CORRELATED SPONTANEOUS EMISSION LASERS.
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abstract
A laser field has an intrinsic frequency linewidth due to spontaneous emission. This linewidth (or equivalently the diffusion of the field's phase) limits the ability to determine precisely the relative phase (or frequency) of two laser fields which diffuse independently. It is possible to correlate the emission with two different laser modes so that the relative phase does not diffuse due to spontaneous emission. Systems with this property are called correlated spontaneous emission lasers (CELs). Such a relative phase can carry information about, for example, the rotation rate of a ring gyroscope or the distance modulation between two mirrors due to passing gravitational radiation in so-called active embodiments of laser interferometers. In particular, in CEL devices the diffusion (rate of growth of the uncertainty) in the relative phase psi between the two lase modes can be given by D( psi ) equals D//0(1-cos psi ), where D( psi ) is the diffusion rate due to random spontaneous emission events of the relative phase between two uncorrelated laser modes. Note that if psi equals 0, D( psi ) vanishes, and there is no diffusion of the relative phase.
