Devices based on the guided-mode resonance (GMR) e®ect are very promising elements in the areas of optics and electromagnetics. They can provide variety of spectral re- sponses only founded on periodically patterning of a single optical layer on a substrate or as a free-standing membrane. Although the main manifestation of the GMR e®ect is sharp reso- nances in the re°ection spectra, by proper selection of device parameters, attainment of variety of optical spectral responses such as narrow bandpass/bandstop ¯lters, broadband re°ectors, po- larizers and so on is possible. Since in this kind of elements, light is coupled into waveguide leaky modes through a subwavelength grating structure, the device works in the second (leaky) stop- band. Response of such devices is highly dependent on the modal characteristics of the guiding layer. Broadband high re°ectors, based on periodically patterned single layers (with substrate or as a membrane), are promising and attractive elements in the area of optical devices and have recently found practical application as top mirror in tunable vertical cavity surface emitting lasers (VCSELs). In this paper, a single layer, strongly-modulated GMR-based broadband high re°ector is designed for 1.45{2.0 ¹m band for TE and TM polarizations using particle swarm optimization (PSO) technique; a robust, easy to implement evolutionary technique inspired from the behavior of particles in a swarm searching for their requirements resources. A silicon-on- insulator (SOI) structure has been chosen in which the binary patterned silicon layer act as both grating and waveguide. The spectral and modal characteristics of these elements are analyzed utilizing rigorous electromagnetic techniques like rigorous coupled-wave analysis (RCWA) and modal techniques. The designed re°ector for TM and TE polarizations provide » 520nm and » 125nm bandwidth at > 99% re°ectance, respectively. Also, showing the re°ection and trans- mission maps as well as the mode pro¯les, we investigate the e®ect of refractive index modulation and the thickness of the grating on device\'s spectral response.

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