Non-linear response of absorbing GaAs/GaAlAs Bragg reflectors

Bragg reflector devices have been built in semiconductor materials. Many applications covering the realization of surface emitting laser diodes and mirrors activated under an electrical field have been demonstrated. Experimental results are obtained showing the optical non-linearities induced by light carrier interactions in GaAs/GaAlAs Bragg reflectors, in the subpicosecond regime. The reflectivity maximum of the mirror is 78% at 675 nm. In this spectral domain GaAs layers are absorbant, so the peak reflectivity is not optimized. By focusing an intense femtosecond pulse on the mirror, the authors saturate the absorption of the GaAs layers. Then they obtain coherent interactions between the light reflected by the front surface of the sample and the light reflected by the deep layers. These interferences lead to a displacement of the secondary maxima towards the main peak and to a better contrast of the interference pattern.