Introduction
NLO effects have been observed since 19thC
- Pockels’ effect
- Kerr effect
High fields associated with laser became available in the 1960s and gave rise to many new NLO effects
- second harmonic generation (SHG)
- third harmonic generation (THG)
- stimulated Raman scattering
- self-focussing
In NLO we are concerned with the effects that the light itself induces as it propagates through the medium
In linear optics the light is deflected or delayed but its frequency (wavelength) is unchanged