〔主要な業績〕Cascade and yoked superfluorescence detected by sum frequency generation spectroscopyK. Kitano; H. Maeda, 筆頭著者, We investigated the superfluorescent decay process of dense rubidium atomic vapor in a cell. Using a femtosecond laser pulse, the atoms were excited from the 5S ground state to the 6P state. The m and m fields were generated on the cascaded decay, 6P → 6S → 5P, which further stimulated the 780 nm forward emission on the 5P → 5S transition. Using sum frequency generation (SFG) spectroscopy, we observed all emission fields and the time delay between them, with sufficient temporal resolution. The experimental results were successfully reproduced using semiclassical simulations., Optica Publishing Group
Optics Letters, 2022年12月20日,
［査読有り］ 〔主要な業績〕Polarization correlation in the superfluorescent decay process
K. Kitano; H. Tomida; D. Takei; H. Maeda, 筆頭著者
Opt. Lett., 2021年10月, ［査読有り］
〔主要な業績〕Nonlinear optical processes driven by superfluorescent fields and their controllability with external laser fields
K. Kitano; M. Sato; Y. Komasaka; H. Maeda, 筆頭著者
Phys. Rev. A, 2020年09月, ［査読有り］
〔主要な業績〕Unveiling the Mechanism of Wavefront Distortion of Superfluorescent Pulses
K. Kitano; H. Maeda, 筆頭著者
Phys. Rev. A, 2019年10月, ［査読有り］
〔主要な業績〕Spatiotemporal profile of yoked superfluorescence from Rb vapor in the strong excitation regime
K. Kitano; H. Maeda, 筆頭著者
Phys. Rev. A, 2018年06月, ［査読有り］
〔主要な業績〕Rabi oscillations in the spatial profiles of superfluorescent pulses from rubidium vapor
K. Kitano; H. Maeda, 筆頭著者
Opt. Express, 2017年10月, ［査読有り］
〔主要な業績〕Selecting rotational two-level coherence in polar molecules by double terahertz pulses
K. Kitano; N. Ishii; T. Kanai; J. Itatani, 筆頭著者
Phys. Rev. A, 2014年10月, ［査読有り］
Carrier-envelope phase-dependent high harmonic generation in the water window using few-cycle infrared pulsesNobuhisa Ishii; Keisuke Kaneshima; Kenta Kitano; Teruto Kanai; Shuntaro Watanabe; Jiro Itatani, High harmonic generation (HHG) using waveform-controlled, few-cycle pulses from Ti:sapphire lasers has opened emerging researches in strong-field and attosecond physics. However, the maximum photon energy of attosecond pulses via HHG remains limited to the extreme ultraviolet region. Long-wavelength light sources with carrier-envelope phase stabilization are promising to extend the photon energy of attosecond pulses into the soft X-ray region. Here we demonstrate carrier-envelope phase-dependent HHG in the water window using sub-two-cycle optical pulses at 1,600 nm. Experimental and simulated results indicate the confinement of soft X-ray emission in a single recombination event with a bandwidth of 75 eV around the carbon K edge. Control of high harmonics by the waveform of few-cycle infrared pulses is a key milestone to generate soft X-ray attosecond pulses. We measure a dependence of half-cycle bursts on the gas pressure, which indicates subcycle deformation of the waveform of the infrared drive pulses in the HHG process., NATURE PUBLISHING GROUP
NATURE COMMUNICATIONS, 2014年02月,
［査読有り］ 〔主要な業績〕Orientation of jet-cooled polar molecules with an intense single-cycle THz pulseK. Kitano; N. Ishii; N. Kanda; Y. Matsumoto; T. Kanai; M. Kuwa; Gonokami; J. Itatani, 筆頭著者, We report the direct observation of the orientation of jet-cooled molecules induced by a THz pulse. The intense THz field (similar to 30 kV/cm) creates a superposition between the rotational ground state (J = 0) and the excited state (J = 1) of HBr molecules. The rotational dynamics is probed by Coulomb explosion imaging of the fragment ions produced by a near-infrared femtosecond laser pulse. Comparing with the simulations based on a time-dependent Schrodinger equation, the rotational wave packets are completely reconstructed, which reveal that similar to 7 x 10(-4) of the ground-state population is transferred to the J = 1 state at an initial temperature of 8 K, achieving a degree of orientation of < cos theta > similar to 0.017., AMER PHYSICAL SOC
Phys. Rev. A, 2013年12月,
［査読有り］ Carrier-envelope phase-dependent high harmonic generation in the water window by few-cycle IR Pulses
Nobuhisa Ishii; Keisuke Kaneshima; Kenta Kitano; Teruto Kanai; Shuntaro Watanabe; Jiro Itatani, We report on the generation of carrier-envelope phase-dependent high harmonics in the water window using few-cycle IR pulses. The results suggest the production of a 50-eV-wide isolated attosecond continuum at the carbon K edge. © OSA 2013.
