Brewster prism coupler for the intracavity excitation of TM guided modes

A new type of prism coupler for intracavity excitation of TM guided modes in a planar waveguide is described. The prism coupler is made in the form of a parallelepiped with input and output faces inclined at the Brewster angle to intracavity radiation. It is shown that the prism base angle and base-to-height ratio are strongly determined by the refractive index of the prism material and the effective waveguide index of the corresponding guided mode of the waveguide structure. The expressions for calculating these parameters are presented.