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arxiv: 2603.18226 · v2 · submitted 2026-03-18 · ⚛️ physics.optics · physics.app-ph

Temperature in Glass Slides: measurement using Phase Sensitive Optical Coherence Tomography and Computational Modeling

Jose M. Folgueiras , Lucas G. Chej , Luis L. Zurdo , Alejandro G. Monastra , Eneas N. Morel , Maria F. Carusela , Jorge R. Torga This is my paper

Pith reviewed 2026-05-15 08:03 UTC · model grok-4.3

classification ⚛️ physics.optics physics.app-ph
keywords phase-sensitive optical coherence tomographytemperature measurementglass slidethermo-optic effectoptical path differencefinite volume methodthermal bath
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0 comments X

The pith

Phase-sensitive OCT measures temperature in glass slides by tracking optical path changes at 12.4 nm per degree Celsius.

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

The paper shows that a common-path spectral-domain OCT system can detect temperature-induced shifts in optical path length through a 1-mm soda-lime glass slide immersed in a thermal bath. Over the 20–52 °C range these shifts follow a clear linear trend, giving an experimental sensitivity of 12.4 ± 1.9 nm/°C. A finite-volume simulation that folds in the glass thermo-optic and thermal-expansion coefficients reproduces the measured values to within 5 % error. Lateral scans at fixed temperature confirm sub-10 nm repeatability, indicating the method can support spatially resolved thermal mapping in transparent solids.

Core claim

The optical path difference through a 1-mm soda-lime glass slide varies linearly with temperature between 20 and 52 °C, yielding an experimental sensitivity of 12.4 ± 1.9 nm/°C. Finite-volume simulations that incorporate the thermo-optic coefficient and thermal expansion coefficient of glass reproduce the measured values within a 5 % error, confirming that the observed changes arise from the combined thermo-optic and expansion effects.

What carries the argument

Phase-sensitive optical coherence tomography in a common-path spectral-domain configuration that registers sub-nanometer optical path difference changes produced by temperature-driven refractive-index and thickness variations inside the glass.

If this is right

  • The same optical path difference signal can be scanned laterally to produce spatially resolved temperature maps inside the slide.
  • The validated model supplies a low-cost calibration route for thermal sensing in any transparent solid whose thermo-optic and expansion coefficients are known.
  • Sub-10 nm repeatability at constant temperature allows the technique to monitor small thermal fluctuations without physical contact.
  • The approach extends contactless temperature measurement to delicate or microscopic transparent samples where traditional sensors cannot be used.

Where Pith is reading between the lines

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

  • The method could be applied to polymers or thin films once their thermo-optic coefficients are independently measured.
  • Combining the OCT temperature signal with structural OCT imaging would allow simultaneous mapping of temperature and refractive-index fields.
  • Calibration against a traceable thermometer remains necessary before quantitative use on materials whose coefficients are not already known.

Load-bearing premise

Observed optical path difference changes arise solely from the thermo-optic effect and thermal expansion of the glass, with negligible contributions from mechanical stress, optical-system drift, or bath-induced convection.

What would settle it

Place an independent contact thermometer at the exact location probed by the OCT beam and verify that the temperature change inferred from the measured optical path difference agrees with the thermometer reading to within 5 % across the 20–52 °C interval.

Figures

Figures reproduced from arXiv: 2603.18226 by Alejandro G. Monastra, Eneas N. Morel, Jorge R. Torga, Jose M. Folgueiras, Lucas G. Chej, Luis L. Zurdo, Maria F. Carusela.

