Development Of Ultrashort Pulse Width Measurement System Based On LabVIEW

In recent years,ultra-short pulse lasers have been well applied and developed in the fields of biomedicine,precision processing,materials chemical engineering and communications.In terms of ultra-fast processing technology,the use of ultra-short light pulses with high peak power to process materials can be effectively reduce the thermal accumulation effect of materials and improve the efficiency of cutting and punching.Because the pulse width of the ultrashort pulse plays a decisive role in the performance of the entire laser,and the development of femtosecond lasers also has clear technical parameter requirements for the pulse width of the laser,so the research and development of the ultrashort pulse width measurement system has important scientific research and practical application value.In this thesis,an autocorrelation device for measuring femtosecond laser pulse width was built based on the principle of non-collinear second harmonic autocorrelation,and a pulse width measurement program was written using LabVIEW software to realize online analysis and processing of measurement data and real-time display of laser pulse width,achieving the purpose of real-time monitoring of the status of femtosecond laser.Based on the analysis of the research progress of ultrashort pulse and the current status of ultrashort pulse width measurement technology at home and abroad,a non-collinear autocorrelation method based on virtual instrument technology platform was proposed,and the theory and experimental model of ultrafast pulse width measurement system were established.According to Maxwell's equations and matter equations,the first type non-collinear transient coupled wave equations and their analytical solutions in the case of small signals were calculated,and according to the principle of the frequency doubling effect of the nonlinear crystal,the generation of the autocorrelation signal was theoretically analyzed.A specific experimental plan was developed.By analyzing the effective nonlinear coefficient,phase matching method,frequency multiplication conversion efficiency and group velocity mismatch of the BBO crystal,the relationship between the type ? phase matching angle of BBO crystal,the non-collinear included angle of incident pulse and the incident wavelength are simulated by MATLAB software.The size of the BBO crystal was determined to be 8mm×8 mm×0.4 mm,and its type ? phase matching angle was 29.2°,thus the overall design of the system was completed,and an ultra-short pulse width measurement system based on LabVIEW was built.Through the online self-calibration method,the accuracy of single pixel was 1.049 fs.On this basis,the femtosecond laser model Mira-900(center wavelength about is 800 nm,repetition frequency is 76 MHz,and pulse width is about 90 fs)was verified and tested,and the obtained Gaussian pulse width was 95.3 fs.The test results show that the autocorrelation device in this thesis can achieve real-time and accurate measurement of laser pulse width within 100 femtoseconds.