A5071075296- Laser-Matter Interactions and Applications
- Advanced Fiber Laser Technologies
- Solid State Laser Technologies
- Laser Design and Applications
- Advanced Fluorescence Microscopy Techniques
- Spectroscopy and Laser Applications
- Photonic and Optical Devices
- Spectroscopy Techniques in Biomedical and Chemical Research
- Optical Network Technologies
- Photorefractive and Nonlinear Optics
- Optical Coherence Tomography Applications
- Laser-Plasma Interactions and Diagnostics
- Photonic Crystal and Fiber Optics
- Laser Material Processing Techniques
- Semiconductor Lasers and Optical Devices
- Advanced Optical Sensing Technologies
- Mass Spectrometry Techniques and Applications
- Laser-induced spectroscopy and plasma
- Nonlinear Dynamics and Pattern Formation
- Nonlinear Optical Materials Studies
- Plasmonic and Surface Plasmon Research
- Quantum Information and Cryptography
- Photoacoustic and Ultrasonic Imaging
- Chaos control and synchronization
- Spectroscopy and Quantum Chemical Studies
Keio University
2015-2024
The University of Tokyo
2008-2015
NTT Basic Research Laboratories
2008
Institute of Materials Structure Science
2008
RIKEN Advanced Science Institute
2008
Japan Atomic Energy Agency
2008
Kansai Photon Science Institute
2008
JTEC Corporation (Japan)
2008
SPring-8
2008
Waseda University
2002-2005
The 13th harmonic of a Ti:sapphire (Ti:S) laser in the plateau region was injected as seeding source to 250-MeV free-electron-laser (FEL) amplifier. When amplification conditions were fulfilled, strong enhancement radiation intensity by factor 650 observed. random and uncontrollable spikes, which appeared spectra Self-Amplified Spontaneous Emission (SASE) based FEL without source, found be suppressed drastically form narrow-band, single peak profile at 61.2 nm. properties seeded well...
Visible lasers are sought for in a variety of applications. They required fields as diverse medicine, materials processing, display and entertainment technology many others. Moreover, contrast to infrared lasers, they enable very simple efficient access the UV spectral range by single frequency doubling step. Currently, choice direct visibly emitting is limited: The 'green gap' prohibits development semiconductor with emission green yellow only few laser active ions allow visible lasing. In...
We have proposed and demonstrated a novel approach for generating high-energy extreme-ultraviolet (XUV) continuum radiation. When two-color laser field consisting of sub-10-fs fundamental its parallel-polarized second harmonic was applied to high-order generation in argon, spectrum centered at 30 nm successfully obtained with an energy as high 10 nJ. This broadband emission indicates the possibility intense single attosecond pulses XUV region.
Computer models developed so far on electron-beam-excited KrF(B–X, 248 nm) lasers that include the vibrational relaxation process in upper lasing B level at finite rate could not predict high intrinsic laser efficiency which was experimentally reported. This is attributed to reduction of extraction efficiency. We have a four-level KrF model includes and also collisional mixing KrF*(B) KrF*(C) levels. The quenching rates for KrF*(B,C) we used were carefully estimated by using effective...
The authors observed −7.2±0.2dB quadrature squeezing at 860nm by using a subthreshold continuous-wave pumped optical parametric oscillator with periodically poled KTiOPO4 crystal as nonlinear medium. level was measured the phase of homodyne detection locked quadrature. blue light induced infrared absorption not in experiment.
We propose and experimentally demonstrate a new method called SF-STAMP for sequentially timed all-optical mapping photography (STAMP) that utilizes spectral filtering. is composed of diffractive optical element (DOE), band-pass filter, two Fourier transform lenses. Using linearly frequency-chirped pulse converting the wavelength to time axis, we realize single-shot ultrafast burst imaging. As an experimental demonstration SF-STAMP, monitor dynamics laser ablation using broadband (>100 nm)...
