High Efficient Terahertz Wave Generation And Micro-nano Structure Devices

Terahertz?THz?waves are typically defined in the frequency range from 0.1 to 10 THz.Due to the reasons of lacking efficient THz wave generation and detection technologies,researches in this frequency range is few,therefore,this frequency range is known as the THz Gap.In this paper,we study high efficient THz wave generation in theories and experiments;moreover,THz functional applications are also studied.The main contents and innovations of this dissertation are summarized as follows:1.Silicon triangular photonic crystal fiber?PCF?has been proposed,it is found that the pump and the generated THz pulses could well confined in this fiber.High efficiency THz pulses are generation via degenerate FWM in a singly resonant optical parametric oscillator?SROPO?with our newly designed silicon triangular PCF with highest conversion efficiency of 1.37%.2.A new method for the generation of high-energy and broadband THz radiation via coherent synthesis from multiple optical rectifications has been proposed.If the same nonlinear crystals are used in this method,the spectrum of synthesized THz pulse is not changed.However,when different nonlinear crystals are used,the synthesized THz pulse has wider spectrum and high energy.This method presents the possibility for generation of mJ level THz pulse.3.A novel type of triangular lattice terahertz photonic crystal fiber with high birefringence and low dispersion in a wide spectrum range has been proposed.The proposed structures have circularand elliptical air holes in the cladding.Through adjusting the structural parameters of the photonic crystal fiber,high birefringence and low dispersion could be achieved in the frequency range from 0.1 THz to5 THz.4.Tunable narrowband THz filter and wavelength division multiplexing based on triangular lattice silicon photonic crystal have been proposed and designed.When point and line defects are added in the structure,narrow-band filter is realized.If magnetically controlled liquid crystal?LC?is added in the defects,transmission frequency and width of passband could be adjusted through controlling the external magnetic field.5.Mid-infrared octave-spanning Kerr frequency combs generation in a dispersion-flattened micro-resonator formed by our newly designed slot cladding hybrid waveguide have been theoretically investigated,which exhibits nearly the same,flat and low anomalous dispersion in the mid-infrared wavelength range from 3 ?m to 5 ?m for both TE and TM modes.Finally,TE and TM modes optical frequency combs with nearly the same results are generated.6.THz pusle generation via pulse front tilted optical rectification in LiNbO₃ crystal has been experimentally studied.It is found that the conversion efficiency of the generated THz pulse is 1×10^-4.Then,we experimentally studied THz pulse generated by difference frequency generation in GaSe crystal.The central wavelength of pump pulse is 1.064?m,the signal pulse with central wavelength of 1.071?m is emitted by MgO:LiNbO₃ optical parametric oscillator.Finally,the pump and signal pulses are collinearly input into the Ga Se crystal,narrow-band THz pulses with the highest peak power of 195 W could be generated.