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Optics Letters

On-chip dense quantum frequency comb generation via SFWM in an AlGaAs-on-insulator resonator

J. S. S. Durán Gómez, Jan Heine, Mina Abdelmeseih, Alí Angulo, Stuart May, Marc Sorel, Michael Kues

Published Jul 14, 2026• 0 citations
Publisher

Abstract

), such as aluminum gallium arsenide (AlGaAs), enable efficient nonlinear interactions at low excitation powers in integrated cavities. Here, we demonstrate a broadband quantum frequency comb (QFC) in a low free spectral range (FSR) (45 GHz) aluminum gallium arsenide on insulator (AlGaAsOI) resonator, with up to 40 pairwise frequency-correlated modes across a 1.97 THz bandwidth in the C-band. The dense mode spacing enables scalable frequency multiplexing and frequency-bin encoding within a compact device operating at a low excitation power of 6.33 µW. The measured joint-spectral intensity (JSI) is well reproduced by a theoretical model, enabling predictive control of spectral correlations across the generated QFC. The moderate Q-factor provides a tradeoff between nonlinear enhancement, broadband phase-matching, and number of accessible modes, supporting dense multimode operation over a large spectral range. These results highlight the potential of AlGaAsOI resonators for scalable low-power QFC sources.

DOI
10.1364/ol.605643

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), such as aluminum gallium arsenide (AlGaAs), enable efficient nonlinear interactions at low excitation powers in integrated cavities. Here, we demonstrate a broadband quantum frequency comb (QFC) in a low free spectral range (FSR) (45 GHz) aluminum gallium arsenide on insulator (AlGaAsOI) resonator, with up to 40 pairwise frequency-correlated modes across a 1.97 THz bandwidth in the C-band. The dense mode spacing enables scalable frequency multiplexing and frequency-bin encoding within a compact device operating at a low excitation power of 6.33 µW. The measured joint-spectral intensity (JSI) is well reproduced by a theoretical model, enabling predictive control of spectral correlations across the generated QFC. The moderate Q-factor provides a tradeoff between nonlinear enhancement, broadband phase-matching, and number of accessible modes, supporting dense multimode operation over a large spectral range. These results highlight the potential of AlGaAsOI resonators for scalable low-power QFC sources.
We reveal the generation of a broadband (> 1.9 THz) bi-photon quantum frequency comb (QFC) in a silicon-on-insulator (SOI) Fabry–Pérot micro-cavity and the control of its spectral correlation properties. Correlated photon pairs are generated through three spontaneous four-wave mixing (SFWM) processes by using a co-polarized bi-chromatic coherent input with power P 1 and P 2 on adjacent resonances of the nonlinear cavity. Adjusting the spectral power ratio r = P 1 /( P 1 + P 2 ) allows control over the influence of each process leading to an enhancement of the overall photon pair generation rate (PGR) μ ( r ) by a maximal factor of μ ( r = 0.5)/ μ ( r = 0) ≈ 1.5, compared to the overall PGR provided by a single-pump configuration with the same power budget. We demonstrate that the efficiency a ND of the non-degenerate excitation SFWM process (NDP) doubles the efficiency a 1 ≈ a 2 of the degenerate excitation SFWM processes (DP), showing a good agreement with the provided model.
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Quantum frequency combs (QFCs) are essential to quantum photonic systems, enabling high dimensional entanglement in both temporal and frequency domains. Silicon photonics offers a promising platform for scalable and monolithic quantum photonic integrated circuits. However, its performance in QFC generation has been hindered by nonlinear losses and restricted phase-matching bandwidth. To overcome these challenges, we introduce a novel design strategy that combines high-order spatial mode engineering with an optimized free-carrier loss suppression structure in a silicon micro-ring resonator. This approach enables a broadband QFC spanning 150 nm, along with a high single pair photon brightness of 6.43 × 109 Hz/mW2/GHz and photon efficiency of 19.9 GHz/mW2 with the collection of 11 frequency bins. The generated QFCs produce heralded single photons with low heralded second-order correlation gh20=0.0024 and energy-time entangled photon pairs with high visibility of 98.19%. Consistent performance across wafer-scale multiple dies confirms the robustness and manufacturability of the designed device. This work establishes a scalable and high-yield pathway toward monolithic quantum photonic integrated circuits.
