Optical Coherence Mode (OCM)

• Optical coherence mode (OCM) is defined in superconductivity as a sharp low-energy resonance observed in the optical self-energy, which aids in probing pairing interactions in cuprates.
• In biophotonics, OCM refers to optical coherence microscopy that leverages high-NA interferometric techniques to achieve microscopy-like lateral resolution for cellular imaging.
• The term spans distinct methodologies—spectroscopic analysis via extended Drude models versus interferometric imaging—which underscores the need for context-driven interpretation in research.

Searching arXiv for recent and relevant papers on "optical coherence mode" and the common acronym usage "optical coherence microscopy". Searching arXiv for “optical coherence mode” and related “optical coherence microscopy” usage. Optical coherence mode (OCM) is a term used in more than one technical sense. In overdoped cuprate superconductors, it denotes a sharp low-energy resonance in the optical response that appears in the superconducting state as a peak in the real part of the optical self-energy and as a step-like feature in the optical scattering rate (Park et al., 24 Sep 2025). In biophotonics and interferometric imaging, however, the acronym “OCM” is used predominantly for optical coherence microscopy, a high-numerical-aperture extension of optical coherence tomography (OCT) designed to obtain microscopy-like lateral resolution (Marchand et al., 2017). The coexistence of these usages makes terminological disambiguation essential: “optical coherence mode” in correlated-electron spectroscopy is a spectroscopic feature, whereas “OCM” in coherence imaging is ordinarily a modality label rather than a mode in the condensed-matter sense (Tateno et al., 13 Nov 2025).

1. Terminology and disciplinary usage

In the superconductivity literature represented here, the optical coherence mode is defined operationally through optical spectroscopy of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (Bi-2212). It is described as the sharp low-energy peak that appears in the real part of the optical self-energy in the superconducting state and is reflected simultaneously as a step-like feature in the optical scattering rate (Park et al., 24 Sep 2025). The same work states that the optical conductivity develops a corresponding dip feature below $\sim 1000\ \mathrm{cm}^{-1}$, consistent with coupling to this mode.

By contrast, the imaging literature uses “OCM” to mean optical coherence microscopy. In that usage, OCM is described as OCT pushed toward microscopy-like, high lateral resolution imaging by using high-NA optics, or as a combination of the coherent detection principle of OCT and confocal microscopy (Komeda et al., 15 Jan 2026); (Ma et al., 2018). Several papers explicitly frame OCM through the OCT–OCM tradeoff: OCT uses low NA and offers long depth of focus, whereas OCM uses high NA to achieve cellular lateral resolution but suffers from a short depth of focus (Tateno et al., 13 Nov 2025).

This terminological divergence is not merely lexical. A plausible implication is that references to “OCM” are field-dependent and must be interpreted from context. In spectroscopy, the term refers to a collective or bosonic-like resonance in an optical self-energy. In coherence imaging, it refers to an interferometric microscopy architecture or family of architectures (Park et al., 24 Sep 2025); (Marchand et al., 2017).

2. Spectroscopic definition in overdoped Bi-2212

Within overdoped Bi-2212, the extended Drude model is used to define the complex optical self-energy as

$$-2\tilde{\Sigma}^{op}(\omega, T ) \equiv -2\Sigma^{op}_1(\omega, T)-2i\Sigma^{op}_2(\omega, T) = i(\Omega_p^2/4\pi)\,[1/\tilde{\sigma}(\omega, T)]-\omega,$$

with

$$-2\Sigma_1^{op}(\omega, T) = \omega\left[\frac{m_{op}^*(\omega, T)}{m_b}-1\right], \qquad -2\Sigma_2^{op}(\omega, T) = \frac{1}{\tau^{op}(\omega, T)}.$$

In this formalism, the optical coherence mode is observed as a sharp peak in $-2\Sigma_1^{op}(\omega,T)$, that is, in the optical effective-mass renormalization, and as a step-like increase in $1/\tau^{op}(\omega,T)$ around $\sim 1000\ \mathrm{cm}^{-1}$ (Park et al., 24 Sep 2025).

The mode is extracted by subtracting the high-temperature background from the low-temperature real self-energy,

$_2$0

The resulting feature is then fit with a Gaussian. This procedure isolates the low-temperature superconducting-state contribution from the broader optical background.

The paper emphasizes that the OCM is not a separate gap feature. Instead, it is a coherent bosonic-like resonance in the optical response that emerges at low temperature near and below $_2$1 (Park et al., 24 Sep 2025). That distinction matters because it places the OCM in the category of collective-response signatures rather than in the category of primary gap parameters.

