标题: | 飞秒及连续波雷射对于微米至次微米粒子之光学捕捉刚度的研究 Optical trapping stiffness investigation of micro- to submicro-meter sphere with femtosecond and CW lasers |
作者: | 吴峻升 增原 宏 应用化学系硕博士班 |
关键字: | 飞秒雷射;连续波雷射;光学捕捉;光学捕捉刚度;femtosecond laser;continous wave laser;optical trapping;optical trapping stiffness |
公开日期: | 2014 |
摘要: | 飞秒脉冲雷射在光学捕捉技术中的应用近来已经受到广泛的注意,我们分别对飞秒脉冲雷射捕捉以及连续波脉冲雷射捕捉进行捕捉刚度的测量,并且藉由两者间刚度的比较,我们希望能对飞秒脉冲雷射捕捉有更深入的认识。在本研究中,单一微米至次微米之二氧化矽粒子被用来做为光学捕捉研究的目标,并分别利用非秒脉冲雷射及连续波雷射进行捕捉。藉由位置感测器纪录被捕捉粒子于捕捉期间的热扰动,我们测量了雷射功率介于0-40 mW间的捕捉刚度。微米粒子在连续波雷射捕捉中的结果显示线性的功率相依性,这与我们的预测以及文献资料相符,并且证明测量系统及方法的可靠性。藉此,我们进一步进行飞秒脉冲雷射捕捉以及连续波脉冲雷射捕捉的比较,对于1和0.5微米粒子而言,两者均在飞秒脉冲雷射捕捉中有更高的捕捉刚度。我们认为这可能是由于高瞬时强度的脉冲所导致,而尽管飞秒脉冲雷射在脉冲间有时间间隔,但如此短暂的间隔可能没有对光学捕捉或是对被捕捉粒子之热扰动造成足够的影响。本研究是我们第一次架设光学捕捉刚度测量系统并进行可靠的测量,而研究成果亦可作为日后其他光学捕捉实验的参考。 Optical trapping utilizing femtosecond laser has received much attention recently. We propose to use a classic method for measuring the trapping stiffness in femtosecond and continuous-wave laser trapping. By comparing the measurement results, we prompt a deeper understanding of femtosecond laser trapping. Therefore, a single silica sphere with a size of one micron or half micron was set to be trapped by femtosecond laser and continuous-wave laser separately. With a position sensing device that records the thermal fluctuation of a trapped silica sphere, the trapping stiffness was investigated in a power range from 0 to 40 mW. The result of a micron silica sphere trapped by continues-wave laser showed a linear power dependency, which is consistent with our expectation and references. Hence, it can be regarded as evidence of the reliability of our measurement. Results of both micron and half micron silica spheres showed higher trapping efficiency for femtosecond laser trapping in this power regime. We deduce that the high intensity pulses, nonlinear optical effects, and temporal force may contribute to this difference. Although there is a relaxation time between pulses, it is too short to cause the significant change in sphere position. As a conclusion, we have constructed a trapping stiffness measuring system for the first time in our group, and reliability of the measurement has been checked experimentally. Also we have made a comparison between femtosecond laser trapping and continuous-wave laser trapping. This comparison can be used for standard reference information in the research of optical trapping. |
URI: | http://140.113.39.130/cdrfb3/record/nctu/#GT070152554 http://hdl.handle.net/11536/125621 |
显示于类别: | Thesis |