Second light-induced generation

Fig. 5.15 Light-induced generation of second-order NLO properties in an electric field-poled PMMA film doped with 25 wt% of a spiropyran (see Chart 5.14). Alternating irradiation at 7 = 355 nm and 7 = 514 nm.

The photoisomerization is induced by irradiation with green light (532 nm) from either a continuous laser or pulsed laser (frequency doubled Nd.-YAG Q-switched laser operated in single pulse mode). The second harmonic is generated by a pulsed optical source such as produced by NdrYLF (1053 nm) or Nd YAG (1064 nm) Q-switched nanosecond laser. The probe... 

Charra, R, Kajzar, R, Nunzi, J.-M., Raimond, R, and Idiart, E. (1993). Light-induced second-harmonic generation in azo-dye polymers. Opt. Lett. 18, 941-943. 

Fiorini, C., Charra, E, Nunzi, J.-M., and Raimond, P. (1994). Six-wave mixing probe of light-induced second harmonic generation example of dye solutions./. Opt.. 5oc. Am. B 11, 2347-2358. 

Thus irradiation of nonlinear optical media with coherent light induces nonlinear dielectric polarization and emission of frequency-converted light. Second harmonic generation (SHG) and third harmonic generation (THG) are typical examples of this effect. They are used for example to generate laser light emitting in the ultraviolet and visible spectral domains. 

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