S. Somekh

Channel optical waveguide directional couplers

We report the first demonstration of channel optical waveguide directional couplers. The closely spaced channel waveguides were fabricated in GaAs by proton implantation. Optical coupling was observed at 1.15 μ with complete light transfer out of the initial channel into adjacent channels in lengths of typically 2 mm.

Phase matching by periodic modulation of the nonlinear optical properties

Abstract Periodic modulation of the optical nonlinear coefficient of a propagation medium is proposed as a new method for phase matching. This proposal is examined in some detail in the case of a thin film waveguide where the prospects of its implementation seem favorable.

Optically pumped GaAs surface laser with corrugation feedback

A GaAs distributed‐feedback laser was fabricated and pumped optically. A narrow stimulated spectrum was obtained around 0.83 μ with threshold pumping power of ∼2 × 105 W/cm2.

Ion beam micromachining of integrated optics components.

Thin film integrated optics components such as light guides, modulators, directional couplers, and polarizers demand high quality edge smoothness and high resolution pattern formation in dimensions down to submicrometer size. Fabrication techniques combining holographic and scanning electron beam lithography with ion beam micromachining have produced planar phase gratings with intervals as small as 2800 A, guiding channel couplers in GaAs, and also wire- grid polarizers for 10.6-,microm radiation.

Phase‐matchable nonlinear optical interactions in periodic thin films

A proposal for a new method of phase matching in nonlinear optical interactions is made. A periodic perturbation of the surface of a thin‐film waveguide generates space harmonics with new propagation constants which can be phase matched. An analysis of this proposal shows it to be particularly interesting for a class of thin‐film nonlinear devices using the cubic optically isotropic semiconductors (such as GaAs, GaP, etc.) which possess high nonlinear optical coefficients but are not phase matchable by the conventional birefringent techniques.

Laser oscillation in epitaxial GaAs waveguides with corrugation feedback

Laser action was observed in GaAs epitaxial films using corrugation feedback. The output wavelength was found to depend on the corrugation period. The loss, threshold gain, and feedback parameters were determined and compared with theoretical predictions.

Channel Optical Waveguides and Directional Couplers in GaAs–Imbedded and Ridged

Two-channel imbedded directional couplers were fabricated with proton implantation, yielding complete light transfer in 2 mm. Ridged channel guides were fabricated by ion-micromachining epitaxial layers, and a method of directional coupling was demonstrated.

Optically pumped GaAs waveguide lasers with a fundamental 0.11 μ corrugation feedback

Abstract Surface corrugations with a period of 0.115 μ were ion-milled on GaAs dielectric waveguides. Laser action was observed under optical pumping. Single mode as well as multimode oscillation was obtained under different pumping conditions.

Optical Directional Couplers

The optical directional coupler, analogous to the microwave element1 of the same name, consists of parallel channel optical waveguides sufficiently closely spaced that energy is transferred from one to another. For this coupling to take place cumulatively over a substantial length, the light must propagate with the same phase velocity in each channel. The fraction of the power coupled per unit length is determined by the overlap of the modes in the separate channels. Thus, it depends on the separation of the guides, the mode penetration into the substrate, and the interaction length. Figure 1 is an example of a multichannel directional coupler. It shows a diagram of a large number of coupled waveguides (produced by proton implantation) and typical intensity profiles of the guided light. The incident light is focused into a single channel at z = 0, but is coupled into the adjacent guides as it propagates.

Theory and fabrication of integrated optics directional couplers in GaAs

Channel optical waveguide couplers will be discussed, citing the fabrication of closely-spaced waveguides by proton implantation. Coupling was observed at 1.15μ and 1.06μ.