| 摘要 |
<p>1362234 Modulating light HEWLETTPACKARD CO 26 Nov 1971 [14 Dec 1970] 55059/71 Heading H4F When a narrow waveband portion of a plane polarized optical wave 14 passing through a birefringent medium 11 is selectively diffracted into the orthogonal polarization by a collinear acoustic wave 5, the frequencies of the diffracted optical and acoustic waves being related by a k-vector matching condition, and when the acoustic frequency is varied to alter the frequency of the diffracted optical wave, there results an instantaneous distribution of acoustic k-vectors along the collinear path whereby coherence between the optical and acoustic waves is reduced and the diffracted optical waveband is lowered in intensity and broadened in frequency, Fig. 3 (not shown). This may be compensated by varying the birefringence of medium 11 along the collinear path. In Fig. 1, a transverse electric field is imposed, its magnitude (and polarity) varying along the collinear path, and being produced, as shown, by a variable voltage source 25 and resistive electrodes 23, 24. Alternatively the variation in birefringence may be produced by a thermal gradient along the collinear path, Fig. 4 (not shown), or by a strain gradient (not shown). An analyser 17 is disposed either to transmit or to reject the diffracted optical wave.</p> |
