Population inversion in fluorescing fragments of super-excited molecules inside an air filament  

作　　者：See-Leang Chin 徐淮良 

机构地区：[1]Department of Physics, Engineering Physics and Optics & Center for Optics, Photonics and Laser (COPL),Laval University, Quebec, QC, G1V 0A6, Canada [2]State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering,Jilin University

出　　处：《Chinese Physics B》2015年第1期36-42,共7页中国物理B（英文版）

基　　金：Project supported by the Canada Research Chairs,the Natural Science and Engineering Research Council of Canada(NSERC),the FRQNT,the Canada Foundation for Innovation(CFI),the National Basic Research Program of China(Grant No.2014CB921300);the National Natural Science Foundation of China(Grant No.61235003);the Research Fund for the Doctoral Program of Higher Education of China;the Scientific Research Foundation for Returned Scholars,Ministry of Education of China

摘　　要：An original idea is reviewed. When a molecule is pumped into a super-excited state, one of its decay channels is neutral dissociation. One or more of the neutral fragments will fluoresce. Hence, if a lower state of such fluorescing fragments was populated through other channels but with a lower probability, population inversion of the fluorescing fragments would be naturally realized. This idea seems to be validated, so far, by comparing published work on three hydrocarbon molecules, CH4, C2H2, C2H4, and water vapor, H2 O. After super-excitation in a femtosecond laser filament in air mixed with these molecules, the fluorescence from the CH or OH fragments exhibits population inversion, i.e., amplified spontaneous emission was observed in the backscattering direction of the filament.An original idea is reviewed. When a molecule is pumped into a super-excited state, one of its decay channels is neutral dissociation. One or more of the neutral fragments will fluoresce. Hence, if a lower state of such fluorescing fragments was populated through other channels but with a lower probability, population inversion of the fluorescing fragments would be naturally realized. This idea seems to be validated, so far, by comparing published work on three hydrocarbon molecules, CH4, C2H2, C2H4, and water vapor, H2 O. After super-excitation in a femtosecond laser filament in air mixed with these molecules, the fluorescence from the CH or OH fragments exhibits population inversion, i.e., amplified spontaneous emission was observed in the backscattering direction of the filament.

关 键 词：femtosecond filament LASING super-excited states 

分 类 号：O437[机械工程—光学工程]