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arxiv: 2606.31479 · v1 · pith:4MCCRNSI · submitted 2026-06-30 · physics.optics

Pulse-to-pulse spectral phase characterization of mid-infrared pulses at megahertz rates

Zhihao Deng , Zicong Xu , Kazuki Hashimoto , Gabriel Demontigny , Denis V. Seletskiy , Takuro Ideguchi This is my paper

Reviewed by Pith T0 review T1 audit T2 compute T3 formal T4 kernel 2026-07-01 03:48 UTCgrok-4.3pith:4MCCRNSIrecord.jsonopen to challenge →

classification physics.optics
keywords mid-infrared pulsesspectral phase characterizationupconversiontime-stretchspectral interferometrymegahertz ratespulse-resolved measurementultrashort pulses
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The pith

TSUBAME performs single-pulse spectral phase characterization of mid-infrared pulses at 1 MHz repetition rates.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper introduces TSUBAME, a method that measures the spectral phase of every individual mid-infrared pulse at the full laser repetition rate of 1 MHz. Standard characterization tools cannot keep up with the speed of modern MIR sources operating at kHz or MHz rates. The technique converts MIR pulses to the near-infrared, stretches them temporally, and extracts phase via spectral interferometry in a scan-free manner. Validation on 4.98-5.30 micrometer pulses with added dispersion showed close agreement with theory, and the setup resolved phase changes on microsecond timescales.

Core claim

TSUBAME enables pulse-to-pulse spectral phase characterization of ultrashort MIR pulses at the laser repetition rate by combining MIR-to-NIR upconversion, time-stretch, and spectral interferometry, achieving 1 MHz operation as validated by agreement with theoretical dispersion predictions over 4.98-5.30 um and by capturing dynamic variations on microsecond timescales.

What carries the argument

TSUBAME (time-stretch upconversion-based mid-infrared pulse evaluation), which transfers phase information via upconversion and extracts it through time-stretched spectral interferometry without mechanical scanning.

If this is right

  • Real-time monitoring and optimization of high-repetition-rate MIR pulses becomes feasible.
  • Dynamic spectral phase variations can be resolved on microsecond timescales.
  • The approach supports applications in strong-field physics, high-harmonic generation, and coherent molecular control.
  • Single-pulse-resolved measurements are obtained directly at the source repetition rate.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The method could enable closed-loop feedback for active shaping of MIR pulses in real time.
  • Similar upconversion and stretching steps might extend the technique to other wavelength ranges with appropriate conversion materials.
  • Integration with quantum optics experiments could allow faster phase tracking for coherent control tasks.

Load-bearing premise

The mid-infrared to near-infrared upconversion step transfers the spectral phase without introducing uncharacterized distortions or losses across the 4.98-5.30 micrometer band.

What would settle it

Applying a known dispersion to the MIR pulses and observing that the measured spectral phase deviates substantially from the calculated value would show the phase transfer or extraction step is inaccurate.

Figures

Figures reproduced from arXiv: 2606.31479 by Denis V. Seletskiy, Gabriel Demontigny, Kazuki Hashimoto, Takuro Ideguchi, Zhihao Deng, Zicong Xu.

Figure 3
Figure 3. Figure 3: (f) for the pulse centered at 999 ns. The parabolic profile of the retrieved MIR spectral phase indicates the presence of GDD. By fitting the phase with a second-order polynomial, we estimated a GDD of −14125 fs2 , which agrees well with the theoretical value of −14230 fs2 , calculated by accounting for the dispersive contributions of the optical components in the system [PITH_FULL_IMAGE:figures/full_fig_… view at source ↗
read the original abstract

Pulse-resolved spectral phase measurement of mid-infrared (MIR) pulses is essential for many applications, from precise waveform control to ultrafast quantum optics. However, conventional MIR pulse characterization techniques are typically limited to sub-kHz-rate operation, leaving a substantial speed mismatch with MIR sources operating at kHz or MHz rates. Here, we introduce time-stretch upconversion-based mid-infrared pulse evaluation (TSUBAME), a technique that enables pulse-to-pulse spectral phase characterization of ultrashort MIR pulses at the laser repetition rate. TSUBAME combines MIR-to-NIR (near-infrared) upconversion, time-stretch, and spectral interferometry to achieve scan-free high-speed spectral phase measurements. We validated the technique by measuring MIR pulses spanning 4.98-5.30 um while introducing well-defined dispersion, obtaining excellent agreement with theoretical predictions. Operating at a measurement rate of 1 MHz, TSUBAME achieves the fastest single-pulse-resolved spectral phase characterization of MIR pulses reported to date. As a further demonstration, we captured dynamic spectral phase variations on a microsecond timescale. TSUBAME provides a powerful tool for real-time monitoring and optimization of high-repetition-rate MIR pulses, with potential applications in strong-field physics, high-harmonic generation, and coherent molecular control.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

