Research Of Analog Signal Processing Based On Time-Lens

Manipulation and characterization of information using ultrafast optical signals is critical for numerous applications in telecommunications, biology, quantum information science and atomic and molecular physics. Electrical signal conditioning systems enable extremely sophisticated processing functionalities by using densely integrated circuits. However, the use of such circuits in ultrafast signal processing systems would impose strict limits on the signal bandwidth and the speed of signal processing. To address the problem, using analog methods to process ultrafast signal has become a new hotspot. In recent years, all kinds of applications of space-time duality have been widely studied theoretically and experimentally. Impressive recent efforts have been done for all-optical ultrafast signal processing using time-lens, such as waveform compression and stretch, time to frequency mapping, temporal cloaking. This subject began the work under such a background. The main research contents of the paper are summarized as follow:Firstly, the research background and the present research status are presented, which include the research significance of ultrafast signal processing and the research of timelens. And the main work of this thesis is summarized.Secondly, this section is the basic theory summary of time-lens, which introduces the principle of space-time duality and time-lens. Compared with the lens in spatial domain, we deduce the different imaging model of the time-lens. And the derivation process is described in detail, which include temporal Fraunhofer far-field dispersion, time-to-frequency transform and temporal imaging. In addition, the most important parameters to evaluate the performance of time-lens are also given.Thirdly, the time-lens based on Four-wave mixing(FWM) is introduced, it provides the key parameters of performance in the FWM based time-lens and the relation between input dispersion, output dispersion and pump dispersion in different imaging models. The derivation process of FWM time-lens and some simulation example are presented, which include waveform stretching, waveform compressing, temporal reversal, Fraunhofer temporal magnification and temporal telescope.Fourthly, a new technique to physically realize the short-time Fourier transform(STFT) of chirped ultrafast pulse using time-lens array is proposed, which enables us to get time-frequency representation without using FFT algorithm. The idea of STFT is physically realized in our scheme. And it separately measures the pulses influenced by second dispersion, third dispersion and SPM by Simulations to investigate performance of the time-frequency representation scheme in comparison with STFT using FFT algorithm. In the last part, optimal measurement of resolution in time and frequency has been discussed, providing the sampling rate it needed based optimal dispersion model.Fifthly, a simple FWM-time-lens experiment based on the nonlinear fiber is presented. A pulse with FWMH of 7.1-ps is stretched to 117-ps in the experiment, which is 16.5 times larger than the original pulse. The limiting factors and deficiency of the experiment is discussed.Lastly, the research of this thesis is summarized and future research is proposed.