Jiao Jiannan, Zhou Donglei, Li Shufan, Low Mun Ji, Gao Yi, An Jianing, Su Pei-Chen, Kim Seung-Woo, Kim Seungchul, Kim Kyujung, Suchand Sandeep C S, Kim Young-Jin
Singapore Centre for 3D Printing, School of Mechanical and Aerospace Engineering, Nanyang Technological University (NTU), 50 Nanyang Avenue, 639798, Singapore.
Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Science Town, Daejeon, 34141, South Korea.
Nanoscale. 2021 Jan 21;13(2):878-885. doi: 10.1039/d0nr06232d.
We demonstrate a high repetition-rate upconversion green pulsed micro-laser, which is prepared by the fast thermal quenching of lanthanide-doped upconversion nanoparticles (UCNPs) via femtosecond-laser direct writing. The outer rim of the prepared upconversion hemi-ellipsoidal microstructure works as a whispering-gallery-mode (WGM) optical resonator for the coherent photon build-up of third-harmonic ultra-short seed pulses. When near-infrared (NIR) femtosecond laser pulses of wavelength 1545 nm are focused onto the upconversion WGM resonator, the optical third-harmonic is generated at 515 nm together with the upconversion luminescence. The weak third-harmonic (TH) seed pulses are coherently amplified in the hemi-ellipsoidal upconversion resonator as a result of the resonant interaction between the incident femtosecond laser field, the TH, the upconversion luminescence and the WGM. This upconversion lasing preserves the original repetition rate of the NIR pump laser and the output polarization state is also coherently aligned to the pump laser polarization. Because of the isotropic nature of the upconversion micro-ellipsoids, the upconversion lasing shows maximum intensity with a linearly polarized pump beam and minimum intensity with a circularly polarized pump beam. Our scheme devised for realizing high-repetition-rate lasing at higher photon energies in a compact micro platform will open up new ways for on-chip optical information processing, high-throughput microfluidic sensing, and localized micro light sources for optical memories.
我们展示了一种高重复率上转换绿色脉冲微激光器，它是通过飞秒激光直写对镧系掺杂上转换纳米颗粒（UCNPs）进行快速热猝灭制备而成。所制备的上转换半椭球形微结构的外缘充当回音壁模式（WGM）光学谐振器，用于第三谐波超短种子脉冲的相干光子积累。当波长为1545 nm的近红外（NIR）飞秒激光脉冲聚焦到上转换WGM谐振器上时，在515 nm处产生光学第三谐波以及上转换发光。由于入射飞秒激光场、第三谐波、上转换发光和WGM之间的共振相互作用，微弱的第三谐波（TH）种子脉冲在半椭球形上转换谐振器中被相干放大。这种上转换激光保持了近红外泵浦激光的原始重复率，并且输出偏振态也与泵浦激光偏振相干对齐。由于上转换微椭球体的各向同性，上转换激光在泵浦光束为线偏振时显示出最大强度，在泵浦光束为圆偏振时显示出最小强度。我们设计的用于在紧凑的微平台中实现更高光子能量下的高重复率激光的方案，将为片上光学信息处理、高通量微流体传感以及用于光学存储器的局部微光源开辟新途径。
