空间散斑场捕获大量吸光性颗粒及其红外显微观测

光镊技术被广泛应用于捕获和操纵微纳米尺寸颗粒,主要包括捕获水中透明性颗粒和空气中吸光性颗粒两种类型.本文用激光束照射毛玻璃散射片,透射光经透镜会聚后在透镜的像平面附近产生了主观散斑场.该散斑场为空间分布,包含大量的亮斑和暗斑.大量由亮斑包围的暗斑如同一个个空间能量陷阱,被用来捕获大量的吸光性墨粉颗粒,被捕获颗粒的尺寸约2—8μm,密度约1—2 g/cm3.采用红外显微镜拍摄到空间散斑场捕获颗粒的红外像,红外图像显示被捕获颗粒吸光后温度升高,证实了空间散斑场捕获吸光性颗粒的机理为光泳力原理.

Trapping of multiple particles by space speckle field and infrared microscopy

Optical tweezer technology is widely used in trapping and manipulating micro-and nano-sized particles, mainly including the trapping of transparent particles in water and the trapping of absorbing particles in air. In this paper, a frosted glass diffuser is irradiated by laser beam, and a subjective speckle field is generated in the image plane of a lens after the laser has transmitted the lens. The speckle field is spatially distributed, and contains multiple bright spots and dark spots. A large number of dark spots surrounded by bright spots are spatial energy traps, and can be used to trap a large number of absorbing particles. The sizes and densities of trapped particles are about 2–8 μm and 1–2 g/cm³. In addition, an infrared microscope is used to record the infrared images of the particles trapped by the speckle field, and the infrared images show that the temperature of trapped particles rises by absorbing the light energy, which verifies that the mechanism of trapping absorbing particles by speckle field is photophoretic force.