Collinear Acousto-optic Interaction Research Articles

Design of Tapered SAW Waveguide for Wavelength-Selective Optical Switches using Weighted Acoustooptic Interaction

Optical wavelength-selectivity in optical switches using waveguide-type collinear acoustooptic interaction is studied from the viewpoint of the sidelobe suppression. It is found that the sidelobe level can be reduced from -9.3 dB to -20 dB by weighting the coupling coefficient over the interaction region. A method to realize the sidelobe suppression by means of modifying the surface acoustic wave (SAW) waveguide is proposed and theoretically analyzed to design the SAW waveguide. A sidelobe suppression at -20 dB is realized with a SAW waveguide of a dense-flint glass strip whose width and thickness are varied accordingly in the ranges of 700-26μm, and 0.4-1.0μm, respectively, on a Y-X LiNbO3 substrate.

Acoustooptical interaction of light beams under conditions of internal conical refraction

The collinear acoustooptical (AO) interaction of light beams under conditions of internal conical refraction is considered. The dependences of the diffraction efficiency on the ratio of radii of light and ultrasonic beams, the AO coupling length, and the ultrasound intensity are found. An analytical expression is obtained describing the diffraction efficiency of collinear AO conversion of annular beams of internal conical refraction.

COLLINEAR ACOUSTO-OPTIC INTERACTION OF LIGHT BEAMS NEAR THE OPTICAL AXES OF BIAXIAL CRYSTALS

Collinear acousto–optic interaction of light beams near the optical axes of biaxial crystals, including gyrotropic ones, is considered. Efficient acousto–optic transformation of fast and slow light beams under the conditions of internal conical refraction has been revealed. It is shown that the width of the transmission band and the central frequency of ultrasound in collinear acousto–optic filtration in a nongyrotropic crystal are determined by the angle at the apex of the cone of wave vectors (by the anisotropy of the crystal) and in a gyrotropic one by the projection of the gyration vector onto the direction of the optical axis.

A tunable filter with collinear acoustooptical TE-TM mode conversion in a GaAs-AlAs multiquantum-well waveguide

We investigate theoretically an acoustooptic tunable filter (AOTF) based on TE-TM mode conversion by collinear acoustooptic interaction, using the high form birefringence that occurs in a GaAs-AlAs multiquantum-well (MQW) rib waveguide. Mode conversion is achieved using a transverse piezoelectric surface acoustic wave. We propose to use a piezoelectric layer (ZnO or AlN) of 6-mm symmetry, which can be deposited by plasma-enhanced chemical vapor deposition. The c axis is then parallel to the plane of the layer. Under this condition, a transverse piezoelectric surface acoustic wave excited by inderdigital electrodes can propagate within the GaAs-AlAs MQW optical waveguide. TE-TM conversion is then possible with a relatively low acoustic frequency (some tens of megahertz), yielding a high diffraction efficiency and a figure of merit 14 times higher than that of conventional LiNbO/sub 3/ filters based on AOTFs.

Formation of acoustooptical bound states by optical pulses

An interesting aspect of the acoustooptical interaction is studied in this paper — the formation of acoustooptical bound states by optical pulses. An analysis is made of the solution of a system of three nonlinear partial differential equations describing the case of collinear acoustooptical interaction. A specific example of this solution is examined for the case of the interaction of a sequence of acoustic pulses with a digital sequence of optical pulses. It is shown that the values of the recorded sequences of scattered light correspond to the logical operation “ AND” operating on the sequence of acoustic and optical pulses, that is, a programmable switching of the input optical digital signal by a sequence of acoustic pulses occurs. The experiment reported in this paper corresponds to the case of detuning of the wave vectors, but on the whole it supports the calculations In summary, this work demonstrates (experimentally and theoretically) the possibility of realizing an optoelectronic programmable switching of optical signals.

Close to collinear acousto-optical interaction in paratellurite

First results on the investigation of close to collinear coustooptical interaction in paratellurite single crystals are presented. Anisotropic Bragg diffraction of light on ultrasound in TeO₂ with a length of interaction of up to several centimeters is examined. A peculiarity of the interaction is optical beam propagation in the crystal collinearly with group velocity of ultrasound. It is shown and verified experimentally that the interaction is characterized by an extremely high selectivity of scattering. Some applications of the examined regime of diffraction are discussed.

Crosstalk in Integrated-Optic Matrix-Vector Processor Using Acoustooptic Effect

Crosstalk in an integrated optic matrix-vector multiplier using collinear acoustooptic interaction is discussed. An acoustic crosstalk between adjacent acoustic waveguides is measured to be ∼-3 and \\lesssim-20 dB for the waveguide separation of 125 and 250 µm, respectively, at 214 MHz. Theoretically, the crosstalk can be suppressed to less than -25 dB for frequencies \\gtrsim150 MHz with the separation of 200 µm. Optical crosstalk caused by the mode conversion along branches is also investigated.

Optimal parameters of single-mode LiNbO3:Ti waveguides for collinear acoustooptic interaction

It is shown that under the collinear acoustooptic interaction conditions there should be just one set of parameters of an anisotropic waveguide which can ensure the maximum interaction efficiency. A calculation is made of the influence of the increment in the refractive index on the efficiency of interaction at several wavelengths.

Influence of emission processes on the collinear acoustooptic interaction of guided modes

It is shown that in the case of the collinear acoustooptic interaction the phase matching conditions may be satisfied simultaneously for two guided modes and three (or more) radiation modes of different polarizations. A solution is found for the equations describing coupled modes in this case. The results of calculations are compared with the available experimental data on the interaction of guided modes in waveguides.

Optical Tunable Switched Directional Couplers Consisting of Two Thin-Film Waveguides Using Surface Acoustic Waves

Control methods of the fraction of optical power transferred between two waveguides using a collinear acousto-optic interaction is theoretically investigated. The effect of a surface acoustic wave (a SAW) on the mode coupling between the fundamental even and odd eigenmodes of a directional coupler system is analysed and two control methods of optical power transferred are proposed. The required SAW powers of the switched couplers using SAW's and thin-film acousto-optic devices such as optical beam deflectors and optical mode convertors are comparable to one another. The efficiently controllable bandwidth of the optical wavelength λ0 are approximately 100 Å and 40 Å at λ0≃0.63 µm for the symmetric and asymmetric switched couplers with the SAW wavelength of 25 µm and the interaction length of 8 mm. The optical center wavelength of the controllable range can be tuned by the SAW frequency.