Optimization Of Terahertz Time Domain System And Control Program Design

Terahertz wave is a kind of electromagnetic wave which frequency between0.1~10THz and wavelength between infrared and microwave with the twoaspects characteristics of optoelectronics and electromagnetism, which widelyexists in the nature.Terahertz time-domain spectroscopy is a kind of phasecoherence technique of electromagnetic radiation, which can also get theamplitude and phase information of terahertz pulse. Therefore, Terahertz time-domain spectroscopy has the very high resolution of time domain and frequencydomain, which can also achieve very high signal-to-noise ratio and widebandwidth, so it can be widely used in many kinds of sample characteristicspectrum detection. With the development of terahertz spectrum instruments athome and abroad and country attaching great importance to development ofscientific instruments, developing terahertz time-domain spectrometer withindependent intellectual property rights is of great significance in improvingapplication of terahertz science and technology. Practical type, miniaturization,high performance is the research and development direction of terahertz time-domain spectrometer. Combining with the characteristics of laboratory Terahertztime-domain spectroscopy system, the article has carried on the miniaturizationwork of laboratory system device with practical guiding direction and made in-depth research on improving the measurement speed of the overall system. Thissystem can also be used to achieve the application of scanning imagingtechnology.With small fiber femtosecond laser instead of titanium gem solid laser, LIA-MV-150modular locked-in amplifier instead of SR830locked-in amplifier andusing NI9215analog signal acquisition card to collect analog signals of locked-inamplifier. We have changed the laboratory original terahertz optical path withindependent desiged light path, which made the emission module, optical delay module and detection module of terahertz redistribute to save a lot of spacethrough concentrated distribution of optical element and compact structure ofoptical path.Compiling a set of program system is applied to the the miniaturization ofterahertz time-domain spectroscopy, which complete system control and dataacquisition of the entire platform. We have written acquisition program of analogsignal and increased the function of sampling rate, which can change thesampling rate of analog signal.Through the function of calling CIF node in LabVIEW to call the functionsin the MC.DLL file of PCI card driver, we can obtain actual location of thestepper moving platform. This way can eliminate the error to get more accuratedelay time.Setting up time constant and appropriate sampling rate to obtain the bestpossible signal quality, which provides reference to improve the measurementspeed of terahertz time-domain spectrometer and we have designed the controlprogram of scanning imaging system, the system has the functions of datacollection, graphic display.