Abstract

Based on the theory of strong field approximation, we simulate the high harmonic and attosecond pulse generation from helium atom irradiated by a dual optical gating pulse composed of an orthogonally polarized field and a second harmonic pulse. The orthogonally polarized field consists of two linearly polarized pulses with a certain time delay, orthogonally polarized directions and 7 fs pulse duration. If the pulse that occurs first is called the driving pulse, the delayed pulse is called the gating pulse. The dual optical gating pulse is realized by adding a linearly polarized second harmonic pulse in the direction of the driving pulse of an orthogonally polarized field. It is found if the time delay between the driving pulse and the gating pulse and the phase difference between the second harmonic pulse and the driving pulse are reasonably adjusted, the high order harmonic generation spectra with higher efficiency and supercontinuum bandwidth can be obtained. After the inverse Fourier transform, an isolated short pulse with 124 as pulse duration can be obtained. Compared with the double optical gating scheme proposed by Chang et al., this experimentally relatively easy-to-operate scheme, on the one hand, overcomes the restrictions on the pulse width and intensity of the incident drive pulse, and on the other hand, avoids the atomic pre-ionization caused by the laser cycles before the polarization gate which is not conducive to the harmonic phase matching.

Graphical abstract

中文翻译：

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通过双光学选通方案生成孤立的阿秒脉冲

摘要

基于强场近似理论，我们模拟了由正交偏振场和二次谐波脉冲组成的双光学选通脉冲辐照氦原子产生的高次谐波和阿秒脉冲。正交极化场由具有一定时间延迟的两个线性极化脉冲，正交极化方向和7 fs脉冲持续时间组成。如果首先出现的脉冲称为驱动脉冲，则延迟的脉冲称为门控脉冲。通过在正交偏振场的驱动脉冲的方向上加上线性偏振的二次谐波脉冲来实现双光选通脉冲。发现如果合理地调整了驱动脉冲与门控脉冲之间的时间延迟以及二次谐波脉冲与驱动脉冲之间的相位差，则可以获得具有更高效率和超连续谱带宽的高阶谐波产生谱。在逆傅立叶变换之后，可以获得具有作为脉冲持续时间的124的隔离的短脉冲。与Chang等人提出的双光学选通方案相比，这种实验上相对易于操作的方案一方面克服了对入射驱动脉冲的脉冲宽度和强度的限制，另一方面，避免了由偏振门之前的激光循环引起的原子预电离，这不利于谐波相位匹配。可以获得具有更高效率和超连续谱带宽的高次谐波产生谱。在逆傅立叶变换之后，可以获得具有作为脉冲持续时间的124的隔离的短脉冲。与Chang等人提出的双光学选通方案相比，这种实验上相对易于操作的方案一方面克服了对入射驱动脉冲的脉冲宽度和强度的限制，另一方面，避免了由偏振门之前的激光循环引起的原子预电离，这不利于谐波相位匹配。可以获得具有更高效率和超连续谱带宽的高次谐波产生谱。在逆傅立叶变换之后，可以获得具有作为脉冲持续时间的124的隔离的短脉冲。与Chang等人提出的双光学选通方案相比，这种实验上相对易于操作的方案一方面克服了对入射驱动脉冲的脉冲宽度和强度的限制，另一方面，避免了由偏振门之前的激光循环引起的原子预电离，这不利于谐波相位匹配。

图形概要