論文 - 神成　文彦

Multichannel dissociative ionization of ethanol in intense ultraviolet laser fields: Energy correlation between photoelectron emission and fragment recoil

Ikuta T., Hosaka K., Akagi H., Kannari F., Itakura R.

Physical Review A （Physical Review A）  106 （ 2 ）  2022年08月

ISSN  24699926

　概要を見る

We investigate multichannel dissociative ionization of ethanol in intense ultraviolet laser fields using a photoelectron-photoion coincidence momentum imaging technique. Product channels are clearly separated with detected photoions, and channel-specific photoelectron spectra exhibit multiple spectral components unambiguously assigned to four- and five-photon ionization to the electronic ground state and the electronically excited state. We measure kinetic energy distributions of fragment ions as a function of the energy of a correlated photoelectron to reveal how much energy is provided to the fragment recoil of fragment ions in the course of photoelectron emission and subsequent electronic excitation. Subsequent electronic excitation rather than photoelectron emission governs the internal energy of ethanol cations. The role of subsequent electronic excitation becomes more decisive as the laser intensity increases.

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Fringe- and speckle-free holographic patterned illumination using time-multiplexed temporal focusing

Ishikawa T., Isobe K., Inazawa K., Michikawa T., Namiki K., Miyawaki A., Kannari F., Midorikawa K.

Applied Physics Express （Applied Physics Express）  15 （ 4 ）  2022年04月

ISSN  18820778

　概要を見る

Multi-photon holographic patterned illumination using temporal focusing (TF) pulses provides 10 μm multi-spots with an axial confinement of 5 μm, enabling parallel photo-stimulation of multi-target cells in three dimensions. However, interference fringes and speckles degrade the uniformity of the spots, causing spatio-temporal fluctuations in photoactivation. Here, we demonstrate fringe- and speckle-free holographic patterned illumination using multifocal time-multiplexed (TM) TF pulses even when the multi-spots overlap spatially. The uniform patterned illumination enabled the expansion of the field-of-view of TM-TF microscopy by more than fivefold and enhanced the axial resolution to 1.3 μm.

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Visible solid-state lasers based on Pr³⁺ and Tb³⁺

Tanaka H., Kalusniak S., Badtke M., Demesh M., Kuleshov N.V., Kannari F., Kränkel C.

Progress in Quantum Electronics （Progress in Quantum Electronics）  2022年

ISSN  00796727

　概要を見る

Visible lasers are sought for in a variety of applications. They are required in fields as diverse as medicine, materials processing, display and entertainment technology and many others. Moreover, in contrast to infrared lasers, they enable very simple and efficient access to the UV spectral range by a single frequency doubling step. Currently, the choice of direct visibly emitting lasers is limited: The ‘green gap’ prohibits the development of semiconductor lasers with emission in the green and yellow spectral range and only few laser active ions allow for efficient visible lasing. In particular trivalent praseodymium (Pr3+) and terbium (Tb3+) ions have been shown to be the most successful candidates for efficient high power visible solid-state lasers. Compared to semiconductor lasers, solid-state lasers also provide other advantages, e.g., in terms of energy storage in Q-switched operation as well as beam quality at high output power. In recent years, visibly emitting solid-state lasers have seen a revival enabled by the increasing commercial availability of GaN-based blue emitting pump diodes and an ever-increasing number of publications evidences the vivid research activities in this field. Still, due to the relatively short history of diode-pumped visible solid-state lasers, these are still in an early stage of their development and up to now only few direct visibly emitting solid-state lasers with comparably low output power are commercially available. However, we are convinced that visibly emitting solid-state lasers based on Pr3+ and Tb3+ have the potential for 100-W-class continuous wave output power levels as well as sub-ns pulse durations in Q-switched and sub-ps-pulse durations in mode-locked operation, which would qualify them to fulfil the requirements of most of the applications named above. In this work, we review the state of the art of continuous wave and pulsed visibly emitting solid-state lasers and amplifiers based on Pr3+ and Tb3+ as the active ion. After an introduction, we briefly review the spectroscopic properties of these two ions and their particularities for laser operation as well as the requirements for suitable host materials. In the third chapter, we present the state of the art in the field of continuous wave Pr3+-lasers emitting in the cyan-blue, green, orange, red, and deep-red spectral range based on fluoride, glass, and oxide host materials and discuss prospects for further power scaling. The fourth chapter is devoted to the current state of Tb3+-based continuous wave green and yellow emitting solid-state lasers. In the fifth and sixth chapter we give an overview over existing pulsed visibly emitting solid-state lasers in Q-switched and mode-locked operation mode, respectively. Finally, the seventh chapter is devoted to pulse amplifiers for ultrafast visible lasers before this review closes with a short conclusion.

