9 Nonlinear Optics

Nonlinear susceptibility tensor

The Physical origin of optical nonlinearities

Oscillator model:

Non-resonant nonlinearities Second-order nonlinearities ((2)) -- Nonlinear frequency mixing

  = 2 - 21= 0  k = k2 -2k 1 = 0 Phase matching Optical frequency conversion (Second Harmonic generation) Energy conservation Momentum conservation k   = 2 - 21= 0  k = k2 -2k 1 = 0 Birefringence Phase Match (BPM)

QPM Condition: k=(k2-2k )-Gm=0 Ln Lp dij Lp+Ln X Y Z X QPM Condition: k=(k2-2k )-Gm=0

Overview of third-order phenomena

The optical Kerr effect and the nonlinear rafractive index Frequency tripling Phase match problem The optical Kerr effect and the nonlinear rafractive index ( degeneate four-wave mixing) No phase match problem (K: Kerr constant)

Stimulated Raman scattering

Resonant nonlinearities

Saturable absorber Resonant nonlinerarities are third-order nonlinear

Resonant nonlinearities in semiconductors