All-optical tuning of a diamond micro-disk resonator on silicon

Benoit Guilhabert; Charalambos Klitis; Erdan Gu; Marc Sorel; Martin D. Dawson; Michael J. Strain; Paul Hill

arxiv: 1907.05492 · v1 · pith:LEC6TJYDnew · submitted 2019-07-11 · ⚛️ physics.optics · physics.app-ph

All-optical tuning of a diamond micro-disk resonator on silicon

Paul Hill , Charalambos Klitis , Benoit Guilhabert , Marc Sorel , Erdan Gu , Martin D. Dawson , Michael J. Strain This is my paper

Pith reviewed 2026-05-24 22:36 UTC · model grok-4.3

classification ⚛️ physics.optics physics.app-ph

keywords diamond micro-disksilicon photonicsoptical tuningthermal tuningQ-factormicro-assemblyintegrated resonator

0 comments

The pith

Diamond micro-disk resonators integrated on silicon waveguides reach loaded Q-factors up to 1.05 times 10^5 and tune continuously over 450 pm with milliwatt optical pumping.

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

The paper demonstrates a method to place a small diamond micro-disk directly onto a silicon-on-insulator waveguide using micro-assembly. The resulting device shows high optical quality factors across multiple modes while the thin silica layer between diamond and silicon allows the disk to heat rapidly under a separate optical pump beam. This heating shifts the resonance wavelength across a 450 pm range without destroying the high Q. The approach addresses two practical barriers for diamond photonics: limited crystal size and lack of easy tuning. If the integration holds, it opens routes to place tunable diamond elements at many locations across large silicon photonic circuits.

Core claim

A diamond micro-disk resonator integrated with a standard single-mode silicon-on-insulator waveguide exhibits an average loaded Q-factor of 3.1 times 10^4 across spatial modes and a maximum of 1.05 times 10^5; the micron-scale size combined with the high thermal impedance of the silica interface layer produces significant thermal loading that enables continuous resonant wavelength tuning over a 450 pm range using only milliwatt-level optical pump power.

What carries the argument

Micro-assembly integration of a diamond micro-disk onto a silicon waveguide that exploits the thermal impedance of the intervening silica layer to convert absorbed pump light into a controlled refractive-index shift.

If this is right

Tunable diamond resonators can be placed at arbitrary locations on existing silicon photonic chips without redesigning the waveguide layer.
The same integration step can be repeated across many sites, allowing arrays of individually addressable diamond devices on one circuit.
Thermal tuning at milliwatt levels removes the need for separate electrical heaters or mechanical actuators on the diamond elements.
The reported Q values remain usable for both classical nonlinear optics and on-chip quantum light sources once the devices are tuned to the desired wavelength.

Where Pith is reading between the lines

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

The technique could be extended to other wide-bandgap materials whose crystals are also available only in small pieces.
If the pump light is delivered through the same waveguide as the signal, the tuning mechanism might be made all-optical and wavelength-selective without extra alignment steps.
The 450 pm range is large enough to compensate for fabrication variations across many devices on one chip, potentially raising overall circuit yield.

Load-bearing premise

The silica layer between the diamond disk and the silicon waveguide supplies enough thermal isolation for milliwatt pumping to produce a 450 pm resonance shift while adding no unacceptable scattering or absorption loss that would degrade the measured Q-factors.

What would settle it

Measure the resonance shift versus pump power on the same device after the silica interface is replaced by a lower-thermal-impedance material or after the disk is placed in direct contact with the silicon; the shift should drop below 450 pm per milliwatt if the thermal-impedance claim is correct.

Figures

Figures reproduced from arXiv: 1907.05492 by Benoit Guilhabert, Charalambos Klitis, Erdan Gu, Marc Sorel, Martin D. Dawson, Michael J. Strain, Paul Hill.

**Figure 1.** Figure 1: Schematic of a hybrid integration scheme where diamond micro-disk resonators are fabricated separately from a host Photonic Integrated Circuit chip. The fully fabricated diamond resonators are transferred onto the silicon photonic chip using a high accuracy transfer printing method. 2. METHODS A. Diamond membrane fabrication and printing The hybrid integration technique presented in this work is based on … view at source ↗

**Figure 3.** Figure 3: Transfer printing process: a) resist is spun and b) patterned on a diamond membrane, c) the pattern is transferred to the diamond using inductively-coupled-plasma reactive ion etching. d)-f) A PDMS stamp is aligned with the diamond chiplet, brought into close contact and retracted to release the chiplet. g)-i) The chiplet is aligned over a host substrate, brought into contact and released, leaving the it … view at source ↗

