A new two-dimensional subwavelength resonant grating filter fabricated by nanoimprint lithography

Subwavelength Resonant Grating (SRG) optical filter is a novel filter that can reflect a specific wavelength and transmit the others. They are easy to fabricate and can readily be integrated with other optical elements, such as laser cavity. Previously, SRG filters with 1D gratings, which are polarization dependent, and SRG filter with 2D holes, which is polarization independent, have been demonstrated. Here, we present the first fabrication by Nanoimprint Lithography (NIL) and characterization of a SRG filter with 2D pillars. SRG filters with 2D structure are generally required to obtain polarization independent operation. Furthermore, NIL is a low-cost, high-throughput, sub-10 nm resolution lithographic technique. Compared with previous 2D SRG filter, the pillar array structure reported here exhibits significantly higher peak efficiency, smaller FWHM, and same resonant wavelength for two orthogonal polarizations. In addition, high performance 1D SRG filter with 0.38 nm FWHM, 98% peak reflection efficiency is demonstrated by NIL here. Both the 2D and 1D SRG filters operate at 1.5 μm spectral range