Research On The Time Differentiation Of The Femtosecond Pulse

On account of the development of atomic clock technology,the accuracy and stability of time-frequency signal have reached the level of 10-18.In order to meet the high precision application requirements of time-frequency signal,scientists have proposed the quantum improved methods of time transfer: Lamine B.proposed a method using the first order differentiated pulse in time domain as local oscillator and the phase noise compressed pulse as signal pulse in homodyne detection,the precision of measured time delay can reach the level of 10^-22-10^-24s in theory.Jian P.indicated that when using the combination of Gaussian pulse and second order field envelope differentiated Gaussian pulse as local oscillator,the measurement sensitivity will be immune to atmospheric fluctuations such as pressure,temperature and humidity.All the scheme above need the differentiated femtosecond pulse in time domain as local oscillator,so it is necessary to do research on femtosecond pulse differentiation method systematically.Limited by the input energy limit or energy conversion efficiency,it is difficult to obtain high power differentiated pulse through current pulse differentiation method,which limits its application in high precision time transfer.In order to In order to perform efficient pulse time domain differentiation,this paper first uses the 4-f Fourier pulse shaping system to carry on the amplitude and phase modulation of the pulse frequency domain to obtain the differentiated pulse in time domain,and the experimental results are compared with the differentiation method based on destructive interference.The main work is:?1?The experimental device based on 4-f Fourier pulse shaping system was constructed,and the grating in 4-f system is adjusted to reduce the introduced dispersion,the dispersion induced by optimized grating is about-170fs².?2?Compensated the pulse dispersion through multiphoton intrapulse interference phase scan?MIIPS?method,got a pulse close to the Fourier transform limit.?3?The congruent relationship between the pixel of the liquid crystal spatial light modulator?LC-SLM?and the wavelength was determined,and the phase and amplitude modulation functions were designed.?4?The time-domain differential operation of the pulse was carried out by using the pulse shaping system and the Solei Babinet compensator?SBC?respectively.The electric field intensity of the differential pulse agreed well with the theoretical value.?5?The phases of differentiated pulse were measured by the interference frequency resolved optical gating?iFROG?method and the Fourier transfrom spectral interference?FTSI?method respectively.The measured results were in agreement with the theoretical expectation.The energy conversion efficiency of the first order electric field differentiated pulse obtained by 4-f pulse shaping system was 72.12%,and the energy conversion efficiency of first order and second order electric field envelope differentiated pulse were 11.10% and 3.53% respectively.The electric field fidelity of three differentiated pulse were 99.53%,98.37% and 97.32% respectively within the effective modulation range?804.5-822nm?of the liquid crystal spatial light modulator?LC-SLM?.Compared with the current pulse differentiation method,this method has the characteristics of high input energy and high energy conversion efficiency,which can produce higher power differentiated pulse.Additionally,this method is able to generate arbitrary order differentiated pulse,which makes it more suitable for high-precision time synchronization applications.