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arxiv: 2606.01550 · v1 · pith:G4QSXMYPnew · submitted 2026-06-01 · ⚛️ physics.optics

Single-Photon Infrared Imaging with a Silicon Camera Based on Long-Wavelength-Pumping Two-Photon Absorption

Jianan Fang , Yinqi Wang , E Wu , Ming Yan , Kun Huang , Heping Zeng This is my paper

Pith reviewed 2026-06-28 13:34 UTC · model grok-4.3

classification ⚛️ physics.optics
keywords single-photon imaginginfrared detectiontwo-photon absorptionsilicon EMCCDnon-degenerate TPAtelecom photonsphoton countingmid-infrared pumping
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The pith

A silicon EMCCD camera detects single telecom photons via long-wavelength-pumped non-degenerate two-photon absorption.

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

The paper demonstrates that a silicon-based EMCCD can image infrared photons at the single-photon level by adding a mid-infrared pump beam. This long-wavelength pumping raises the two-photon absorption coefficient while cutting background noise from the pump itself. The result is more than 30 times higher counting rates than the usual degenerate two-photon approach, reaching a sensitivity of one photon per pixel per pulse. The setup needs no phase-matched crystal, delivers 13 micrometer spatial resolution, broadband response, and 5 picosecond timing through optical gating.

Core claim

The authors experimentally demonstrate an ultra-sensitive imaging system for telecom photons based on the non-degenerate two-photon absorption in a silicon-based EMCCD. The proposed long-wavelength-pumping scheme with mid-infrared pulsed excitation could not only effectively increase the two-photon absorption coefficient, but also significantly suppress the background noise caused by the harmonic absorption of the strong pumping field. In comparison to the photoelectric response via the degenerate two-photon absorption, the implemented configuration could offer over 30-folded enhancement of the photon-counting rate in the infrared imaging. The resulting detection sensitivity up to 1 photon/p

What carries the argument

long-wavelength-pumping non-degenerate two-photon absorption in a silicon EMCCD

Load-bearing premise

The observed counting-rate increase and noise suppression are caused by the long-wavelength-pumping non-degenerate two-photon absorption mechanism rather than by unstated changes in alignment, pump intensity, or sensor settings.

What would settle it

A side-by-side measurement of counting rate with the mid-infrared pump on versus off, while holding alignment, intensity, and camera settings fixed, would show whether the claimed 30-fold gain arises from the proposed absorption process.

Figures

Figures reproduced from arXiv: 2606.01550 by E Wu, Heping Zeng, Jianan Fang, Kun Huang, Ming Yan, Yinqi Wang.

Figure 1
Figure 1. Figure 1: Experimental setup for the 2PA-based infrared imaging in a silicon electron multiplying CCD (EMCCD) camera. The pump field at 3070 nm promotes [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: (a) Infrared signal beam captured by the mid-infrared pumped silicon [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Recorded images with ND-2PA for the horizontal (a) and vertical [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
Figure 6
Figure 6. Figure 6: Infrared imaging of a silicon wafer engraved with the university logo [PITH_FULL_IMAGE:figures/full_fig_p005_6.png] view at source ↗
Figure 5
Figure 5. Figure 5: Captured images based on the ND-2PA for various incident pulse [PITH_FULL_IMAGE:figures/full_fig_p005_5.png] view at source ↗
Figure 7
Figure 7. Figure 7: Detected count rates for three selected pixels vary as a function of the temporal delay between the pump and signal pulses. The images on the top [PITH_FULL_IMAGE:figures/full_fig_p006_7.png] view at source ↗
read the original abstract

We experimentally demonstrated an ultra-sensitive imaging system for telecom photons based on the non-degenerate two-photon absorption in a silicon-based electron multiplying charge-coupled device (EMCCD). The proposed long-wavelength-pumping scheme with mid-infrared pulsed excitation could not only effectively increase the two-photon absorption coefficient, but also significantly suppress the background noise caused by the harmonic absorption of the strong pumping field. In comparison to the photoelectric response via the degenerate two-photon absorption, the implemented configuration could offer over 30-folded enhancement of the photon-counting rate in the infrared imaging. The resulting detection sensitivity up to 1 photon/pixel/pulse was unprecedentedly approached, thus facilitating the single-photon operation. The elimination of the stringent phase matching as typically required in the optical parametric conversion has led to a high spatial resolution of 13 $\mu$m. Moreover, the on-chip nonlinearity of the optical imager would enable a broadband spectral window and an enlarged field of view. In combination with the 5-ps temporal resolution due to the coincident optical gating, the presented imaging system would find various promising applications, such as low-light fluorescence lifetime microscopy and photon counting time-of-flight 3D imaging.

