Optical Guided-Wave Focusing and Diffraction*

One-dimensional focusing and diffraction techniques for thin-film optical waveguides are examined in terms of their effectiveness and fabrication requirements. Impetus for the study is derived from potential application of optical planar guided waves to analog signal-processing systems. Methods of altering modal-phase velocities to achieve ray deflection are investigated and include the use of substrate and film-embedded refractive-index discontinuities, multilayer films, thickness-profiled layers, and absorptive-material deposition on the guiding films. Thin-film lenses having f numbers as low as 2 to 3 may be fabricated by vacuum deposition of high-index materials, such as CeO2. Experimental results obtained with glass-sputtered films illustrating basic operation of thin-film lenses, gratings, and prisms are presented.