**Figure 4.** Figure 4: a) Two 45 deg tilted-view SEM micrographs combined to show 8 membranes that were printed for AFM measurements, the black arrow indicates the direction of largest thickness gradient. b) A plot showing the mean AFM heights for each of the 8 membranes demonstrating the ability of fine and coarse thickness selection [PITH_FULL_IMAGE:figures/full_fig_p003_4.png] view at source ↗

**Figure 6.** Figure 6: An optical microscope image showing a 12.5 µm radius diamond disk integrated with a silicon waveguide using micro-transfer printing [PITH_FULL_IMAGE:figures/full_fig_p004_6.png] view at source ↗

**Figure 7.** Figure 7: Optical measurement setup used for spectral characterisation of the integrated micro-disk. The pump laser source, EDFA and OSA are onsly used for the pump/probe thermal tuning measurements. C. Measurement setup The spectral characterisation of the micro-disk resonator and the optical tuning were both realised with the same measurement setup, as shown in [PITH_FULL_IMAGE:figures/full_fig_p004_7.png] view at source ↗

**Figure 11.** Figure 11: Transmission spectra of the diamond resonator measured using a continuously swept laser source with on-chip source power as a parameter. conductivity of silica is 1.5 W/m.K, providing good thermal isolation of the diamond micro-disk. Therefore, in this geometry, the combined effect of the optical mode confinement and the thermal isolation of the small diamond resonator, allows for significant temperature… view at source ↗

**Figure 9.** Figure 9: a) Measured transmission and fit to analytic all-pass resonator function for a mode around the average loaded Qfactor of the device. b) Measured transmission and fitted curve for the highest measured loaded Q-factor resonance. κ is the power cross-coupling coefficient and the loss refers to the distributed propagation loss value of the resonator [PITH_FULL_IMAGE:figures/full_fig_p005_9.png] view at source ↗

**Figure 10.** Figure 10: Power cross-coupling coefficients (squares) and distributed losses (circles) as a function of measured loaded Qfactor [PITH_FULL_IMAGE:figures/full_fig_p005_10.png] view at source ↗

**Figure 12.** Figure 12: Probe measured wavelength shift of a resonance centred at ~1547 nm for different pump powers injected in the 1563 nm resonance. Inset: Probe spectral measurements of a resonant mode at 0 mW and 4.25 mW on-chip pump powers [PITH_FULL_IMAGE:figures/full_fig_p006_12.png] view at source ↗

**Figure 13.** Figure 13: Simulation of thermal diffusion in the hybrid diamond-on-silica-on-silicon stack showing high confinement in the printed diamond micro-disk. a) Schematic of the material stack, b) thermal simulation close to the micro-disk region. of the thermal energy to the diamond material, supporting the thermo-optic tuning effects observed in the measurements. 4. CONCLUSION In conclusion, micro-fabrication and trans… view at source ↗

read the original abstract

High quality integrated diamond photonic devices have previously been demonstrated in applications from non-linear photonics to on-chip quantum optics. However, the small sample sizes of single crystal material available, and the difficulty in tuning its optical properties, are barriers to the scaling of these technologies. Both of these issues can be addressed by integrating micron scale diamond devices onto host photonic integrated circuits using a highly accurate micro-assembly method. In this work a diamond micro-disk resonator is integrated with a standard single mode silicon-on-insulator waveguide, exhibiting an average loaded Q-factor of 3.1x10^4 across a range of spatial modes, with a maximum loaded Q-factor of 1.05x10^5. The micron scale device size and high thermal impedance of the silica interface layer allow for significant thermal loading and continuous resonant wavelength tuning across a 450 pm range using a mW level optical pump. This diamond-on-demand integration technique paves the way for tunable devices coupled across large scale photonic circuits.

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.

Desk Editor's Note private letter to a colleague

The paper shows a workable micro-assembly route for diamond microdisks on SOI waveguides that delivers loaded Q up to 1.05e5 and 450 pm all-optical tuning, but the thermal mechanism rests on an unquantified assumption about the silica interface.

read the letter

The main takeaway is that micro-assembly lets you put small diamond resonators onto standard silicon waveguides and tune them continuously with a milliwatt optical pump, reaching loaded Q values of 3.1e4 on average and 1.05e5 at best. This directly tackles the scaling problem of small diamond samples by allowing placement on larger photonic circuits. The reported numbers on Q across multiple spatial modes and the 450 pm tuning range are concrete experimental outcomes, which is useful for anyone trying to build hybrid diamond-silicon devices for nonlinear or quantum optics. The all-optical approach also keeps the device simple, with no added electrodes. The integration itself appears to preserve reasonable optical performance, which is the practical advance here. The soft spot is the thermal tuning claim. It depends on the silica interface layer supplying enough thermal resistance for noticeable local heating while adding negligible scattering or absorption that would degrade the Q. The abstract gives no thickness, thermal conductivity, absorbed power fraction, or measured temperature rise to back this up. If the actual heat flow is lower than needed, either the tuning range shrinks or the pump power rises enough to introduce extra loss. That part of the story needs the supporting measurements or calculations to stand on its own. This work is aimed at integrated photonics researchers who need tunable diamond elements on silicon platforms. A reader looking for fabrication methods or resonator performance data will find usable numbers. It deserves a serious referee because the core experimental result is specific and falsifiable even if the thermal details require more evidence.

