A5061497220- Photonic and Optical Devices
- Terahertz technology and applications
- Advanced Fiber Laser Technologies
- Laser Material Processing Techniques
- Photonic Crystals and Applications
- Laser-Matter Interactions and Applications
- Microwave Engineering and Waveguides
- Laser-induced spectroscopy and plasma
- Nonlinear Optical Materials Studies
- Optical Coatings and Gratings
- Photorefractive and Nonlinear Optics
- Ocular and Laser Science Research
- Spectroscopy and Laser Applications
- Gyrotron and Vacuum Electronics Research
- Semiconductor Lasers and Optical Devices
- Phase-change materials and chalcogenides
- Quantum Dots Synthesis And Properties
- Chalcogenide Semiconductor Thin Films
- Solid State Laser Technologies
- Semiconductor Quantum Structures and Devices
- Millimeter-Wave Propagation and Modeling
- Spectroscopy Techniques in Biomedical and Chemical Research
- Optical Network Technologies
- Superconducting and THz Device Technology
- Copper Interconnects and Reliability
The University of Tokyo
2016-2024
Graduate School USA
2016-2021
NTT Basic Research Laboratories
1988-2005
NTT (Japan)
1985-2003
University of Arizona
1993-1994
We report the first observation to our knowledge of optical bistability in CdS(x)Se(1-x)-doped glasses with rise and fall times 25 psec for bistable switching. The third-order nonlinear susceptibility chi((3)) was estimated experimentally be 1.3 x 10(-9) esu, which is good agreement value reported previously. high-speed switching show that caused by an nonlinearity attributed band-filling effect.
We theoretically study high-order-harmonic generation (HHG) from solids driven by intense laser pulses using a one-dimensional model periodic crystal. By numerically solving the time-dependent Schr\"odinger equation directly on real-space grid, we successfully reproduce experimentally observed unique features of solid-state HHG such as linear cutoff-energy scaling and sudden transition single- to multiple-plateau structure. Based simulation results, propose simple that incorporates...
For the first time, 3D printed metal-pipe rectangular waveguides (MPRWGs) have been demonstrated in WM-380 (500–750 GHz) and WM-250 (750 GHz–1.1 THz) waveguide bands. The ultra-high spatial resolution offered by new RECILS additive manufacturing technology enables precision fabrication of these prototype MPRWGs at such high frequencies. This enabling avoids need for access to expensive microfabrication resources and, thus, opens up terahertz spectrum low-cost manufacture passive components.
Absorption and photoluminescence peak shifts due to the quantum size effect are observed in CdSxSe1−x microcrystallites with average radii ranging from several angstroms 100 Å. For microcrystallite between 15 Å, can be described using an effective mass of 0.46m0 (m0 is free-electron mass), which 4.6 times as large reduced CdS0.12Se0.88. When radius less than mass, estimated experimental results, increases. The discrepancy theoretical prediction obtained results discussed.
We investigate the multielectron effects on high-harmonic generation from solid-state materials using time-dependent Hartree-Fock theory. find qualitative change in harmonic spectra, particular, multiple-plateau formation at significantly lower laser intensities than within independent-electron approximation. reveal its origin terms of interband polarization, i.e, electron-hole enabling excitation remote crystal momenta via Coulomb potential.
This paper investigates the size dependence of effective nonlinear cross section σeff and carrier recombination time on CdS0.12Se0.88 microcrystallites with average radii 10, 30, 50, 100 Å by degenerate four-wave mixing (DFWM) experiments. The decay curves DFWM signal as a function probe delay have fast slow components. As microcrystallite decreases, component becomes dominant 2 ps was observed in 10-Å microcrystallites. diffraction efficiency is almost same for all microcrystallites, that...
We designed, fabricated, and measured anti-reflection coating (ARC) on sapphire that has 116% fractional bandwidth transmission of at least 97% in the millimeter wave band. The ARC was based patterning pyramid-like sub-wavelength structures (SWS) using ablation with a 15 W femto-second laser operating 1030 nm. One side each two disks fabricated SWS had pitch 0.54 mm height 2 mm. average volume removal rate 1.6 mm3/min. Measurements two-disk sandwich show higher than between 43 161 GHz....
Anti-reflection (AR) coatings aiming at the reduction of Fresnel reflection losses has come into demand in terahertz (THz) region. Implementation such a coating practice is difficult task, partially because broad spectrum THz signal to control. Here, we propose and demonstrate moth-eye AR structure capable suppressing range 0.3 2.5 for high-resistivity silicon, resulting maximum transmission 91%. The comprises pyramid-like structures with height about 100 μm created on material surface by...
We fabricated a 302 mm diameter low-pass filter made of alumina that has an anti-reflection coating (ARC) with laser-ablated sub-wavelength structures (SWS). The been integrated into and is operating the MUSTANG2 instrument, which coupled to Green Bank Telescope. average transmittance in band between 75 105 GHz 98%. Reflective loss due ARC 1%. difference transmission s- p-polarization states less than To within 1% accuracy we observe no variance these results when measured six independent...
