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REVIEW 4 major objections 4 minor 42 references

High resolution up-conversion imaging in the 10 {\mu}m band under incoherent illumination

T0 review · 4 major / 4 minor · reviewed 2026-08-07 · deepseek-v4-flash

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Pith's one-line read This paper demonstrates the first high-resolution up-conversion imaging of incoherent 10 µm thermal targets, reaching near the diffraction limit and deriving analytical depth-of-field and astigmatism formulas that match experiment.

desk verdict A real experimental first: incoherent thermal LWIR up-conversion imaging near the diffraction limit, but the analytic models and the resolution criterion need scrutiny. read the letter →

arxiv 2505.24367 v1 pith:ZNANQBGL submitted 2025-05-30 physics.optics physics.app-ph

Zhao-Qi-Zhi Han , Xiao-Hua Wang , Jin-Peng Li , Bo-Wen Liu , Zheng-He Zhou , He Zhang , Yin-Hai Li , Zhi-Yuan Zhou
show 1 more author
Bao-Sen Shi
This is my paper
classification physics.opticsphysics.app-ph
keywords up-conversionimaginglong-wavelengthinfraredsum-frequencygenerationincoherentthermalilluminationdepthoffieldastigmatismAGScrystalRayleighresolution
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

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

The reading

Long-wavelength infrared (8–14 µm) light is hard to detect: traditional semiconductor detectors are slow, noisy, and costly, while silicon cameras ignore it. This paper reports the first up-conversion imaging of incoherent thermal targets in the 10 µm band, in which 9.6 µm heat radiation is mixed with a continuous-wave pump in an AGS crystal to create sum-frequency light that a silicon camera can read. The authors report that the system resolves line pairs down to about 99 µm at λ ≈ 9.6 µm, within a few percent of the diffraction limit set by the effective aperture (the smaller of the pump waist and crystal aperture). They also derive the first analytical equations for depth of field and astigmatic aberration in up-conversion imaging and show they agree with experiment under two different focal lengths. A separate measurement places the effective pump-aperture boundary at 57% of peak intensity, replacing the 1/e or 1/e² convention used in earlier work.

What carries the argument

The load-bearing mechanism is non-collinear sum-frequency generation in a type-II AGS (AgGaS₂) crystal: pump photons at 1078.22 nm and 9.625 µm signal photons satisfy $k_{\mathrm{SF}} \sin\theta_{\mathrm{SF}} = k_{\mathrm{MIR}} \sin\theta_{\mathrm{MIR}}$ and $k_{\mathrm{SF}} \cos\theta_{\mathrm{SF}} + \Delta k = k_{\mathrm{MIR}} \cos\theta_{\mathrm{MIR}} + k_p$, with conversion efficiency proportional to $\mathrm{sinc}^2(\Delta k L / 2)$. The effective imaging aperture is the smaller of the crystal aperture and the pump-beam waist, and the system's resolution is governed by the Rayleigh formula $d_R = 1.22\lambda f / D_{\mathrm{eff}} = 0.61\lambda / \mathrm{NA}$, with a line pair counted as resolved when the valley-to-peak intensity ratio $I_{\min}/I_{\max} < 0.8$. Newly derived formulas $d_{\mathrm{DOF}} = \lambda / \mathrm{NA}^2$ and the astigmatism equation connect these quantities to focal length, magnification, lens refractive index, and aperture angle, and the measured 0.57 peak-intensity boundary defines how the Gaussian pump truncates the aperture.

What would settle it

Re-extract the valley-to-peak ratios from the recorded USAF-1951 images and evaluate the same resolution, effective-aperture, DOF, and astigmatism numbers with a stricter cutoff (say $I_{\min}/I_{\max} < 0.5$) or with an MTF-based threshold; if the resolved elements and fitted depths change by more than the reported error bars, the claimed agreement with Eqs. (2)–(4) would not survive.

