激光驱动晶体发射低阶谐波强度随激光波长的变化规律

The dependence of low-order harmonic efficiency with driving wavelength in crystals driven by laser field

通过数值求解激光驱动下电子在一维周期势场中运动的薛定谔方程,研究了晶体在激光场中发射的低阶谐波强度随激光波长的变化规律,结果表明,晶体发射低阶谐波强度随激光波长的变化规律与晶体发射高次谐波第一平台区域的变化规律不同.已有的研究表明晶体发射高次谐波第一平台区域的强度会随激光波长的增加而衰减,而我们发现晶体发射低阶谐波的强度会随激光波长的增加而增加.通过对晶体发射低阶谐波的时频分析、晶体价带能量变化与激光光子能量的关系,解释了晶体发射低阶谐波强度随激光波长增加而增加的原因.

By numerically solving a time-Schrodinger equation of electron in one dimensional periodic potential under a laser field, the change of low-order harmonic intensity emitted by the crystal with the laser wavelength is calculated. Our results show that the change of low order harmonic intensity of crystal emission with laser wavelength. Our results show that the low-order harmonic intensities of crystal emission with laser wavelength are different from that of the first plateau region of high-order harmonic generation. Previous studies have shown that the efficiency of crystal emission of high-order harmonics in the first plateau decreases with the increase of laser wavelength. We found that the intensities of low-order harmonics emitted by crystal increase with the increase of laser wavelength. By analyzing the time-frequency of the low-order harmonics from crystal and the relationship between the energy of valence band in laser and the photon energy of laser, the reason that the low-order harmonics emitted from crystal increase with the laser wavelength is explained.