Resonant Waveguide Grating Structures

Abstract

Resonant waveguide gratings are subwavelength structures that possess the ability to selectively reflect or transmit light in terms of wavelength, incidence angle and polarization state. They are of interest in a large variety of optical sensors and optoelectronic devices. Resonant waveguide gratings have also emerged as low-noise optical components in high-precision metrology, for example frequency stabilized laser systems for the realization of optical clocks or gravitational wave detectors. In these applications, Brownian thermal noise of optical coatings, sets a severe limitation to the feasible sensitivity. In this chapter, we will discuss the relevance of the mechanical loss of optical thin film coatings for Brownian thermal noise. We will present monolithic resonant waveguide gratings to circumvent the use of amorphous coatings to reduce thermal noise. First, we will introduce a method to characterize the mechanical loss of optical coatings and discuss its implications for high-precision metrology. Afterwards we will explain the working principle of resonant waveguide gratings. Then, several characterization techniques for the dimensional and optical characterization will be discussed and experimental results for monolithic waveguide gratings with one-dimensional and two-dimensional periodicity will be presented.