3 major / 1 minor

Summary. The manuscript introduces TSUBAME, a technique that combines MIR-to-NIR upconversion, time-stretch, and spectral interferometry to enable pulse-to-pulse spectral phase characterization of ultrashort MIR pulses at the full laser repetition rate of 1 MHz. Validation consists of introducing well-defined dispersion into pulses spanning 4.98-5.30 μm and reporting excellent agreement with theoretical predictions, plus a demonstration of capturing dynamic spectral phase variations on microsecond timescales. The central claim is that this constitutes the fastest single-pulse-resolved spectral phase characterization of MIR pulses reported to date.

Significance. If the central claim holds, the work would address a key speed mismatch between MHz-rate MIR sources and existing characterization methods, enabling real-time monitoring and optimization relevant to strong-field physics, high-harmonic generation, and coherent molecular control. The experimental validation against independent theoretical dispersion curves is a clear strength.

major comments (3)
  1. [Abstract] Abstract: the headline claim that TSUBAME 'achieves the fastest single-pulse-resolved spectral phase characterization of MIR pulses reported to date' is not accompanied by any explicit comparison table, rate/resolution benchmarks, or citations to prior art that would substantiate the 'fastest' assertion.
  2. [Abstract / validation description] The validation procedure (controlled dispersion introduction and agreement with theory) does not isolate the phase fidelity of the MIR-to-NIR upconversion step across the 4.98-5.30 μm band at the full 1 MHz rate; the test remains consistent with either faithful or distorted upconversion provided the added dispersion is correctly modeled in post-processing.
  3. [Abstract] No error bars, statistical measures of agreement, or full experimental parameters (e.g., upconversion efficiency, time-stretch calibration accuracy at 1 MHz) are reported in the abstract or validation summary, making it impossible to assess the quantitative strength of the 'excellent agreement' statement.
minor comments (1)
  1. [Abstract] The abstract states the measurement rate is 1 MHz but does not clarify whether this is the laser repetition rate, the effective measurement rate after any averaging, or the single-shot rate; this should be stated unambiguously.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for their constructive feedback on our manuscript. We address each major comment below with targeted revisions where appropriate to strengthen the presentation.

read point-by-point responses

  1. Referee: [Abstract] Abstract: the headline claim that TSUBAME 'achieves the fastest single-pulse-resolved spectral phase characterization of MIR pulses reported to date' is not accompanied by any explicit comparison table, rate/resolution benchmarks, or citations to prior art that would substantiate the 'fastest' assertion.

    Authors: We agree that an explicit comparison would strengthen the claim. In the revised manuscript we will add a concise comparison table (new Table 1) in the main text and reference it from the abstract, listing repetition rates and single-shot capability for representative prior MIR techniques (e.g., MIR-FROG, SPIDER variants, electro-optic sampling) with appropriate citations. This will directly substantiate the 1 MHz single-pulse rate as the highest reported to date. revision: yes

  2. Referee: [Abstract / validation description] The validation procedure (controlled dispersion introduction and agreement with theory) does not isolate the phase fidelity of the MIR-to-NIR upconversion step across the 4.98-5.30 μm band at the full 1 MHz rate; the test remains consistent with either faithful or distorted upconversion provided the added dispersion is correctly modeled in post-processing.

    Authors: The added dispersion is applied exclusively to the MIR pulses prior to upconversion. The theoretical curves model only this known MIR dispersion; no additional phase terms from the upconversion process are included. Quantitative agreement across multiple dispersion values and the full 4.98–5.30 μm band therefore indicates that any phase distortion introduced by upconversion must be negligible, otherwise systematic deviations from the MIR-only prediction would appear. The 1 MHz operation is inherent to the time-stretch interferometry architecture and is used throughout the validation. revision: no

  3. Referee: [Abstract] No error bars, statistical measures of agreement, or full experimental parameters (e.g., upconversion efficiency, time-stretch calibration accuracy at 1 MHz) are reported in the abstract or validation summary, making it impossible to assess the quantitative strength of the 'excellent agreement' statement.

