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Volume 49, Issue 4
Topical Papers on Time Stretch Spectroscopy and Applications −Space-Time Duality in Ultrafast Optical Signal Processing−
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Topical Papers on Time Stretch Spectroscopy and Applications -Space-Time Duality in Ultrafast Optical Signal Processing-
Topical Paper
Laser Review
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Fumihiko KANNARI2021 Volume 49 Issue 4 Pages 197-
Published: 2021
Released on J-STAGE: April 11, 2024
JOURNAL FREE ACCESSAdvances in Fourier optics and information processing technology have facilitated a variety of new research areas in telecommunications, biology, quantum information science, spectroscopy, and atomic and molecular physics. The concept of space-time duality plays an important role as a system design tool for ultrafast optical processing and characterization. In particular, time-lens-based temporal imaging systems enable additional features such as waveform expansion and compression that are particularly useful for ultrafast optical signal processing. The time-equivalent optical setup of a spatial 2-f system, which acts as a Fourier processor (time-to-frequency and frequency-to-time conversion)，can be used as a basic component of more complex temporal imaging systems. This special issue focuses on timestretch spectroscopy, which uses frequency chirp ultrafast laser pulses to capture ultrafast phenomena in real time.View full abstractDownload PDF (390K) -
Masayuki SUZUKI2021 Volume 49 Issue 4 Pages 200-
Published: 2021
Released on J-STAGE: April 11, 2024
JOURNAL FREE ACCESSTime stretch spectroscopy enables a successive single-shot spectrum measurement over a couple of millisecond time span in real-time. This powerful method can be applied for ultrafast biomedical imaging but also for understanding complex nonlinear novel dynamics in a mode-locked fiber laser. This review introduces the recent results on the transient spectral dynamics of pulse formation in mode-locking and the shot-to-shot spectral fluctuation of supercontinuum generation from a photonic crystal fiber pumped by Yb fiber chirped-pulse amplification system.View full abstractDownload PDF (680K) -
Ryosuke SHIMIZU2021 Volume 49 Issue 4 Pages 206-
Published: 2021
Released on J-STAGE: April 11, 2024
JOURNAL FREE ACCESSThe time-frequency duality of light is the fundamental concept for ultrafast laser science and technologies. Although the 1D Fourier transform connects electric field distributions between time and frequency domains, 1D treatment is insufficient for understanding the behavior of time-frequency entangled photons. Elucidation of the Fourier duality of entangled-photon wave packets is key for further development of quantum photonics in the ultrafast regime; unfortunately, it hasn’t yet been demonstrated. Here we present the duality as it appears in the frequency spectrum and the temporal shape of the entangled- photon wave packet with two-photon coincidence measurements in the time and frequency domains to extract two-photon time-frequency distributions. We also estimate the time-bandwidth product values in 2D time-frequency space to confirm the Fourier-limited conditions of the entangled-photon wave packets and discuss the prospects of ultrafast quantum optics with time-frequency entangled photons.View full abstractDownload PDF (1140K) -
Masataka KOBAYASHI, Jun TAKEDA, Ikufumi KATAYAMA2021 Volume 49 Issue 4 Pages 212-
Published: 2021
Released on J-STAGE: April 11, 2024
JOURNAL FREE ACCESSHigh-repetition-rate ultrafast pump-probe and terahertz spectroscopies were achieved by combining time-stretching and time-encoding techniques. We used chirped probe pulses to map the temporal information to the spectrum and observed its pump-induced change using a combination of a chirped fiber Bragg grating and a photodiode. The repetition rate of the waveform acquisition is as high as 75 kHz, which is limited by the repetition rate of the excitation laser. We applied the method to the observation of ultrafast dynamics in the formation of laser-induced periodic surface structures (LIPSS) and laser ablation in a phase change material, Ge2Sb2Te5 thin film. The observed pulse-to-pulse change of the ultrafast dynamics during LIPSS formation reveals the importance of ultrafast processes for energy relaxation, demonstrating promising capability of our proposed method.View full abstractDownload PDF (813K) -
Katsuhiro ISHII, Hiroshi HASEGAWA, Hideaki FURUKAWA2021 Volume 49 Issue 4 Pages 217-
Published: 2021
Released on J-STAGE: April 11, 2024
JOURNAL FREE ACCESSA technique called time-stretch dispersive Fourier transformation provides the rapid spectroscopy of the ultrashort pulses of light at a repetition from a few tens MHz to a few tens GHz. Time-stretch OCT using time-stretch dispersive Fourier transformation has also been studied in recent years. This paper reviews the recent researches and shows the principle of time-stretch OCT. We also introduce the in-situ measurement of a keyhole shape in the laser welding process that we are developing and show how to achieve real-time signal analysis in time-stretch OCT as well as the current status of real-time measurement.View full abstractDownload PDF (762K) -
