激光3D纳米打印温度敏感的微球激光器

Femtosecond laser 3D printing temperature sensitive microsphere lasers

耳语回廊模式(WGM)微腔具有品质因子高、模式体积小、制作工艺简单多样、同时对周围环境敏感性极高等优点,已被广泛应用于传感和检测.然而,真正的尺寸可控的三维微腔却少有报道.本文报道了一种有源回音壁模式微球腔,由商业光刻胶 SU-8 作为腔体材料,有机染料罗丹明 B 作为增益介质.利用飞秒激光双光子聚合,可以得到尺寸精确可控的真三维微球激光器.同时,由于有机染料的特殊发光机理,随着环境温度的变化,染料荧光带飘移,且会与腔体本征模式形成新的共振激发.在一定温度变化范围内(20 ℃- 35 ℃),微球激光器的主激射峰波长与温度呈类线性相关.研究结果对合理设计具有理想性能的小型化激光器具有积极的启发.

The whispering gallery mode (WGM) microcavity has been widely used for sensing and detection because of its high quality factor, small mode size, simple and diverse manufacturing process, and high sensitivity to the surrounding environment. Microsphere cavityand microdisk cavity are typical whispering gallery mode microcavities. However, the real controllable size of the on-chip three-dimensional microsphere cavity has rarely been reported because it is difficult to prepare by photolithography. At the same time, most of the current microsphere cavity are prepared by hot melting, which have the poor ability to control the size. In this article, we have mainly demonstrated the fabrication of a dye-doped polymer whispering gallery mode microsphere by femtosecond laser two-photon polymerization, which shows good surface smoothness with a fabrication spatial resolution beyond the diffraction limit. The microsphere cavity consists with commercial photoresist SU-8 as the cavity material and Rhodamine B as the gain medium. With the 532 nm pump, the RhB-doped SU-8 can emit fluorescence in the spectral range of 600 –700 nm, and thus resonant whispering gallery laser modes in this spectral region can be eventually formed in the microsphere cavities. The microcavity shows excellent lasing performance with a quality factor of ~2000. Due to the special luminescence mechanism of organic dyes, the fluorescence spectrum of the dye drifts with the change of ambient temperature, and it will form a new resonance excitation with the eigenmode of the cavity. Within a certain temperature range (20 ℃-35 ℃), the wavelength of the main lasing peak is linearly related to temperature. The results shows that the organic dye doped micro-resonator has a unique laser mechanism which can be used to construct a new type of microlaser. Moreover, the tunable microsphere laser can be used as a temperature sensor after further optimized. We believe our work will provide a positive inspiration for the rational design of miniaturized lasers with ideal performance.