population inversion
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2021 ◽  
Vol 104 (3) ◽  
Author(s):  
Siqi Wang ◽  
Erik Lötstedt ◽  
Jincheng Cao ◽  
Yao Fu ◽  
Hongwei Zang ◽  
...  

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Byeong-Seok Moon ◽  
Tae Kyung Lee ◽  
Woo Cheol Jeon ◽  
Sang Kyu Kwak ◽  
Young-Jin Kim ◽  
...  

AbstractMicroscale lasers efficiently deliver coherent photons into small volumes for intracellular biosensors and all-photonic microprocessors. Such technologies have given rise to a compelling pursuit of ever-smaller and ever-more-efficient microlasers. Upconversion microlasers have great potential owing to their large anti-Stokes shifts but have lagged behind other microlasers due to their high pump power requirement for population inversion of multiphoton-excited states. Here, we demonstrate continuous-wave upconversion lasing at an ultralow lasing threshold (4.7 W cm−2) by adopting monolithic whispering-gallery-mode microspheres synthesized by laser-induced liquefaction of upconversion nanoparticles and subsequent rapid quenching (“liquid-quenching”). Liquid-quenching completely integrates upconversion nanoparticles to provide high pump-to-gain interaction with low intracavity losses for efficient lasing. Atomic-scale disorder in the liquid-quenched host matrix suppresses phonon-assisted energy back transfer to achieve efficient population inversion. Narrow laser lines were spectrally tuned by up to 3.56 nm by injection pump power and operation temperature adjustments. Our low-threshold, wavelength-tunable, and continuous-wave upconversion microlaser with a narrow linewidth represents the anti-Stokes-shift microlaser that is competitive against state-of-the-art Stokes-shift microlasers, which paves the way for high-resolution atomic spectroscopy, biomedical quantitative phase imaging, and high-speed optical communication via wavelength-division-multiplexing.


2021 ◽  
Vol 118 (22) ◽  
pp. 224003
Author(s):  
Zhikun Han ◽  
Yuqian Dong ◽  
Xiaopei Yang ◽  
Shuqing Song ◽  
Luqing Qiu ◽  
...  

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