title: Prism coupler jig: interference fringes enable observation of the coupling gap.
abstract: A prism coupler jig is described which enables a coupling region to be quickly and easily found when the waveguide is a thin film on a microscope slide. Interference fringes formed on reflection allow observation of the air gap. Consideration is given to the formation of white light and quasi-monochromatic interference fringes. A suitable choice of the refractive index of the right-angle prism enables the m lines to be observed in a convenient observation space.
authors.forename: J T
authors.initials: JT
authors.lastname: Chilwell