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Extended reading notes

Core claim

In this system, an incoherent thermal emitter illuminating a USAF-1951 target is imaged through a 4f relay whose common focal point lies in a type-II AGS crystal, where mid-infrared signal photons (center wavelength 9.625 µm) combine with a 1078.22 nm pump to produce sum-frequency photons detected by an sCMOS camera. The paper's central claim is that this arrangement achieves high-resolution up-conversion imaging of incoherent LWIR thermal radiation for the first time, with the measured minimum resolvable line-pair widths of 198.4 µm (50 mm lens) and 396.8 µm (100 mm lens) close to the theoretical limits of 195.7 µm and 391.4 µm given by Eq. (2). It further claims that the depth of field is quantitatively described by $d_{\mathrm{DOF}} = \lambda/\mathrm{NA}^2$ and astigmatism by the derived formula, with experimental values agreeing reasonably with theory under both focal lengths (e.g., 6.1 mm and 8.9 mm vertical/horizontal DOF at 50 mm versus a theoretical 10.67 mm; measured astigmatism 5.7 mm versus 5.04 mm theoretical). The paper also reports the first measurement that the effective aperture boundary in the Gaussian pump sits at 0.57 of peak intensity, and that pump-beam shape changes alter resolution anisotropically.

Load-bearing premise

All reported resolutions, depths of field, and astigmatism measurements rest on the assumption that a line pair is resolved exactly when the dark-line intensity drops to 80% of the bright-line intensity; if the true resolvability cutoff differs, the resolution numbers and fitted curves would shift.

Editorial extensions

If this is right

  • Incoherent room-temperature thermal targets in the 10 µm band can be imaged by a silicon sCMOS camera at near-diffraction-limited resolution, bypassing the need for cooled LWIR detectors.
  • The measured resolution scales with collection-lens focal length as predicted by the Rayleigh criterion, so using shorter-focal-length collection lenses should further improve the resolvable line-pair width.
  • The pump-beam waist acts as the effective aperture when it is smaller than the crystal aperture; designing the waist to place its effective boundary at 57% of peak intensity is now supported by measurement.
  • The analytical depth-of-field and astigmatism equations provide quantitative design curves for up-conversion imaging systems under different focal lengths, magnifications, and off-axis angles.
  • The approach is claimed to generalize to other up-conversion imaging configurations, giving a design path for future thermal and molecular-fingerprinting cameras.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • Editorial inference: The 0.57 boundary-intensity rule, if it holds for other crystals and pump geometries, lets future systems set the pump waist from a single intensity measurement rather than from a full resolution scan.
  • Editorial inference: Because resolution here scales linearly with collection-lens focal length, pushing to shorter, faster lenses or larger pump apertures could take line-pair resolution well below 100 µm, potentially into the few-micron regime if the crystal aperture and phase-matching angular bandwidth permit.
  • Editorial inference: The derived astigmatism and depth-of-field formulas should transfer to off-axis thermal up-conversion imagers in other mid-infrared windows (3–5 µm and 8–14 µm), where they could be used to predict focus tolerance before hardware is built.
  • Editorial inference: Combining this scheme with high-frame-rate sCMOS readout may open a route to video-rate thermal monitoring of warm objects, a step the paper itself does not claim.
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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

4 major / 4 minor

Summary. The manuscript reports up-conversion imaging of incoherent thermal targets in the 10 µm band by sum-frequency generation in an AGS crystal, detected with a silicon sCMOS camera. The authors present resolved USAF-1951 target images for two collection lens focal lengths (100 mm and 50 mm), extract an effective aperture from pump-beam intensity profiles, measure depth of field and astigmatism, and propose analytical expressions for DOF and astigmatism. They claim this is the first demonstration of high-resolution up-conversion imaging of incoherent thermal radiation in the LWIR region, with resolution nearly at the theoretical diffraction limit. The supplementary materials are referenced for derivations and additional details but were not included in the reviewed manuscript.

