Diffraction characteristics of general dielectric planar (slab) gratings and surface-relief (corrugated) gratings are reviewed. Applications to laser-beam deflection, guidance, modulation, coupling, filtering, wavefront reconstruction, and distributed feedback in the fields of acoustooptics, integrated optics, holography, and spectral analysis are discussed. An exact formulation of the grating diffraction problem without approximations (rigorous coupled-wave theory developed by the authors) is presented. The method of solution is in terms of state variables and this is presented in detail. Then, using a series of fundamental assumptions, this rigorous theory is shown to reduce to the various existing approximate theories in the appropriate limits. The effects of these fundamental assumptions in the approximate theories are quantified and discussed.

Analysis and applications of optical diffraction by gratings

Deposited films of transition metals (Ti, V, and Ni) have been diffused into LiNbO3 crystals to form low‐loss TE and TM mode optical waveguides Using Ti, single‐mode low‐loss waveguides which confine the guided light to within ∼1 μm of the surface have been constructed The choice of diffusion parameters allows independent control of important waveguide parameters

Metal‐diffused optical waveguides in LiNbO3

Integrated optics and new wave phenomena in optical waveguides

We report the realization, in titanium‐diffused lithium niobate, of an integrated optical switch/modulator consisting of an active directional coupler with a novel electrode configuration. Efficient switching is observed with 6 V applied.

Electrically switched optical directional coupler: Cobra

A detailed study has been carried out on the propagation-mode characteristics of graded-index planar optical waveguides formed by silver-sodium ion exchange. It has been found that the index profile can be accurately modeled by a monotonic decrease from a maximum value at the surface, following a second-order polynomial distribution. Definition of an effective diffusion constant leads to a universal mode-dispersion diagram applicable over a wide range of fabrication conditions. Interferometric observations of the refractive-index profile, together with electron microprobe analysis, give further support to the second-order polynomial distribution. The index profile has also been compared with silver-concentration profiles predicted by interdiffusion theory. Results obtained are also relevant to methods of coupling between planar and circular fiber-optical waveguides, where sections of optical fiber undergo ion exchange.

Planar optical waveguides formed by silver-ion migration in glass

Low‐loss LiNbxTa1−xO3 optical waveguides have been made by a simple diffusion technique. They are used to demonstrate over 80% base band electro‐optic modulation with frequency capabilities extending to the microwave range. Voltages below 5 V and drive powers below 2/10 mW/MHz are required.

W. Phillips

Papers

Low‐loss single‐mode optical waveguides and efficient high‐speed modulators of LiNbxTa1−xO3 on LiTaO3