We demonstrate the high-power continuous-wave operation of a Pr3+:YLF laser end pumped by blue diodes. As pump source, we used four 5 W single-emitter diodes and >20 fiber-coupled module. In single-emitter-diode pumping, obtained pump-limited output powers 6.7 3.7 at 640 607 nm, respectively. successfully suppressed thermal aberration an power 3.4 slope efficiency 25% nm with good beam quality in module pumping.
We captured ultrafast two-dimensional (2D)-burst images of the crystalline-to-amorphous phase transition Ge2Sb2Te5. These transitions were induced by a femtosecond laser pulse, and images, with sub-picosecond temporal resolution, acquired on single-shot basis through change in local optical transmittance. employed 2D-burst imaging method sequentially timed all-optical mapping photography utilizing spectral filtering (SF-STAMP). The SF-STAMP system consists 25-beam-generating diffractive...
By developing a comprehensive computer code for <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</tex> -beam excited XeCl lasers, we studied mainly the effect of Ar and Ne diluents on performance characteristics lasers. According to analysis XeCl* formation process, relaxation 308 nm absorption it is found that efficiency determined by rate charge transfer process (from Ar+ Ne+ diluent ions Xe+); in other words, difference between ionic...
The dissociative ionization of ethanol C2H5OH in an intense laser field is investigated with a chirped pulse. From the sensitive dependence relative yields fragment ions on absolute values linear chirp rate, it shown that light-dressed potential-energy surface (LDPES) at singly charged stage governs nuclear dynamics, and wave packet flow into breaking either C–C C–O chemical bonds could be characterized by holding time thold during which LDPESs are maintained. It also understood term...
We demonstrate a Ti:sapphire laser pumped directly with green diode laser. A single 1 W InGaN operating at 518 nm is used as the pump source. Pulse durations short 62 fs and average output powers of up to 23.5 mW are obtained chirped-mirror-based dispersion compensation semiconductor saturable absorber mirror (SESAM).
We experimentally reveal the pump-induced loss in a Ti:sapphire laser crystal with 451-nm indium gallium nitride (InGaN) diode pumping and show that 478-nm can reduce such loss. The influence of at is significant even for exhibits higher effective figure-of-merit excellent performance 520-nm pumping. demonstrate power scaling by combining 478- InGaN diodes obtain CW output 593 mW.
Crystalline thin films of polytetrafluoroethylene were deposited on Si(100) wafers by F2 laser (157 nm) ablation in 200 mTorr Ar gas atmosphere. X-ray photoemission spectra indicated that the composition was similar to source material. The surface morphology at room temperature contained numerous fibrous structures size 100–400 nm, but they smoothed out elevated wafer ∼370 K, while crystalline feature still maintained. refractive index ∼1.35 633 nm.
A cw Pr(3+):LiYF(4) laser at 639 nm pumped by a high-power GaN diode (444 nm) is demonstrated. The highest power of 112 mW achieved with an optical-optical conversion efficiency 33.5%. Characteristics this elevated temperatures are also investigated for practical applications such as projector.
The resonant and non-resonant two-photon single ionization processes of He were investigated using intense free electron laser light in the extreme ultraviolet (XUV) region (53.4–61.4 nm) covering 1s–2p 1s–3p transitions He. On basis dependences yield He+ on XUV light-field intensity at 53.4, 58.4, 56.0 61.4 nm, absolute values cross sections four different wavelengths their dependence determined for first time.
We experimentally prove that a Cr4+-doped Y3Al5O12 (YAG) crystal exhibits saturable absorption in visible wavelengths at 639, 607, and 521 nm. From z-scan measurements, the saturation energies measured using laser pulse widths of 25 66 ns 639 nm are estimated to ∼11.5 21.2 mJ/cm2, respectively. Therefore, response time will be shorter than these widths. Using Cr4+:YAG absorber, we demonstrate for first time, best our knowledge, passive Q-switched mode-lock Pr3+-doped LiYF4 (YLF) lasers...
