The University of Tokyo · Engineering
Professor Kazuki Hashimoto's research lab specializes in ultrafast optical spectroscopy and advanced interferometric techniques for high-speed, high-resolution molecular analysis. The lab focuses on developing next-generation Fourier-transform and coherent anti-Stokes Raman spectroscopy systems that achieve unprecedented measurement speeds—exceeding 20,000 spectra per second—while maintaining high signal-to-noise ratios. Key innovations include rapid-scanning interferometers, dual-comb configurations, and phase-controlled detection schemes tailored for broadband mid-infrared and Raman spectroscopy. The lab’s work enables real-time monitoring of transient chemical dynamics, with applications in materials science, chemistry, and biomedical diagnostics.
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High-speed measurement confronts the extreme speed limit when the signal becomes comparable to the noise level. In the context of broadband mid-infrared spectroscopy, state-of-the-art ultrafast Fourier-transform infrared spectrometers, in particular dual-comb spectrometers, have improved the measurement rate up to a few MSpectra s<sup>-1</sup>, which is limited by the signal-to-noise ratio. Time-stretch infrared spectroscopy, an emerging ultrafast frequency-swept mid-infrared spectroscopy techni
We present a Fourier-transform coherent anti-Stokes Raman scattering (FT-CARS) spectroscopy technique that achieves broadband CARS measurements at an ultrahigh scan rate of more than 20,000 spectra/s - more than 20 times higher than that of previous broadband coherent Raman scattering spectroscopy techniques. This is made possible by an integration of a FT-CARS system and a rapid-scanning retro-reflective optical path length scanner. To demonstrate the technique's strength, we use it to perform
We demonstrate ultra-broadband Fourier-transform coherent anti-Stokes Raman scattering (FT-CARS) spectroscopy spanning over 3,000 cm<sup>-1</sup> with a rapid-scan Michelson interferometer at a scan rate of 24,000 spectra/s. Using sub-10-fs optical pulses from a mode-locked laser, we measure broad CARS spectrum covering both the fingerprint region (500-1,800 cm<sup>-1</sup>) and the C-H, N-H, O-H stretching region (2,700-3,600 cm<sup>-1</sup>). To the best of our knowledge, this is the first dem
Fourier-transform spectroscopy (FTS) has been widely used as a standard analytical technique over the past half-century. FTS is an autocorrelation-based technique that is compatible with both temporally coherent and incoherent light sources, and functions as an active or passive spectrometer. However, it has been mostly used for static measurements due to the low scan rate imposed by technological restrictions. This has impeded its application to continuous rapid measurements, which would be of
Abstract Fourier‐transform infrared spectroscopy (FTIR) is the golden standard of mid‐infrared (MIR) molecular spectroscopic analysis through optically encoded vibrational signatures. Michelson‐type FTIR and MIR dual‐comb spectrometers allow us to simultaneously investigate multiple molecular species via the broadband and high‐resolution spectroscopic capabilities. However, these are not applicable to high‐speed measurements due to the low temporal resolution which is fundamentally limited by th
Abstract Nonlinear interferometry with entangled photons allows for characterizing a sample without detecting the photons interacting with it. This method enables highly sensitive optical sensing in the wavelength regions where efficient detectors are still under development. Recently, nonlinear interferometry has been applied to interferometric measurement techniques with broadband light sources, such as Fourier‐transform infrared spectroscopy and infrared optical coherence tomography. However,
We present a simple method for continuous snapshot multispectral imaging or multispectral videography that achieves high-speed spectral video recording without the need for mechanical scanning and much computation for datacube construction. The enabling component of this method is an array of periscopes placed in a prism-based spectral shaper that spectrally separates the image without image deformation. As a proof-of-principle demonstration, we show five-color multispectral video recording in t
Abstract Fourier-transform infrared spectroscopy (FTIR) is an indispensable analytical method that allows label-free identification of substances via fundamental molecular vibrations. However, traditional FTIR spectrometers require mid-infrared (MIR) elements, including low-efficiency MIR photodetectors. SU(1,1) interferometry has previously enabled FTIR with undetected MIR photons via spontaneous parametric down-conversion in the low-parametric-gain regime, where the number of photons per mode
Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text K. Hashimoto and T. Ideguchi, "Nyquist-Limited Efficient Fourier-Transform Spectroscopy," in Conference on Lasers and Electro-Optics, OSA Technical Digest (Optica Publishing Group, 2019), paper SM1N.4. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article
Fourier-transform infrared spectroscopy (FTIR) is the golden standard of mid-infrared (MIR) molecular spectroscopic analysis through optically-encoded vibrational signatures. Michelson-type FTIR and MIR dual-comb spectrometers allow us to simultaneously investigate multiple molecular species via the broadband and high-resolution spectroscopic capabilities. However, these are not applicable to high-speed measurements due to the low temporal resolution which is fundamentally limited by the signal-
電柱は電気通信を支える重要なインフラ設備であるが，これまで震災による地盤の液状化によって，多くの電柱が沈下，傾斜の被害を受けている．過去にも電柱への液状化対策の研究は行われていたが，電柱1箇所毎に実施する対策としては，規模が大きくなる等の課題があった．本研究は，液状化による電柱の沈下，傾斜被害への対策として，グラベルドレーン機能を付与した建柱工法（根入れ部の砕石埋戻し工法）を検討し，模型実験により効果の検証を行ったものである．本実験では，電柱根入れ部への小規模な対策であっても電柱周囲の液状化発生を遅らせる効果や，地盤支持力の増大による沈下，傾斜を抑える効果を期待できることが確認された．
Fourier-transform infrared spectroscopy (FTIR) is an indispensable analytical method that allows label-free identification of substances via fundamental molecular vibrations. However, the sensitivity of FTIR is often limited by the low efficiency of mid-infrared (MIR) photodetectors. SU(1,1) interferometry has previously enabled FTIR with undetected MIR photons via spontaneous parametric down-conversion in the low-parametric-gain regime, where the number of photons per mode is much less than one
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Nonlinear interferometry with entangled photons allows for characterizing a sample without detecting the photons interacting with it. This method enables highly sensitive optical sensing in the wavelength regions where efficient detectors are still under development. Recently, nonlinear interferometry has been applied to interferometric measurement techniques with broadband light sources, such as Fourier-transform infrared spectroscopy and infrared optical coherence tomography. However, they wer
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