LASER COOLING OF 3-LEVEL ATOMS IN 2 STANDING WAVES

We present a general theoretical description of laser cooling of three -level atoms in a Lambda configuration in two standing waves. Detuning s, intensity, and spatial phase difference of the two waves are arbitr ary. We demonstrate that, for a zero spatial phase shift, sub-Doppler cooling requires equal detunings. The basic mechanism is then coherent population trapping. For different detunings sub-Doppler cooling occu rs only when the spatial phases of the two standing waves are differen t. This effect can be traced back to a mechanism of the Sisyphus type. These schemes of sub-Doppler cooling require neither polarization gra dients nor magnetic fields. (C) 1997 Optical Society of America.