Wavelength Dispersive Planar Waveguide Devices: Echelle and Arrayed Waveguide Gratings

This chapter deals with the wavelength dispersive planar waveguide devices which are waveguide echelle grating (EG) and arrayed waveguide grating (AWG). It conveys about the principles of EG and AWG. In waveguide EG each grating facet represents a small source reflecting and transmitting incident light according the laws of reflection and refraction, and simultaneously acts as a narrow diffraction slit, thus determining the envelope of the far-field diffraction pattern, also called the slit function (SF). The advances of planar waveguide EG devices were developed in silica-on-silicon by Optenia Inc. and InGaAsP/InP by MetroPhotonics Inc., with performances comparable to arrayed waveguide gratings and significantly smaller sizes. By controlling the phase relationship between the beams emitted by the individual elements of the array, antenna radiation direction can be changed without mechanical movements.