Figure 1
Figure 1. Figure 1: Schematic of the low-coherence interferometer [PITH_FULL_IMAGE:figures/full_fig_p005_1.png] view at source ↗
Figure 3
Figure 3. Figure 3: Photograph of the experimental setup showing: [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗
Figure 5
Figure 5. Figure 5: 3D computational model (left) and mesh (right) of the experimental setup simulated in OpenFOAM. The [PITH_FULL_IMAGE:figures/full_fig_p007_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: OPD measurements during steady-state conditions (Series S5). Each plateau corresponds to a stable [PITH_FULL_IMAGE:figures/full_fig_p007_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: Linear regression of OPD vs. temperature for S2 Series (slope = ( [PITH_FULL_IMAGE:figures/full_fig_p008_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: Comparison of experimental (PT100 sensor measurements - red open squares) and simulated (open blue circles) water temperature. Simulation based on Series S3 (upward) and S4 (downward) data. 4.1 Measurement Uncertainty Evaluation An uncertainty analysis was performed to estimate the uncertainty associated with the temperature measurements ob￾tained with the proposed system. The main contributors considered … view at source ↗
Figure 9
Figure 9. Figure 9: Repeatability analysis of OPD measurements showing (a) superimposed scan profiles (OPD includes refractive [PITH_FULL_IMAGE:figures/full_fig_p010_9.png] view at source ↗
read the original abstract

Phase-sensitive optical coherence tomography (PhS-OCT) enables precise, contactless measurements of temperature-dependent changes in transparent solids. In this work, we used a common-path spectral-domain OCT system to measure optical path differences (OPD) in a 1-mm-thick soda-lime glass slide immersed in a thermal bath. The OPD variation showed a strong linear correlation with temperature in the range of 20-52{\deg}C, with an experimentally determined sensitivity of 12.4 +- 1.9 nm/{\deg}C. A theoretical model incorporating the thermo-optic and thermal expansion coefficients of glass was proposed to interpret the measurements, and numerical simulations based on finite volume methods were performed to account for spatial temperature gradients in the system. The simulations showed agreement with experimental results within 5% error, validating the approach. Additionally, repeatability tests using lateral scans at constant temperature demonstrated sub-10 nm stability, supporting future extensions to spatially resolved thermal mapping. This technique provides a low-cost platform for localized temperature sensing in solid transparent materials.

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 / 2 minor

Summary. The manuscript describes the use of phase-sensitive optical coherence tomography (PhS-OCT) to measure temperature-induced changes in optical path difference (OPD) in a 1-mm-thick soda-lime glass slide placed in a thermal bath. Experimental results show a linear relationship between OPD and temperature over 20-52°C, yielding a sensitivity of 12.4 ± 1.9 nm/°C. A finite-volume computational model incorporating thermo-optic and thermal expansion coefficients is used to simulate spatial temperature gradients, with results agreeing with experiments within 5%. Repeatability is demonstrated with sub-10 nm stability at constant temperature.

Significance. If the assumptions hold, this provides a contactless, low-cost platform for localized temperature sensing in transparent solids with potential for spatially resolved thermal mapping. The experimentally determined sensitivity and 5% simulation-experiment agreement constitute a concrete, falsifiable result that could support extensions of PhS-OCT to thermal characterization of solids.

major comments (3)
  1. [Results] Results section: The reported sensitivity of 12.4 ± 1.9 nm/°C and the 5% simulation agreement are presented without the underlying linear-fit statistics (number of points, R², or uncertainty propagation method), preventing independent assessment of whether the quoted error bar supports the claimed agreement level.
  2. [Computational modeling] Computational modeling section: The finite-volume model uses literature glass coefficients but provides no boundary-condition details at the glass-bath interface (e.g., convective heat-transfer coefficient) or sensitivity analysis; unmodeled convection could alter the internal temperature field and render the 5% match non-validating for the thermo-optic interpretation.
  3. [Experimental methods] Experimental methods: No independent verification (thermocouple array, alternate heating geometry, or stress measurement) is reported to bound contributions from mechanical constraint stress, bath convection, or system drift, which are assumed negligible relative to the thermo-optic term in the central OPD-temperature claim.
minor comments (2)
  1. [Abstract] Abstract and text use raw LaTeX fragments such as 20-52{°}C; these should be rendered as proper degree symbols in the final manuscript.
  2. [Results] The repeatability statement (“sub-10 nm stability”) would benefit from a quantitative metric (e.g., standard deviation over N lateral scans) and a figure showing the raw time series.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for the constructive comments and positive overall assessment of the work. We address each major comment below and indicate the revisions that will be made.

read point-by-point responses

  1. Referee: [Results] Results section: The reported sensitivity of 12.4 ± 1.9 nm/°C and the 5% simulation agreement are presented without the underlying linear-fit statistics (number of points, R², or uncertainty propagation method), preventing independent assessment of whether the quoted error bar supports the claimed agreement level.