We demonstrate super-resolution imaging with background fluorescence rejection by interferometric temporal focusing microscopy, in which is combined structured illumination. The lateral resolution and the optical sectioning capability are simultaneously improved factors of 1.6 1.4, respectively, compared to conventional microscopy. Fluorescent beads (200 nm diameter) that difficult distinguish from clearly visualized
We measure the absorption recovery time, ground- and excited-state cross sections of a Cr4+:YAG crystal at 640 nm for first time. A pump-probe measurement reveals existence two times 26 ns 5.6 μs. By Z-scan experiment, are estimated to be 1.70 - 1.75 × 10(-17) 0.95 1.00 10(-17)cm2, respectively. The adequacy proposed model accuracy parameters saturable absorber verified by reproducing experimentally obtained performance passively Q-switched Pr3+:YLF laser with from rate equation analysis.
Ultrafast surface plasmon polariton (SPP) nanofocusing on a plasmonic metal tapered tip with femtosecond laser pulses enables background-free localized excitation beyond the diffraction limit. We demonstrate simultaneous of ultrafast SPP at 440 and 800 nm, which were coupled common grating structure fabricated an aluminum (Al) tip, to apex radius ∼35 nm. achieved selective coherent anti-Stokes Raman scattering (CARS) microscopy that combined nm (ω) pump pulse, achieves vibrational by...
Single-shot optical imaging based on ultrashort lasers has revealed nonrepetitive processes in subnanosecond timescales beyond the recording range of conventional high-speed cameras. However, nanosecond photography without sacrificing short exposure time and image quality is still missing because gap recordable between ultrafast electronic Here, we demonstrate ultrawide time-range using a spectrum circuit that produces interval-tunable pulse trains while keeping durations. We capture shock...
We measured the space–time profile of ultrashort optical pulses shaped with a Fourier pulse shaper. Spatial chirp, which originated in coupling at shaper, was observed directly two-dimensional spatial spectral interferometry. By analyzing fringe pattern, we successfully obtained and temporal distribution both amplitude phase for pulses. Numerically predicted spatiotemporal patterns were compared experimental results.
Dissociative multiple ionization processes of N2 were investigated by irradiating with an intense extreme ultraviolet (XUV) light at 50.3nm generated a compact self amplified spontaneous emission free electron laser source. From the analysis momentum distribution N+ ejected through Coulomb explosion and single-shot correlation between yields N2+ N+, it was confirmed that double occurred two-photon absorption XUV light.
We propose two-photon excited fluorescence (TPEF) microscopy employing a novel phase modulation technique of ultra-broadband laser pulses, which allows the relative excitation an individual fluorophore with respect to other fluorophores. This is based on generation multi-wavelength pulse train, independently interacts each fluorophore. Our applied dual-color imaging cells expressing two types fluorescent proteins. achieve selective one over and vice versa. The product maximum contrast ratios...
We attain stable mode-locking of an InGaN laser-diode-pumped Pr3+:YLF laser with a pump power 2.8 W using semiconductor saturable absorption mirror. A maximum averaged output 65 mW was obtained 45-ps pulse width at repetition rate 108 MHz. also attempted Kerr-lens by employing SF57 glass in cavity as Kerr medium.
We demonstrated the power scaling of a passively Q-switched Pr3+:LiYF4 (YLF) laser at 523, 607, and 640 nm with Co2+:MgAl2O4 (MALO) saturable absorber analyzed experimental results numerical simulation based on rate equations. A maximum pulse energy 33.5 µJ was obtained width 30.9 ns repetition 64.0 kHz nm. ultraviolet generation 261 320 by intracavity frequency doubling 63.3-ns pulses 7.0 64.6 as well 356-ns 261-nm 0.2 82.0 kHz. To best our knowledge, is shortest wavelength directly...