Zhi-Gang ZHANG, Feng-Rui LIU, Qing-Chuan ZHANG, Teng CHENG, and Xiao-Ping WU
Optical tweezers technology is widely used in trapping and manipulating micro-and nano-sized particles, mainly including trapping of transparency particles in water and 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 transmitting the lens. The speckle field is spatial 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 quantity of absorbing particles. The size and density of trapped particles are about 2~8μm and 1~2g/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 rise by absorbing the light energy, which verifies that the mechanism of trapping absorbing particles by speckle field is photophoretic force.
DOI
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