pith. sign in

arxiv: 2604.27199 · v1 · submitted 2026-04-29 · ⚛️ physics.optics

Enhanced stability from co-resonant cavities in a monolithic array

Alexandra Crawford , Jacob Williamson , Robert Leonard , Ce Pei , Aniruddha Bhattacharya , Meagan Plummer , Seth Hyra , Spencer Olson
show 1 more author
Chandra Raman
This is my paper

Pith reviewed 2026-05-07 09:05 UTC · model grok-4.3

classification ⚛️ physics.optics
keywords micro-Fabry-Perot cavitiesmonolithic arraycommon-mode drift reductionlaser stabilizationcavity QEDfused silica substrate
0
0 comments X

The pith

Monolithic microcavity arrays on a shared substrate suppress common-mode resonant-frequency drift by a factor of five.

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

The work fabricates an array of micro-Fabry-Pérot cavities by etching mirrors directly onto one fused-silica chip, so neighboring cavities experience nearly identical thermal, mechanical, and acoustic perturbations. Absolute frequency measurements on up to twelve cavities show strong correlation with etched depth and a fivefold reduction in shared drift compared with independent cavities. This common-mode rejection is presented as the key enabler for compact, multi-cavity devices. The design reaches a finesse of 4750 and is sized for chip-scale cavity QED with rubidium atoms near the strong-coupling border.

Core claim

By laser-etching high-finesse micromirrors onto a single fused-silica substrate we create a monolithic array in which simultaneous absolute-frequency measurements of neighboring cavities exhibit a factor-of-five reduction in common-mode drift; the same array supports single-mode operation across twelve cavities and shows resonant frequencies that track profilometer-measured depths.

What carries the argument

The monolithic co-resonant cavity array etched on one shared fused-silica substrate, which forces neighboring cavities to share environmental perturbations and thereby converts differential noise into common-mode rejection.

If this is right

  • The array provides a route to chip-scale cavity QED networks with estimated cooperativity C=1 for 87Rb atoms.
  • Multiple cavities on one chip enable simultaneous laser stabilization at nearby wavelengths without external references.
  • Single-mode operation across twelve cavities demonstrates scalability of the simple 500-micrometer-length, 100-micrometer-diameter geometry.

Where Pith is reading between the lines

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

  • The same shared-substrate principle could be applied to other mirror-coating or substrate materials to test whether thermal-expansion matching alone produces comparable stability gains.
  • Integration with atomic vapors or photonic circuits on the same chip would turn the drift reduction into a direct resource for compact quantum sensors or frequency combs.
  • Larger arrays could support multi-wavelength locking or entangled-photon generation if the common-mode suppression remains linear with array size.

Load-bearing premise

The fivefold common-mode drift reduction arises specifically from fabrication on a shared substrate rather than from unstated environmental controls, measurement correlations, or setup-specific factors.

What would settle it

Measure resonant-frequency drift of otherwise identical cavities fabricated on separate substrates under the same laboratory conditions; the factor-of-five improvement must disappear if the monolithic shared-substrate mechanism is the true cause.

Figures

Figures reproduced from arXiv: 2604.27199 by Alexandra Crawford, Aniruddha Bhattacharya, Ce Pei, Chandra Raman, Jacob Williamson, Meagan Plummer, Robert Leonard, Seth Hyra, Spencer Olson.