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Adaptive optics with spatio-temporal lock-in detection for temporal focusing microscopy

Ishikawa T., Isobe K., Inazawa K., Namiki K., Miyawaki A., Kannari F., Midorikawa K.

Optics Express （Optics Express）  29 （ 18 ） 29021 - 29033 2021年08月

　概要を見る

Wavefront distortion in temporal focusing microscopy (TFM) results in a distorted temporal profile of the excitation pulses owing to spatio-temporal coupling. Since the pulse duration is dramatically changed in the excitation volume, it is difficult to correct the temporal profile for a thick sample. Here, we demonstrate adaptive optics (AO) correction in a thick sample. We apply structured illumination microscopy (SIM) to an AO correction in wide-field TFM to decrease the change in the pulse duration in the signal detection volume. The AO correction with SIM was very successful in a thick sample for which AO correction with TFM failed.

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Enhancement of optical sectioning capability of temporal focusing microscopy by using time-multiplexed multi-line focusing

Inazawa K., Isobe K., Ishikawa T., Namiki K., Miyawaki A., Kannari F., Midorikawa K.

Applied Physics Express （Applied Physics Express）  14 （ 8 ）  2021年08月

ISSN  18820778

　概要を見る

Temporal focusing (TF) microscopy has a trade-off between temporal resolution, optical sectioning capability, and field of view. To improve this trade-off, we demonstrate time-multiplexed multi-line temporal focusing (TM-ML-TF) microscopy, which combines the time-multiplexed TF technique with multi-line focusing using a digital micromirror device. Compared with those for TF microscopy, the optical sectioning capability and the signal-to-background ratio were improved by factors of 2.5 and 4.17, respectively. In addition, by applying post-processing for structured illumination microscopy to TM-ML-TF microscopy, the optical sectioning capability and the signal-to-background ratio were further enhanced by factors of 1.2 and 4.63, respectively.

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Independently programmable frequency-multiplexed phase-sensitive optical parametric amplification in the optical telecommunication band

Omi A., Hosaka A., Tomita M., Yamagishi Y., Wakui K., Niimura S., Takahashi K., Takeoka M., Kannari F.

Optics Express （Optics Express）  29 （ 14 ） 21683 - 21697 2021年07月

研究論文（学術雑誌）, 査読有り

　概要を見る

We experimentally demonstrate programmable multimode phase-sensitive amplification multiplexed in the frequency domain for flexible control of parallelly generated squeezed states. We utilize the unique phase-matching condition of a type-II periodically poled potassium titanyl phosphate (PPKTP) crystal and pulse shaping technique to fully control the frequency-domain parallel generation of squeezed states in the optical telecommunication band. We experimentally verify that the independent programmability of phase-sensitive optical parametric amplification (OPA) for the modes corresponding to different frequency bands can be achieved by shaping the pump laser pulse from optical parametric gain measurements using a coherent probe light generated by a degenerate synchronously pumped optical parametric oscillator.

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Arbitrary mixing of frequency-range multimode quantum states using nonlinear waveguide crystals based on dispersion engineering

Yamagishi Y., Hosaka A., Tanji K., Kurimura S., Kannari F.

