| The chirped pulse amplification technology makes people go further and further on the way to obtain ultra-short and ultra-intense laser?Stronger light means stronger fields,which means more exotic physics;As a result,all kinds of powerful laser facilities in the world began to be established one after another.In the ultra-intense laser facilities,most of the energy of the pulse comes from the power amplifier behind the laser facility;The higher the pump energy,the greater the output theoretically,but this is not the case;The appearance of parasitic oscillation seriously consumes the energy of pump light and limits the extraction of energy.How to improve the energy conversion efficiency of power amplifier is a key problem;In combination with previous research results and the needs of our laboratory,we built a pulse power amplifier and a fourgrating pulse compressor based on the chirp pulse amplification technology,which constitutes the first chapter of this paper.In the first chapter,we improve the output energy of the pump source by optimizing its internal structure.And the use of diffraction optical element to improve the spot quality to obtain flat top round spot,in order to avoid the damage caused by the titanium sapphire crystal in the amplification process;In the aspect of restraining parasitic oscillation,the refraction index matching solution of doped absorber coated with titanium-precious stone crystal is used to significantly improve the parasitic oscillation threshold and energy conversion efficiency.To prevent damage to the optical elements behind the amplifier,we built a new four-grating compressor and successfully compressed the pulse to a width very close to its Fourier transform limit: 40 fs.In recent years,strong terahertz sources have become a hot research topic due to their advantages of strong field and low single photon energy.There are many ways to generate terahertz.In terms of its simplicity,the field intensity,stability and adjustability that can be achieved by the source,etc.,we have built a strong terahertz source based on the tilted pulse-front on the Pulsar20 device;The second chapter describes: by optimizing the parameters of pump light and using refractive index matching material to reduce the internal surface reflection,our terahertz source obtained the output of 0.2thz central frequency and 0.2mj terahertz pulse energy at room temperature,We get the field intensity of 4MV/cm through off-axis paraboloid focusing;In addition,we study the influence of pump light spectrum,chirp and polarization state on the energy and spectrum of THz.It is found that the central frequency of terahertz is sensitive to the spectral distribution of incident pump light and its energy is not symmetrical to the polarization state of pump light.The spatial chirp on the terahertz surface is measured.This work is important for better use of the tilted pulse-fronts source and for understanding the tilted pulse-front theory.In terahertz detection,the detection of its waveform is important.We know its energy spectrum from the waveform information.In addition,by investigating the change of terahertz pulse before and after passing through the material,we can also obtain the refractive index,transmission rate,absorption rate,absorption spectrum and other information of the material in the terahertz band.In order to overcome the measurement error of terahertz waveform caused by the energy and spectral jitter of high-power and low-repetition rate laser,and to see the THz spectrum in real time,we built a single terahertz waveform measurement device based on spectral interferometry.In addition,the distribution of terahertz waveform on the one-dimensional line is measured by using cylindrical lens focusing and two-dimensional CCD array receiving spectrum.We developed a computer program to achieve very convenient acquisition for terahertz waveform,spectrum;This brings great convenience to the application of terahertz source. |
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