Thresholdless coherence in a superradiant laser  

作　　者：Seung-Hoon Oh Jinuk Kim Junseo Ha Gibeom Son Kyungwon An 

机构地区：[1]Department of Physics and Astronomy&Institute of Applied Physics,Seoul National University,Seoul,Korea [2]Korea Research Institute of Standards and Science,Daejeon,Korea

出　　处：《Light(Science & Applications)》2024年第11期2549-2555,共7页光（科学与应用)（英文版）

基　　金：supported by the Korea Research Foundation(Grant No.2020R1A2C3009299).

摘　　要：Lasing threshold in the conventional lasers is the minimum input power required to initiate laser oscillation.It has been widely accepted that the conventional laser threshold occurring around a unity intracavity photon number can be eliminated in the input-output curve by making the so-calledβparameter approach unity.The recent experiments,however,have revealed that even in this case the photon statistics still undergo a transition from coherent to thermal statistics when the intracavity mean photon number is decreased below unity.Since the coherent output is only available above the diminished threshold,the long-sought promise of thresholdless lasers to produce always coherent light has become questionable.Here,we present an always-coherent thresholdless laser based on superradiance by two-level atoms in a quantum superposition state with the same phase traversing a high-Q cavity.Superradiant lasing was observed without the conventional lasing threshold around the unity photon number and the photon statistics remained near coherent even below it.The coherence was improved by reducing the coupling constant as well as the excited-state amplitude in the superposition state.Our results pave a way toward always-coherent thresholdless lasers with more practical media such as quantum dots,nitrogen-vacancy centers and doped ions in crystals.

关 键 词：LASER COHERENT LASING 

分 类 号：TN248[电子电信—物理电子学]