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Volume 43, Issue 4
Topical Papers on Cutting-Edge Photon Science Applying Fourier Optics
Displaying 1-10 of 10 articles from this issue
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Topical Papers on Cutting-Edge Photon Science Applying Fourier Optics
Topical Paper
Laser Review
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Fumihiko KANNARI2015 Volume 43 Issue 4 Pages 191-
Published: 2015
Released on J-STAGE: December 17, 2020
JOURNAL FREE ACCESSDownload PDF (228K) -
Masashi UGAWA, Takuro IDEGUCHI, Keisuke GODA2015 Volume 43 Issue 4 Pages 193-
Published: 2015
Released on J-STAGE: December 17, 2020
JOURNAL FREE ACCESSPrecision measurement of fast non-repetitive dynamics is essential in all branches of science. However, conventional spectroscopy and imaging methods cannot capture some of such dynamical processes since their scan rate is limited by the charge download rate of CCD and CMOS image sensors. While the pump-probe method can circumvent this predicament without the need for a high-speed detector, it only works for easy-to-reproduce events for repetitive time-delayed measurements. In this review article, we introduce a method based on temporal dispersion known as dispersive Fourier transformation (DFT) which can overcome these limitations in the conventional methods and hence capture fast non-repetitive processes at a frame rate up to 100 MHz. With this advantage, DFT can find its way in a variety of applications in basic research, industry, and medicine. In this review article, we first discuss the principle of DFT and then introduce its application to ultrafast imaging.View full abstractDownload PDF (1667K) -
Keiichi NAKAGAWA2015 Volume 43 Issue 4 Pages 199-
Published: 2015
Released on J-STAGE: December 17, 2020
JOURNAL FREE ACCESSHigh-speed photography is a powerful tool for exploring various types of dynamics and has played a critical role in discovery of fast processes and establishment of new theories. For capturing ultrafast events on sub-nanosecond timescales, we have developed a high-speed imaging method distinct from conventional CCD or CMOS image sensors, known as sequentially timed all-optical mapping photography (STAMP). This method does not require repetitive measurement, which is mandatory in the pump-probe method, and thus is able to capture phenomena that can never be investigated with conventional methods. To show the broad utility of the camera, we use it to obtain motion pictures of laser ablation and lattice vibrational waves, both of which were previously difficult to observe with conventional methods in a single shot.View full abstractDownload PDF (2057K) -
Qiyuan SONG, Aoi NAKAMURA, Kenichi HIROSAWA, Keisuke ISOBE, Katsum ...2015 Volume 43 Issue 4 Pages 203-
Published: 2015
Released on J-STAGE: December 17, 2020
JOURNAL FREE ACCESSWe review the technique of 2-dimensional spatiotemporal focusing (2D STF). STF employs ultrashort lasers pulses, which are spatially chirped by a diffractive grating, to generate the Fourier-transform-limited pulse only at a focal plane. STF offers a widefield illumination feature in two-photon excited fluorescence microscopy. 2D STF inherits this idea but uses a 2D spectral disperser to further stretch the out-of-focus pulse in spatiotemporal domain. By giving a simple mathematical analysis, we show the improved sectioning ability of 2D STF compared with STF. 2D STF based two-photon excitation fluorescence microscopy can realize fast volume imaging. An example to trace the 3-dimensional Brownie motion is demonstrated.View full abstractDownload PDF (1319K) -
Jun TAKEDA, Yasuo MINAMI, Ikufumi KATAYAMA2015 Volume 43 Issue 4 Pages 208-
Published: 2015
Released on J-STAGE: December 17, 2020
JOURNAL FREE ACCESSWe proposed broadband single-shot femtosecond spectroscopy in a time-frequency space using a reflective echelon mirror that makes a spatially encoded time-delay for a white-light continuum probe pulse. It produces a temporal step of 66 fs and an overall time-delay of 33 ps. With this technique, we observed an ultrafast crystalline-to-amorphous phase-change in chalcogenide alloys: Ge2Sb2Te5 (GST) and GeTe thin films. We even measured the absorbance change that accompanied the ultrafast amorphization for laser fluences above the critical value, where a permanent recording mark was formed. The observed rise time to reach amorphization was 130~200 fs both in GST and GeTe thin films, suggesting that ultrafast amorphization can be attributed to the rearrangement of Ge atoms from an octahedral to a tetrahedral structure.View full abstractDownload PDF (761K) -
Akira SUDA, Hiroshi TAKAHASHI, Keisuke TODA2015 Volume 43 Issue 4 Pages 213-
Published: 2015
