Acousto-optic photonic crossbar switch. Part I: design

Switch multiplexer of fiber-optic channels Based on multibeam acousto-optic diffraction

The peculiarities of the multibeam acousto-optic Bragg diffraction of light by a multifrequency acoustic signal are investigated. The investigation is related to design of fiber-optic space division switch multiplexer 1xN. It is proved that a specialized two-dimensional acousto-optic deflector can perform high efficiency multifunctional light switching of fiber-optic channels. The device has advanced characteristics--the number of channels is up to a few hundred, the switching time is about a few microseconds, and the cross talk is limited to -45 dB.

Doppler-free, multiwavelength acousto-optic deflector for two-photon addressing arrays of Rb atoms in a quantum information processor

We demonstrate a dual wavelength acousto-optic deflector (AOD) designed to deflect two wavelengths to the same angles by driving with two RF frequencies. The AOD is designed as a beam scanner to address two-photon transitions in a two-dimensional array of trapped neutral Rb87 atoms in a quantum computer. Momentum space is used to design AODs that have the same diffraction angles for two wavelengths (780 and 480 nm) and have nonoverlapping Bragg-matched frequency response at these wavelengths, so that there will be no cross talk when proportional frequencies are applied to diffract the two wavelengths. The appropriate crystal orientation, crystal shape, transducer size, and transducer height are determined for an AOD made with a tellurium dioxide crystal (TeO(2)). The designed and fabricated AOD has more than 100 resolvable spots, widely separated band shapes for the two wavelengths within an overall octave bandwidth, spatially overlapping diffraction angles for both wavelengths (780 and 480 nm), and a 4 micros or less access time. Cascaded AODs in which the first device upshifts and the second downshifts allow Doppler-free scanning as required for addressing the narrow atomic resonance without detuning. We experimentally show the diffraction-limited Doppler-free scanning performance and spatial resolution of the designed AOD.

Analysis of an optically controlled photonic switch

The principle that the coupling of light between two fiber waveguides can be controlled by the resonant interference of a third waveguide has been developed [Attard, Appl. Opt. 37, 2296-2302 (1998)]. Here significant details concerning the operation of a photonic switch are obtained, and a more complete analysis is presented. Multiple-resonant conditions are identified for slab and fiber control waveguides at large indices of refraction. Thus a selection of materials with an appropriate refractive index and a Kerr coefficient is rendered more easily. Furthermore it is shown that the light used to control the index of refraction in the control waveguide does not enter the output of the photonic switch but remains confined to the control waveguide, for either a slab or a multimode fiber control waveguide. Spatial fluctuations of the control light beam in the control waveguide do not affect the operation of the photonic switch. Tolerances have been determined for the spacing between the control waveguide and the photonic coupler and also for the index of refraction of the control waveguide.

Modulation of coupling in a photonic switch by resonant interference

A novel photonic switch structure is described in which the coupling of light between two fiber waveguides is controlled by the resonant interference of a third waveguide. The switching action is controlled by a small variation of the index of refraction of the control waveguide by the application of either photo-optical (Kerr) techniques or electro-optical (Pockels) techniques. The control waveguide can be either a fiber waveguide or a slab waveguide. The equations for the waveguide coupling were obtained by analytical approximations from coupled-mode theory. A beam-propagation simulation was also used. The results of the two models were compared. Multiple resonant interferences were observed in the case of a slab waveguide.