Optics InfoBase Conference Papers （Optics InfoBase Conference Papers）  2021年

　概要を見る

As a method of quantum pulse gating in a quantum simulator, we experimentally demonstrate arbitrary mixing of multimode quantum states prepared in the frequency domain.

Single-shot ultrafast burst imaging using an integral field spectroscope with a microlens array

Nemoto H., Suzuki T., Kannari F.

Optics Letters （Optics Letters）  45 （ 18 ） 5004 - 5007 2020年09月

研究論文（学術雑誌）, 査読有り,  ISSN  01469592

　概要を見る

© 2020 Optical Society of America To fully utilize the functions of a center-wavelength-sweeping pulse train generated by a free-space angular-chirp-enhanced delay optical layout for a probe laser pulse in sequentially timed all-optical mapping photography (STAMP), we introduced an integral field spectroscopy (IFS) method using a microlens array (MLA) to produce hyperspectral images, referring to the technique as lens array (LA)-STAMP. Compared with the previous STAMP utilizing spectral filtering where a bandpass filter generated hyperspectral images, LA-STAMP achieved much higher optical throughput. In a prototype setup, we used a 60 × 60 MLA and demonstrated single-shot burst imaging of a femtosecond laser-induced ablation process on a glass surface with 300 ps frame intervals in a 1.8 ns time window. Each frame image was constructed by assembling spectrally dispersed 36 × 36 monochromatic segments distributed by each lenslet on 5 × 5 pixels of a CCD camera. The spatial resolution was ∼4.4 µm, which was determined by the MLA’s pitch and the magnification of the microscope lens. We limited the number of frames to seven in this prototype setup, although it can be scaled to ∼24 with a spatial resolution of ∼1 µm by designing IFS with a fine pitch MLA.

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Reduction of graphene oxide by nanofocused ultrafast surface plasmon pulses

Tomita K., Matsuda T., Kannari F.

OSA Continuum （OSA Continuum）  3 （ 9 ） 2441 - 2452 2020年09月

研究論文（学術雑誌）, 査読有り

　概要を見る

We used ultrafast surface plasmon polariton (SPP) pulses that were focused into several tens of nm at the apex of a tapered metal tip to induce photoreduction of graphene oxide (GO), and we successfully fabricated nano graphene stripes with a minimum width of ∼200 nm. GO was reduced using about 10 shots of SPP pulse irradiation. We evaluated the GO reduction with selective in situ coherent anti-Stokes Raman scattering measurements using spectrally focused SPP pulses. 10

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Transition-metal-doped saturable absorbers for passive Q-switching of visible lasers

Tanaka H., Kränkel C., Kannari F.

Optical Materials Express （Optical Materials Express）  10 （ 8 ） 1827 - 1842 2020年08月

　概要を見る

We experimentally investigate crystals doped with tetravalent chromium or divalent cobalt as saturable absorbers for passive Q-switching of visible solid-state lasers. The recovery time of the ground-state and excited-state absorption cross sections are determined by pump-probe and Z-scan measurements, respectively. We provide saturation intensities, useful wavelength ranges of the investigated materials, and advices to realize passive Q-switching of visible lasers using these crystals as saturable absorbers.

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Characteristics of Ti:Sapphire Laser Pumped by 450-nm Blue Diode Laser at Cryogenic Temperatures

Shioya Y., Fujita S., Kannari F.

2020 Conference on Lasers and Electro-Optics Pacific Rim, CLEO-PR 2020 - Proceedings （2020 Conference on Lasers and Electro-Optics Pacific Rim, CLEO-PR 2020 - Proceedings）  2020年08月

研究論文（学術雑誌）, 査読有り,  ISSN  9780646825045

　概要を見る

We experimentally examine the characteristics of a continuous wave Ti:sapphire laser pumped by a 449-nm diode-laser at cryogenic temperatures, including the temperature dependence of the pump laser absorption and the fluorescence efficiency.

