Unintended filtering in a typical photodiode detection system for optical tweezers
Unintended filtering in a typical photodiode detection system for optical tweezers
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DOI：
10.1063/1.1554755
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发表时间：
2003-03-15
影响因子：
3.2
通讯作者：
Flyvbjerg, H
中科院分区：
文献类型：
--
作者：
Berg-Sorensen, K;Oddershede, L;Flyvbjerg, H
我们描述了基于Si-PIN光电二极管和波长1064 nm激光器的光检测系统的频率相关响应，该系统通常与光镊一起使用。我们在斩波频率为200hz ~ 14khz的范围内对激光束进行斩波，发现探测系统的响应呈指数级延迟，特征延迟时间约为20 μ s。造成这种时间延迟的物理机制是硅对1064nm光的透明度：光子被吸收并产生载流子，不仅在二极管的耗尽层中，它们在纳秒内被检测到，而且主要在n层中，它们在通过热扩散传输出去之前一直未被检测到。二极管的响应由该延迟主导，该延迟可以表征为一阶低通滤波器，其3db频率为8- 9khz，具体取决于激光强度。测量频率接近或高于这个3db频率，必须对这种意外的滤波器效应进行校正。我们描述了如何做到这一点，以及如何诊断可能存在或不存在相同问题的其他系统。解释是为光检测系统的用户准备的，并提供了一些需要理解的半导体物理。(C) 2003年美国物理研究所。
We characterize the frequency-dependent response of a photo detection system based on a Si-PIN photodiode and a laser with wavelength 1064 nm, a system commonly used with optical tweezers. We chopped the laser beam with chopper frequencies from 200 Hz to 14 kHz, and found an exponentially delayed response of the detection system with a characteristic delay time of similar to20 mus. The physical mechanism causing this time delay is silicon's transparency to 1064 nm light: Photons are absorbed and create charge carriers not only in the diode's depletion layer, where they are detected within nano-seconds, but predominantly in the n-layer, where they remain undetected till transported out by thermal diffusion. The diode's response is dominated by this delay which can be characterized as a first-order low-pass filter with a 3dB-frequency of 8-9 kHz, depending on laser intensity. Measurements exploiting frequencies near or above this 3dB-frequency must be corrected for this unintended filter effect. We describe how to do this, and how to diagnose other systems which may or may not have the same problem. Explanations are intended for users of photo detection systems, and present the little semi-conductor physics needed to make sense. (C) 2003 American Institute of Physics.