This paper reports on the excited state Faraday anomalous dispersion spectrum (FADS) of rubidium based on transition 5P3/2→5D5/2. Theoretical analysis and experimental studies have been made. The results showed that the peak transmission occurred at the central frequency of the transition, there was an optimal magnetic intensity at a certain temperature and pump power, and peak transmission increased with the enhancement of pump power. 16% transmission was predicted when the density of 5P3/2 atoms was sufficient.

Coherent optical communications systems are of higher sensitivity than that in systems employing the direct detection. However, interferences such as the wavefront distortion and the random vibration of polarization caused by the turbulent atmosphere limit the development of terrestrial coherent wireless optical communications system. This paper presents a novel heterodyne optical wireless communications system and method based on the grating writing and reading of the multiple-quantum-we Udevice (MQW). The MQW, a new generation of photoelec-tric device developed in 1990's, is of the attractive features including high sensitivity and fast response. Compared with the conventional coherent detection method, our method eliminates the complicated intermediate-frequency tracking system. Experimental results show that our method can repress the wavefront distortion introduced in transmission through the atmosphere.

We report a digital speace iptical communication svstem with new features both in the transmitting and in the receiving ends. The diode iaser source is stabilized to within=100kHz by locking its frequency to the transmission peak of a Faraday anomalous dispersion iptical filter FADOF1, The optical filter in the receiver usestwo FADOF's that are linked to eliminate the muitipeak strueture and achieve a single-peak bandwidth of i GHz. The detection sensitivity of this system is 23 times higher than that of a system with a traditional interference rilter.

In this paper the existence of optimal frequency detuning in the pumping process of the excited state Faraday anomalous dispersion optical filter ESFADOF, also referred as active FADOF.is reported. We measured this detuning and its variation versus cell temperature. Moreover, the dependence of the ESFADOF transmission on the cell temperature and pumping power was also studied experimentally. On the basis of these results, the transmission of rubidium 775.9nm ESFADOF was raised by more than two orders of magnitude under optimized working conditions. q1998 Elsevier Science B.V. All rights reserved.