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

2 major / 1 minor

Summary. The manuscript experimentally demonstrates an ultra-sensitive telecom-photon imaging system based on non-degenerate two-photon absorption (TPA) in a silicon EMCCD camera using long-wavelength mid-infrared pulsed pumping. It reports that this scheme increases the TPA coefficient while suppressing harmonic-absorption noise, yielding >30-fold enhancement of the photon-counting rate relative to degenerate TPA, a detection sensitivity of 1 photon/pixel/pulse, 13 μm spatial resolution, and 5 ps temporal resolution via optical gating, thereby enabling single-photon operation without phase-matching constraints.

Significance. If the reported sensitivity and enhancement are substantiated by quantitative controls and raw data, the work would constitute a notable experimental advance in on-chip nonlinear infrared imaging. The elimination of phase-matching requirements, combined with silicon-camera compatibility, broadband operation, and large field of view, could open practical routes to single-photon IR detection for applications such as fluorescence lifetime microscopy and time-of-flight imaging.

major comments (2)
  1. [Abstract] Abstract: the central claims of 'over 30-folded enhancement of the photon-counting rate' and 'detection sensitivity up to 1 photon/pixel/pulse' are stated without accompanying raw counts, error bars, statistical tests, or calibrated before/after data, preventing independent evaluation of the sensitivity figure.
  2. [Abstract] Abstract: the attribution of the observed rate increase and noise reduction specifically to the long-wavelength-pumping non-degenerate TPA mechanism (larger β and suppressed harmonic absorption) is not supported by quantitative controls that hold total intensity, beam overlap, alignment, and EMCCD gain/settings fixed between the degenerate and non-degenerate cases; without such isolation the 30-fold claim cannot be assigned to the proposed mechanism.
minor comments (1)
  1. [Abstract] Abstract: '30-folded' is nonstandard; '30-fold' is the conventional phrasing.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive comments on our manuscript. We agree that the abstract claims require stronger quantitative support and explicit controls to substantiate the mechanism. We will revise the manuscript to address these points directly.

read point-by-point responses

  1. Referee: [Abstract] Abstract: the central claims of 'over 30-folded enhancement of the photon-counting rate' and 'detection sensitivity up to 1 photon/pixel/pulse' are stated without accompanying raw counts, error bars, statistical tests, or calibrated before/after data, preventing independent evaluation of the sensitivity figure.

    Authors: We accept this criticism. The abstract is intentionally concise, but the supporting data (raw counts, error bars, and calibrated measurements) appear in the main text and figures. In the revised version we will modify the abstract to include explicit references to these quantitative results and add a brief statement of the statistical basis for the 1 photon/pixel/pulse figure. revision: yes

  2. Referee: [Abstract] Abstract: the attribution of the observed rate increase and noise reduction specifically to the long-wavelength-pumping non-degenerate TPA mechanism (larger β and suppressed harmonic absorption) is not supported by quantitative controls that hold total intensity, beam overlap, alignment, and EMCCD gain/settings fixed between the degenerate and non-degenerate cases; without such isolation the 30-fold claim cannot be assigned to the proposed mechanism.

    Authors: We agree that the attribution requires explicit isolation of variables. The current manuscript presents comparative data but does not include a dedicated control experiment holding total intensity, overlap, alignment, and camera settings strictly fixed. We will add this control measurement (or a clear supplementary figure) in the revision so that the 30-fold enhancement can be unambiguously assigned to the non-degenerate long-wavelength-pumping scheme. revision: yes

Circularity Check

0 steps flagged

No derivation chain present; experimental demonstration is self-contained

full rationale

The paper is an experimental report on measured photon-counting enhancements in an EMCCD camera using non-degenerate TPA. No equations, models, or fitted parameters are introduced that could reduce to their own inputs. Claims rest on observed counts rather than any predictive derivation, self-citation load-bearing step, or ansatz. This matches the most common honest finding of no circularity.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

No free parameters, axioms, or invented entities are introduced; the paper reports an experimental configuration that relies on standard two-photon absorption physics already present in the literature.

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discussion (0)

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Reference graph

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