Significance. If the claims are correct, the work is a clear advance: it would demonstrate that room-temperature LWIR thermal scenes can be up-converted to the visible and imaged with a silicon camera at near-diffraction-limited resolution, a capability not previously shown. The paper also introduces a quantitative framework for DOF and astigmatism in up-conversion imaging and reports a useful design parameter, the effective-aperture boundary intensity ratio of 0.57. The experimental data are presented in detail, with raw images and intensity line profiles, and the resolution scaling with focal length is consistent with the diffraction formula. However, as detailed below, the resolution criterion is not independently justified, the derivation of Equation (4) is not accessible without the supplementary materials, and one DOF comparison shows a 43% discrepancy. The central claims therefore deserve major revision before publication.

major comments (4)
  1. [Section 3.2.1] The criterion for resolution, Imin/Imax < 0.8, is called the Rayleigh criterion, but the standard Rayleigh two-point criterion corresponds to a valley intensity ratio of approximately 0.735, and bar-target contrast criteria in several standards are stricter than 0.8. The manuscript provides neither a derivation nor a reference for the 0.8 threshold. Every quantitative claim in the paper—the resolved USAF elements in Figures 4 and 6, the effective aperture values in Figure 5(b), the DOF fits in Figure 6(b), and the astigmatism values—is evaluated with this threshold. Please justify the threshold explicitly, or provide a robustness analysis showing that the reported resolved elements and fitted parameters are insensitive to the choice of criterion within a reasonable range. Without this, the claim that 'the resolution has almost reached its theoretical limits' is not established.
  2. [Section 3.2.2, Eq. (4)] Equation (4), the astigmatism expression, is presented without a derivation in the main text. The manuscript states that 'detailed derivation are shown in supplementary materials,' but the supplementary materials were not included with the submitted manuscript, so the derivation is currently unavailable to the reader. Since Eq. (4) is load-bearing for the astigmatism comparisons (the 5.7 mm versus 5.04 mm and 21.71 mm versus 19.45 mm results), please provide the derivation in the main text or ensure that the supplementary document is complete and accessible.
  3. [Section 3.2.2, Figure 6(b)] For f = 50 mm, the fitted vertical DOF is 6.1 mm while the theoretical value from Eq. (3) is 10.67 mm, a discrepancy of 43%. The abstract and Discussion claim 'excellent agreement' and 'consistent' results, but only the horizontal DOF (8.9 mm) is in reasonable agreement. This partial agreement substantially weakens the claim that Eq. (3) accurately predicts DOF in this system. Please analyze whether the vertical discrepancy can be reconciled, for example by using the smaller vertical effective aperture (2.96 mm) rather than the horizontal one (3.00 mm) in Eq. (3), or by including the effect of beam ellipticity. The one-sided measurement for f = 100 mm (37 mm versus 42.67 mm) should also be discussed more carefully, since it is not a full DOF determination.
  4. [Section 3.2.1, Figure 5] The value 0.57 for the effective-aperture boundary intensity ratio is obtained by fitting the resolution data (Figure 5(a)) and is then used to interpret the same effective-aperture model. This is circular: the fit and the model are not independently validated. To support the claim that the pump-beam waist should be defined at 0.57 of peak intensity, please compare this fitted value with a direct measurement from the recorded pump beam profile, or perform a sensitivity analysis showing that the inferred effective aperture and resolution limits change negligibly when the boundary ratio is varied within a plausible range.
minor comments (4)
  1. [Abstract] The abstract states 'for the first time' without qualification; the Introduction more carefully says 'to our best knowledge.' Please add this qualifier to the abstract to match the actual claim.
  2. [References] References 37 and 42 appear to be the same article (both cite P. Tidemand-Lichtenberg and C. Pedersen, 'Long-wavelength, high-resolution microscopy using upconversion in ultra-thin crystals,' APL Photonics 9 (2024)). Please consolidate or disambiguate.
  3. [Section 3.2.1] The sentence 'the beam waist should be more appropriately defined as 0.57 of peak power' is inconsistent with the preceding sentence, which defines the boundary as 0.57 times the peak intensity. Please make the terminology uniform.
  4. [Figures 5(b) and 6(b)] The blue/red color coding for vertical and horizontal resolution may be difficult to distinguish in grayscale reproductions; please add distinct symbols or line styles to the data and fitting curves.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the central imaging claim rests on direct USAF target observations and on theoretical limits computed from the known crystal aperture; the 0.8 threshold and 0.57 boundary intensity are calibration/validity concerns, not circular reductions.

