Enhancement of Vacuum-Ultraviolet Laser Generation through Near-Threshold Harmonics Driven by a Few-Cycle Two-Color Laser Field

Vacuum-ultraviolet (VUV) lasers are critical and foundational tools in scientific research and various industrial applications. Traditional methods for generating VUV lasers involve large, expensive facilities, such as free-electron lasers and synchrotron sources. Recent studies suggest that near-threshold harmonic (NTH) generation offers a viable alternative for creating compact, tabletop sources of femtosecond coherent VUV lasers. However, the relatively low pulse energy limits their broader application. To address this issue, theoretically, a few-cycle, two-color femtosecond laser field is utilized to generate and enhance NTH. This approach allows one to effectively control the excitation of low Rydberg states, significantly increasing the intensity of the VUV laser by 2 orders of magnitude in rarefied gases compared to previous long-duration two-color methods. Additionally, varying the driven laser’s ellipticity and wavelength allows for adjustment of the VUV laser’s ellipticity and wavelength. These findings contribute to the development of femtosecond, high-intensity, ellipticity, and wavelength-adjustable VUV lasers, promising significant advancements in VUV laser technology.