Published papers

アルミ製ナノテーパチップを用いて、400nmおよび800nmのフェムト秒レーザー励起プラズモンパルスを<80nmの領域に局在化させ、分子振動選択型の走査型CARS分光を達成した。

© 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.

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.

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。

© 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.

© 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.

© OSA 2018 We generate 1.57-m squeezed vacuum pulses by degenerate spontaneous parametric down conversion (DSPDC) and observe 3.5dB anti-squeezing and -0.48dB squeezing using local oscillator pulses generated from a degenerate synchronously pumped optical parametric oscillator.

© 2018 OSA. We generate 1.57-μm squeezed vacuum pulses by degenerate spontaneous parametric down conversion (DSPDC)and observe 3.5dB anti-squeezing and -0.48dB squeezing using local oscillator pulses generated from a degenerate synchronously pumped optical parametric oscillator.

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.

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.

© 2019 IEEE. Since terahertz (THz) electromagnetic wave exhibits high transparency for various matters and can probe fingerprint spectra of various substances, THz imaging is expected for various quality inspections. Thus, it is desireble to capture 2-D images without spatial scanning. Moreover, if we can capture 2-D burst images of ultrafast transient phenomena in a single shot basis, it will be a powerful tool to understand the response of matters under high electric fields. However, with the conventional terahertz imaging method[1], iterative measurements are always required for capturing dynamic 2-D images.

© OSA 2018 We generate a spectrally sweeping 100-ps-interval pulse train for ultrafast burst imaging. Adopting those pulses to sequentially timed all-optical mapping photography utilizing spectral filtering (SF-STAMP), we realize single-shot burst imaging with a sub-nanosecond time window.

© 2018 OSA. We generate a spectrally sweeping 100-ps-interval pulse train for ultrafast burst imaging. Adopting those pulses to sequentially timed all-optical mapping photography utilizing spectral filtering (SF-STAMP), we realize single-shot burst imaging with a sub-nanosecond time window.

© 2019 IEEE High-power picosecond lasers in the visible and ultraviolet wavelength hold a lot of advantages in various applications. The high absorption efficiency in the various metals leads to the higher removal rates, and the shorter pulse widths can suppress thermal influence during the material processing. Recently, the significant progress in the output power of indium gallium nitride (InGaN)-based laser diodes (LDs) has developed the compact high-power lasers which oscillate directly in the visible wavelength. For example, a continuous-wave laser output power of >6.7 W at the fundamental wavelength of 639 nm was reported with a praseodymium-doped LiYF4 crystal (Pr:YLF) [1]. Moreover, mode-locked picosecond lasers were also reported using a SESAM saturable absorber with Pr:YLF lasers [2,3]. Further scaling of visible picosecond laser pulse requires an amplifier, but only few experiments were reported on the visible laser amplifiers [4]. For example, the maximum amplification factor of 10 was demonstrated at 478 nm [5]. In this paper, a 639-nm picosecond-pulse regenerative amplifier using a Pr:YLF crystal is demonstrated for the first time.

© 2019 IEEE. High-power picosecond lasers in the visible and ultraviolet wavelength hold a lot of advantages in various applications. The high absorption efficiency in the various metals leads to the higher removal rates, and the shorter pulse widths can suppress thermal influence during the material processing. Recently, the significant progress in the output power of indium gallium nitride (InGaN)-based laser diodes (LDs) has developed the compact high-power lasers which oscillate directly in the visible wavelength. For example, a continuous-wave laser output power of >6.7 W at the fundamental wavelength of 639 nm was reported with a praseodymium-doped LiYF4 crystal (Pr:YLF) [1]. Moreover, mode-locked picosecond lasers were also reported using a SESAM saturable absorber with Pr:YLF lasers [2,3]. Further scaling of visible picosecond laser pulse requires an amplifier, but only few experiments were reported on the visible laser amplifiers [4]. For example, the maximum amplification factor of 10 was demonstrated at 478 nm [5]. In this paper, a 639-nm picosecond-pulse regenerative amplifier using a Pr:YLF crystal is demonstrated for the first time.

© 2019 IEEE To capture ultrafast non-repeatable phenomena, we had developed two methods of single-shot ultrafast two-dimensional (2D)- imaging of sequentially timed all-optical mapping photography (STAMP) [1] and STAMP utilizing spectral filtering (SF-STAMP) [2, 3]. In these STAMP schemes, spectral images measured by a linearly frequency-chirped laser pulse corresponds to time-resolved snapshots. So far, we achieved single-shot burst imaging of ultrafast phenomena in picosecond time windows with sub-picosecond temporal resolutions. However, it is not straightforward to extend the time window beyond 10 ps by a conventional method to chirp the probe laser pulse using material dispersion. Currently, we applied a new scheme of free-space angular-chirp-enhanced delay (FACED) [4] composed of a tilted pair of mirrors to SF-STAMP and achieved a sub-ns time window [5]. In this work, we generated spectrally sweeping burst pulses with a 300-ps-pulse interval by FACED, and captured single-shot ultrafast 2D-burst images with a few-nanosecond time window. Furthermore we combined a 1-kfps fast camera. Repetitive laser ablation was captured with 10-frame, 300-ps interval images at every 1 ms.

© 2019 IEEE. To capture ultrafast non-repeatable phenomena, we had developed two methods of single-shot ultrafast two-dimensional (2D)-imaging of sequentially timed all-optical mapping photography (STAMP) [1] and STAMP utilizing spectral filtering (SF-STAMP) [2, 3]. In these STAMP schemes, spectral images measured by a linearly frequency-chirped laser pulse corresponds to time-resolved snapshots. So far, we achieved single-shot burst imaging of ultrafast phenomena in picosecond time windows with sub-picosecond temporal resolutions. However, it is not straightforward to extend the time window beyond 10 ps by a conventional method to chirp the probe laser pulse using material dispersion. Currently, we applied a new scheme of free-space angular-chirp-enhanced delay (FACED) [4] composed of a tilted pair of mirrors to SF-STAMP and achieved a sub-ns time window [5]. In this work, we generated spectrally sweeping burst pulses with a 300-ps-pulse interval by FACED, and captured singleshot ultrafast 2D-burst images with a few-nanosecond time window. Furthermore we combined a 1-kfps fast camera. Repetitive laser ablation was captured with 10-frame, 300-ps interval images at every 1 ms.

© OSA 2018 We propose a multistage quantum pulse gate which efficiently mix multimode quantum states in the frequency domain. Furthermore we introduce a practicable quantum simulator for calculating Frank Condon factors.

© 2018 OSA. We propose a multistage quantum pulse gate which efficiently mix multimode quantum states in the frequency domain. Furthermore we introduce a practicable quantum simulator for calculating Frank Condon factors.

© 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.