We demonstrated the design, fabrication and characterization of three Resonant Waveguide Gratings (RWGs) with
different polymer substrate materials [polycarbonate (PC), cyclic-olefin-copolymer (COC) and Ormocomps). The RWGs
are designed by Fourier Modal Method and fabricated by Electron Beam Lithography, Nanoimprinting and Atomic
Layer Deposition. RWGs are investigated for athermal filtering device operation over a wide range of temperatures.
Spectral shifts of RWGs are described in terms of thermal expansion and thermo-optic coefficients of the selected
substrate and waveguide materials. Furthermore, the spectral shifts are explained on the basis of shrinkage strains,
frozen-in stresses and the molecular chain orientation in polymeric materials. The thermal spectral stability of these
filters was compared by theoretical calculations and experimental measurements. For PC gratings, there is a good
agreement between calculated and measured results with a net spectral shift of 0.8 nm over 75 °C wide temperature
range. Optical spectral characterization of COC and Ormocomp gratings showed larger red spectral shifts than predicted
by theoretical calculations. The deviation (0–1.5 nm) for the COC grating may result in by high modulus and inherent
stresses which were relaxed during heating and accompanied with the predominance of the thermal expansion
coefficient. The Ormocomps gratings were subjected to UV-irradiation, causing the generation of compressive
(shrinkage) strains, which were relieved on heating with a net result of expansion of material, demonstrated by thermal
spectral shifts towards longer wavelengths (0–2.5 nm). The spectral shifts might also be caused partially by the
reorientation and reconfiguration of the polymer chains.