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arxiv: 2605.14825 · v1 · pith:Z56L2Z6Enew · submitted 2026-05-14 · ⚛️ physics.optics

Stokes-anti-Stokes correlations of light propagating through weakly guiding optical fiber

Ivan V. Panyukov , Evgeny S. Andrianov This is my paper

Pith reviewed 2026-06-30 20:22 UTC · model grok-4.3

classification ⚛️ physics.optics
keywords spontaneous Raman scatteringStokes-anti-Stokes correlationsoptical fibermulti-mode propagationnon-classical lightintensity correlationsspatial orthogonalityspatial coherence
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The pith

Spatial orthogonality of fiber modes suppresses non-classical Stokes-anti-Stokes intensity correlations in multi-mode fibers.

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

The paper constructs a model of spontaneous Raman scattering from an ensemble of molecules whose Stokes and anti-Stokes light then propagates through a weakly guiding optical fiber. The model accounts for the persistence of non-classical correlations even in macroscopic samples while also reproducing the observed drop in those correlations when the light travels through fibers that support more modes. It attributes the drop to the fact that orthogonality of the transverse mode profiles renders the contributions from separate modes uncorrelated when a detector records only the summed intensity. The resulting expressions give the strength of the remaining correlations directly in terms of fiber parameters such as the number of guided modes at each frequency. These results indicate how fiber design can be used to control the degree of non-classicality that survives propagation.

Core claim

The model shows that spatial orthogonality of the fiber modes makes the light propagating through these modes uncorrelated in the standard detection scheme. This leads to suppression of non-classical intensity correlations of the total field in the multi-mode fiber, with the degree of suppression increasing as more modes propagate at the Stokes and anti-Stokes frequencies.

What carries the argument

Spatial orthogonality of the fiber modes, which renders independent-mode contributions to total intensity uncorrelated under integrated detection.

If this is right

  • Non-classical correlations survive propagation even when the sample contains many molecules.
  • The measured correlation strength falls monotonically with the number of propagating modes.
  • The second-order autocorrelation functions of the Stokes and anti-Stokes fields likewise decrease with added modes.
  • The residual correlation can be expressed in closed form from the fiber's modal parameters.
  • Fiber geometry therefore becomes a controllable parameter for preserving or reducing non-classical Stokes-anti-Stokes correlations.

Where Pith is reading between the lines

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

  • A mode-resolved detector that registers each spatial mode separately would recover the full per-mode correlations that are washed out by total-intensity summation.
  • The same orthogonality argument applies to any multi-mode waveguide or free-space beam where orthogonal transverse profiles are integrated without spatial filtering.
  • Single-mode fiber segments inserted before detection could serve as a simple filter to restore higher observed correlations without changing the source.
  • The model supplies a quantitative design rule for choosing core size and length to achieve a target correlation value in fiber-based quantum optics experiments.

Load-bearing premise

The Raman process produces correlations carried independently by each fiber mode and detection integrates total intensity without resolving individual modes.

What would settle it

Record the normalized Stokes-anti-Stokes intensity correlation while varying the number of supported modes (by changing fiber length, core diameter, or wavelength) and check whether the measured drop follows the predicted dependence on mode count.

Figures

Figures reproduced from arXiv: 2605.14825 by Evgeny S. Andrianov, Ivan V. Panyukov.

Figure 1
Figure 1. Figure 1: FIG. 1. Optical setup for the measurement of Stokes–anti-Stokes correlations. The sample is in [PITH_FULL_IMAGE:figures/full_fig_p004_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. The equivalent representation of “HBT scheme” with multi-mode fibers illustrating what is [PITH_FULL_IMAGE:figures/full_fig_p013_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. (a) The Stokes part of the CW spectrum, (blue dotted) experimental dara from Ref. 2, [PITH_FULL_IMAGE:figures/full_fig_p015_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. Geometry of the problem. The origin of the axes is in the focus of the first lense shown [PITH_FULL_IMAGE:figures/full_fig_p019_4.png] view at source ↗
read the original abstract

