Methods of determining the beat length of planar waveguides

The paper presents two methods of determining the planar waveguide birefringence and the measuring stands, which are used to determine the beat length of planar waveguide structures. The light is introduced into the waveguide through a prism coupler. The first method applies measurements of scattered light. The second method uses an immersion coupler. The most fundamental property of an immersion coupler is the possibility to change fluently the propagation length while immersing the waveguide.