  Thanks to the atomic coherence in coupling laser driven atomic system,
sub-Doppler absorption has been observed in Doppler-broadened cesium vapor cell
via the /Lambda-type three-level scheme. The linewidth of the sub-Doppler
absorption peak become narrower while the frequency detuning of coupling laser
increases. The results are in agreement with the theoretical prediction by G.
Vemuri et al.[PRA,Vol.53(1996) p.2842].
