Impact of Atomic Layer Deposition to the fabrication of athermal guided mode resonance filters

Abstract

We study athermal properties of guided mode resonance filters in polymeric substrate coated by high index, amorphous, and isotropic TiO 2 thin film. The narrow spectral linewidth filter's are designed by Fourier Modal Method and fabricated by Electron Beam Lithography (EBL), Nano-imprint Lithography (NIL), and Atomic Layer Deposition (ALD) and characterized by Scanning Electron Microscope (SEM), Atomic Force Microscope (AFM) and variable angle ellipsometer. Thin layers of ALD coated optical materials are fabricated as waveguide layers to confine and propagate waveguide modes. The thermo-spectral properties of such filters are studied by accompanying thermal expansion coefficient (TEC) and thermo-optic coefficient (TOC) effects of the layered materials. It is demonstrated theoretically and experimentally that the effects of TEC and TOC compensate for each other to stabilize narrow spectral peak within fraction of a nanometer. The wavelength shift in spectral reflectance peak (< 1 nm) is a small fraction of the peak's Full Width Half Maximum (FWHM ∼11nm) at 100 °C temperatures.