Development of Laser Microsensors for Monitoring of Local Environment

已知诸如液滴、聚合物颗粒等的微粒能够充当用于发射发光染料的激光的光学腔，其中发光正好在颗粒表面内部周向传播。我们最近观察到粒子中的激光通过倏逝场泄漏到位置较近的粒子;光子从激光到非激光粒子的隧穿。这一事实表明，激光微粒可以用于微传感器通过监测发射光谱和强度。为了将激光粒子作为微传感器应用于局部环境监测，需要对激光粒子进行精确的定位控制和操纵。在众多的操纵技术中，激光操纵是实现微粒非接触、非破坏性定位控制的最有潜力的方法之一。在本研究计划中，我们尝试了在水溶液中对椭球形的罗丹明B（RhB）掺杂的聚甲基丙烯酸甲酯（PMMA）乳胶粒子同时进行三维光学操纵和激光发射，观察了光阱下椭球形RhB-PMMA乳胶粒子在水溶液中的发射光谱。粒子激光发射峰的波长强烈依赖于泵浦光在粒子上的聚焦位置，这与球形粒子的激光发射行为相反。这意味着粒子的共振波长随粒子的位置而变化。此外，我们还利用激光扫描操纵技术研究了激光粒子和非激光粒子之间的光子隧穿。这些事实表明，同时激光捕获和激光个别椭球微粒提供了多功能的微传感器监测当地环境。

Microparticles such as liquid droplets, polymer particles and so forth are known to be able to act as an optical cavity for lasing of a luminescent dye where the luminescence propagates circumferentially just inside of the surface of the particle. We recently observed lasing light in the particle leak to the closely-positioned particle through the evanescent field ; photon tunneling from the lasing to nonlasing particles. This fact suggests that lasing microparticles can be utilized for a microsensor by monitoring the emission spectrum and intensity. To apply the lasing particles as microsensors for monitoring of local environment, precise positioning control and manipulation of the particles are necessary. Among various manipulation techniques, laser manipulation is one of the potential candidates for noncontact and nondestructive positioning control of microparticles. In this research project, we attempted that simultaneous three-dimensional optical manipulation and lasing of ellipsoidal-shaped, rhodamine B (RhB)-doped poly (methyl methacrylate) (PMMA) latex particles in water.Emission spectra from an optically-trapped ellipsoidal RhB-PMMA particle in water were observed. The wavelength of laser emission peaks from the particle strongly depended on th position of focused pumping laser on the particle, and it was contrary to the behavior of spherical lasing particle. This means that the resonant wavelength of the particle varies with the position of the particle. Furthermore, we demonstrated photon tunneling between the lasing and nonlasing particles on the basis of the laser scanning manipulation technique. These facts indicate that simultaneous laser trapping and lasing of individual ellipsoidal microparticles provide versatile microsensors for monitoring local environment.