Coupling of angle polished waveguides to high-Q whispering gallery mode resonators

In this work the authors propose the alternative use of robust angle polished waveguides which can be made on a number of different substrates, which, in turn, can be selected with the proper index in order to fulfil the phase matching condition with the resonator. The simple equation θ=acos(n_WGM/n_WG) holds, where n_WGM and n_WG are the WGM and the waveguide effective indices, respectively.