Theoretical treatment of thermal shifts in resonant grating waveguide
Resonant grating waveguide structures are discussed as extreme narrow-band reflection filters. Their spectral response may shift due to environmental impact, e.g. from temperature, pressure or humidity, making it interesting for sensor applications. The present paper derives approximate analytical expressions for spectral rejection band shifts caused by changes in the refractive index of the waveguiding layer and compares these expressions with corresponding shifts of the reflection band of high-low multilayer stacks due to environmental changes. It is shown that a minimum shift is expected for the highest grating period that fulfils the coupling condition.