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Sum-frequency generation

Sum-frequency generation (SFG) is a second order nonlinear optical process based on the mixing of two input photons at frequencies ω 1 {\displaystyle \omega _{1}} and ω 2 {\displaystyle \omega _{2}} to generate a third photon at frequency ω 3 {\displaystyle \omega _{3}} . As with any χ ( 2 ) {\displaystyle \chi ^{(2)}} optical phenomenon in nonlinear…

Phase-matching, Sum frequency generation spectroscopy & Second-harmonic generation