Released on J-STAGE: December 17, 2020
JOURNAL FREE ACCESS -
Tomoya OKINO, Yusuke FURUKAWA, Yasuo NABEKAWA, Kaoru YAMANOUCHI, K ...2015 Volume 43 Issue 4 Pages 217-
Published: 2015
Released on J-STAGE: December 17, 2020
JOURNAL FREE ACCESSNonlinear Fourier transform spectroscopy is extended to the attosecond temporal domain and extreme ultraviolet wavelength region to perform two-color two-photon photofragment excitation spectroscopy of molecules and to investigate ultrafast molecular dynamics such as temporal evolution of vibrational and electronic wavepackets. Molecular nonlinear responses are encoded in the fringe-resolved autocorrelation trace of an attosecond pulse train through non-sequential two-photon processes. Femtosecond vibrational motion of molecules can be traced in real-time through sequential two-photon processes. By introducing a velocity map imaging spectrometer, momentum image of photofragment ions and/or photoelectrons can be measured to investigate coupled electron-nuclear dynamics from femtosecond to attosecond.View full abstractDownload PDF (867K)
Laser Original
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Yo SUZUKI, Wei QI, Shun SATO, Masaru FUJIWARA, Hiroyuki HIRAMATSU, Nat ...2015 Volume 43 Issue 4 Pages 222-
Published: 2015
Released on J-STAGE: December 17, 2020
JOURNAL FREE ACCESSWe realized the palm-size (Dimension: L56 mm × W69 mm × H43 mm, Weight: 500 g) wide-field spectroscopic imager based on the proposed imaging-type 2-dimensional Fourier spectroscopy. We installed the variable phase-filter at optical Fourier transform plane of infinity corrected optical systems. Because of the wavefront-division-type phase-shift-interferometer, the proposed near-common-path interferometer between objective beams has strong robustness for mechanical vibrations. But destructive interference phenomena in accordance with phase-shift value were occurred between adjacent singlebright points. To improve visibilities especially for low spatial frequencies of wide-field mid-infrared images, we also proposed the conjugate-plane multi-slit superimpose method for thinning out adjacent single-bright points. Thereby, we could demonstrate the omnidirectional spectroscopic imaging with 50-degree view angle by a hyperboloidal mirror. In this paper, we clarified the optical phenomenon that results in phase-shift destructions between adjacent single-bright points. And then, we demonstrated feasibilities of wide-field spectroscopic imaging in visible and mid-infrared light region.View full abstractDownload PDF (2947K) -
Haruyasu ITOH, Satoshi HASEGAWA, Yoshio HAYASAKI, Haruyoshi TOYODA2015 Volume 43 Issue 4 Pages 227-
Published: 2015
Released on J-STAGE: December 17, 2020
JOURNAL FREE ACCESSHolographic laser processing using a spatial light modulator (SLM) enhances the efficiency and accuracy of such laser processing as precise periodic structuring, welding, optical storage, and dicing. In this paper, we experimentally confirmed the stability of SLM in a laser processing setup using a high-power femtosecond laser. A temperature-controlled SLM indicated enough stability for a regenerative amplified femtosecond laser with 5.7 W power. In addition, we applied SLM to large-scale parallel laser processing with a high-power femtosecond laser. On a glass sample, we successfully performed 1005 parallel laser processing by an optimized computer-generated hologram (CGH). In large-scale parallel laser processing, the required pulse energy was sufficiently smaller than the SLM’s damage threshold.View full abstractDownload PDF (1902K)
Regular Paper
Technical Note
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Masao OGAKI, Shinji WAKUI2015 Volume 43 Issue 4 Pages 233-
Published: 2015
Released on J-STAGE: December 17, 2020
JOURNAL FREE ACCESSAccording to the progress of optical reaction materials and so on, various laser flash photolysis systems have been developed. In the photolysis, a xenon lamp with high flashing intensity is used as a reference light source. However, a flashing jitter inherent in the xenon lamp has a harmful influence on the measurement accuracy. In detail, flashing light of a nanosecond laser dose not coincide with that of the xenon lamp so often. In order to overcome the above issue, a xenon flashing circuit such that generates lamp intensity with flat region is proposed. This paper shows the proposed flashing circuit having a LC cascade circuit with trimming components between DC voltage source and the xenon lamp. By using this circuit, the xenon light intensity with the flat region more than 20 μs is realized and it is shown that its feature contributes the research of the photolysis.View full abstractDownload PDF (896K)
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