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Arbitrary Mixing of Spectral Multimode Quantum States Generated by Dispersion-Engineered Nonlinear Crystal

Yamagishi Y., Omi A., Hosaka A., Takahashi K., Kannari F.

2020 Conference on Lasers and Electro-Optics Pacific Rim, CLEO-PR 2020 - Proceedings （2020 Conference on Lasers and Electro-Optics Pacific Rim, CLEO-PR 2020 - Proceedings）  2020年08月

研究論文（学術雑誌）, 査読有り,  ISSN  9780646825045

　概要を見る

We generate spectral multimode squeezed states and demonstrate quantum mode mixing, a method to arbitrarily mix the spectral multimode quantum states of light using a type-II PPLN waveguide, which is applicable to quantum simulators.

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Single-Shot Ultrafast Burst Imaging using Integral Field Spectrograph with a Lenslet Array

Itoyama S., Nemoto H., Takasawa K., Watase R., Kannari F.

2020 Conference on Lasers and Electro-Optics Pacific Rim, CLEO-PR 2020 - Proceedings （2020 Conference on Lasers and Electro-Optics Pacific Rim, CLEO-PR 2020 - Proceedings）  2020年08月

研究論文（学術雑誌）, 査読有り,  ISSN  9780646825045

　概要を見る

We propose an extension of the single-shot burst imaging scheme STAMP by introducing a lenslet array-based integral field spectrograph to improve light utilization efficiency and achieve better matching with spectrally sweeping burst probe pulses.

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640-nm Pr:YLF regenerative amplifier seeded by gain-switched laser diode pulses

Hara Y., Fujita S., Shioya Y., Kannari F.

Applied Optics （Applied Optics）  59 （ 17 ） 5098 - 5101 2020年06月

研究論文（学術雑誌）, 査読有り,  ISSN  1559128X

　概要を見る

© 2020 Optical Society of America We demonstrated the regenerative amplification of picosecond laser pulses generated by a gain-switched laser diode at 640 nm with a Pr:YLF crystal that was continuously pumped by a multimode blue laser diode. A 0.7-pJ seed pulse energy sufficiently suppressed the self-oscillation in the amplifier. The amplified pulse energy reached 33 µJ at a repetition rate of 10 kHz. The spatial beam quality was nearly TEM00. We also demonstrated second- and third-harmonic generation and obtained 320- and 213-nm pulse energies of 18 and 0.83 µJ at 10 kHz.

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Output characteristics of Pr:YAlO<inf>3</inf> and Pr:YAG lasers pumped by high-power GaN laser diodes

Fujita S., Tanaka H., Kannari F.

Applied Optics （Applied Optics）  59 （ 17 ） 5124 - 5130 2020年06月

研究論文（学術雑誌）, 査読有り,  ISSN  1559128X

　概要を見る

© 2020 OSA - The Optical Society. All rights reserved. We investigated whether Pr:YAlO3 and Pr:Y3Al5O12 (YAG) can work as gain media for high-power visible lasers and replace trivalent praseodymium (Pr)-doped fluoride crystals, with particular focus on thermal loading resistivity. Pr:YAlO3 exhibits a high laser gain at 747 nm, and we obtained a maximum output power of 1.2 W and a slope efficiency of 26.7% with high-power GaN laser diode pumping. Excited state absorption and large phonon energy hinder laser oscillation of Pr:YAG at room temperature. We obtained 616 nm laser oscillation of Pr:YAG at 40 K. Furthermore, we achieved a visible laser with Pr:YAG ceramics for the first time. The maximum output power is ∼30 mW with a slope efficiency of ∼0.7%.

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Extension of time window into nanoseconds in single-shot ultrafast burst imaging by spectrally sweeping pulses

Nemoto H., Suzuki T., Kannari F.

