Efficient Frequency Conversion through Flash-Ionization

Contemporary high-energy lasers are constrained to produce light at a handful of wavelengths where efficient media exist, and conversion mechanisms to non-harmonic frequencies are generally inefficient. Here, we study how the changing refractive index in both space and time, in a laser-driven ionization scheme, produces frequency upshifts to non-harmonic frequencies. We use a pump-probe configuration where pumps of varying geometry ionize the gas, and the probe experiences the frequency upshift. This approach provides insight into ionization dynamics in intense laser-plasma interactions and potentially provides an efficient source of ultraviolet to extreme-ultraviolet radiation.