arXiv subjects

Takahiro Kageyama

Publications and source records attributed to Takahiro Kageyama.

3 recordsLinked to original sources

arXiv2025

Fiber-based mid-infrared frequency-swept laser at 50 MScans/s via frequency down-conversion of time-stretched pulses

Increasing the sweep rate of mid-infrared (MIR) frequency-swept sources offers significant potential for various high-speed spectroscopy-based applications. While continuous-wave frequency-swept lasers have achieved sweep rates up to 1 MHz, a recently demonstrated time-stretched ultrashort pulsed laser has reached a significantly higher sweep rate, up to tens of MHz. However, the previous system relied on a bulky femtosecond optical parametric oscillator and produced only ~30 discrete spectral elements due to the use of a free-space time stretcher. In this work, we present a fiber-based frequency-swept MIR source that utilizes the frequency down-conversion of time-stretched near-infrared pulses, employing a compact mode-locked fiber laser and telecommunication fiber. As a proof-of-concept demonstration, we performed MIR spectroscopy of methane gas around 3.4 um at a rate of 50 MSpectra/s, capturing 220 spectral elements over a range of 19.0 cm-1. This compact and robust high-speed MIR frequency-swept laser system holds the potential for deployment in field applications.

physics.optics↗

arXiv2022

Upconversion time-stretch infrared spectroscopy

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, which is limited by the signal-to-noise ratio. Time-stretch infrared spectroscopy, an emerging ultrafast frequency-swept mid-infrared spectroscopy technique, has shown a record-high rate of 80 Mspectra/s with an intrinsically higher signal-to-noise ratio than Fourier-transform spectroscopy by more than the square-root of the number of spectral elements. However, it can measure no more than ~30 spectral elements with a low resolution of several cm-1. Here, we significantly increase the measurable number of spectral elements to more than 1,000 by incorporating a nonlinear upconversion process. The one-to-one mapping of a broadband spectrum from the mid-infrared to the near-infrared telecommunication region enables low-loss time-stretching with a single-mode optical fiber and low-noise signal detection with a high-bandwidth photoreceiver. We demonstrate high-resolution mid-infrared spectroscopy of gas-phase methane molecules with a high resolution of 0.017 cm-1. This unprecedentedly high-speed vibrational spectroscopy technique would satisfy various unmet needs in experimental molecular science, e.g., measuring ultrafast dynamics of irreversible phenomena, statistically analyzing a large amount of heterogeneous spectral data, or taking broadband hyperspectral images at a high frame rate.

physics.optics↗

arXiv2021

Compressive dual-comb spectroscopy

Broadband, high resolution and rapid measurement of dual-comb spectroscopy (DCS) generates a large amount of data stream. We numerically demonstrate significant data compression of DCS spectra by using a compressive sensing technique. Our numerical simulation shows a compression rate of more than 100 with 3% error in mole fraction estimation of mid-infrared (MIR) DCS of two molecular species in a broadband (~30 THz) and high resolution (~115 MHz) condition. We also numerically demonstrate a massively parallel MIR DCS spectrum of 10 different molecular species can be reconstructed with a compression rate of 10.5 with a transmittance error of 0.003 from the original spectrum.

eess.SP↗