Applied Optics （Applied Optics）  59 （ 17 ） 5210 - 5215 2020年06月

研究論文（学術雑誌）, 査読有り,  ISSN  1559128X

　概要を見る

© 2020 Optical Society of America We achieved single-shot 2D-burst imaging with a ∼22 ps temporal resolution in a nanosecond time window using sequentially timed all-optical mapping photography with a spectral filtering (SF-STAMP) scheme, where a single snapshot of spectral images measured with a linear frequency chirped laser pulse forms time-resolved snapshots. We combined a pulse-stretching scheme of a free-space angular-chirp-enhanced delay (FACED) composed of a pair of tilted mirrors and a 4f -system. With a 4f -FACED system, we generated collinearly propagating burst laser pulses with a different center wavelength and a tunable time interval and demonstrated single-shot burst imaging with a 303 ps interval in a 1.5 ns time window by an SF-STAMP with spectrally sweeping probe pulses.

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1000-fps consecutive ultrafast 2D-burst imaging with a sub-nanosecond temporal resolution by a frequency-time encoding of SF-STAMP

Suzuki T., Nemoto H., Takasawa K., Kannari F.

Applied Physics A: Materials Science and Processing （Applied Physics A: Materials Science and Processing）  126 （ 2 ）  2020年02月

研究論文（学術雑誌）, 査読有り,  ISSN  09478396

　概要を見る

© 2020, Springer-Verlag GmbH Germany, part of Springer Nature. We demonstrated real-time, in-situ operation of a single-shot, frequency-time-encoding burst imaging method of sequentially timed all-optical mapping photography utilizing spectral filtering (SF-STAMP) by employing a high-speed camera with the frame rate of a 1000 fps as a detector. We obtained single-shot burst images of a pulse-by-pulse femtosecond laser ablation of a glass by a chirped probe laser pulse with a 1–2-ps frame interval or by a spectrally sweeping burst laser pulse train with a 300-ps interval. We observed burst images of plasma generation during the early stage of laser ablation in a glass with a short frame interval by a chirped probe laser pulse. We also captured burst images of plume and shock-wave generation in air with a 1.5-ns observation time window by a spectrally sweeping probe laser pulse train.

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Diode-pumped picosecond 640-nm Pr:YLF regenerative laser amplifier

Kannari F., Hara Y., Sugiyama N., Fujita S., Tanaka H.

Advanced Solid State Lasers - Proceedings Laser Congress 2019 (ASSL, LAC, LS and C) （Advanced Solid State Lasers - Proceedings Laser Congress 2019 (ASSL, LAC, LS and C)）  2019年09月

研究論文（学術雑誌）, 査読有り,  ISSN  9781943580682

　概要を見る

© 2019 The Author(s). We demonstrated generative picosecond laser pulse amplification at 640 nm for the first time using a Pr3+:YLF crystal, which was continuously pumped by an InGaN diode laser, with a mode-locked Pr3+:YLF oscillator.

Resistance to optical distortions in three-dimensional interferometric temporal focusing microscopy

神成 文彦

Optics Communications （Optics Communications）  430   486 - 496 2019年08月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  00304018

　概要を見る

２次元時間集光と構造証明法を組み合わせた３D-ITF法が波面歪みに対して耐性が強いことを数値シミュレーションから明らかにし、散乱性材料の２光子励起蛍光顕微鏡に適した手法であることを議論した。

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Frequency-domain linear interferometer with spectrally shaped photons

Hosaka A., Tomita M., Tsujimoto Y., Niimura S., Omi A., Wakui K., Fujiwara M., Shikano Y., Takeoka M., Kannari F.

2019 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2019 （2019 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2019）  2019年06月

研究論文（学術雑誌）, 査読有り,  ISSN  9781728104690

　概要を見る

© 2019 IEEE. Beam splitters and phase shifters compose linear photonic circuits and are the most fundamental elements in photon-based quantum information processing. While integration of these linear components on a chip for spatial modes has been dramatically developed in recent years [1], there is another approach for integrated quantum circuits : wavelength division multiplexing (WDM). The degrees of freedom of light allow photons exhibiting different wavelengths to exist independently in the same space, therefore using such characteristics can allow further integrating of photons and modes in a small space.

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