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Chapter I Brief Introduction...
Figure: 1.6 Schematic representation of Sum frequency generation.
If ω3 and ω1 are fixed, then ω2 is also fixed. Notwithstanding, in the case of
only ω3 is fixed, then the other two are free to range over many values; this
effect is called as the parametric amplification. This is used to produce
coherent radiation at frequencies in ultraviolet region [18, 19]. The additional
wave length made available by harmonic generation and parametric
oscillation find applications in photochemistry, high resolution spectroscopy
and the remote detection and identification of atmospheric pollutants by
optical radar or LIDAR [20].
Optical Parametric Generation (OPG)
Optical Parametric Generation (OPG) is an inverse process of sum
frequency generation. It splits one high-frequency photon (pumping
wavelength, λp) into two low-frequency photons (signal, λs, and idler
wavelength, λi). If two mirrors are added to form a cavity, an Optical
Parametric Oscillator (OPO) is established. For a fixed pump wavelength, an
infinite number of signal and idler wavelengths can be generated by tilting a
crystal. Therefore, OPG is an excellent source for generating wide tunable
range coherent radiation. The OPG is shown in figure (1.7) schematically.
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