Hiroshi Takuma

Ultrabroadband flat continuum generation in multichannel propagation of terrawatt Ti:sapphire laser pulses

Frequency detuning as a result of self-phase modulation that exceeds by four times the primary laser frequency is demonstrated. The white light, ranging from the IR to 150 nm, was generated by a self-trapped femtosecond Ti:Al2O3 laser pulse in atmospheric-pressure rare gases. Spectral intensities in the UV and the visible regions are 100 MW/nm and 1 GW/nm, respectively. The beam divergence was measured to be 1 mrad.

Accurate measurement of the pressure broadening of the ν1 Raman line of CH4 in the 1–50 atm region by inverse Raman spectroscopy

Abstract The lineshape of the ν 1 Raman band of methane is measured as a function of pressure between 1 and 50 atm by inverse Raman spectroscopy using the 488 nm output of a cw Ar + laser as a probe beam and the output of a pulsed dye laser as a Stokes pump beam. The linewidth is found to increase linearly in this pressure region, and the fwhm Δν (in cm −1 ) can be expressed as Δν = 0.32 + 0.012 p , p being the methane pressure in atm.

Four-beam laser trap of neutral atoms

An efficient spontaneous-force laser trap of neutral atoms without standing waves is demonstrated by using the Ne 1s(5) metastable state. The metastable Ne beam is decelerated by a laser by using Zeeman tuning and is trapped in a trap consisting of a quadrupole magnetic field and four laserbeams in a tetrahedral configuration. The dynamics of atomic motion from the deceleration stage to the trap is discussed.

UV saturable absorber for short-pulse KrF laser systems.

A derivative of the linear tricyclic compound, acridine, is shown to be useful as a saturable absorber for short-pulse KrF lasers. The saturation characteristics and absorption recovery of a methanol solution of acridine for a 20-psec KrF laser pulse are reported. We obtain a saturation fluence of 1.2 mJ/cm(2) and a ratio of the primary to the excited absorption cross section of 6.25:1.

A high intensity metastable neon trap

Abstract A high intensity laser trap for metastable neon atoms has been developed. It is composed of a two-dimensional transverse laser collimator, a Zeeman-tuned longitudinal decelerator and a tetrahedral spontaneous-force trap. Using a gas with natural abundance,trapping of 10 8 , 2.5 × 10 7 and 3 × 10 6 atoms is achieved for 20 Ne, 22 Ne and 21 Ne, respectively.

Generation of an intense low-velocity metastable-neon atomic beam

A metastable neon (1S5) atomic beam with a velocity of 394 m/s (373 K) and an intensity of 1.1×1015 s−1 sr−1 is produced with a novel construction using a dc glow discharge.

Amplified spontaneous emission in high power KrF lasers

A three‐dimensional computer code of amplified spontaneous emission for a high power krypton fluoride (KrF) laser amplifier having a cylindrical symmetry and small aspect ratio is developed. The analysis using the present code indicates that the transverse and the longitudinal gain‐length product should be smaller than 3 and 10, respectively, if high extraction efficiency is required. Together with a recent experimental result obtained in our 500‐J laser, the present code guarantees high efficiency extraction of 500 kJ in a single beam having a 2×3 m2 cross section and a pulse duration of 1 μs.

Vacuum ultraviolet transitions from rare‐gas alkali ionic excimers (XeRb)+ and (KrRb)+ by electron beam excitation

Vacuum UV fluorescences from ionic rare‐gas alkali excimer molecules were observed by electron beam excitation. A gas mixture of xenon or krypton with a hot vapor of rubidium was excited to obtain a diffuse emission band centered at 164 nm from (XeRb)+ and 133 nm from (KrRb)+ molecular ions. The observed emission bands are assigned to the 21Σ+→11Σ+ transition of (XeRb)+ and (KrRb)+, respectively.

Stark Phase Shift and Deflection in the Ultracold Atomic Interferometer

Phase shift and deflection of interference patterns induced by the static electric field are studied in an optically cooled 1s3 metastable neon interferometer with Youngs double-slit configuration.

Na 2 c Σ3g+→a Σ3u+ bound–free emission by electron-beam excitation

The first bound-free triplet emission band c Σ3g+→a Σ3u+ of Na2 was observed by electron-beam excitation of a dense Na vapor. The unfavorable selection rules for optical pumping the upper state were found to be compensated for by collisional energy transfer from the 3P-state atom, which was efficiently excited by the electron beam. The main mechanisms of energy transfer for the upper-state formation are proposed to be three-body collision recombination and atom–molecule collisional energy transfer.