John J. Kester

Second-harmonic generation in planar waveguides of doped silica.

Second-harmonic generation was produced in germanium-doped silica planar waveguides prepared by simulfaneous illumination with 1064- and 532-nm laser light. During preparation using prism coupling to specific waveguiding modes, the film-generated second-harmonic intensity grew as a function of preparation time until it saturated. The growth rate and saturation level for p-polarized second-harmonic intensity was an order of magnitude greater than that observed for the s polarization. The efficiency for a 2-cm waveguide length was at least 0.5%. The comparison of experimental results indicates a mechanism for this planar geometry that is similar to that producing harmonic effects in optical fibers.

Modal properties of second‐harmonic generation in doped‐silica planar waveguides

Planar waveguides of germania‐doped silica have been optically modified to allow second‐harmonic generation in various waveguiding modes. After optical modification, the propagation of only the fundamental wave produced film‐generated second‐harmonic light in the same waveguide mode with which it had been prepared. The relative efficiencies of several mode combinations were all measured to be within an order of magnitude of one another and in reasonable agreement with theoretical predictions. Furthermore, we discuss the discrepancy between the theoretical calculations and experimental observations of the modal properties of second‐harmonic generation in fibers.

All-optical programmable AND gate implementation in a germanium-doped silica planar waveguide

We report the results of an all-optical programmable AND logic gate. This gate consists of a germanium-doped silica planar waveguide, a laser, and the means of coupling two fundamental frequency beams into different guiding modes of the waveguide along with a second harmonic beam coupled into one guiding mode. These waves interfere in the film generating a set of semipermanent second-order susceptibility gratings which give rise to the waveguide, the film-generated second harmonic light wave made to behave as an output of a logic AND gate. The fundamental and second harmonic light were sent into the waveguide during the programming sequence, but only the fundamental light was injected to probe the logic gate to produce an output. The measured signal-to-noise ratio was 17 dB.

Use of the asymmetric photoionization model to explain the length and time dependence of second-harmonic generation in fibers

The growth of Second Harmonic Generation (SHG) in fibers has been observed to saturate with time as well as with length and can actually decrease after prolonged exposure to fundamental light. We have measured the length dependence of the SHG as a function of time during preparation, saturation and subsequent exposure to IR light. We have also measured the time dependence of erasure of the (chi) (2) grating with exposure to various amounts of green light. Based on these measurements we have been able to determine the parameters of the asymmetric photoionization model, specifically the current and two photon absorption rate. We have performed preliminary experiments using planar waveguides to measure the asymmetric photocurrent.

Electric field measurements associated with second harmonic generation in thin film waveguides

We investigate the process by which induced static electric fields are produced in waveguide materials during SHG. Most of the models for the production of these fields rely on a photoionization process within the waveguide which has a preferential photoejection direction, i.e., a net current flow. Our work models the current that produces the static electric field and measures the electric fields outside the waveguide surface that are produced by this internal current flow.<<ETX>>