CONVERSION OF LASER PHASE NOISE TO AMPLITUDE NOISE IN AN OPTICALLY THICK VAPOR

As laser light propagates through a resonant vapor, laser phase noise (PM) is converted to laser intensity noise (AM) because of the sensiti vity of atomic coherence to laser phase fluctuations. In experiments r eported here it is shown that this PM-to-AM conversion process is high ly efficient and can cause the relative intensity noise of transmitted diode laser light to be 1 to 2 orders of magnitude larger than the la ser's intrinsic relative intensity noise. By use of a semiclassical de scription of the phenomenon, including the effect of optical pumping, reasonably good agreement between theory and experiment is obtained. T he PM-to-AM conversion process discussed here has important consequenc es for atomic clock development, in which diode-laser optical pumping in thick alkali vapors holds the promise for orders-of-magnitude impro vement in atomic clock performance. (C) 1998 Optical Society of Americ a [S0740-3224(98)01303-4].