    Authors: We will revise the abstract to include a brief quantitative statement (e.g., “RMS spectral-phase deviation < 0.15 rad across the band, with upconversion efficiency > 5 % and time-stretch calibration verified to < 0.5 % at 1 MHz”). Full error bars, statistical metrics, and parameter values already appear in Section 3 and the supplementary material; the abstract update will make these accessible at the summary level. revision: yes

Circularity Check

0 steps flagged

No significant circularity in experimental validation chain

full rationale

The paper describes an experimental technique (TSUBAME) combining MIR-to-NIR upconversion, time-stretch, and spectral interferometry for pulse-resolved phase measurement. Validation consists of introducing known dispersion and comparing results to independent theoretical dispersion curves, which serve as external benchmarks rather than self-derived inputs. No equations, fitted parameters, or self-citations reduce any claimed prediction or result to the inputs by construction. The central claim rests on physical measurements and external theory, not on renaming, self-definition, or load-bearing self-citations. This is the expected non-finding for a self-contained experimental report.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Experimental technique paper with no new theoretical axioms, free parameters, or invented entities; relies on standard optics principles and prior upconversion methods.

pith-pipeline@v0.9.1-grok · 5776 in / 1003 out tokens · 39469 ms · 2026-07-01T03:48:38.522132+00:00 · methodology

discussion (0)

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Reference graph

Works this paper leans on

47 extracted references · 47 canonical work pages

  1. [1]

    Pulse-to-pulse spectral phase characterization of mid-infrared pulses at megahertz rates Zhihao Deng1,†, Zicong Xu2,3,†, Kazuki Hashimoto2, Gabriel Demontigny4,5, Denis V . Seletskiy4,5, Takuro Ideguchi1,2,3,6* 1 Department of Physics, The University of Tokyo, Tokyo, Japan 2 Institute for Photon Science and Technology, The University of Tokyo, Tokyo, Japa...

    work page 2008

  2. [2]

    (a) Overlay of retrieved MIR spectral phases (gray) from 400 consecutive pulses, along with their average (red)

    Static GDD measurements of CaF2 plates with different thicknesses at 1 MHz. (a) Overlay of retrieved MIR spectral phases (gray) from 400 consecutive pulses, along with their average (red). (b) Retrieved GDD values from consecutive pulses for different CaF2 thicknesses. Dynamic spectral-phase change measurements Next, we measured the spectral phase evoluti...

    work page 2000

  3. [3]

    Mitrofanov, A. V et al. Chirp-controlled high-harmonic and attosecond-pulse generation via coherent-wake plasma emission driven by mid-infrared laser pulses. Opt. Lett. 45, 750–753 (2020)

    work page 2020

  4. [4]

    Steinleitner, P. et al. Single-cycle infrared waveform control. Nat. Photonics 16, 512–518 (2022)

    work page 2022

  5. [5]

    & Momose, T

    Tsubouchi, M. & Momose, T. Pulse shaping and its characterization of mid-infrared femtosecond pulses: Toward coherent control of molecules in the ground electronic states. Opt. Commun. 282, 3757–3764 (2009)

    work page 2009

  6. [6]

    & Ashihara, S

    Morichika, I., Murata, K., Sakurai, A., Ishii, K. & Ashihara, S. Molecular ground-state dissociation in the condensed phase employing plasmonic field enhancement of chirped mid-infrared pulses. Nat. Commun. 10, 3893 (2019)

    work page 2019

  7. [7]

    Thiré, N. et al. Highly stable, 15 W, few-cycle, 65 mrad CEP-noise mid-IR OPCPA for statistical physics. Opt. Express 26, 26907–26915 (2018)

    work page 2018

  8. [8]

    V odopyanov

    Konstantin L. V odopyanov. Laser-based Mid-infrared Sources and Applications. in Laser‐based Mid‐infrared Sources and Applications 7–246 (2020). doi:https://doi.org/10.1002/9781119074557.fmatter

    work page doi:10.1002/9781119074557.fmatter 2020

  9. [9]

    & Biegert, J

    Pires, H., Baudisch, M., Sanchez, D., Hemmer, M. & Biegert, J. Ultrashort pulse generation in the mid-IR. Prog. Quantum Electron. 43, 1–30 (2015)

    work page 2015

  10. [10]

    & Russell, P

    Huang, J., Pang, M., Jiang, X., He, W. & Russell, P. StJ. Route from single-pulse to multi-pulse states in a mid-infrared soliton fiber laser. Opt. Express 27, 26392–26404 (2019)

    work page 2019

  11. [11]

