Page 333 - Tunable Lasers Handbook

Norman P. Barnes
NASA Langle! Research Center-
Hanipton. I i'rginia

I. INTRODUCTION

Optical parametric oscillators are a convenient method to create a widely
tunable sour'ce of laser radiation. An optical parametric oscillator begins with a
pump laser. In many cases the pump laser is a well-behaved solid-state laser
such as a Ndl:YAG laser or a frequency-doubled Nd:YAG laser. To complete the
system, a nonlinear crystal between a set of mirrors is required. As such, the
optical parametric oscillator by itself is an extremely simple device. Using an
optical parametric oscillator, any wavelength longer than the pump wavelength
and nominally within the transparency region of the nonlinear crystal can be cre-
ated. However. practical problems limit the range of generated wavelengths to
those that are somewhat longer than the pump wavelength, nominally a factor of
1.2 or so.
Optical parametric oscillators may be regarded as photon splitters. That is, a
pump photon is split into two photons or one photon divides itself to create two
photons. To satisfy conservation of energy, the sum of the energy of the two cre-
ated photons must equal the energy of the pump photon. With the energy of a
photon given by hv where 12 is Planck's constant and v is the frequency of the
photon, the conservation of energy can be written as

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