Referee Report

1 major / 0 minor

Summary. The manuscript reports the micro-assembly integration of a diamond micro-disk resonator onto a standard single-mode silicon-on-insulator waveguide. It measures an average loaded Q-factor of 3.1×10^4 (maximum 1.05×10^5) across spatial modes and demonstrates continuous all-optical resonant tuning over a 450 pm range using mW-level optical pumping, which the authors attribute to thermal loading enabled by the high thermal impedance of the silica interface layer between diamond and silicon.

Significance. If the thermal mechanism is properly substantiated, the result would be significant for scalable integration of high-Q diamond resonators with silicon photonic circuits, directly addressing sample-size and tuning limitations for quantum-optics and nonlinear-photonic applications. The reported Q values and micron-scale device size constitute concrete experimental strengths.

major comments (1)

[Abstract] Abstract: the central claim that the 'high thermal impedance of the silica interface layer' simultaneously supplies sufficient thermal resistance for 450 pm tuning at mW pump powers while adding negligible scattering or absorption (thereby preserving the stated loaded Q-factors) is unsupported by any reported layer thickness, thermal-conductivity value, absorbed-power fraction, temperature calibration, or loss budget at the pump wavelength. Without these data the headline tuning result cannot be verified and remains load-bearing for the paper's performance claims.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for their careful reading of the manuscript and for identifying the need for greater quantitative support of the thermal-tuning claim. We address the single major comment below and will revise the manuscript to incorporate additional details.

read point-by-point responses

Referee: [Abstract] Abstract: the central claim that the 'high thermal impedance of the silica interface layer' simultaneously supplies sufficient thermal resistance for 450 pm tuning at mW pump powers while adding negligible scattering or absorption (thereby preserving the stated loaded Q-factors) is unsupported by any reported layer thickness, thermal-conductivity value, absorbed-power fraction, temperature calibration, or loss budget at the pump wavelength. Without these data the headline tuning result cannot be verified and remains load-bearing for the paper's performance claims.

Authors: We agree that the abstract would be strengthened by explicit supporting parameters. The manuscript already reports the experimental demonstration of 450 pm continuous tuning under mW-level pumping together with the preservation of the stated loaded Q-factors, which directly shows that any additional loss from the interface is negligible at the signal wavelength. The attribution to the silica layer follows from the device geometry (diamond micro-disk on SOI with a silica interface) and the observed power dependence. In the revised manuscript we will (i) update the abstract to reference the key parameters, (ii) add the silica-layer thickness taken from the commercial SOI wafer specification, (iii) include a simple thermal-resistance estimate using literature values for the thermal conductivity of silica and the known device dimensions, (iv) provide an order-of-magnitude absorbed-power fraction based on published absorption coefficients of diamond and silica at the pump wavelength, and (v) add a short loss-budget discussion confirming that interface scattering and absorption remain below the level that would degrade the measured Q. Direct temperature calibration was not performed in the original experiment; we will explicitly state this limitation and note that the continuous, reversible, and power-dependent character of the shift is consistent with a thermal mechanism. These textual additions will allow the claim to be verified from the existing data without new measurements. revision: yes

Circularity Check

0 steps flagged

No circularity: experimental measurements only

full rationale

The paper reports direct experimental results on device fabrication, measured loaded Q-factors (average 3.1e4, max 1.05e5), and observed 450 pm tuning under mW optical pumping. No equations, derivations, fitted parameters renamed as predictions, or self-citation chains appear in the provided text or abstract. The central claims rest on measured quantities rather than any self-referential logic or ansatz, satisfying the self-contained experimental benchmark for score 0.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Central claim rests on experimental fabrication and optical/thermal measurements using standard domain techniques in photonics; no free parameters, invented entities, or ad-hoc axioms beyond routine assumptions about thermal-optic effects and waveguide coupling.

axioms (1)

domain assumption Thermal-optic coefficient and thermal impedance of silica interface enable measurable resonance shift from mW-level absorption without dominant optical loss.
Implicit in attributing the 450 pm tuning to thermal loading at the interface.

pith-pipeline@v0.9.0 · 5720 in / 1267 out tokens · 63362 ms · 2026-05-24T22:36:26.322125+00:00 · methodology

discussion (0)

Reference graph

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