full rationale

The paper's central claim—high-resolution up-conversion imaging of incoherent thermal targets in the 10 μm band—is supported by direct USAF-1951 target images in Fig. 4, and the quoted theoretical resolution limits (391.4 μm and 195.7 μm) are computed from Eq. (2) using the known crystal aperture (3 mm), not from the measured resolution. The 0.8 valley-to-peak threshold is an asserted criterion, not a fitted parameter, and the paper explicitly labels it as the Rayleigh criterion; whether this threshold is the correct resolvability standard is a validity or calibration concern, not circularity, because the resolved element data are independent observations. The 0.57 boundary-intensity ratio is an empirical extraction: the effective aperture is first obtained by inverting Eq. (2) from the threshold-labeled resolution, and the pump-beam intensity at that radius is then measured; it is not used to predict the same resolution from which it was derived. The DOF and astigmatism comparisons use the same 0.8 criterion but test independent observables (axial range and astigmatic separation), so the agreement is not forced by construction. Self-citations (refs. 17, 25, 26, 30) appear but none carries a load-bearing uniqueness or derivation claim; the phase-matching relation in Eq. (1) is a standard momentum-conservation result and is also supported by external literature. Because the main demonstration and the derived parameter study do not reduce to their own inputs, no circular step is identified under the stated rules.

Assumptions & free parameters 2 free parameters · 5 assumptions · 0 invented entities

The central experimental demonstration rests on standard nonlinear-optical phase matching and the 4f imaging geometry. The resolution interpretation depends on the 0.8 contrast criterion and the effective-aperture assumption. The two equations presented as new models depend on missing derivations, and the astigmatism comparison depends on an estimated off-axis angle. The 0.57 boundary intensity ratio is a fitted calibration. No new physical entities are introduced.

free parameters (2)
  • effective_aperture_boundary_intensity_ratio = 0.57 of peak intensity
    Inferred in Section 3.2.1 from the pump beam profile at apertures back-calculated from the measured resolution; proposed as a general design rule for pump waist. It is a fitted calibration, not a derived constant.
  • off_axis_angle_theta_for_astigmatism = approximately 4 degrees
    Used in Equation (4) to compute the theoretical astigmatism of 5.04 mm; the value is described as approximately 4 degrees with no uncertainty or independent measurement, so it could be adjusted to improve agreement.
assumptions (5)
  • standard math Non-collinear phase matching is governed by transverse momentum conservation plus a scalar phase mismatch Δk, Equation (1).
    Invoked in Section 2 to compute angular and spectral conversion bandwidths; rests on standard nonlinear optics, namely Boyd and Shen.
  • domain assumption The effective aperture is the smaller of the crystal aperture and the pump beam waist in the crystal.
    Stated without proof in Section 3.2.1; it determines D_eff in the resolution formula Equation (2).
  • ad hoc to paper A line pair is resolved when the valley-to-peak intensity ratio Imin/Imax is below 0.8.
    Used throughout Section 3.2 to assign resolutions and to fit DOF curves; called the Rayleigh criterion but no reference or derivation is given for this specific threshold.
  • domain assumption Equations (3) and (4) for depth of field and astigmatism are valid for this imaging geometry.
    The derivations are deferred to a missing supplementary document; the equations are nonstandard, especially Equation (4), and cannot be checked from the main text.
  • domain assumption The target is located at an angle of approximately 4 degrees off the lens axis when applying Equation (4).
    This angle is an estimate without uncertainty in Section 3.2.2; the astigmatism comparison hinges on it.

