Figure P.4.94 shows a prism-coupler arrangement developed at the Bell Telephone Laboratories. Its function is to feed a laserbeam into a thin (0.000 01-inch) transparent film, which then serves as a sort of waveguide. One application is that of thin-film laserbeam circuitry€”a kind of integrated optics. How do you think it works?

Figure P.4.94

Laserbeam Prism Adjustable coupling gap ~^/2 Thin film Glass substrate