采用超连续谱激光的双光束光纤光阱实验

Double-beam fiber optical trap experiments based on supercontinuum laser

以超连续谱激光器作为捕获光源,首次提出并搭建了超连续谱双光束光纤光阱实验系统,实现了聚苯乙烯微球的捕获和操控。通过改变光纤端面间隔和调整捕获光功率的方式精确控制微球的位置,采用CCD图像分析方法实现了微球位置的精确测量。对微球受限布朗运动下的位置变化进行傅里叶变换,计算得到功率谱,与理论功率谱函数拟合后求出了其光阱刚度。结果表明,捕获光束的功率为28 mW时,光阱刚度达到1.3×10-6N/m,高于相同实验条件下单波长光纤光阱的刚度。与传统采用单色光作为捕获光源的光镊系统不同,超连续谱双光束光阱系统利用其宽谱优势,通过研究被捕获微粒的散射光谱信息可获取其尺寸、折射率等物理特征参数。

The experimental system of dual-beam fiber optical trap is proposed and built for the first time which can realize the trapping and manipulation of polystyrene microspheres by taking the supercontinuum laser as the trapping light source. The position of the microsphere is manipulated by changing the relative position of the two optical fiber end faces and output power of the fibers. The CCD image analysis method is used to measure the position of the microsphere. The power spectrum is calculated by Fourier transform of the position variation of the confined Brown motion. After fitting the theoretical power spectrum function, the optical trap stiffness is obtained. The results show that when the power of the captured beam is 28 mW, the optical trap stiffness can reach 1.3 × 10-6 N/m, which is higher than that of the single wavelength optical trap under the same experimental conditions. By taking advantage of the wide spectrum of the dual-beam optical trap system, the physical parameters such as the size and refractive index can be obtained by studying the scatteringspectrum information of the captured particles which is different from the traditional use of monochromatic light as the captured light of the optical tweezers.