Nonlinear shift of absorption resonance

Peter Powers

Taro Hasegawa

The nonlinear absorption process and associated phase shift in coupled optical cavities are studied experimentally by observing optical resonance properties. In the coupled cavity configuration, two optical cavities, one for a fundamental beam and the other for a second-harmonic (SH) beam, are coupled by a nonlinear crystal for the second-harmonic generation (SHG). The cavity for the SH beam effectively extends the nonlinear crystal length so that the frequency-conversion efficiency of the SHG, which is proportional to the square of the crystal length, is enhanced. In the observation, power reduction of the fundamental beam at resonance is observed as a small dip in the resonance curve. According to a model calculation, it is found that this power reduction is caused by blue-induced infrared absorption.

Wolfgang Demtröder

H. M. Gibbs

Intrinsic optical bistable devices have the potential for very fast all-optical logic.1 Achievement of high speeds necessitates short devices. Semiconductors are attractive materials for providing the essential optical nonlinearity because they can have absorption coefficients of order (μm)-1, ensuring strong interactions in short lengths. Furthermore, they have relatively sharp absorption features, e.g., an exciton, biexciton, or band-edge resonance, which permits very large nonlinear phase shifts via near-resonance enhancement but with low absorption by off-resonance operation.

Wolfgang Demtröder

Семибаламут Владимир Михайлович, Е. А. Титов

A calculation is made of the absorption coefficient of a standing-wave field in a gas of two-level molecules allowing for transit effects to within the second order of the saturation parameter. The rate of the field broadening of a nonlinear power resonance is investigated for various dimensions of a light beam. An analysis is also made of the rates of the field shift of the maximum of such a nonlinear resonance because of the quadratic Doppler effect and hyperfine structure of the line.