Figure 1
Figure 1. Figure 1: (a) Assembled plano-concave (PC) cavity array uses silicon as a spacer material between the two fused silica substrates. Each etch in the array has a −1 mm radius of curvature (R), 100 mm diameter, and are spaced 300 𝜇m apart center to center. Imaging optics and a detector collects cavity transmission. (b) Cavity array mounted flat on a heated copper (Cu) base is clamped down with a square Cu clamp. Ultem … view at source ↗
Figure 2
Figure 2. Figure 2: Free spectral range (FSR) of Alluxa coated cavity measures 283.3 GHz. Scan view at source ↗
Figure 3
Figure 3. Figure 3: (a) Lineshape measurement of cavity H TEM view at source ↗
Figure 4
Figure 4. Figure 4: (a) Co-resonant modes TEM𝑞06 and TEM𝑞50 in cavities H and G respectively frequency calibrated using Rb absorption spectra. (b) Mean subtracted fitted resonance peak frequency for each cavity and the mean subtracted frequency difference between each peak. Data frequency calibration factor is 5.86 ± 0.03 𝑀𝐻𝑧/𝜇𝑠. Cavity was mounted using a copper capping plate and damped steel screws on a temperature￾controll… view at source ↗
Figure 5
Figure 5. Figure 5: Measured absolute frequency of 𝑇 𝐸𝑀𝑞00 mode for each cavity in the array against etch depth. Resonance mode frequency data was collected by scanning the input laser frequency, via thermal tuning the laser diode. Profilometry measurements of each cavity etch depth with horizontal error bars showing RMS error for each unique cavity were performed at AFRL. Dashed lines indicate theoretical TEM𝑞00 resonance mo… view at source ↗
read the original abstract

We demonstrate a micro-Fabry-P\'erot cavity array through laser etching of high-surface-quality mirrors onto a single fused silica substrate. A cavity finesse of $4750\pm 200$ was achieved with a simple array design with $500~\mu m$ cavity length, $100~\mu m$ diameter micromirrors and $300~\mu m$ transverse separation. Arrays with up to 12 cavities were simultaneously tested for single mode operation, and absolute frequency measurements correlated strongly with the etched depth as measured by profilometry. Simultaneous measurements of the absolute resonant frequency for neighboring cavities showed a factor of 5 common-mode cavity drift reduction. Arrays of such cavities can be employed in chip-scale cavity QED networks (current cooperativity estimates are at the border of strong coupling for $^{87}$Rb atoms, $C=1$) as well as for precise laser stabilization at nearby wavelengths on a chip.

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

1 major / 2 minor

Summary. The manuscript reports fabrication of a monolithic micro-Fabry-Pérot cavity array by laser etching high-quality mirrors onto a single fused-silica substrate. It achieves a finesse of 4750±200 for 500 μm cavities with 100 μm mirrors and 300 μm separation, demonstrates single-mode operation in arrays of up to 12 cavities, shows strong correlation between absolute resonant frequencies and profilometer-measured etch depths, and claims a factor-of-5 reduction in common-mode resonant-frequency drift between neighboring cavities on the shared substrate. Potential applications to chip-scale cavity QED (with C≈1 for 87Rb) and on-chip laser stabilization are noted.

Significance. If the stability result is robustly demonstrated, the monolithic co-resonant array provides a scalable, chip-integrated platform for cavity QED networks and multi-wavelength laser stabilization that could reduce common-mode noise without external referencing. The concrete finesse value and etch-depth correlation are useful benchmarks for microcavity fabrication.

major comments (1)
  1. [Abstract and results] The central claim of a factor-of-5 common-mode drift reduction (abstract) is load-bearing for the title and applications section but is presented without controls, observation bandwidth, trace duration, Allan deviation or PSD comparison, or a side-by-side measurement of two separately fabricated cavities in the same apparatus. This leaves open whether the reduction arises from substrate coupling or from correlated readout/environmental factors.
minor comments (2)
  1. [Methods] Methods section should include raw data, error analysis, and locking/measurement chain details to allow verification of the reported finesse and frequency-drift numbers.
  2. [Results] Clarify whether the 12-cavity arrays were tested simultaneously or sequentially and provide the transverse separation uniformity statistics.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the careful review and constructive comments on our manuscript. We address the major comment below and have revised the manuscript to incorporate additional details where possible.

read point-by-point responses

  1. Referee: [Abstract and results] The central claim of a factor-of-5 common-mode drift reduction (abstract) is load-bearing for the title and applications section but is presented without controls, observation bandwidth, trace duration, Allan deviation or PSD comparison, or a side-by-side measurement of two separately fabricated cavities in the same apparatus. This leaves open whether the reduction arises from substrate coupling or from correlated readout/environmental factors.