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Cite this review

Pith. "Pith review of High resolution up-conversion imaging in the 10 {\mu}m band under incoherent illumination." pith.science (2026). https://pith.science/paper/ZNANQBGL

@misc{pith2026250524367,
  author       = {Pith},
  title        = {Pith review of: High resolution up-conversion imaging in the 10 \mum band under incoherent illumination},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/ZNANQBGL}},
  note         = {Machine review of arXiv:2505.24367}
}
read the original abstract

Long-wavelength infrared band exhibits significant utility in thermal signature acquisition and molecular spectral analysis, among other applications. The up-conversion detection technique enables effective signal transduction into the detection bandwidth of silicon-based photodetectors, thereby facilitating high-sensitivity photonic measurements. We realized high-resolution up-conversion imaging for incoherent thermal targets in the 10 {\mu}m spectral regime for the first time. Furthermore, this work presents the first derivation of analytical models characterizing depth of field and astigmatic aberration in up-conversion imaging systems, which show excellent agreement between theoretical and experimental results. The results demonstrate generalisability to various up-conversion imaging systems, thus providing critical insights for the design and optimisation of such systems.

Figures

Figures reproduced from arXiv: 2505.24367 by the authors.

Figure 1
Figure 1. Schematic diagram of non-collinear phase match. (a) Schematic diagram [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Numerical calculation results of wavelength and angle conversion bandwidth. [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 3
Figure 3. Schematic diagram of the experimental setup. L terms: the lenses; DM: [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
Figures from the paper (3 more)
Figure 4
Figure 4. Figure 4: Up-conversion imaging results demonstrating optimal resolution in both lens [PITH_FULL_IMAGE:figures/full_fig_p006_4.png]
Figure 5
Figure 5. Figure 5: The dependence of imaging resolution on the pump beam waist with L3 focal [PITH_FULL_IMAGE:figures/full_fig_p006_5.png]
Figure 6
Figure 6. Figure 6: The depth of field and astigmatism of the up-conversion imaging system while [PITH_FULL_IMAGE:figures/full_fig_p007_6.png]

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Works this paper leans on

42 extracted references · 41 canonical work pages

  1. [1]

    Dielectric sphere clusters as a model to understand infrared spectroscopic imaging data recorded from complex samples,

    I. L. Rasskazov, N. Spegazzini, P. S. Carney, and R. Bhargava, “Dielectric sphere clusters as a model to understand infrared spectroscopic imaging data recorded from complex samples,” Anal. Chem.89, 10813–10818 (2017). PMID: 28895722

    work page 2017

  2. [2]

    Engineering mid-infrared nanoantennas for surface enhanced infrared absorption spectroscopy,

    R. Adato, S. Aksu, and H. Altug, “Engineering mid-infrared nanoantennas for surface enhanced infrared absorption spectroscopy,” Mater. Today18, 436–446 (2015)

    work page 2015

  3. [3]

    Application of mid-infrared tuneable diode laser absorption spectroscopy to plasma diagnostics: a review,

    J. Röpcke, G. Lombardi, A. Rousseau, and P. B. Davies, “Application of mid-infrared tuneable diode laser absorption spectroscopy to plasma diagnostics: a review,” Plasma Sources Sci. Technol.15, S148 (2006)

    work page 2006

  4. [4]

    Broadband laser-based mid-infrared spectroscopy employing a quantum cascade detector for milk protein analysis,

    A. Dabrowska, M. David, S. Freitag,et al., “Broadband laser-based mid-infrared spectroscopy employing a quantum cascade detector for milk protein analysis,” Sensors Actuators B: Chem.350, 130873 (2022)

    work page 2022

  5. [5]

