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We studied petahertz electronic oscillations with 1.16-PHz frequency using gallium nitride (GaN) wide-bandgap semiconductor. An isolated attosecond pulse with coherent broadband spectrum reveals dipole oscillation with 860-as periodicity in the GaN electron and hole system.
We demonstrate optical drive with 1.16-PHz frequency using gallium nitride (GaN) wide-bandgap semiconductor. An isolated attosecond pulse with coherent broadband spectrum reveals dipole oscillation with 860-as periodicity in the GaN electron and hole system.
We demonstrate a novel light source based on coherent two-channel waveform multiplexing employing 28-fs carrier-envelope-phase stable pulses. The two-channel pulse energy reaches 50 mJ, which is the highest energy ever reported for a parallel synthesizer.
Plasma-induced frequency shift can be found in angularly resolved harmonic spectrographs by non-collinear high-harmonic generation. Based on the results we derive time-dependent ionization degree of the gaseous medium during high-harmonic conversion process.
We characterized a dipole response with an inner shell induced by an isolated attosecond pulse. We reconstruct the dipole response from the spectral interferogram constructed with two fields of electromagnetic radiation in a neon atom.
Transient fluorescent variations of enhanced green fluorescent protein and enhanced yellow fluorescent protein indicate the existence of two transient dark states including the lowest triplet state and the other dark state with a longer life time.
High-harmonic generation by non-collinear wave mixing in ionized media is demonstrated, in which the phase matching is realized in the direction of difference frequency mixing. The emission angle temporally varies depending on the ionization degree.
We demonstrate that temporal focusing microscopy with structured illumination provides super-resolution even if wavefront distortion within the sample results in stretching the point spread function of the microscope.
We present the measurement of photobleaching spectra of fluorescent proteins with nonlinear Fourier-transform spectroscopy using ultrabroadband femtosecond pulses. Photobleaching of two-photon excited fluorescent molecules occurs through one-photon excited-state absorption.
We characterized field emission from autoionization transition in atomic neon stimulated by isolated attosecond field. The spectrum of the emitted field broadens approximately 1 eV bandwidth, which corresponds to shorter than 2.5 fs-duration.
We investigate the photobleaching of fluorescent proteins as functions of pulse interval, chirp, and pulse energy of femtosecond excitation lights and find out that the photobleaching occurs via one-photon excited-state absorption of the triplet state.
We demonstrate nonlinear optical microscopy modulating the spatial overlap between two-color pulses, which provides the enhancement of the three-dimensional spatial resolution and the suppression of the out-of-focus signals in deep imaging.
One of the most crucial issues for the present attoscience is to increase the energy of isolated attosecond pulses (IAP's). Typical pulse energy of IAP's reported before is order of pJ, which is enough for streaking-type experiments[1], but not for fundamental pump-and-probe-type experiments using IAP's only. For this purpose, there are two crucial experimental challenges to demonstrate; one is to...
We observe nonlinear wavelength conversion processes of high harmonics for the first time. The energies of the generated photons are up-converted and momenta of them are narrowly-distributed.
We demonstrate high-resolution fluorescence microscopy based on a cyclic sequential multiphoton process, which gives rise to fluorescence emission following a sequence of cyclic transitions between the bright and dark states of a fluorophore.
We have demonstrated the generation of 5 fs, 5 mJ pulses at 1kHz repetition rate using a pulse compression technique in a hollow fiber with a pressure gradient.
This paper reviews and discusses the concept of nonlinear optical spectroscopy (NLOS) and microscopy employing ultra-broadband laser pulses. A spectral phase modulation technique of the ultra-broadband pulses, which allows the control of nonlinear optical processes, enables multimodal imaging in nonlinear optical microscopy. This technique uses the difference of the excitation spectra of molecules...
We present that adaptive control can be applied to achieve the highest contrast ratio at the desired fluorescence intensity from a target fluorophore in the selective excitation with ultrabroadband optical pulses.
We show that the selective excitation of vibrational mode is achieved by a single broadband pulse to focus its bandwidth into a narrow spectral region. The spectral focusing is performed by controlling the spectral phase.
We present that adaptive control can be applied to achieve the highest contrast ratio at the desired fluorescence intensity from a target fluorophore in the selective excitation with ultrabroadband optical pulses.
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