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arxiv: 2606.05987 · v1 · pith:E6E4L6FPnew · submitted 2026-06-04 · ⚛️ physics.optics · physics.atom-ph

Laser fractional frequency instability at mathbf{4times 10⁻¹⁷} with a room temperature optical reference cavity

Adam L. Parke , Eve Clulow , Wei Huang , Namneet Kaur , Reinhard Karembera , Jacques-Olivier Gaudron , Xi Zhang , Matias Risaro
show 3 more authors
Jacob Tunesi Henry Bourne Marco Schioppo
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Pith reviewed 2026-06-27 23:59 UTC · model grok-4.3

classification ⚛️ physics.optics physics.atom-ph
keywords ultrastable lasersoptical reference cavityfrequency instabilityroom temperaturelaser linewidthoptical frequency metrologyspectral purity
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The pith

A 68 cm room-temperature optical cavity achieves 4×10^{-17} laser fractional frequency instability and 12 mHz linewidth.

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 laser locked to a 68 cm long optical reference cavity at ambient room temperature reaches fractional frequency instability of 4×10^{-17}. The same setup produces a laser linewidth of 12 mHz full width at half maximum. These numbers are presented as the lowest reported for any room-temperature system. The result indicates that ultrastable performance no longer requires cryogenic cooling or other specialized temperature control. This makes high-stability lasers available for a wider set of optical frequency metrology applications.

Core claim

We demonstrate laser fractional frequency instability at 4×10^{-17} and laser frequency linewidth of 12 mHz full width at half maximum, employing a 68 cm long optical reference cavity operating at room temperature. To the best of our knowledge, both frequency instability and linewidth are the lowest ever reported for a room temperature system.

What carries the argument

A 68 cm long optical reference cavity operating at room temperature, used to stabilize the laser via its length stability.

If this is right

  • State-of-the-art frequency stability becomes achievable without cryogenic systems.
  • Spectral purity at the 12 mHz level is possible in room-temperature setups.
  • Ultrastable lasers can be deployed by a broader range of users in optical frequency metrology.
  • Measurement speed and stability limits for optical frequency standards improve without specialized infrastructure.

Where Pith is reading between the lines

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

  • Portable or field-deployable ultrastable lasers may now be feasible without large cryogenic setups.
  • The result narrows the performance gap between room-temperature and cryo-stabilized cavities, potentially simplifying next-generation optical clock designs.
  • Further work could test whether similar cavities maintain this stability when integrated into smaller or mobile systems.

Load-bearing premise

The reported instability and linewidth are not limited by unaccounted systematic effects or measurement artifacts, and the cavity truly operates at ambient room temperature without undisclosed stabilization techniques.

What would settle it

An independent frequency comparison against a second, separately verified room-temperature reference that yields instability above 4×10^{-17} or linewidth above 12 mHz would falsify the claim.

Figures

Figures reproduced from arXiv: 2606.05987 by Adam L. Parke, Eve Clulow, Henry Bourne, Jacob Tunesi, Jacques-Olivier Gaudron, Marco Schioppo, Matias Risaro, Namneet Kaur, Reinhard Karembera, Wei Huang, Xi Zhang.

