A new model to describe the origin of optical nonlinearity is presented. In this model, the interaction between light and medium is reduced to the coupling of photons with phonons, which occurs in the crystal lattice vibrating anharmonically. Then the optical nonlinearity originates from the nonlinear photon–phonon coupling or the interaction among phonons themselves. In this paper, more attention is drawn to the latter. By the given model, (1) degenerate and (2) nondegenerate parametric oscillations, (3) Stokes and (4) anti-Stokes Raman scattering, (5) sum-frequency and (6) second harmonic generation and (7) two-photon absorption are dealt with systematically and quantum-mechanically. The results of theoretical analysis show that the effects (1)–(4) are associated with threshold phenomenon, whereas the effects (5)–(7) with the saturation phenomenon.

Optical nonlinearity via phonons as an intermediary

As a continuation of the work, published in JNOPM 10(1), 65 (2001), in which it is considered that the optical nonlinearity has its origin in multi-phonon processes in the crystalline medium, this paper deals with the optical effects of four-wave mixing and coherent Raman scattering (including first- and higher-order processes), where the phonon modes participating in interaction are more than three.

Optical nonlinearity via phonons as an intermediary (continuation) — four-wave mixing and coherent raman processes

We present herein an approach to the interaction of coherent light with the anharmonic lattice vibration of ionic crystal and give a mechanism for increasing absorption optical bistability.

Tingwan Wu

Papers

Anharmonic vibration of ionic crystal and increasing absorption optical bistability