Metal-Dielectric Composite Filters With Controlled Spectral Windows of Transparency

In this report we show the possibility of broadband low-pass filters with windows of transparency in pre-set spectral ranges. Those filters are based on the unique optical properties of metal-dielectric composites near the percolation threshold. In such composites, metal clusters of different sizes and shapes have different plasmon resonances and resonate nearly independently at different wavelengths. All together, the resonant plasmon modes cover a very broad spectral range. Applying the effect of spectrally selective photo-modification, we develop a procedure that creates mid-infrared windows of transparency within the broadband filters. We also investigate the possibilities of making low-pass filters composed of spheroids and conductive sticks with certain distributions of aspect ratios.