Figure 1
Figure 1. Figure 1: (a) Cavity ULE68a at an earlier stage of assembly. The numbered parts are (1) ULE spacer, with dimensions 13 cm × 13 cm × 68 cm, and edges chamfered at 45◦ , (2) fused silica cavity mirror, (3) Zerodur bar, (4) PEEK supports, (5) base of thermal shields, (6) base of vacuum chamber, (7) venting holes, and (8) Viton disk, one on each PEEK support as its only point of contact with the cavity spacer. (b) Top v… view at source ↗
Figure 2
Figure 2. Figure 2: (a) Schematic of the three-cornered hat (TCH) measurement set-up. ULE48a, ULE48b and the frequency comb are located in the same building, connected by short compensated fibers (not pictured). Beat ULE48a–ULE48b is produced from directly beating the 1064 nm lasers stabilized to the ULE48a and ULE48b cavities. The frequency comb is locked to ULE48a on the 1064 nm branch, and comb light at 1542 nm is sent to … view at source ↗
Figure 3
Figure 3. Figure 3: (a) Phase noise power spectral density Sφ of ULE68a, extracted with the three-cornered hat method, starting from the time series of the beats. The black dashed line represents the flicker frequency noise ν 2 0 h−1 f −3 , with h−1 = 1.7 × 10−33 and ν0 the optical carrier frequency for the wavelength 1542 nm. The inset plot shows the rms phase noise integration of Sφ. Gray short-dashed lines indicate where φ… view at source ↗
Figure 4
Figure 4. Figure 4: Drawings and finite-element-method (FEM) simulations performed to minimize the sensitivity to accelerations of the ULE68a cavity. Vertical deformation ×105 Side section view x z Longitudinal displacement (nm) -10 10 8 6 4 2 0 -2 -4 -6 -8 [PITH_FULL_IMAGE:figures/full_fig_p007_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: Side section view of FEM analysis for an optical cavity geometry of ULE68a optimized for minimal sensitivity to accelera￾tions. The vertical deformation is shown exaggerated by 105 , while the longitudinal displacement is represented by the color scale on the right of the figure. Both the Airy points configuration (null angular tilt of the cavity ends) and anti-symmetric longitudinal displacement are achie… view at source ↗
Figure 6
Figure 6. Figure 6: Photo of one of the four pillars supporting the ULE68a cavity. A Viton disk mediates contact between the cavity spacer and the PEEK supporting pillar. An aluminum clamp holds the PEEK pillar to the two Zerodur bars that run alongside the cavity. Below this, there is a PEEK sphere between the aluminum clamp and the base of the innermost thermal shield. The extra arrange￾ment of post and clamps seen on the s… view at source ↗
Figure 7
Figure 7. Figure 7: Photos of ULE68a’s cavity spacer during the machining process. (a) Milling of cuboid geometry. The cavity spacer is held securely and the milling tool moves in order to cut it. (b) Drilling of the bore hole for the optical path [PITH_FULL_IMAGE:figures/full_fig_p008_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: (a) Photo of ULE68a during interferometric characterization of the flatness and parallelism of the cavity’s end faces. (b) Fringes on the area of the bore hole from the parallelism test. Counting of the fringes allows for calculation of the angle between the end faces. pitch roll In-loop seismometer Out-of-loop seismometer In-loop tiltmeter Acoustic enclosure Breadboard on commercial AVI [PITH_FULL_IMAGE:… view at source ↗
Figure 9
Figure 9. Figure 9: Photo of the ULE68a set-up inside its acoustic enclosure. The photo was taken with one side of the acoustic enclosure open for access. The cavity is within the vacuum system on top of the optical breadboard, which sits on a commercial active vibration isolation (AVI) system. Also on the breadboard are two seismometers and one tiltmeter. The acceleration outputs of one seismome￾ter are used for out-of-loop … view at source ↗
Figure 10
Figure 10. Figure 10: Frequency beat ULE68a-ULE48a during the three-cornered hat measurement, with offset removed and counter integration time of 0.5 s. The linear drift of ULE48a is hardware-removed at the beginning of this measurement [PITH_FULL_IMAGE:figures/full_fig_p010_10.png] view at source ↗
read the original abstract

Ultrastable lasers play a key role in optical frequency metrology, setting measurement speed and ultimately impacting both stability and accuracy of optical frequency standards. Here we demonstrate laser fractional frequency instability at ${4}\times10^{-17}$ and laser frequency linewidth of $12\,$mHz full width at half maximum, employing a 68 cm long optical reference cavity operating at room temperature. To the best of our knowledge, both frequency instability and linewidth are the lowest ever reported for a room temperature system. This work highlights that state-of-the-art frequency stability and spectral purity are achievable at room temperature, making them accessible to a broader range of users.

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 / 2 minor

Summary. The manuscript reports an experimental demonstration of ultrastable laser performance using a 68 cm room-temperature optical reference cavity, achieving a fractional frequency instability of 4×10^{-17} and a linewidth of 12 mHz FWHM. These values are stated to be the lowest reported for any room-temperature system, with the work emphasizing accessibility without cryogenic cooling.

Significance. If the reported performance is substantiated by the full measurement data and error analysis, the result would establish that state-of-the-art stability and spectral purity are attainable at ambient temperature. This could broaden the use of ultrastable lasers in optical frequency metrology by removing the need for specialized cryogenic infrastructure.

minor comments (2)
  1. The abstract and introduction should explicitly reference the specific prior room-temperature results (with citations and numerical values) that are being surpassed, to allow readers to verify the 'lowest ever reported' claim without external lookup.
  2. Figure captions and methods sections should include the exact averaging times, integration methods, and reference laser details used to extract the 4×10^{-17} instability and 12 mHz linewidth, ensuring reproducibility from the presented data.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for the positive assessment of our work, the recognition of its potential impact, and the recommendation for minor revision. No specific major comments were provided in the report.

Circularity Check

0 steps flagged

No significant circularity

full rationale

This is an experimental measurement report demonstrating achieved laser frequency instability and linewidth with a room-temperature cavity. No derivation chain, equations, fitted parameters renamed as predictions, or self-citation load-bearing steps exist in the provided text or abstract. The central claims rest on direct experimental results rather than any reduction to prior inputs by construction, satisfying the default expectation of no circularity for such papers.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Experimental demonstration paper. No mathematical derivation or free parameters are introduced in the abstract; the result rests on the physical measurement of laser frequency stability against the cavity.

pith-pipeline@v0.9.1-grok · 5681 in / 1037 out tokens · 19140 ms · 2026-06-27T23:59:22.032523+00:00 · methodology

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Reference graph

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    2 of the main text was taken over a continuous period of 10 hours

    LINEAR DRIFT The three-cornered hat measurement presented in Fig. 2 of the main text was taken over a continuous period of 10 hours. The linear drift of ULE48a is hardware-removed at the mHz s−1 level, measured with an optical atomic clock. The hardware de-drift rate for ULE48a is set at the beginning of the measurement of the beat ULE68a-ULE48a. In this ...