    Mid-infrared tunable laser-based broadband fingerprint absorption spectroscopy for trace gas sensing: A review,

    Z. Du, S. Zhang, J. Li,et al., “Mid-infrared tunable laser-based broadband fingerprint absorption spectroscopy for trace gas sensing: A review,” Appl. Sci.9 (2019)

    work page 2019

  6. [6]

    Mid-infrared absorption spectroscopy with enhanced detection performance for biomedical applications,

    D. An, F. Sun, Y. Bian,et al., “Mid-infrared absorption spectroscopy with enhanced detection performance for biomedical applications,” Appl. Spectrosc. Rev.58, 834–868 (2023)

    work page 2023

  7. [7]

    Label-free autofluorescence-detected mid-infrared photothermal microscopy of pharmaceutical materials,

    A. Razumtcev, M. Li, J. Rong,et al., “Label-free autofluorescence-detected mid-infrared photothermal microscopy of pharmaceutical materials,” Anal. Chem.94, 6512–6520 (2022). PMID: 35446548

    work page 2022

  8. [8]

    The progress of operational forest fire monitoring with infrared remote sensing,

    L. Hua and G. Shao, “The progress of operational forest fire monitoring with infrared remote sensing,” J. For. Res. 28, 215 – 229 (2017). Cited by: 95

    work page 2017

Show all 42 references
  1. [9]

    Mid-infrared emission prior to strong earthquakes analyzed by remote sensing data,

    D. Ouzounov and F. Freund, “Mid-infrared emission prior to strong earthquakes analyzed by remote sensing data,” Adv. space research33, 268–273 (2004)

    2004

  2. [10]

    Four typical variation patterns of mid-infrared spectra of the mafic mineral anomalies for fault zone identification,

    Z. XU, T. HAN, T. YU, and P. LIN, “Four typical variation patterns of mid-infrared spectra of the mafic mineral anomalies for fault zone identification,” Tunn. Undergr. Space Technol.162, 106599 (2025)

    2025

  3. [11]

    Mid-infrared sensing of organic pollutants in aqueous environments,

    B. Pejcic, M. Myers, and A. Ross, “Mid-infrared sensing of organic pollutants in aqueous environments,” Sensors9, 6232–6253 (2009)

    2009

  4. [12]

    Laser-based sensing in the long-wavelength mid-infrared: chemical kinetics and environmental monitoring applications,

    A. Elkhazraji, M. K. Shakfa, N. Abualsaud,et al., “Laser-based sensing in the long-wavelength mid-infrared: chemical kinetics and environmental monitoring applications,” Appl. Opt.62, A46–A58 (2023)

    2023

  5. [13]

    Mid infrared lasers for remote sensing applications,

    B. M. Walsh, H. R. Lee, and N. P. Barnes, “Mid infrared lasers for remote sensing applications,” J. Lumin.169, 400–405 (2016)

    2016

  6. [14]

    The mid-infrared reflectance of mineral mixtures (7–14𝜇m),

    J. L. Thomson and J. W. Salisbury, “The mid-infrared reflectance of mineral mixtures (7–14𝜇m),” Remote. Sens. Environ. 45, 1–13 (1993)

    1993

  7. [15]

    Emerging type-ii superlattices of inas/inassb and inas/gasb for mid-wavelength infrared photodetectors,

    D. O. Alshahrani, M. Kesaria, E. A. Anyebe,et al., “Emerging type-ii superlattices of inas/inassb and inas/gasb for mid-wavelength infrared photodetectors,” Adv. Photonics Res.3, 2100094 (2022)

    2022

  8. [16]

    Recentadvancesofphotodetectiontechnologybasedonmaingroupiii–vsemiconductors,

    J.Ai,M.Qin,M.Xue, et al.,“Recentadvancesofphotodetectiontechnologybasedonmaingroupiii–vsemiconductors,” Adv. Funct. Mater.34, 2408858 (2024)

