An optical device having a mat including plural nanofibers configured to transmit light having wavelengths above a cutoff wavelength and to reject light at wavelengths below the cutoff wavelength. The nanofibers have an average fiber diameter comparable in size to the cutoff wavelength.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
 The present invention was made in part with U.S. Government support under Department of Energy Grant No. DE-FC26-06NT42861. The U.S. Government may have certain rights to this invention.