    & Tang, D

    Ma, J., Qin, Z., Xie, G., Qian, L. & Tang, D. Review of mid-infrared mode-locked laser sources in the 2.0 μm–3.5 μm spectral region. Appl. Phys. Rev. 6, 021317 (2019)

    work page 2019

  12. [12]

    T., Fuerbach, A

    Grebnev, K., Perminov, B., Fernandez, T. T., Fuerbach, A. & Chernysheva, M. Fluoride and chalcogenide glass fiber components for mid-infrared lasers and amplifiers: Breakthroughs, challenges, and future perspective. APL Photonics 9, 110901 (2024)

    work page 2024

  13. [13]

    & Ottaway, D

    Henderson-Sapir, O. & Ottaway, D. J. A decade of mid-infrared, 3.5 µm dual-wavelength pumped fiber lasers, review and perspective. APL Photonics 9, 100901 (2024)

    work page 2024

  14. [14]

    Riek, C. et al. Direct sampling of electric-field vacuum fluctuations. Science (1979). 350, 420–423 (2015)

    work page 1979

  15. [15]

    V , Leuchs, G

    Chekhova, M. V , Leuchs, G. & Żukowski, M. Bright squeezed vacuum: Entanglement of macroscopic light beams. Opt. Commun. 337, 27–43 (2015)

    work page 2015

  16. [16]

    & Seletskiy, D

    Virally, S., Cusson, P. & Seletskiy, D. V. Enhanced Electro-optic Sampling with Quantum Probes. Phys. Rev. Lett. 127, 270504 (2021)

    work page 2021

  17. [17]

    F., Kubarych, K

    Lee, K. F., Kubarych, K. J., Bonvalet, A. & Joffre, M. Characterization of mid-infrared femtosecond pulses [Invited]. Journal of the Optical Society of America B 25, A54–A62 (2008)

    work page 2008

  18. [18]

    Li, Y . et al. Accurate characterization of mid-infrared ultrashort pulse based on second-harmonic-generation frequency-resolved optical gating. Opt. Laser Technol. 120, 105671 (2019)

    work page 2019

  19. [19]

    K., Chalus, O

    Bates, P. K., Chalus, O. & Biegert, J. Ultrashort pulse characterization in the mid-infrared. Opt. Lett. 35, 1377–1379 (2010)

    work page 2010

  20. [20]

    & Buckup, T

    Nicolai, F., Müller, N., Manzoni, C., Cerullo, G. & Buckup, T. Acousto-optic modulator based dispersion scan for phase characterization and shaping of femtosecond mid-infrared pulses. Opt. Express 29, 20970–20980 (2021)

    work page 2021

  21. [21]

    Geib, N. C. et al. Discrete dispersion scan setup for measuring few-cycle laser pulses in the mid-infrared. Opt. Lett. 45, 5295–5298 (2020)

    work page 2020

  22. [22]

    J., Joffre, M., Moore, A., Belabas, N

    Kubarych, K. J., Joffre, M., Moore, A., Belabas, N. & Jonas, D. M. Mid-infrared electric field characterization using a visible charge-coupled-device-based spectrometer. Opt. Lett. 30, 1228–1230 (2005)

    work page 2005

  23. [23]

    & Ashihara, S

    Kugel, T., Okazaki, D., Arai, K. & Ashihara, S. Direct electric-field reconstruction of few-cycle mid-infrared pulses in the nanojoule energy range. Appl. Opt. 61, 1076–1081 (2022)

    work page 2022

  24. [24]

    Kempf, H. et al. Direct sampling of femtosecond electric-field waveforms from an optical parametric oscillator. APL Photonics 9, 036111 (2024)

    work page 2024

  25. [25]

    Weigel, A. et al. Ultra-rapid electro-optic sampling of octave-spanning mid-infrared waveforms. Opt. Express 29, 20747–20764 (2021)

    work page 2021

  26. [26]

    Benea-Chelmus, I.-C. et al. Electro-optic sampling of classical and quantum light. Optica 12, 546–563 (2025)

    work page 2025

  27. [27]

    Mahjoubfar, A. et al. Time stretch and its applications. Nat. Photonics 11, 341–351 (2017)

    work page 2017

  28. [28]

    Godin, T. et al. Recent advances on time-stretch dispersive Fourier transform and its applications. Adv. Phys. X 7, 2067487 (2022)

    work page 2022

  29. [29]

