Optical System Design Of Reflective Ultrashort Pulse Measurement System

With the rapid development of ultrashort pulse technology,the time width of ultrashort pulses is getting narrower and the peak power is getting higher and higher,making ultra-short pulses more widely used in various research fields.In these applications,it is necessary to obtain pulse width and bit-level detailed parameters of the pulse,so accurate measurement of ultrashort pulses becomes more important.Due to the presence of transmissive elements in ultrashort pulse measurement systems,when the pulses pass through the measurement system will be broadened,resulting in large errors in the measurement results.In order to solve the problem of pulse broadening,this paper studies the pulse transmission characteristics of GRENOUILLE,and designs an reflective ultrashort pulse measurement system.The main work of this paper has the following aspects.Firstly,the development history and research status of ultrashort pulse measurement are briefly reviewed.The theoretical basis of GRENOUILLE is introduced,including transient coupling wave equation,autocorrelation signal generation mechanism,theory of pulse demodulation and system calibration theory.Secondly,Designed an reflective ultrashort pulse measurement system based on GRENOUILLE.In the designed systemFresnel bi-mirrors are used to generate time delay,cylindrical mirrors and thin crystals and gratings are used to generate spectra,which avoids the generation of dispersion in the system.Under the premise of satisfying the sampling rate,the sampling range of the FROG trace is analyzed to obtain the time delay and frequency doubling bandwidth required by the measurement system.With this constraint,the relation between the pulse width of the pulse to be measured and the parameters of Fresnel bi-mirrors,cylindrical mirror is deduced.Finally,an reflective measurement system and a dual-pulse calibration device were built.According to the derivation operation of the double pulse calibration theory,the wavelength calibration value and the frequency calibration value of the reflective measurement system are determined.The accuracy of the pulse demodulation algorithm and the importance of denoising processing are tested by preprocessing the ideal FROG trace.The high correlation between the spectrum obtained by the reflective measurement system and the experimental measured spectrum indicates the correctness of the measurement results,and the phase of the demodulated pulse is approximately a straight line,indicating that there is no broadening in the measured pulse,indicating that the measurement system does not introduce dispersion.When the actual FROG trace is substituted into the pulse reconstruction program,the reconstruction pulse and the real pulse match are very high,which indicates that the reflective measurement system effectively improves the measurement capability of the ultrashort pulse.