Abstract Basic studies on ultrafast laser ablation processes are important for expanding their utility. In particular, understanding the ablated morphology in relation to incident pulse is critical micromachining, and an benchmark simulations. However, current morphological analyses rely vast simplifications of experimental conditions, such as a singular fluence value reduce unique beam profile, or maximum crater depth diameter describe morphology. Here, we develop analysis method which take...
It is shown that a wide tunability range of greater than 500 nm can be obtained in the 2μm band an 18 mm long periodically poled lithium niobate chip with single quasiphase-matching grating period at constant temperature. This letter demonstrates difference frequency generation bandwidth. A tunable bandwidth over 130 experimentally confirmed region. broad realized by means phase-match curve distortion caused singularity. The wavelength conversion temperature dependence also for several periods.
Optical nonlinearity of a sputtered SiO2 film containing CdSe microcrystallites with an average diameter 15 Å is measured by degenerate four-wave mixing (DFWM) experiments. An effective nonlinear cross section σeff 1.4×10−16 cm2 obtained. The DFWM signal as function the probe delay time shows biexponential behavior fast decay 10 ps and slow 60 ps, which give carrier recombination times 20 120 ps. third-order susceptibility ‖χ(3)‖ estimated to be 1.3×10−8 esu. photodarkening laser annealing...
Circularly polarized light in the vacuum ultraviolet (VUV) region is important for probing structural and electronic properties of matter. Moreover, a circularly VUV coherent enables one to observe dynamics biomolecules electron spins solids. The development table-top technology directly generate great value, owing limitation polarization control elements region. However, solid-state nonlinear media this purpose, which simplifies setup, have not been presented. Here, we demonstrate...
Tb 3+ -doped glass emits GFP-like fluorescence and is versatile for various biological research purposes.
The utilization of sub-100 fs pulses has attracted attention as an approach to further improve the quality and precision femtosecond laser microfabrication. However, when using such lasers at pulse energies typical for processing, nonlinear propagation effects in air are known distort beam's temporal spatial intensity profile. Due this distortion, it been difficult quantitatively predict final processed crater shape materials ablated by lasers. In study, we developed a method ablation shape,...
A new scheme is proposed for the realization of all-optical ultrafast functional devices, such as self-modulators and multistable elements, utilizing a nonresonant chi((3)) process. The basic physical mechanism involved intensity-dependent self-induced change in polarization state light during propagation an optically anisotropic Kerr-like medium with large linear birefringence.
Tunable coherent light sources operating in the vacuum ultraviolet (VUV) region 100–200-nm (6–12 eV) wavelength range have important spectroscopic applications many research fields, including time-resolved angle-resolved photoemission spectroscopy. Recent advances laser technology enabled upconversion of visible femtosecond lasers to and extreme regions. However, complexity their experimental setups scarcity bulk nonlinear crystals for VUV generation hampered its widespread use. Here, we...
We present a breadboard model development status of the polarization modulator unit (PMU) for low-frequency telescope (LFT) LiteBIRD space mission. is next-generation cosmic microwave background satellite to measure primordial B-mode with science goal σr < 0.001. The baseline design consists reflective and refractive medium-and-high-frequency telescopes. Each employs PMU based on continuous rotating half-wave plate (HWP) at aperture. critical instrument achieve because it significantly...
In this work, we study THz generation and detection using cadmium telluride (CdTe) crystals pumped by amplified (1.025 μm wavelength) oscillator (1.045 ytterbium (Yb) lasers. For each laser, compare the performances of CdTe emitter detector to those GaP crystals. Under optimum conditions, demonstrate that former shows 3 5 times better compared with latter for generation, respectively. When an Yb find crystal is more efficient than emission at optical fluences lower 250 μJ/cm2. Although has...
We report on the results of degenerate four-wave mixing experiments at a wavelength 1.06 μm number heavy-metal gallate glasses. The replacement lead (Pb) and/or bismuth (Bi) by thallium (Tl) leads to an enhancement optical nonlinearity, resulting in largest nonresonant electronic nonlinearity yet reported for oxide glass. χ(3) is proportional concentration Tl; samples with more than 25 cation % Tl have larger that carbon disulfide (CS2). has off-resonant origin, which confirmed measurements...
We aimed to identify metallic materials that could be used construct metal-coated dielectric terahertz (THz) waveguides. examined seven different metals: gold (Au), copper (Cu), silver (Ag), aluminum (Al), nickel (Ni), chromium (Cr), and titanium (Ti). The propagation losses of our in-house parallel-plate waveguide (PPWG) were experimentally determined. developed a physical model estimate the two key parameters determining performance waveguides: critical film thickness required for bulk...
Abstract Observing ultrafast pulse-to-pulse dynamics of highly photoexcited materials could foster a comprehensive understanding the initial stage irreversible photoinduced events, such as phase change, structural deformation, and laser ablation. In this study, using high-repetition-rate single-shot spectroscopy microscope, energy relaxation in Ge 2 Sb Te 5 thin films are revealed under high-density photoexcitation that induces sequential events involving crystalline-to-amorphous transition,...
We have demonstrated ultrafast switching behavior in a current injected GaAs/AlGaAs multiple-quantum-well nonlinear directional coupler at room temperature. The results show low crossover pulse energy (10 pJ) and full recovery within 1 ps.