Study On Energy Pooling And Photoionization Processes In Rb DPAL

With the advantages of both solid and gas laser, DPAL has the potential ofbecoming high power laser. However, during the actual operation of DPAL, the alkalimetal atoms with energy levels ofnP1/2andnP3/2may be excited to higher energylevels or ionization state by energy pooling and photoionization process. With thefurther scaling of DPAL, the influence degree of these effects comes into researcher’sconcern.In this paper, the theoretical and experimental research is made taking energypooling and photoionization of rubidium DPAL as the research objects. The maincontents are as follows:1. This paper establishes the end-pumped rubidium DPAL rate equation modelbased on energy pooling of energy level5D3/2and5D5/2and discusses the influenceof energy pooling on rubidium atom concentration of different energy level, laseremission intensity, heat, fluorescence, scattering and the pumping absorption rate underdifferent pumping intensity and different temperature conditions. It also analyzes thedeficiencies of the model and the differences to the actual situation.2. Qualitative experimental study is given to the energy pooling andphotoexcitation processes. The pump light of780.2nm and780.2+776nm is usedrespectively to excite rubidium atoms and420nm blue fluorescence which is generatedby energy pooling and photoexcitation is observed at170℃and110℃, proving theexistence of5D rubidium atoms in rubidium DPAL.3. With rubidium hollow cathode lamp as measuring device, kinetics process in theconstant electric field is studied though optogalvanic method and the issue that it isdifficult to measure the ionization degree in confined rubidium vapor cell is solved. Theinfluence of pump light intensity, bias voltage and rubidium atom concentration on theoptogalvanic signal is discussed as well. The calculated rubidium ion concentration is1.5×105~106/cm3according to experiment and the ionization degree is less than2.4×10-7. It is demonstrated that weak plasma was formed.