Li@C60 thin films: characterization and nonlinear optical properties

A facile way is shown to obtain thin films of Li@C60 as well as their characterization and nonlinear optical properties. Our results suggest Li@C60 to be a suitable candidate for high-harmonic generation.

The effect of initial phase on the emission characteristics of forward electron colliding with a tightly focused linearly polarized few-cycle laser pulse

We have studied the high harmonic radiation property from the scattering of an electron with a focused few-cycle laser pulse by analyzing the distribution of the radiation field and the motion state of the electron. In the time domain, temporal width of the compressed radiation can reach 33 zs (zeptosecond), thus an ultrashort x-ray pulse was generated in the interaction process. The radiation in this process is vastly similar to high harmonic generation in the process of atomic strong-field. The latter depends to a large extent on the phase of carrier-envelope (CE) driving laser pulse. The cutoff of radiation spectrum can reach 1 × 10 5 ω 0 , and whether the high-order harmonic spectrum in the cut-off region can be well resolved depends on the CE phase. We have investigated the relationship between the maximum radiation intensity and the CE phase, and discussed a potential method to characterize the CE phase of an intense few-cycle laser pulse for broader application prospects.

Spontaneous polarization effects on solid high harmonic generation in ferroelectric lithium niobate crystals

High-order harmonic generation (HHG) in ferroelectric lithium niobate (LiNbO$_{3}$) is investigated theoretically by solving the semi-conductor Bloch equations. Because of the spontaneous polarization, even-order harmonics are produced in the HHG spectra of the LiNbO$_{3}$ crystal driven by a monochromatic multi-cycle 3300-nm laser. Our numerical calculation shows that they are originated from the suppression of one half-optical cycle HHG process in each cycle of the driving field due to the spontaneous polarization. We also illustrate that the spontaneous polarization will increase the harmonic yield and extend the maximally attainable cutoff energy at the same time. We further report that the carrier-envelope phase dependence of HHG spectra changes from a minimum period of $\pi$ rad to 2$\pi$ rad when the laser polarization direction is parallel/anti-parallel to the spontaneous polarization direction in LiNbO$_{3}$ crystal. This is promising to be utilized as an isolated attosecond pulse (IAP) gating mechanism. Moreover, the two-color relative phase dependence of HHG in LiNbO$_{3}$ is also investigated and shows broken inversion-symmetry.