Friese M E, Rubinsztein-Dunlop H, Heckenberg N R, Dearden E W
Appl Opt. 1996 Dec 20;35(36):7112-6. doi: 10.1364/AO.35.007112.
A single-beam gradient trap could potentially be used to hold a stylus for scanning force microscopy. With a view to development of this technique, we modeled the optical trap as a harmonic oscillator and therefore characterized it by its force constant. We measured force constants and resonant frequencies for 1-4-μm-diameter polystyrene spheres in a single-beam gradient trap using measurements of backscattered light. Force constants were determined with both Gaussian and doughnut laser modes, with powers of 3 and 1 mW, respectively. Typical values for spring constants were measured to be between 10(-6) and 4 × 10(-6) N/m. The resonant frequencies of trapped particles were measured to be between 1 and 10 kHz, and the rms amplitudes of oscillations were estimated to be around 40 nm. Our results confirm that the use of the doughnut mode for single-beam trapping is more efficient in the axial direction.
单光束梯度阱有可能用于固定用于扫描力显微镜的探针。为了开发这项技术，我们将光阱建模为一个简谐振子，因此用其力常数对其进行表征。我们使用背向散射光测量，在单光束梯度阱中测量了直径为1 - 4μm的聚苯乙烯球体的力常数和共振频率。分别在功率为3 mW和1 mW的高斯激光模式和甜甜圈激光模式下测定力常数。测得的弹簧常数典型值在10^(-6)至4×10^(-6) N/m之间。测得被捕获粒子的共振频率在1至10 kHz之间，振荡的均方根振幅估计约为40 nm。我们的结果证实，在单光束捕获中使用甜甜圈模式在轴向方向上更有效。
