Sub-nanometer linewidth resonant grating filters

Abstract

Narrowband filters are important optical components that have numerous applications. Conventional interference narrowband filters suffers low peak efficiency due to the roughness of the film coatings especially the roughness of the spacer layers. The minimum linewidths of interference filters are typically 1 nm for the visible regime, while the peak efficiencies are less than 40%. Spectral stability of interference filters is poor because spacer layers absorb water vapors and cause shifting of the peak wavelength. Usually the coatings have to be sandwiched in between two substrates, which are then sealed along the side. In addition, narrowband interference filters are structure-complex; 60 layers are not uncommon for 1 nm interference filters. The large number of layers imposes great difficulty in the use of advanced film deposition techniques such as chemical vapor deposition (CVD) methods.