Generation Of THz Linear Frequency Modulated Pulse Based On Terahertz Photonics

Terahertz wave is the electromagnetic wave with a frequency lying from 0.1 THz to 10THz,which features high carrier frequency,large ope rating bandwidth,high penetration,specific spectrum finger,and hence is potentially promising in applications,such as high-speed wireless communication,spectroscopy,imaging,radar,and so on.THz radar takes advantage of THz wave has recently attracted great interests from both the academic and the industrial societies.A number of electronics-based THz radar systems have been recently proposed and developed,which are however typically limited by the performance of employed electronics devices like expensive and bulky frequency multipliers and arbitrary waveform generators(AWGs).By contrast,photonic approach provides a simple manner to process large bandwidth signals in the optical domain and easily convert them into the THz domain,and hence breaking the bottleneck of electronic bandwidth.Therefore,we propose to develop technologies for generating linear frequency modulated(LFM)pulse in the terahertz domain based on THz photonics.In this dissertation,we firstly investigate the principle of frequency-time mapping and complete the theory of chirp pulse generation from intensity mapping and phase mapping,respectively.Next,a series of experiments are carried out to support the investigated theory,and Subsequently,we propose an approach for photonic generation of THz LFM pulses centered at 350 GHz,by using an unbalanced dispersion optical interferometer based FTM technique and state-of-the-art ultrafast THz transceivers.The generated LFM pulses operates at a carrier frequency as high as 350 GHz and a bandwidth as large as 62 GHz leading to a time-bandwidth product(TBWP)up to 527 in the experiment,which can potentially reach a range resolution of 5.7 mm.To the best of our knowledge,it is the first work to demonstrate the extremely broadband THz chirp pulse in 350 GHz band.Furthermore,we also conduct a basic experiment to measure the positioning ability of the generated chirp pulse with a bandwidth of 22 GHz under the lower output power condition.Besides that,to satisfy the application scenario of the THz broadband signal,we proposed an approach to generate a dual-band frequency division multiplexing signal with the flexible ability of carrier and bandwidth adjustment.Finally,we hope our work can provide a new solution and technology for future THz photonics pulse compression radar system.