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Abstract

This thesis deals with the modulation and deflection of an optical beam, utilising the electrically induced refractive index variations in electro-optic crystals. The modulator and deflector configurations considered utilise phase gratings produced by surface deposited interdigital electrodes on a crystal face. When the electrodes are arranged symmetrically, a Raman-Nath type of diffraction pattern is obtained in the far field. However an asymmetrically electroded arrangement gives rise to preferential deflection of the zero order light beam to a higher order diffraction position. A typical unoptimised device, which has been developed during the course of this work, and having asymmetrical electrodes deflected about 81 % of the incident light having a wavelength of 0.63 pm to the first order at an applied d.c. voltege of 157 volts. 53 % of the incident energy was deflected to the second order with this device at an applied d.c. voltage of 255 Volts.

Acoustic resonances were observed in the devices developed when operated under a.c. conditions, In the symmetrical electrode arrangement both bulk and surface wave resonances were observed. However in the asymmetrical arrangement only bulk waves were observed. The bulk resonances were almost completely suppressed by placing an absorber on the face opposite to the electrode face.

An extension of the principle of the internal reflection modulator device to a double reflection modulator produced about 50 % reduction in the zero order extinction voltage

Publication Type:	Thesis (Doctoral)
Subjects:	T Technology > TA Engineering (General). Civil engineering (General) T Technology > TJ Mechanical engineering and machinery T Technology > TK Electrical engineering. Electronics Nuclear engineering
Departments:	School of Science & Technology > Department of Engineering School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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