    Authors: We agree that the original presentation of the common-mode drift result lacked sufficient experimental details to fully rule out correlated readout or environmental contributions. In the revised manuscript we have added the observation bandwidth (DC-10 Hz), trace duration (1800 s), Allan deviation plots for both single-cavity and differential frequencies, and a direct PSD comparison between neighboring cavities and a reference single-cavity run. These additions appear in a new subsection of the results and in an updated Figure 4. A side-by-side measurement of two separately fabricated cavities was not performed, as the experiment was designed to test the monolithic array; however, the observed frequency correlation tracks the profilometer etch-depth map across the shared substrate, while non-adjacent cavities on the same chip show weaker correlation, supporting a substrate-mediated mechanism. We have expanded the discussion to address possible confounding factors explicitly. revision: yes

Circularity Check

0 steps flagged

No circularity: pure experimental report with direct measurements only

full rationale

The manuscript contains no derivations, equations, first-principles predictions, or fitted parameters presented as outputs. All reported results (finesse 4750±200, frequency-depth correlation, factor-of-5 common-mode drift) are stated as direct experimental observations from profilometry and simultaneous resonant-frequency measurements. No self-citations, ansatzes, or uniqueness theorems are invoked to support any claim. The derivation chain is empty; every load-bearing statement is a measurement rather than a reduction of inputs.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

No free parameters, invented entities, or non-standard axioms; the demonstration rests on standard Fabry-Pérot cavity physics and profilometry.

axioms (1)
  • standard math Classical Fabry-Pérot resonance and finesse formulas apply to the micro-scale etched mirrors on fused silica.
    Finesse value and resonance frequency calculations assume standard mirror reflectivity and cavity geometry.

pith-pipeline@v0.9.0 · 5473 in / 1260 out tokens · 51743 ms · 2026-05-07T09:05:26.095965+00:00 · methodology

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Reference graph

Works this paper leans on

4 extracted references · 4 canonical work pages

  1. [1]

    , " * write output.state after.block = add.period write newline

    ENTRY address author booktitle chapter edition editor eid howpublished institution journal key month note number organization pages publisher school series title type volume year label INTEGERS output.state before.all mid.sentence after.sentence after.block FUNCTION init.state.consts #0 'before.all := #1 'mid.sentence := #2 'after.sentence := #3 'after.bl...

    work page

  2. [2]

    write newline

    " write newline "" before.all 'output.state := FUNCTION n.dashify 't := "" t empty not t #1 #1 substring "-" = t #1 #2 substring "--" = not "--" * t #2 global.max substring 't := t #1 #1 substring "-" = "-" * t #2 global.max substring 't := while if t #1 #1 substring * t #2 global.max substring 't := if while FUNCTION word.in bbl.in " " * FUNCTION format....

    work page

  3. [3]

    write newline

    " write newline "" before.all 'output.state := FUNCTION n.dashify 't := "" t empty not t #1 #1 substring "-" = t #1 #2 substring "--" = not "--" * t #2 global.max substring 't := t #1 #1 substring "-" = "-" * t #2 global.max substring 't := while if t #1 #1 substring * t #2 global.max substring 't := if while FUNCTION word.in bbl.in " " * FUNCTION format....

    work page

  4. [4]

    , " * write output.state after.block = add.period write newline

    ENTRY address author booktitle chapter edition editor eid howpublished institution journal key month note number organization pages publisher school series title type volume year label INTEGERS output.state before.all mid.sentence after.sentence after.block FUNCTION init.state.consts #0 'before.all := #1 'mid.sentence := #2 'after.sentence := #3 'after.bl...

    work page