Interferometers and the Group Index


RAYLEIGH pointed out the importance of the group index in optics more than half a century ago, but the simplifications which the use of a group index G make possible do not appear to have been recognized, though Craven1 has pointed the way. G is defined as where v is the wave-number ½ and N is the refractive index.

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  1. 1

    Craven, Proc. Phys. Soc., 57, 97 (1945).

  2. 2

    Williams, W. E., "Interferometry", 27 (1929).

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CANDLER, A. Interferometers and the Group Index. Nature 157, 444 (1946).

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