基于高次谐波产生的极紫外偏振涡旋光

Extreme ultraviolet polarization vortex beam based on high harmonic generation

突破传统涡旋光场束缚,发展短波极紫外涡旋光场是实现阿秒脉冲偏振控制的有效途径.本研究利用自制的平场光栅光谱仪和超快时间保持的单色仪,以800 nm,35 fs高斯或具有偏振奇点的涡旋光脉冲驱动诱导氩原子产生高次谐波,分别获得相应的高次谐波光谱以及谐波谱单阶光源的分布.实验结果表明,基于高次谐波产生实现近红外波段的涡旋光束特性转移到极紫外波段,优化后的极紫外涡旋可以实现每秒108光子数输出.同时发现极紫外波段的涡旋场和高斯场高次谐波产生具有相似相位匹配机制.基于高次谐波产生的极紫外波段的偏振涡旋光为探究和操控原子分子量子态的含时演化动力学以及形成阿秒矢量光束提供了重要的方法和技术手段.

Polarization is a property of vector beam that is widely used in many areas of science and technology.And vector beam is also called polarization vortex beam.Radially polarized beam and azimuthally polarized beam are the paradigm of vector beam.Extreme ultraviolet(EUV)vector beam could be applied in many fields such as diffractive imaging,Extreme Ultraviolet Lithography(EUVL),or ultrafast control of magnetic properties.In our experiments,a home-made EUV spectrometer was used to generate a tunable ultrafast EUV coherent light source based on high-order harmonic generation(HHG)by intense femtosecond laser.The apparatus features by using the plane grating in conical diffraction.The radially polarized vector beam and Gaussian beam with 800 nm,35 fs laser pulses were applied to interact with Argon atoms,respectively.The high harmonic spectrums with a polarization singularity and a Gaussian distribution were observed.The experimental results demonstrate that the EUV vector beam could be transfered from near-infrared driven laser during the highly nonlinear interaction.The short-wavelength radiation with a polarization singularity can reach a photon flux of 108 per second.And the harmonic orders produced by Gaussian beam are significantly higher than that of vector field.The mechanism of macroscopic phase matching was discussed.It indicates that the phase matching for vector harmonic yields is similar with that driven by a Gaussian beam.In this case,EUV vector beam through HHG has been obtained,which provides one important method for attosecond vector pulses and opens new possibilities for exploring and manipulating the time-dependent evolution of quantum states in atom and molecule.