CLEO: QELS_Fundamental Science, CLEO:QELS FS 2013, 2013年
Sub-two-cycle, carrier-envelope phase-stable, intense optical pulses at 1.6 mu m from a BiB3O6 optical parametric chirped-pulse amplifierN. Ishii; K. Kaneshima; K. Kitano; T. Kanai; S. Watanabe; J. Itatani, We report on the generation of 9.0 fs, 550 mu J, carrier-envelope phase (CEP)-stabilized optical pulses around 1.6 mu m at 1 kHz. Few-cycle IR pulses are obtained from a BiB3O6 optical parametric chirped-pulse amplifier. The amplification of nearly octave-spanning ultrabroad pulses without spectral broadening results in good stability in output energy (0.85% rms) and CEP (160 mrad rms). We observed high harmonics in the water window from a neon cell that corresponds to a laser intensity of 4.1 x 10(14) W/cm(2). (C) 2012 Optical Society of America, OPTICAL SOC AMER
OPTICS LETTERS, 2012年10月,
［査読有り］ 〔主要な業績〕High degree of molecular orientation by a combination of THz and femtosecond laser pulses
K. Kitano; N. Ishii; J. Itatani, 筆頭著者
Phys. Rev. A, 2011年11月, ［査読有り］
Carrier-Envelope-Phase-Preserving, Octave-Spanning Optical Parametric Amplification in the Infrared Based on BiB3O6 Pumped by 800nm Femtosecond Laser PulsesNobuhisa Ishii; Kenta Kitano; Teruto Kanai; Shuntaro Watanabe; Jiro Itatani, We demonstrate the octave-spanning optical parametric amplification (OPA) of infrared pulses in the range from 1100 to 2200 nm using a BiB3O6 (BIBO) crystal and 800nm pump pulses. Difference frequency generation is used to produce carrier-envelope-phase(CEP)-stabilized octave-spanning seed pulses. BIBO-based degenerate OPA amplifies the seed pulses to the 10 mu J level, while preserving their bandwidth and phases. We use an f-to-2f interferometer without external spectral broadening to measure the CEP of the output pulses from OPA. (C) 2011 The Japan Society of Applied Physics, JAPAN SOC APPLIED PHYSICS
APPLIED PHYSICS EXPRESS, 2011年02月,
［査読有り］ CEP-preserving, octave-spanning IR OPA using BIBO and 800-nm pump pulsesNobuhisa Ishii; Kenta Kitano; Teruto Kanai; Shuntaro Watanabe; Jiro Itatani, We report on octave-spanning OPA of IR pulses from 1100 to 2200 nm using BIBO and 800-nm pump. We confirmed that 10-mu J OPA output pulses were CEP-stabilized using an f-to-2f interferometer without spectral broadening., IEEE
2011 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO), 2011年,
［査読有り］ Molecular orientation by intense visible and THz optical pulsesK. Kitano; N. Ishii; J. Itatani, We propose an all-optical method for molecular orientation by using intense visible and THz optical pulses. We show numerically that the highest degree of orientation <cos 0>similar to 0.6 in HBr is feasible under experimentally available conditions., IEEE
2011 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO), 2011年,
［査読有り］ 〔主要な業績〕Ultrafast Angular Momentum Orientation by Linearly Polarized Laser Fields
K. Kitano; H. Hasegawa; Y. Ohshima, 筆頭著者
Phys. Rev. Lett., 2009年11月, ［査読有り］
