Polarization Independent Birefringent Tunable Filters

Novel, polarization-insensitive, birefringent, broadband tunable filter arrangements that allow high throughput, based on a combination of tunable birefringent layers or polarization dependent filters, in combination with one or more of the following components (i) thin film achromatic quarter waveplates based on the form birefringence of dielectric subwavelength grating structures, (ii) nano wire-grid polarizers made of metallic wire grids; (iii) omnidirectional dielectric mirrors, (iv) polarization conversion mirrors, (v) reflective polarized beam splitters for circularly polarized light, (vi) metallic subwavelength gratings with lines having Gaussian profile, and (vii) Faraday mirror. All of these components may be implemented in thin film form on one or more substrates, such that a compact and cost effective filter can be produced. The birefringent layers can be any birefringent or magneto-optic layer but especially liquid crystals. The use of novel polarization conversion disposition of the components of the filter results in a filter having high throughput.