Electro-optically induced phase-grating-type devices may be used for deflection and modulation of an incident optical beam. Experimental observations of the variations of the electrical input impedance suggests that by judicious selection of the crystal dimensions and the relative spacings of the electrodes, the acoustic resonances occurring in the devices when operated in AC conditions can be suppressed. The advantages in using an asymmetrically electroded arrangement over the symmetrically electroded arrangement for light-beam modulation and deflection are discussed in this paper.
The total internal reflection electro-optic deflector/modulator has so far been limited by the subdiffraction patterns that appear in the far field when light is transmitted through the device with zero applied voltage. This paper isolates the causes of these subdiffraction patterns and describes a simple means of removing them from the far field without affecting the performance of the device. The results of measurements taken at zero applied voltage are included and give an indication of the order of this effect.
Grating based electro-optic modulators exhibit acoustic resonances. The performance of a device whose operation is based on the electro-optic variations of the refractive index may be affected by the piezoelectric resonances when operated with AC signals. The author isolates the causes of these observed acoustic resonances and describes simple experimental procedures adopted to suppress them without affecting the modulation characteristics of the device.
New developments of the electro-optic light deflector using total internal reflection of the light are given. By arranging the electrodes in the manner described it has been possible to deflect over 80% of the transmitted light from the zero to either of the first orders. The arrangement is ideally suited for further miniaturization and it is anticipated that switching between the orders will eventually be possible with an applied voltage of only a few volts. Suitable applications include beam steering, multi-stage deflectors and information processing.
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