Tunable infrared structured laser generation and opto-thermal trapping of micro/nano particles
Abstract
This talk covers the experimental research and theoretical investigation of mid-infrared tunable optical vortex sources with versatile orbital angular momentum (OAM) and opto-thermophoretic trapping of micro and nano particles with mid-infrared fiber lasers. As a typical structured light, optical vortex with a helical wavefront exhibits interesting physical properties, including an annular spatial intensity profile and an OAM of owing to an on-axial phase singularity. Such properties of the vortex beam have been widely utilized in diverse applications. In the talk, Dr. Mamuti presents generation of optical vortices with versatile OAM states from a nanosecond optical parametric oscillator (OPO) by appropriately shortening or extending the cavity. The system with a compact cavity configuration enables the production of a millijoule-level signal (idler) output with l =1~3 (0~-2) simply by tuning the wavelength of signal output. The system was further developed to create coherently coupled OAM states, i.e., flower-shaped signal and wheel-shaped idler outputs, arising from the coherent superposition of opposite-signed OAM states.
Furthermore, Dr. Mamuti proposed a method for opto-thermophoretic trapping with a 2 μm Tm-doped fiber laser. The infrared continuous-wave laser beam is directly and strongly absorbed by water solution, and some local temperature gradient is generated around the focus. The particles are migrated along the temperature gradient and form a hexagonal close-packed structure at a bottom-glass solution interface. She has investigated the dependence of the phenomenon on the material, particle size, and laser power. Since the water molecules have a significant absorption in the 3-μm wavelength band, a midinfrared Er:ZBLAN tunable fiber laser is applied for opto-thermophoretic trapping of particles diffusing in water. Through the laser wavelength dependence and single particle tracking analysis, they found that particles are rapidly collected at the laser focus which is much faster than near infrared lasers. The system with 2 μm and 3 μm direct optothermal trapping could be extended in various fields, such as bio sensing, detection, and sorting.
Biography
Dr. Roukuya Mamuti received her Master’s and Ph.D. degrees in Optical Engineering from laser laboratory, Chiba University, Japan. Her graduate research mainly focused on the generation of tunable infrared structured lasers. After graduation, she worked as a postdoctoral researcher at Laser Lab (the same lab where she earned her degree). Dr. Mamuti received 2 million Japanese yen of research grant from Kambayashi foundation (private funding). Later, she worked in the Laser Science Laboratory at Toyota Technological Institute, to develop optical trapping of micro/nano particles. Now, she is seeking a research position to pursue her profession in laser-related research fields.
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