City Research Online

Abstract

This work deals with an analysis of diffraction processes which may offer promise as light deflection/ modulation methods. Discrete device applications are considered and two configurations found to be promising. One is a phased array with individually controlled sources followed by a transform lens and a grading mask while the other is a fine impressed phase grating form giving a Raman-Nath type farfield. Both approaches are assessed and both devices realised. The array realisation appears unpromising as yet but the phase grating approach device, constructed by employing the effect of interdigitated electrodes on an electro-optic crystal with the light beam totally internally reflected from the electrode area, proves of considerable interest. This device is assessed in a basic LINBO3 realisation and the tradeoffs of device construction identified. A typical unoptimised device at 0.63/u offers zero order extinction at ~ 70 volts. Q switching operation at 1.06/ u by such a device is also reported using only 90 volts.

An assessment of device development prospects suggests that much work remains to be done of these TIR devices and it appears that the electro-optic discrete diffraction modulator has considerable advantages over the orthodox birefringent device and is comparable in many respects to the acousto-optic device. These advantages include low insertion loss, ease of driving, and ease of fabrication.

Publication Type:	Thesis (Doctoral)
Subjects:	T Technology > TA Engineering (General). Civil engineering (General)
Departments:	School of Science & Technology > Department of Engineering School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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