    2024

  9. [17]

    Quantum frequency transducer and its applications,

    Z.-Q.-Z. Han, Z.-Y. Zhou, and B.-S. Shi, “Quantum frequency transducer and its applications,” Adv. Devices & Instrum. 4, 0030 (2023)

    2023

  10. [18]

    Broadband mid-infrared frequency upconversion and spectroscopy with an aperiodically poled linbo 3 waveguide,

    T. W. Neely, L. Nugent-Glandorf, F. Adler, and S. A. Diddams, “Broadband mid-infrared frequency upconversion and spectroscopy with an aperiodically poled linbo 3 waveguide,” Opt. letters37, 4332–4334 (2012)

    2012

  11. [19]

    Nonlinear optical down-and up-conversion in ppln waveguides for mid-infrared spectroscopy,

    K.-D. Buchter, M.-C. Wiegand, H. Herrmann, and W. Sohler, “Nonlinear optical down-and up-conversion in ppln waveguides for mid-infrared spectroscopy,” inCLEO/Europe-EQEC 2009-European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference, (IEE...

    2009

  12. [20]

    Ultrasensitive mid-infrared up-conversion imaging at few-photon level,

    Q. Zhou, K. Huang, H. Pan,et al., “Ultrasensitive mid-infrared up-conversion imaging at few-photon level,” Appl. Phys. Lett.102(2013)

    2013

  13. [21]

    Wide-fieldmid-infraredsingle-photonupconversionimaging,

    K.Huang,J.Fang,M.Yan, et al.,“Wide-fieldmid-infraredsingle-photonupconversionimaging,”Nat.communications 13, 1077 (2022)

    2022

  14. [23]

    Mid-infrared single-photon computational temporal ghost imaging,

    W. Zhang, K. Huang, X. Wang,et al., “Mid-infrared single-photon computational temporal ghost imaging,” Laser & Photonics Rev. p. 2402180 (2025)

    2025

  15. [24]

    Real-timehigh-resolutionmid-infraredopticalcoherencetomography,

    N.M.Israelsen,C.R.Petersen,A.Barh, et al.,“Real-timehigh-resolutionmid-infraredopticalcoherencetomography,” Light. Sci. & Appl.8, 11 (2019)

    2019

  16. [25]

    In-lab high-resolution midinfrared up-conversion stellar interferometer based on a synthetic long baseline,

    Z.-Q.-Z. Han, Z. Ge, W.-T. Luo,et al., “In-lab high-resolution midinfrared up-conversion stellar interferometer based on a synthetic long baseline,” Phys. Rev. D110, 063019 (2024)

    2024

  17. [26]

    Midinfrared up-conversion imaging under different illumination conditions,

    Z. Ge, Z. Han, Y. Liu,et al., “Midinfrared up-conversion imaging under different illumination conditions,” Phys. Rev. Appl. 20, 054060 (2023)

    2023

  18. [27]

    Room-temperature mid-infrared single-photon spectral imaging,

    J. S. Dam, P. Tidemand-Lichtenberg, and C. Pedersen, “Room-temperature mid-infrared single-photon spectral imaging,” Nat. photonics6, 788–793 (2012)

    2012

  19. [28]

    Theory for upconversion of incoherent images,

    J. S. Dam, C. Pedersen, and P. Tidemand-Lichtenberg, “Theory for upconversion of incoherent images,” Opt. Express 20, 1475–1482 (2012)

    2012

  20. [29]

    Mid-infrared coincidence measurements on twin photons at room temperature,

    M. Mancinelli, A. Trenti, S. Piccione,et al., “Mid-infrared coincidence measurements on twin photons at room temperature,” Nat. communications8, 15184 (2017)

    2017

  21. [30]

