Resonant Optical Structure for Optical Power Limiting Devices Designed for Near IR Active Imaging
P. Feneyrou and G. Berginc
Optical power limiting (OPL) around 1.5 μm becomes an issue to protect active imaging systems against self–dazzling and laser aggression. The main characteristics of OPL devices required for near infrared active imaging systems are presented. The system characteristics that are different from passive systems and that could be used in the design of OPL devices are underlined. Resonant optical structures can take advantage of the reduced spectral band and field of view of optical configurations designed for active imaging systems. In particular, structures using coupled optical cavities with a non-linear material in the central cavity can increase the apparent non-linear response of the material: the attenuation is linked to both the non-linear absorption and the de-coupling of the cavities arising from complex refractive index change of the central cavity. Theoretical OPL performance is illustrated on a three cavity structure using non-linear material presenting both two photon absorption and Kerr non-linear refractive index.
Keywords: Optical power limiting, active imaging, optical bi-stability, two photon absorption, nonlinear refraction, coupled cavities.