3. Doping evolution, broadening, and collapse at critical doping

The OCM is confined to the superconducting dome and evolves strongly with overdoping. At lower overdoping it is relatively sharp and strong; as doping increases toward the edge of the dome it becomes broader and weaker; and at the highest measured doping, $_2$2, it is essentially gone (Park et al., 24 Sep 2025). The same work identifies this highest doping as the critical doping,

$_2$3

depending on whether it is extracted from scaling or from the OCM weight.

Three quantitative trends are highlighted. First, the center frequency scales roughly with the superconducting transition temperature,

$_2$4

Second, the width grows only mildly up to about $_2$5, but then rapidly broadens for higher doping. Third, the mode weight decreases with doping and is fit by

$_2$6

with

$_2$7

The step size in the scattering rate, $_2$8, decreases with doping and tracks the OCM weight almost perfectly (Park et al., 24 Sep 2025).

These observations are interpreted as a loss of coherence on approaching criticality. The paper states that the OCM becomes incoherent because quantum fluctuations grow strong near the critical doping. This suggests that the mode is not simply weakened by conventional overdoped broadening, but is destabilized by the same critical regime that governs the normal-state transport scaling (Park et al., 24 Sep 2025).

4. Relation to strange metallicity and quantum critical scaling

The same overdoped Bi-2212 study connects the fate of the OCM to strange metallicity through $_2$9 scaling. At the critical doping $_2$0, the optical scattering rate and effective mass collapse when plotted versus

$_2$1

Specifically,

$_2$2

show excellent data collapse as functions of $_2$3, while

$_2$4

at $_2$5, which the authors describe as consistent with marginal Fermi liquid phenomenology and quantum critical scaling (Park et al., 24 Sep 2025).

Away from $_2$6, the breakdown of scaling is quantified by

$_2$7

and the crossover temperature follows

$_2$8

with the fit yielding

$_2$9

The paper argues that the scale $_{8+\delta}$0 collapses continuously to zero at the same doping where the OCM disappears. On that basis, it interprets $_{8+\delta}$1 as the energy scale of a mode that becomes critical at $_{8+\delta}$2 (Park et al., 24 Sep 2025). This suggests a direct link between the collapse of the OCM, the onset of $_{8+\delta}$3 scaling, and the approach to a quantum critical point.

Possible microscopic origins are discussed but not resolved. The authors mention a Leggett mode in a multiband or effectively two-component superconducting state, a mode related to pair-density-wave physics, a collective excitation connected to nematic fluctuations, or a mode tied to the magnetic resonance seen in cuprates (Park et al., 24 Sep 2025). The paper does not settle among these possibilities.

5. Distinction from optical coherence microscopy in coherence imaging

Outside correlated-electron spectroscopy, “OCM” overwhelmingly denotes optical coherence microscopy. In that domain, OCM is an imaging modality rooted in low-coherence interferometry and high-NA optics, not a superconducting resonance. This alternative usage is widespread in both methodological and application-oriented work.

A representative formulation states that OCM uses a high-numerical-aperture objective to achieve cellular-level lateral resolution, but that its practical imaging depth range is limited by the depth of focus (Tateno et al., 13 Nov 2025). Another paper describes OCM as a combination of the coherent detection principle of OCT and confocal microscopy, giving better axial and lateral resolution than conventional OCT (Ma et al., 2018). In developmental imaging, a custom OCM system using a supercontinuum source and spectral-domain detection acquired in vivo cross-sectional images of the beating Drosophila heart with axial resolution $_{8+\delta}$4, transverse resolution $_{8+\delta}$5, and sensitivity $_{8+\delta}$6 (Duan et al., 2018).

The following table summarizes the acronym split.

Usage of “OCM”	Domain	Meaning
Optical coherence mode	Correlated-electron spectroscopy	A sharp low-energy peak in the real part of the optical self-energy, with a corresponding step-like feature in optical scattering rate
Optical coherence microscopy	Biophotonics and interferometric imaging	A high-NA coherence-gated microscopy modality derived from OCT

This distinction is central to avoiding category errors. A spectroscopy paper that reports the disappearance of the OCM near $_{8+\delta}$7 is not describing a microscopy system (Park et al., 24 Sep 2025). Conversely, an imaging paper that reports extended-focus OCM, full-field swept-source OCM, or quantum optical coherence microscopy is not referring to the cuprate optical resonance (Marchand et al., 2017); (Yepiz-Graciano et al., 2022).