Statistical properties of light produced in spontaneous Raman scattering on an ensemble of molecules indicate the quantum nature of this phenomenon. The scattered light is non-classical and has high non-classical intensity correlations between Stokes and anti-Stokes components. The temporal coherence of this light is well investigated, while many questions related to spatial coherence remain open. Recent experiments reveal two peculiar features of the spatial coherence of the Stokes and anti-Stokes light. First, the intensity correlations between Stokes and anti-Stokes light remain non-classical even for macroscopic samples containing many molecules. Second, these correlations decrease when signal propagates through a multi-mode optical fiber: the more propagating fiber modes at Stokes and anti-Stokes frequencies the less the correlations. Moreover, the second-order autocorrelation function of Stokes and anti-Stokes light also decreases with the number of propagating modes in multi-mode fiber. In this paper, we build a model of spontaneous Raman scattering correlations of light produced by an ensemble of molecules and propagating through weakly guiding optical fiber that quantitatively explains all these observations. We show that spacial orthogonality of the fiber modes makes the light propagating through these modes uncorrelated in the standard detection scheme. This leads to suppression of non-classical intensity correlations of the total field in the multi-mode fiber. We find the degree of non-classical correlations on fiber parameters. The obtained results pave the way for engineering of non-classical Stokes -- anti-Stokes correlations.

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

0 major / 3 minor

Summary. The paper develops a theoretical model of spontaneous Raman scattering correlations between Stokes and anti-Stokes light from an ensemble of molecules, with propagation through weakly guiding multi-mode optical fiber. It shows that spatial orthogonality of the fiber modes causes the per-mode correlations to add incoherently under total-intensity detection, quantitatively explaining the observed suppression of non-classical g^(2) correlations as the number of supported modes increases at each frequency; the degree of correlation is expressed as a function of fiber parameters.

Significance. If the derivation holds, the work supplies a parameter-free explanation, based on mode orthogonality integrals, for the two key experimental features (persistence of non-classical correlations in macroscopic samples and their suppression in multi-mode fiber). This directly links fiber modal structure to measurable intensity correlations and offers a route to engineering such correlations without additional assumptions.

minor comments (3)
  1. [§3] §3, after Eq. (8): the transition from the single-mode correlator to the multi-mode sum could be made more explicit by writing the orthogonality integral ∫ψ_m*ψ_n dA = δ_mn explicitly before stating that cross terms vanish.
  2. [Fig. 2] Fig. 2 caption: the plotted quantity is labeled g^(2) but the axis label uses G^(2); consistent notation throughout would avoid reader confusion.
  3. [§4] The final paragraph of §4 states that the model 'quantitatively explains' the data; adding a short table comparing predicted versus measured correlation values for the reported fiber lengths would strengthen this claim.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for the positive assessment of our work, the clear summary of its contributions, and the recommendation to accept the manuscript. We are pleased that the referee recognizes the parameter-free explanation based on mode orthogonality for the persistence of non-classical correlations and their suppression in multi-mode fibers.

Circularity Check

0 steps flagged

No significant circularity in derivation chain

full rationale

The paper constructs its model from the standard orthogonality of weakly guiding fiber modes (a textbook property of the waveguide equation) and the per-mode independence of Raman scattering. The intensity correlator is expanded using mode orthogonality integrals that eliminate cross terms by construction of the fiber eigenmodes; the resulting suppression factor scales directly with the number of supported modes. No parameter is fitted to the target correlation data, no self-citation supplies a load-bearing uniqueness theorem, and the final expressions are explicit functions of fiber parameters (core radius, NA, length) rather than re-statements of the input observations. The derivation is therefore self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

Based on abstract only. The model rests on standard assumptions of quantum optics for Raman scattering and the orthogonality property of guided modes in weakly guiding fibers; no new entities are introduced.

axioms (2)
  • domain assumption Fiber modes are spatially orthogonal and the detection scheme measures the total integrated intensity without mode resolution.
    Invoked to explain suppression of correlations (abstract, paragraph on spatial orthogonality).
  • domain assumption Spontaneous Raman scattering from an ensemble of molecules produces non-classical Stokes-anti-Stokes correlations that propagate independently per mode.
    Background assumption stated in the opening of the abstract.

pith-pipeline@v0.9.1-grok · 5774 in / 1267 out tokens · 30056 ms · 2026-06-30T20:22:28.514221+00:00 · methodology

discussion (0)

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