Integrated photonic microresonators have become an essential resource for generating photonic qubits for quantum information processing, entanglement distribution and networking, and quantum communications. The pair-generation rate is enhanced by reducing the microresonator radius, but this comes at the cost of increasing the frequency-mode spacing and reducing the quantum information spectral density. Here, we circumvent this rate-density trade-off in an Al Ga As -on-insulator photonic device by multiplexing an array of 20 small-radius microresonators, each producing a 650-GHz-spaced comb of time-energy entangled-photon pairs. The resonators can be independently tuned via integrated thermo-optic heaters, enabling control of the mode spacing from degeneracy up to a full free spectral range. We demonstrate simultaneous pumping of five resonators with up to 50 -GHz relative comb offsets, where each resonator produces pairs exhibiting time-energy entanglement visibilities up to 95 % , coincidence-to-accidental ratios exceeding 5000 , and an on-chip pair rate up to 2.6 G Hz / mW 2 per comb line—an improvement over prior work by more than a factor of 40. As a demonstration, we generate frequency-bin qubits in a maximally entangled two-qubit Bell state with fidelity exceeding 87 % ( 90 % with background correction) and detected frequency-bin entanglement rates up to 7 kHz (an approximately 70 MHz on-chip pair rate) using a pump power of approximately 250 μ W . Multiplexing small-radius microresonators combines the key capabilities required for programmable and dense photonic qubit encoding while retaining high pair-generation rates, heralded single-photon purity, and entanglement fidelity.
Integrated microresonator facilitates the realization of quantum frequency comb (QFC), which provides a large number of discrete frequency modes with broadband spectral range and narrow linewidth. However, all previous demonstrations have focused on the generation of energy-time or time-bin entangled photons from QFC. Realizing polarization-entangled quantum frequency comb, which is a useful resource for the fundamental study of quantum mechanics and quantum information applications, remains challenging. Here, we demonstrate a broadband polarization-entangled quantum frequency comb by combining an integrated silicon-nitride microresonator with a Sagnac interferometer. With a free spectral range of about 99 GHz and a narrow linewidth of about 190 MHz, our source provides 22 polarization-entangled photon pairs with frequency covering the whole telecom C-band. The entanglement fidelities for all 22 pairs are above 81%, including 17 pairs with fidelities higher than 90%. Our demonstration paves the way for employing the polarization-entangled quantum frequency comb in quantum network using CMOS technology as well as standard dense wavelength division-multiplexing technology.
Integrated quantum photonics requires bright, high-fidelity photon-pair sources capable of spectral multiplexing, correlation control, and circuit-compatible extraction. Cavity-enhanced spontaneous parametric down-conversion (SPDC) increases pair generation, but triply resonant operation imposes stringent pump-signal-idler spectral-alignment constraints. Moreover, the trade-off between intrinsic generation and coincidence-to-accidental ratio (CAR) does not capture the usable output flux, which depends on photon extraction. Here, we demonstrate a single-pass-pumped, resonator-enhanced quantum frequency comb (QFC) source based on a periodically poled lithium niobate photonic-crystal Fabry-Peˊéeˊrot microresonator. The device yields intrinsic and loaded brightnesses of 69.9 and 1.88 MHz/μμμW, respectively, and a maximum CAR of 16,000. Frequency-resolved measurements reveal 461 cavity-defined bins spanning 1495-1570 nm, and loaded spectral brightness approaching 4.29×1094.29\times10^94.29×109 pairs/(s⋅\cdot⋅mW⋅\cdot⋅nm). Heralded autocorrelation measurements yield a second-order autocorrelation gH(2)(0)g_H^{(2)}(0)gH(2)​(0) as low as 4.0×10−44.0\times10^{-4}4.0×10−4 for a selected high-CAR cavity-defined bin pair. In particular, tuning the single-pass pump deterministically selects correlated frequency-bin pairings within the fixed QFC grid while preserving brightness and pairwise coincidence rates. We further separate intrinsic generation from output photon-pair flux, revealing the loaded-brightness-CAR relation. Together, pump-selectable bin pairing and extraction-aware loading point to tailored SPDC QFCs as chip-integrated nonclassical light resources for multichannel quantum-state transport and information processing.