Takashi KATO, Kaoru MINOSHIMA2021 Volume 49 Issue 4 Pages 222-
Published: 2021
Released on J-STAGE: April 11, 2024
JOURNAL FREE ACCESSWe developed a one-shot 3D measurement method using an optical frequency comb. High transverse spatial resolution was achieved by all-optical processing with precise phase control of the optical frequency comb. High speed, high accuracy, and wide dynamic range were achieved simultaneously. Such results have not been done by conventional methods. We also demonstrated 3D profile measurements with sub-μm uncertainty and a dynamic range over six digits. This method can also perform ultrafast 3D imaging with a single picosecond pulse. Using a 16-ps chirped pulse of an optical frequency comb, we demonstrated fully single-pulse 3D surface profile imaging with μm-level uncertainty and high image resolution with 100-square-pixels, determined by the resolution of the optics and the image sensors. Electric-field-induced picosecond transient 3D imaging was also demonstrated.View full abstractDownload PDF (819K) -
[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...2021 Volume 49 Issue 4 Pages 228-
Published: 2021
Released on J-STAGE: April 11, 2024
JOURNAL FREE ACCESSPlatelets are multifunctional cells whose primary function is to stop bleeding through stimulus-dependent activation. In addition to the hemostatic process, platelets are also involved in pathological thrombosis. Furthermore, according to recent reports, platelet activation and thrombus formation are a crucial factor in predicting the severity of COVID-19. However, due to the highly dynamic nature of platelets, traditional technologies fail to provide comprehensive information of platelets. Fortunately, the advent of optical time-stretch imaging enables the high-throughput, label-free single-cell imaging for analyzing platelets and platelet aggregates in blood. Recent studies also show that a combination of optical timestretch imaging, microfluidics, and deep learning provides a promising laboratory testing tool for examining the morphology of platelets on a large scale. This review article introduces the principles of optical time-stretch imaging and its application to the diagnosis of COVID-19-associated thrombosis.View full abstractDownload PDF (992K) -
Fumihiko KANNARI2021 Volume 49 Issue 4 Pages 234-
Published: 2021
Released on J-STAGE: April 11, 2024
JOURNAL FREE ACCESSVarious hyper-spectral imaging schemes can be used in sequaentially-timed all-optical mapping photography (STAMP) which captures ultrafast phenomena in the sub-picosecond to the nanosecond range by single-shot burst images. Temporal images are encoded in spectral images probed by a frequency chirped ultrafast laser pulse. To fully utilize the functions of a center-wavelength-sweeping pulse train generated by a free-space angular-chirp-enhanced delay (FACED) optical layout for a probe laser pulse in STAMP, we introduced an integral field spectroscopy (IFS) method using a microlens array (MLA) to produce hyperspectral images, referring to the technique as LA-STAMP.View full abstractDownload PDF (884K)
Laser Original
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[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...2021 Volume 49 Issue 4 Pages 240-
Published: 2021
Released on J-STAGE: April 11, 2024
JOURNAL FREE ACCESSWe propose two-color sequentially timed all-optical mapping photography with glass-block chirping, which allows transmission spectroscopic imaging for analyzing ultrafast phenomena with five frames of high pixel resolution images (350 × 350 pixels), captured at a frame rate of approximately 1 Tfps in a single shot. The effectiveness of the proposed method was demonstrated by capturing laser ablation of glass at 400 and 800 nm bands. The imaging results showed that the plasma absorption and scattering caused different transmittance changes in the two colors. The proposed method could be applied to the multifaceted analysis of non-repetitive ultrafast phenomena.View full abstractDownload PDF (754K) -
Yoshimasa KAWATA2021 Volume 49 Issue 4 Pages 264-
Published: 2021
Released on J-STAGE: April 11, 2024
JOURNAL FREE ACCESSThis paper describes the overview of special issues for the recent progress and developments on living- cell imaging technique for analysis of cell functions. The topics of this issues covers digital holography for imaging of phase object, super resolution imaging with laser scanning confocal microscope, nonlinear Raman scattering, multi-spectrum stimulated Raman scattering, a new type annular illumination technique for phase objects, near-infrared hyper spectrum imaging.View full abstractDownload PDF (209K)
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