Nariyuki Saito

Attosecond streaking measurement of extreme ultraviolet pulses using a long-wavelength electric field.

Long-wavelength lasers have great potential to become a new-generation drive laser for tabletop coherent light sources in the soft X-ray region. Because of the significantly low conversion efficiency from a long-wavelength light field to high-order harmonics, their pulse characterization has been carried out by measuring the carrier-envelope phase and/or spatial dependences of high harmonic spectra. However, these photon detection schemes, in general, have difficulty in obtaining information on the spectral phases, which is crucial to determine the temporal structures of high-order harmonics. Here, we report the first attosecond streaking measurement of high harmonics generated by few-cycle optical pulses at 1.7 μm from a BiB3O6–based optical parametric chirped-pulse amplifier. This is also the first demonstration of time-resolved photoelectron spectroscopy using high harmonics from a long-wavelength drive laser other than Ti:sapphire lasers, which paves the way towards ultrafast soft X-ray photoelectron spectroscopy.

Dual wavelength oscillation by electronic tuning of a Ti:sapphire laser for difference-frequency generation

The recent success of cw tunable radiation has brought much attention to difference-frequency generation (DFG) as a tunable infrared source. We have succeeded in developing an electronically tuned pulsed Ti:sapphire laser with an acousto-optic device. The dual wavelength oscillation in a single cavity as well as rapidly random-access tuning capability at 700-1000 nm is quite advantageous for DFG. Using the electronically controlled dual-wavelength Ti:sapphire laser, the rapidly and randomly tunable DFG with broad tuning range can be provided without rotation of a nonlinear crystal DFG mixing. An acousto-optic tunable filter is the key component for electrical tuning of the Ti:sapphire laser.