Development And Application Of Low-noise Ultrafast Pump-probe System Based On LabVIEW

Ultrafast pump-probe system can distinguish process of change at femtosecond time resolution, it has important applications in various fields, such as physics,biology, chemistry, biology, medicine and so on. Doing ultrafast pump-probe experiments need to change the optical path difference of the pump light and the probe light for hundreds of times, and need to record the power of probe light each time. Cumbersome data recording and monotonous optical path difference controlling is difficult to carry out by manual labor. Automatic controlling of low-noise pump-probe system is the key to its application.In addition, the light source of ultrafast pump-probe system is typically with large jitter, which makes the test result poor signal to noise ratio. It is also the key to ultrafast pump-probe system to obtain a high signal to noise ratio. This thesis focuses on how to design and build a low-noise ultrafast pump-probe automation control systems. It has developed a ultrafast pump-probe test system based on Lab VIEW, and combined with lock-in amplifier studied its SNR characteristics.The paper's main work includes two aspects.First, we have designed an automatic control software based on lab VIEW virtual instrument platform, which controls instruments in the system via RS232 and GPIB protocol. This software enables automatic control and data collection. It also paints graph with measured data, which provides a useful reference for the experimenter.Second, we used a lock-in amplifier to reduce noise. In ultrafast pump-probe system, an optical chopper is used to modulate the laser to a specific frequency, and the output of the chopper signal is used as a reference signal to the lock-in amplifier,then the lock-in amplifier only detects the ingredients of the test signal the same frequency to reference signal, so that the other frequency components of the test signal are subjected to substantially reduce. Compared with using a power meter,the variance have reduced from 0.0001 to 0.000006. Using the pump-probe system to test the ultrafast dynamics of CS2, it proved that the method is effective...