Tunable Coherent Radiation by Frequency-Mixing Techniques

2 Tunable Coherent Radiation by Frequency-Mixing Techniques 

In a general way, when the radiation from two laser beams with frequencies (oi and (02 are superimposed in a medium with a sufficiently large nonlinear part of the susceptibility, each atom is induced to undergo forced oscillations and generates 

Therefore, it is clear that different frequency conversion processes, together with the variety of lasers, have led to a great variety of coherent sources with large and differing tuning ranges. The whole spectral range of 185-3400 nm can be covered by different methods. 

We will restrict our description to those processes and systems that have been developed more over recent years those based on the optical parametric oscillation or amplification processes. The practical devices involve two of the most relevant solid state lasers nowadays the Nd YAG laser and the Ti-sapphire laser. 

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