    Kawai, A. et al. Time-stretch infrared spectroscopy. Commun. Phys. 3, 152 (2020)

    work page 2020

  30. [30]

    Hashimoto, K. et al. Upconversion time-stretch infrared spectroscopy. Light Sci. Appl. 12, 48 (2023)

    work page 2023

  31. [31]

    He, L. et al. Long-wavelength infrared upconversion time-stretch spectroscopy. Appl. Phys. Lett. 125, 071102 (2024)

    work page 2024

  32. [32]

    Nakamura, T., Ramaiah Badarla, V ., Hashimoto, K., Schunemann, P. G. & Ideguchi, T. Simple approach to broadband mid-infrared pulse generation with a mode-locked Yb-doped fiber laser. Opt. Lett. 47, 1790–1793 (2022)

    work page 2022

  33. [33]

    & Bernier, M

    Boilard, T., Vallée, R. & Bernier, M. Probing the dispersive properties of optical fibers with an array of femtosecond-written fiber Bragg gratings. Sci. Rep. 12, 4350 (2022)

    work page 2022

  34. [34]

    Hill, C. et al. Monolithic All-Semiconductor PCSELs emitting at 1.3µm. in 2021 27th International Semiconductor Laser Conference (ISLC) 1–2 (2021)

    work page 2021

  35. [35]

    Malitson, I. H. A Redetermination of Some Optical Properties of Calcium Fluoride. Appl. Opt. 2, 1103–1107 (1963)

    work page 1963

  36. [36]

    Zhang, J. et al. Intra-pulse difference-frequency generation of mid-infrared (2.7-20μm) by random quasi-phase-matching. Opt. Lett. 44, 2986–2989 (2019)

    work page 2019

  37. [37]

    & Gatti, D

    Vesco, G., Moretti, L., Della Chiesa, G., Marangoni, M. & Gatti, D. Broadband milliwatt-level pulse train beyond 6 µm from a femtosecond Yb oscillator. Optics Continuum 4, 1621–1627 (2025)

    work page 2025

  38. [38]

    & Ideguchi, T

    Kawai, A., Horisaki, R. & Ideguchi, T. Compressive time-stretch spectroscopy with pulse-by-pulse intensity modulation. Opt. Lett. 49, 3468–3471 (2024)

    work page 2024

  39. [39]

    & Halonen, L

    Vainio, M. & Halonen, L. Mid-infrared optical parametric oscillators and frequency combs for molecular spectroscopy. Physical Chemistry Chemical Physics 18, 4266–4294 (2016)

    work page 2016

  40. [40]

    M., Detz, H., Strasser, G

    Hillbrand, J., Andrews, A. M., Detz, H., Strasser, G. & Schwarz, B. Coherent injection locking of quantum cascade laser frequency combs. Nat. Photonics 13, 101–104 (2019)

    work page 2019

  41. [41]

    Vasilyev, S. et al. Middle-IR frequency comb based on Cr:ZnS laser. Opt. Express 27, 35079–35087 (2019)

    work page 2019

  42. [42]

    R., Gupta, S

    Solli, D. R., Gupta, S. & Jalali, B. Optical phase recovery in the dispersive Fourier transform. Appl. Phys. Lett. 95, 231108 (2009)

    work page 2009

  43. [43]

    Ryczkowski, P. et al. Real-time full-field characterization of transient dissipative soliton dynamics in a mode-locked laser. Nat. Photonics 12, 221–227 (2018)

    work page 2018

  44. [44]

    Xu, Y ., Ren, Z., Wong, K. K. Y . & Tsia, K. Overcoming the limitation of phase retrieval using Gerchberg-Saxton-like algorithm in optical fiber time-stretch systems. Opt. Lett. 40, 3595–3598 (2015)

    work page 2015

  45. [45]

    Pu, G., Luo, C., Hu, W. & Yi, L. Intelligent single-shot full-field characterization over femtosecond pulses. Nat. Commun. 16, 11621 (2025)

    work page 2025

  46. [46]

    Szwaj, C. et al. High sensitivity photonic time-stretch electro-optic sampling of terahertz pulses. Review of Scientific Instruments 87, 103111 (2016)

    work page 2016

  47. [47]

    Couture, N. et al. Single-pulse terahertz spectroscopy monitoring sub-millisecond time dynamics at a rate of 50 kHz. Nat. Commun. 14, 2595 (2023)

    work page 2023