Frequency-resolved time-gated high-order harmonics

Wigner time-frequency distribution of high-order harmonics

We investigate the time-frequency characteristics of high-order harmonics generated in atomic gases by intense femtosecond laser pulses, using the Wigner distribution function. The dynamically induced chirp of high harmonics is calculated both quantum mechanically and semiclassically, and a good agreement between them is reached as long as the tunneling effect is properly taken into account. Us...

Time-resolved reaction imaging by intense few- cycle laser pulses and laser high-order harmonics

We discuss two novel approaches to visualize ultrafast dynamics of polyatomic molecules using few-cycle intense laser pulses and the high-order harmonics in the soft X-ray region, respectively. First, we present the real-time Coulomb explosion imaging of ultrafast isomerization of C2D2 by using intense fewcycle laser pulses (<10 fs, ~1 PW/cm, ~800 nm) to show that the hydrogen migration proceed...

Generation of high-brightness high-order harmonics

Optimization of high-order harmonic generation has been studied with a 30 fs laser at an intensity of < 2×1014 W/cm in a quasi-static gas cell filled with argon and Neon. The effect of propagation length and gas density on the conversion efficiency and spatial quality of high-order harmonics are investigated comprehensively. As a result of phase-matched propagation, both the spatial quality and...

Ramsey-type spectroscopy with high-order harmonics.

We present an experiment where Ramsey-type spectroscopy is applied to autoionizing states of krypton by using the ninth harmonic (88 nm) of a femtosecond Ti:sapphire laser. The ionization process, detected by an electron-energy spectrometer, shows the characteristic quantum interference pattern. The behavior of the fringe contrast compares favorably with a simple essential-state model, whose pa...

Spatial Mode Control of High-Order Harmonics.