    Authors: We agree that the linear-fit statistics should have been reported explicitly. In the revised manuscript we will add the number of data points used in the regression, the R² value of the fit, and a description of how the uncertainty on the slope was propagated from the phase measurements and temperature readings. This will allow independent evaluation of the quoted sensitivity and the claimed level of agreement with the simulations. revision: yes

  2. Referee: [Computational modeling] Computational modeling section: The finite-volume model uses literature glass coefficients but provides no boundary-condition details at the glass-bath interface (e.g., convective heat-transfer coefficient) or sensitivity analysis; unmodeled convection could alter the internal temperature field and render the 5% match non-validating for the thermo-optic interpretation.

    Authors: We acknowledge the omission of explicit boundary-condition values and sensitivity analysis. The revised manuscript will state the convective heat-transfer coefficient applied at the glass-bath interfaces and will include a short sensitivity study showing that plausible variations in this coefficient keep the predicted OPD within the reported 5 % agreement with experiment. This will strengthen the validation of the thermo-optic interpretation. revision: yes

  3. Referee: [Experimental methods] Experimental methods: No independent verification (thermocouple array, alternate heating geometry, or stress measurement) is reported to bound contributions from mechanical constraint stress, bath convection, or system drift, which are assumed negligible relative to the thermo-optic term in the central OPD-temperature claim.

    Authors: The sub-10 nm stability measured in the constant-temperature repeatability scans already constrains combined drift and mechanical contributions to a level far below the observed temperature-induced OPD changes. The close match to the thermo-optic model provides additional support that these effects are secondary. We will add an explicit discussion of this assumption and its limitations in the revised text, noting that independent verification (e.g., thermocouple arrays) would be a valuable extension for future work. revision: partial

Circularity Check

0 steps flagged

No circularity: experimental sensitivity measured directly from OPD-temperature data; model uses independent literature coefficients for validation.

full rationale

The paper's central result is a direct experimental measurement: OPD variation is recorded via PhS-OCT on a glass slide in a thermal bath, yielding a linear fit with sensitivity 12.4 ± 1.9 nm/°C over 20-52°C. The theoretical model simply inserts standard literature values for the thermo-optic coefficient and thermal expansion coefficient of soda-lime glass; these are not fitted to the present OPD dataset. Finite-volume simulations then solve the heat equation with those fixed coefficients and the known bath boundary conditions, producing a predicted OPD that is compared to the measured values (5% agreement reported). No equation reduces the reported sensitivity to a parameter fitted from the same data, no self-citation supplies a uniqueness theorem or ansatz, and the repeatability test (sub-10 nm stability) is an independent experimental check. The modeling assumptions (negligible stress, convection, drift) are explicit modeling choices whose consequences are tested by the external agreement rather than assumed by construction. This is a standard experimental-plus-simulation validation workflow with no load-bearing step that collapses to its own inputs.

Axiom & Free-Parameter Ledger

1 free parameters · 2 axioms · 0 invented entities

The central claim rests on standard physical properties of soda-lime glass and modeling assumptions about optical path changes; no new entities are introduced.

free parameters (1)
  • experimentally determined sensitivity = 12.4 nm/°C
    Linear fit coefficient extracted from OPD versus temperature data across 20-52 °C
axioms (2)
  • domain assumption Optical path difference changes are linearly proportional to temperature via the thermo-optic coefficient and the coefficient of thermal expansion of soda-lime glass
    Invoked to interpret measured OPD variation and to construct the theoretical model
  • domain assumption Finite-volume numerical simulation accurately reproduces the spatial temperature distribution inside the immersed glass slide
    Basis for claiming 5% agreement between experiment and model

pith-pipeline@v0.9.0 · 5519 in / 1504 out tokens · 42202 ms · 2026-05-15T08:03:39.608467+00:00 · methodology

discussion (0)

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