Investigations of Optical Limiting Involving Light-Matter Interactions

摘要

An optical limiter keeps the power, intensity, energy or energy density transmitted by an optical system below a predetermined maximum value that is independent of the size of the input pulse while maintaining a high transmittance at low input power. The many applications of the device include laser power regulation, laser mode-locking, optical pulse shaping, signal level processing, and sensor/detector protection. Important applications include protection of sensors, such as human eyes of pilots and photodetectors, from laser damage. In order to determine the parameters required for optimization of optical limiters, we are developing an extremely sophisticated numerical code. Additionally, new materials are needed with increased nonlinearity. Thus we also calculate the imaginary part of the third order optical non-linearity for an array of semiconductor quantum dots in an organic host and show that it leads to large two-photon absorption. The calculated two-photon absorption is greater than currently measured materials. The large non-linearity results from a hybrid exciton formed in the inorganic-organic medium. The band gap of the semiconductor dot determines the spectral region of the resonances that vary from the visible to the near, mid and far infrared regions. We show that relatively small changes in the ratio of the quantum dot size to the quantum dot-to-dot spacing result in significant changes in the non-linearity. We briefly describe applications in communications, optical filters, and bio photonics for thin films comprising these hybrid excitons.