The Doppler frequency shift of an optical wave can be made, not only by moving media, but by a moving boundary separating two media at rest.
The moving interface can be produced by a travelling step-function electric or magnetic field applied to a nonlinear material, for example.
This paper describes the experimental Doppler frequency shift of a He-Ne laser by the moving boundary, which is produced in nitrobenzene (C
6H
5NO
2) by a high voltage pulse transmitted along a strip line in a liquid cell. The frequency of the transmitted light to the end of the cell is shifted by about 15 MHz. The shifted frequency of the reflected light by the boundary has not, however, been observed yet, because the variation of the refractive index of the medium is too little. The results of this paper show that a large amount of the laser frequency shift will be expected, if the medium with a large Kerr constant is discovered in the near future.
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