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Off Bragg blazing for TM polarization with rectangular gratings

University of British Columbia

Perfect blazing to the m=-l spectral order was once assumed to be possible for only Bragg angle incidence, i.e. for an angled = sin- 1 (^) from the normal to the grating surface, where d/A is the grating period in wavelengths. The diffracted beam is then back in the direction of incidence, an inconvenience in most applications such as multiplexers, de-multiplexers and frequency scanned antennas. Off Bragg blazing is preferable and now can be done with high efficiency. Here off Bragg blazing for T M polarized incidence on rectangular groove gratings is investigated numerically and design curves are presented. It is a consequence of reciprocity that off Bragg blaze angles must occur in pairs #1 and 62 and these are related by a generalization of the Bragg equation sin 9\ + sin 92 — 2 • F°r groove width to period ratios a/d=0.5 perfect off Bragg blazing occurs most frequently for periods 0.9<d/A<1.0 and groove depth 0.1<h/A<0.24. It is for periods d/A in this range that the larger deviations 6\ — 82 are possible. Off Bragg blazing is found to occur for 0.4<a/d<0.9999, but the larger deviations and hence the more potentially useful designs appear to occur foxa/d K, 0.5. The numerical results correlate well with earlier numerical and experimental data. E.V.

Thesis/Dissertation

application/pdf

2009-01-09

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http://hdl.handle.net/2429/3414

Electrical and Computer Engineering

University of British Columbia

UBCV

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