Heterogeneously Integrated Efficient and Widely Tunable Lasers at 795 nm for Rubidium-Based Quantum Technologies
Max Kiewiet, Stijn Cuyvers, Tom Reep, Konstantinos Akritidis, Gaudhaman Jeevanandam, Manuel Reza, Roelof Jansen, Pol Van Dorpe, Günther Roelkens, Kasper Van Gasse, Bart Kuyken
physics.opticsquant-phSubmitted Sep 10, 2026• Announced Sep 11, 2026
Scaling quantum processors and optical atomic clocks fundamentally requires orders-of-magnitude reductions in the size, weight, power, and cost of optical control systems. Photonic integration of lasers is critical to fulfill these requirements. At the near-infrared wavelengths required for atomic clocks and quantum computing through manipulation of rubidium atoms, laser integration is hindered by difficulty in light coupling and poor heat dissipation. Here, we introduce a wafer-scalable method utilizing micro-transfer printing to integrate GaAs-based amplifiers in etched recesses, directly butt-coupled to silicon nitride waveguides. We demonstrate extended-cavity single-mode lasers using this integration approach. Our compact microgear laser achieves a narrow 3 kHz fundamental linewidth at an on-chip output power of >22 mW -- a record for a single-mode heterogeneously integrated laser in the 780-800 nm band -- with a wall-plug efficiency of 9.4%, showcasing the high-power and efficiency potential of this integration approach. Additionally, we demonstrate a widely tunable laser leveraging Vernier filters to achieve lasing with 9 nm coarse tuning, a quasi-continuous fine-tuning range exceeding 140 GHz, and a mode-hop-free tuning range of 45 GHz. Our scalable integrated laser toolkit shows great promise for replacing macroscopic external-cavity diode lasers in next-generation quantum technologies and optical atomic clocks.
Comments
12 pages, 7 figures, 1 table. Supplementary information (4 pages, 2 figures) is included as an ancillary file
Scaling quantum processors and optical atomic clocks fundamentally requires orders-of-magnitude reductions in the size, weight, power, and cost of optical control systems. Photonic integration of lasers is critical to fulfill these requirements. At the near-infrared wavelengths required for atomic clocks and quantum computing through manipulation of rubidium atoms, laser integration is hindered by difficulty in light coupling and poor heat dissipation. Here, we introduce a wafer-scalable method utilizing micro-transfer printing to integrate GaAs-based amplifiers in etched recesses, directly butt-coupled to silicon nitride waveguides. We demonstrate extended-cavity single-mode lasers using this integration approach. Our compact microgear laser achieves a narrow 3 kHz fundamental linewidth at an on-chip output power of >22 mW -- a record for a single-mode heterogeneously integrated laser in the 780-800 nm band -- with a wall-plug efficiency of 9.4%, showcasing the high-power and efficiency potential of this integration approach. Additionally, we demonstrate a widely tunable laser leveraging Vernier filters to achieve lasing with 9 nm coarse tuning, a quasi-continuous fine-tuning range exceeding 140 GHz, and a mode-hop-free tuning range of 45 GHz. Our scalable integrated laser toolkit shows great promise for replacing macroscopic external-cavity diode lasers in next-generation quantum technologies and optical atomic clocks.
With quantum optical technologies advancing toward real-world deployment, their success depends on reducing the size, weight, and power (SWaP) of the laser sources that drive them. While photonic integrated circuit (PIC)-based lasers have emerged as promising replacements to traditional bulky lasers, achieving a PIC-based laser system that satisfies both optical and functional requirements demands a system-level co-design of optics, electronics, and software that has not yet been realized. Here, we demonstrate a low-SWaP, tunable, and narrow-linewidth laser system based on PICs and programmable control electronics for the 780 nm region of the near-infrared spectrum. By leveraging the Vernier effect between a Fabry-Pérot laser diode (FPLD) and a microring resonator (MRR), we design the PIC to serve as an external cavity to self-injection lock the FPLD, resulting in a tunable laser with narrow linewidth. We package this PIC-laser into a standard butterfly package and drive it using a custom digital laser controller with a user-friendly interface. We design the programmable control electronics to meet the specific requirements of a PIC-laser as well as enable advanced functionalities that support cutting-edge quantum and classical optical applications. The complete laser system, which also includes optical isolators and fiber coupling, achieves up to 9.5 nm coarse tuning, 50 GHz mode-hop-free fine tuning, 30 mW free-space output power (before isolators), kHz-level intrinsic linewidth, and over 50 dB side-mode suppression ratio (SMSR). To exemplify the applicability of our laser system for quantum technologies, we perform spectroscopy on rubidium D2 transition lines and frequency-lock it to the cycling transition for days in a non-controlled environment with significant temperature fluctuations. We envision that our compact, fully integrated laser system will be a key enabler for scalable and deployable quantum and classical optical technologies.