6. Optical coherence microscopy as the dominant acronymic meaning

In coherence imaging, OCM encompasses multiple implementations that elaborate the same basic premise: coherence gating from OCT combined with microscopy-scale transverse resolution. Extended-focus visible-spectrum OCM (“visOCM”) uses an ultra-broad visible-to-near-IR spectrum with a bandwidth of about $_{8+\delta}$8–$_{8+\delta}$9 centered at $\sim 1000\ \mathrm{cm}^{-1}$0, achieving $\sim 1000\ \mathrm{cm}^{-1}$1 axial and $\sim 1000\ \mathrm{cm}^{-1}$2 lateral resolution maintained over a depth of $\sim 1000\ \mathrm{cm}^{-1}$3 (Marchand et al., 2017). Spatially coherent full-field OCM (SC-FFOCM) combines full-field acquisition, spatial coherence, swept-source OCT detection, computational refocusing, and dynamic OCT repeated acquisition to obtain cellular-level lateral resolution over the full depth of human breast adenocarcinoma spheroids (Tateno et al., 13 Nov 2025). Quantum optical coherence microscopy (QOCM) adapts quantum optical coherence tomography into a microscopy-oriented, full-field format that retains factor-of-2 axial resolution enhancement and dispersion cancellation (Yepiz-Graciano et al., 2022).

Theoretical work likewise treats OCT/OCM jointly. A four-dimensional image-formation theory for OCT/OCM introduces a fourth coordinate associated with optical frequency and argues that high-NA OCT/OCM requires a 4D pupil function and a corresponding 4D point-spread function (Fukutake et al., 21 Jan 2025). A quantitative forward model for OCT, directly relevant to coherence-based imaging, replaces plane-wave illumination with a Gaussian-beam, focus-aware, angle-aware model in which the measured signal is the interference cross-term after dual-balance detection,

$\sim 1000\ \mathrm{cm}^{-1}$4

(Veselka et al., 2021).

Applications of OCM in this imaging sense include automated segmentation of Drosophila heart dynamics with an average IoU across 10 folds of approximately $\sim 1000\ \mathrm{cm}^{-1}$5 (Duan et al., 2018), computer-aided diagnosis of label-free 3-D OCM images of human cervical tissue with $\sim 1000\ \mathrm{cm}^{-1}$6 five-class classification accuracy and binary-task AUC $\sim 1000\ \mathrm{cm}^{-1}$7 (Ma et al., 2018), and neural-network-based dynamic OCT using full-field swept-source OCM in which high-definition logarithmic intensity variance images are generated from only four OCT volumes instead of thirty-two, reducing data size, transfer time, and processing time by a factor of eight (Komeda et al., 15 Jan 2026).

A plausible implication is that the acronym “OCM” has become institutionally anchored to optical coherence microscopy in imaging science. As a result, the condensed-matter phrase “optical coherence mode” is comparatively specialized and can be misread unless explicitly written out.

7. Conceptual significance and common sources of confusion

Two distinct misconceptions arise from the shared acronym. The first is to assume that the optical coherence mode in cuprates is a general optical-coherence imaging concept. The superconductivity paper does not use the term in that sense; it uses it for a low-temperature optical resonance inside the superconducting dome, visible in self-energy and scattering-rate data (Park et al., 24 Sep 2025). The second is to assume that all papers labeled “OCM” are discussing that resonance. In fact, the imaging literature uses OCM almost exclusively for optical coherence microscopy and often discusses OCT/OCM as a modality pair (Fukutake et al., 21 Jan 2025).

The disciplinary separation is also methodological. The condensed-matter OCM is inferred from optical conductivity and extended Drude analysis. Imaging OCM is implemented through interferometers, spectrometers, high-NA objectives, full-field cameras, computational refocusing, and related OCT-derived reconstruction methods (Tateno et al., 13 Nov 2025); (Marchand et al., 2017). Even when both usages invoke “optical coherence,” they do so at different levels of description: one as a spectroscopic signature of correlated-electron dynamics, the other as the basis of low-coherence interferometric sectioning.

Taken together, the available literature supports a narrow and a broad reading. In the narrow reading, optical coherence mode refers specifically to the Bi-2212 superconducting resonance that broadens and disappears near $\sim 1000\ \mathrm{cm}^{-1}$8, in tandem with the onset of quantum-critical $\sim 1000\ \mathrm{cm}^{-1}$9 scaling (Park et al., 24 Sep 2025). In the broad acronymic reading, OCM denotes optical coherence microscopy, a mature branch of coherence-gated imaging spanning extended-focus, full-field, dynamic, quantum, and computational implementations (Marchand et al., 2017); (Yepiz-Graciano et al., 2022). The term therefore has no single field-independent meaning; its interpretation depends on the research context in which it appears.