HIGHER-ORDER   NONLINEAR   EFFECTS

As we have mentioned earlier, not all materials have a nonlinear a₂ coefficient only 10% of all natural crystals do but all materials, including glass, have a third-order coefficient. However, as this coefficient is extremely small compared

Figure 1.1. Generation of high-order harmonics.

to a second-order coefficient, much less efficiency is expected for third-harmonic generation. Calcite, for example, can be used as a third-harmonic generator with efficiencies of less than 10^-5. Alternatively, series nonlinear crystals can be used to generate third-harmonic light: the first crystal producing second-harmonic light at 532 nm and the second crystal mixing this light with the original 1064-nm fundamental wavelength, the second crystal often being type I phase-matched. Both methods are outlined in Figure 1.1.

مواضيع ذات صلة

Mirror reflections

The sensation of color

Physiochemistry of color vision

The mechanism of color vision

The chromaticity diagram

Measuring the color sensation

Color depends on intensity

Aberration

The ω,k four-vector

Moving sources

Anomalous refraction

The intensity of reflected light