<title>Control of two-photon absorption by using electromagnetic field in sodium and rubidium vapors</title>

Abstract

We applied a pumping field to couple the middle level of two- photon absorption with the fourth level. Two-photon absorption minimum was observed. This is the first observation and experimental analysis of such phenomenon after it was predicted four years ago. In sodium vapor, two-photon absorption strength of 3S1/2(Fequals2)-3P3/2-4D3/2 was measured by detecting the fluorescence at 568.3 nm (4D3/2-3P1/2). Levels 3P3/2 and 5S1/2 were connected by pumping field. Experimental data of two-photon absorption strength vs detuning from middle level (TADM) shows that the two-photon absorption was reduced by 60% at line center in the presence of resonant pumping field. In rubidium vapor, two-photon absorption of 5S1/2(Fequals3)-5P3/2-8S1/2(Fequals3) was measured by detecting the fluorescence at 607 nm (8S1/2-5P1/2). Levels 5P3/2 and 5D5/2(Fequals5) were connected by pumping field. The TADM profiles under different experimental condition indicate that the maximum reduction of two-photon absorption can be 80%. And the reduction effect reduced with lower strength, higher detuning frequency and wider line width of pumping field. At the same time, the position of minimum absorption depends on the detuning of pumping field. All the experimental profiles were fitted well with theoretical calculation results.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.