limitations. On the other hand, AgGaS, could be tuned over
a much wider range, from about 2.0 to beyond 10.0 ym. However, this tuning
range would require a variation in the phase-matching angle of about 20". Since
the Nd:YAG laser has enjoyed a significant amount of development, such a sys-
tem appears to be very attractive.