High harmonic spectroscopy in solids is emerging as a new tool to investigate ultrafast electron dynamics the presence of strong optical fields. However, observed high spectra do not usually reflect microscopic origin generation (HHG) because nonlinear and/or linear propagation effects. Here, we systematically HHG reflection and transmission from gallium arsenide exposed intense mid-infrared pulses. In geometry, find that properties harmonics are drastically changed by effects during even...

We demonstrate the generation of 21 fs (1.8 optical cycle), 45-µJ, carrier-envelope phase (CEP)-stable pulses with an octave-spanning spectrum from 2.2 to 4.9 µm. Multi-cycle output (120 fs, 149 µJ, 3.5 µm, and 300 Hz) a KTA-based parametric amplifier are compressed down sub-two-cycle regime using YAG Si plates. The single-shot CEP stability is measured be 283 mrad for 500 s. This robust compact scheme realizes field strength 282 MV/cm f/11 focusing, opening new attosecond strong-field...

The optical control of a biological system has been challenging, although the energy transfer and isomerization reaction successfully demonstrated. Here, we report on our studies ultrafast electron-transfer (ET) dynamics in protein flavodoxin as function pump-pulse chirp. With transform-limited excitation pulse 25 femtoseconds, observed excited-state wave packet ET reactions with dephasing time within 1 ps. By modulating phase pulses, was found to change from 100 300 fs due different packets...

Recently, circularly polarized high harmonics (HHs) have attracted great attention from the viewpoint of their application to ultrafast spectroscopy magnetic materials and chiral molecules. However, HHs gaseous media require a complicated setup due strong constraints upon high-harmonic generation (HHG) mechanism. HHG solids is new approach this problem. Because mechanism solid intrinsically different that gas HHG, can be generated under single-color excitation. Their polarization states been...

We experimentally study the field-intensity dependence of high-harmonic generation in bulk gallium arsenide reflection geometry. find oscillatory behavior at high fields where a perturbative scaling law no longer holds. By constructing theoretical framework based on Luttinger-Kohn model, we succeed reproducing observed behavior. The qualitative agreement between experiment and theory indicates that field-induced dynamic band modification is crucial nonperturbative regime. consider origin...

Short-range protein electron transfer (ET) is crucially important in light-induced biological processes such as photoenzymes and photoreceptors often occurs on time scales similar to those of environment fluctuations, leading a coupled dynamic process. Herein, we use semiquinone Anabaena flavodoxin characterize the ultrafast photoinduced redox cycle wild type seven mutants by spectroscopy. We have found that forward backward ET dynamics show stretched behaviors few picoseconds (1-5 ps),...

The understanding of ultrafast short-range electron transfer (ET) in proteins remains challenging, and thorough studies on well-defined biological systems are demanding. Here, we utilized two types flavodoxins designed a series mutants positions to systematically characterize the complete photoinduced redox cycles. We identified one position with favorable orientation distance for ET few femtoseconds other is relatively flexible longer time scale. found that all forward back dynamics...

Far-red cyanobacteriochromes (CBCRs) are bilin-based photosensory proteins that promise to be novel optical agents in optogenetics and deep tissue imaging. Recent structural studies of a far-red CBCR 2551g3 have revealed unique all-Z,syn chromophore conformation the far-red-absorbing Pfr state. Understanding photoswitching mechanism through bilin photoisomerization is important for developing biomedical applications. Here, we employ femtosecond spectroscopy site-directed mutagenesis...

Optical control of dynamic processes has been challenging yet only demonstrated in several chemical and biological systems. The a reaction passing the widely present conical intersection not realized. Here, we modulated phase excitation pulse to dynamics β-carotene through accessing (CI). We observed different 110–220 fs into CI consecutive process 400–600 another by various chirped pulses. successfully controlled those ultrafast wavepacket CIs on femtosecond time scales. method developed...

We present a valence orbital method of calculating high-order harmonic generation from diatomic molecule with arbitrary orientation by using space rotation operator. evaluate the effects each on emissions N2 and O2 molecules in detail separately. The calculation results confirm different properties yields which are well consistent available experimental data. observe that due to dependence σ π orbitals, bonding (σ2pz)2 determines maximum emission when molecular axis is aligned parallel laser...

Molecular wave functions are used to calculate the harmonic emission of diatomic molecules based on a time-dependent Schr\"odinger equation. Tunable effects shown for both magnitudes and molecular-alignment-dependent properties with different electronic excited states or mixed as initial states. The calculated results consistent experimental signals from ${\mathrm{N}}_{2}$ under rotational temperatures laser intensities. molecular-alignment dependence is rapidly weakened increasing levels...

We report the harmonic spectral properties of Xe at low gas pressure and significant amount redshift blueshift spectra. Different amounts frequency shift are obtained by adjusting peak laser intensity; namely, varying ionization medium. The observed shows that nondiabatic effects in ionized medium play a major role, while toward higher is attributed to decrease electron density due defocusing electron–ion recombination. demonstrate possibility coherently tuning soft x-ray source taking...

The optical quantum control has been successfully applied in modulating biological processes such as energy transfer and bond isomerization. Among the reactions realizing functions, electron (ET) process is fundamental; hence, over an ET reaction of far-reaching significance. Here, we realized ultrafast a protein, flavodoxin, by applying various chirped excitation pulses. We observed wavepacket dynamics within dephasing time less than 1 ps. Within this window, found that photoinduced can be...

We experimentally study high harmonic generation from elliptically polarized femtosecond laser pulses. The intensity as a function of ellipticity is measured. show that the atomic dependence stronger than molecular dependence.

The buleshift properties of high-harmonic generation with phase matching different filling pressures and laser intensities are experimentally investigated in this paper. generated gas cell, about 0.13 nm plateau 0.07 cutoff is obtained. influenced by simply changing the pressure intensity, namely, varying density free electrons cell.

We experimentally study the harmonics from a Xe-He gas mixture using tight-focusing femtosecond laser pulses. The spectrum in mixed gases exhibits an extended cutoff region harmonic H21 to H27. potential explanation is that photons Xe contribute electrons of He atoms transmit into excited-state. Therefore, are emitted easily. Furthermore, we show there suppressed H15 and H17 gases. underlying mechanism destructive interference between generated different atoms. Our results indicate HHG...