基于LabVIEW的低噪声超快泵浦-探测系统开发及应用

发布时间：2018-10-25 11:34

【摘要】：超快泵浦-探测系统可以在飞秒时间量级分辨事物的变化过程,在物理、生物、化学和医学等各个领域均有重要的应用。超快泵浦-探测实验需上百次的改变泵浦光与探测光之间的光程差,且需记录对应光程差探测光的功率。繁琐的数据记录和光程差控制难于手动完成因此,自动化控制系统是其应用的关键。此外,超快泵浦-探测系统使用的激光源通常抖动较大,这导致测试结果的信噪比较低。如何获得高信噪比的探测信号也是泵浦-探测的关键技术。本论文围绕设计和搭建低噪声超快泵浦-探测自动化控制系统开展工作,基于Lab VIEW开发了超快泵浦-探测自动测量系统,并结合锁相放大器研究了其信噪比特性。论文主要工作包括:(1)基于Lab VIEW虚拟仪器开发平台,设计了超快泵浦-探测自动化控制软件。该软件通过RS232与GPIB协议控制测量系统中仪器,实现了系统的自动化控制与数据的自动化采集。并且,自动化控制软件可以将测量数据实时作图,简少了泵浦-探测实验系统的工作量。(2)结合光学斩波器和锁相放大器,实验搭建了低噪声的超快泵浦-探测系统。在超快泵浦-探测系统中,使用斩波器将激光调制成特定的频率。将斩波器输出的信号做为参考信号输入至锁相放大器,锁相放大器只检测被测信号中与参考信号频率相同的成分,其它频率的成分则受到大幅度抑制。若直接使用功率计测量激光功率,其方差为0.0001;使用锁相放大器测量,当积分时间常数设置为3 s时,测量方差为0.000006。通过超快泵浦-探测系统测试二硫化碳的超快动力学特性,验证了该降噪方法的有效性。
[Abstract]:Ultra-fast pump-detection system can distinguish the change process of things in femtosecond order of magnitude. It has important applications in physics, biology, chemistry and medicine. It is necessary to change the optical path difference between the pump light and the probe light hundreds of times in the ultra-fast pumping-detection experiment and to record the power of the detection light corresponding to the optical path difference. Tedious data recording and optical path difference control are difficult to be accomplished manually. Therefore, automatic control system is the key to its application. In addition, the laser source used in the ultra-fast pump-probe system is usually jitter, which results in a low SNR of the measured results. How to obtain high SNR detection signal is also the key technology of pump-detection. This paper focuses on the design and construction of a low-noise ultra-fast pump-probe automatic control system. Based on Lab VIEW, the ultra-fast pump-probe automatic measurement system is developed, and the signal-to-noise ratio (SNR) characteristics of the system are studied in combination with the phase-locked amplifier. The main work of this paper is as follows: (1) based on the Lab VIEW virtual instrument development platform, an automatic control software for ultra-fast pumping and detection is designed. The software realizes the automatic control of the system and the automatic collection of data by means of the RS232 and GPIB protocol to control the instrument in the measuring system. Moreover, the automatic control software can map the measurement data in real time, which reduces the workload of the pump-detection experiment system. (2) combining the optical chopper and the phase-locked amplifier, a low-noise ultra-fast pump-detection system is built. In an ultra-fast pump-probe system, a chopper is used to modulate the laser to a specific frequency. The chopper output signal is input to the phase-locked amplifier as the reference signal. The phase-locked amplifier only detects the same component of the measured signal as the reference signal frequency, while the other frequency components are greatly suppressed. If the laser power is measured directly by the power meter, the variance is 0.0001, and when the integral time constant is set to 3 s, the variance is 0.000006 when the phase-locked amplifier is used to measure the laser power. The effectiveness of the proposed noise reduction method is verified by testing the ultra-fast kinetic characteristics of carbon disulfide by ultra-fast pump detection system.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TP311.52;TN722;TN24

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