    Quantum entanglement and interference at 3𝜇m,

    Z. Ge, Z.-Q.-Z. Han, F. Yang,et al., “Quantum entanglement and interference at 3𝜇m,” Sci. Adv.10, eadm7565 (2024)

    2024

  22. [31]

    Quantum key distribution based on mid-infrared and telecom band two-color entanglement source,

    W.-Z. Li, C. Zhou, Y. Wang,et al., “Quantum key distribution based on mid-infrared and telecom band two-color entanglement source,” arXiv preprint arXiv:2408.07552 (2024)

    2024 arXiv

  23. [32]

    Mid-infrared single-photon upconversion spectroscopy based on temporal-spectral quantum correlation,

    Y. Cai, Y. Chen, X. Xin,et al., “Mid-infrared single-photon upconversion spectroscopy based on temporal-spectral quantum correlation,” Photonics Res.10, 2614–2621 (2022)

    2022

  24. [33]

    Broadband long-wavelength upconversion in ultra-short nonlinear crystals,

    P. Tidemand-Lichtenberg and C. Pedersen, “Broadband long-wavelength upconversion in ultra-short nonlinear crystals,” Opt. Lett.49, 2233–2236 (2024)

    2024

  25. [34]

    Room-temperature, high-snr upconversion spectrometer in the 6–12 µm region,

    P. J. Rodrigo, L. Høgstedt, S. M. M. Friis,et al., “Room-temperature, high-snr upconversion spectrometer in the 6–12 µm region,” Laser & Photonics Rev.15, 2000443 (2021)

    2021

  26. [35]

    Investigation of silver gallium sulfide and silver gallium selenide for upconversion beyond10𝜇𝑚,

    P. Tidemand-Lichtenberg, R. L. Pedersen, L. Appignani, and C. Pedersen, “Investigation of silver gallium sulfide and silver gallium selenide for upconversion beyond10𝜇𝑚,” Opt. Lett.49, 6868–6871 (2024)

    2024

  27. [36]

    High responsivity mid-infrared indirect detection based on nonlinear crystal baga4se7,

    L. Guo, P. Liu, F. Qi,et al., “High responsivity mid-infrared indirect detection based on nonlinear crystal baga4se7,” Infrared Phys. & Technol.131, 104705 (2023)

    2023

  28. [38]

    R. W. Boyd,Nonlinear Optics (Academic Press, 2020)

    2020

  29. [39]

    Shen,Principles of nonlinear optics (Wiley-Interscience, 1984)

    Y.-R. Shen,Principles of nonlinear optics (Wiley-Interscience, 1984)

    1984

  30. [40]

    Mid-infrared upconversion spectroscopy,

    P. Tidemand-Lichtenberg, J. S. Dam, H. Andersen,et al., “Mid-infrared upconversion spectroscopy,” J. Opt. Soc. Am. B33, D28–D35 (2016)

    2016

  31. [41]

    Thermo-optic dispersion formula for aggas2,

    E. Takaoka and K. Kato, “Thermo-optic dispersion formula for aggas2,” Appl. optics38, 4577–4580 (1999)

    1999

  32. [42]

    Long-wavelength, high-resolution microscopy using upconversion in ultra-thin crystals,

    P. Tidemand-Lichtenberg and C. Pedersen, “Long-wavelength, high-resolution microscopy using upconversion in ultra-thin crystals,” APL Photonics9 (2024)

    2024

  33. [43]

    Video-rate, mid-infrared hyperspectral upconversion imaging,

    S. Junaid, S. Chaitanya Kumar, M. Mathez,et al., “Video-rate, mid-infrared hyperspectral upconversion imaging,” Optica 6, 702–708 (2019)

    2019

  34. [44]

    Mid-infraredfourierptychographicupconversionimaging,

    T.Zheng,Z.Wei,K.Huang, et al.,“Mid-infraredfourierptychographicupconversionimaging,”Optica 11,1716–1724 (2024)

    2024

Pith tools

Reviewed August 7, 2026 · model on record in the stance chip above.