Precision atomic and quantum experiments rely on ultra-stable narrow linewidth lasers constructed using table-top ultra-low expansion reference cavities. These experiments often require multiple lasers, operating at different wavelengths, to perform key steps used in state preparation and measurement required in quantum sensing and computing. This is traditionally achieved by disciplining a cavity-stabilized laser to a key atomic transition and then transferring the transition linewidth and stability to other lasers using the same reference cavity in combination with bulk-optic frequency shifting such as acousto-optic modulators. Transitioning such capabilities to a future potentially low-cost photonic-integrated platform will enable a wide range of portable, low power, scalable quantum experiments and applications. Yet, today’s bulk optic approaches pose challenges related to lack of cavity tunability, large free spectral range, and limited photonic integration potential. Here, we address these challenges with demonstration of an agile photonic-integrated 780 nm ultra-high-Q tunable silicon nitride reference cavity that performs multiple critical experimental steps including laser linewidth narrowing, high resolution rubidium spectroscopy, dual-stage stabilization to a rubidium transition, and stability transfer to other lasers. We achieve up to 20 dB of frequency noise reduction at 10 kHz offset, precision spectroscopy over a 250 MHz range, and dual-stage locking to rubidium with an Allan deviation of 8.5 × 10 −12 at 1 s and up to 40 dB frequency noise reduction at 100 Hz frequency offset. We further use the rubidium-disciplined cavity to provide atomic-referenced frequency stability to a second laser and demonstrate multi-wavelength Rydberg electrometry quantum sensing. These results pave the path for integrated, compact, and scalable solutions for quantum sensing, computing, and other atomic and trapped ion applications.
Abstract Programmability and precise control of laser frequency are essential for quantum experiments and applications such as atomic clocks, quantum computers, and cold-atom sensors. Current systems use bulky, power-hungry modulators and frequency shifters which are difficult to integrate and limit portability and scalability. We report an electrically controllable, agile optical frequency source based on a semiconductor laser stabilized to a photonic integrated resonator cavity with a lead zirconate titanate (PZT) actuator. We demonstrate this approach with precision programmable frequency control of a 780-nm laser that can periodically reference to rubidium-87 ( 87 Rb) spectroscopy followed by fast, programmable, arbitrary frequency tuning sequences for quantum control. We use this approach to demonstrate sub-Doppler cooling of 87 Rb without any external modulators, achieving atom-cloud temperatures as low as 16 μ K. The device achieves a tuning strength up to 1 GHz/V with 11 MHz modulation bandwidth while consuming only 10 nW of electrical power. This work establishes a route toward compact, low-power, and chip-scale laser systems for next-generation quantum and atomic sensing technologies.
Programmability and precise control of laser frequency are essential for quantum experiments and applications such as atomic clocks, quantum computers, and cold-atom sensors. Current systems use bulky, power-hungry modulators and frequency shifters which are difficult to integrate and limit portability and scalability. We report an electrically controllable, agile optical frequency source based on a semiconductor laser stabilized to a photonic-integrated, lead zirconate titanate (PZT)-actuated resonator cavity. We demonstrate this approach with precision programmable frequency control of a 780-nm laser that can periodically reference to rubidium spectroscopy followed by fast, programmable, arbitrary frequency tuning sequences for quantum control. We use this approach to demonstrate sub-Doppler cooling of rubidium-87 without any external modulators, achieving atom-cloud temperatures as low as 16 μK. The device achieves a tuning strength up to 1 GHz/V with 11 MHz modulation bandwidth while consuming only 10 nW of electrical power. This work establishes a route toward compact, low-power, and chip-scale laser systems for next-generation quantum and atomic sensing technologies.
We report system-level evaluation of manufacturable, quantum-optimized 795-nm vertical-cavity surface-emitting lasers (Q-VCSELs) for rubidium (Rb) atomic sensors, with emphasis on integration into an 87Rb coherent population trapping (CPT) clock prototype. Operation at 795 nm (Rb D1) is constrained by increased internal loss/absorption, polarization instability, and stringent requirements on spectral purity. At the component level, we employ epitaxial and layout engineering to improve mode discrimination, polarization robustness, and high-temperature efficiency, achieving stable single-transverse-mode emission and linear polarization from 20–80 °C with side-mode suppression ratio (SMSR) >30 dB and polarization extinction ratio (PER) >20 dB. The devices exhibit low threshold current (<400 µA at 80 °C) and slope efficiency >0.5 mW/mA, enabling >1 mW single-mode, single-polarization output power in chip-scale form factors. Quantum-relevant characterization shows linewidth on the order of ~30–35 MHz and relative intensity noise below −130 dB/Hz at frequencies greater than 1KHz. We then integrate the Q-VCSEL into an 87Rb CPT clock setup and demonstrate a clear CPT resonance, achieving ~2.5% contrast and ~3 kHz CPT linewidth (FWHM), corresponding to a measured figure of merit of ~8.2 ppm. We further map key operating tradeoffs relevant to clock optimization, including optical power broadening (contrast peaking near ~50–60 µW while CPT linewidth increases with optical power) and RF-drive dependence across representative modulation powers. These results connect device-level laser characteristics to clock-level observables and provide a manufacturable component pathway for scalable Rb-based timing modules.
Heterogeneous integration of gain and strongly nonlinear materials with ultra-low-loss silicon nitride (SiN) photonics offers a route to scalable quantum circuits, but concurrent wafer-scale manufacturability, low interlayer loss, and high performance have been challenging to realize. Here we demonstrate a wafer-scale III-V-on-SiN quantum photonic platform that directly integrates III-V layers to foundry-fabricated SiN circuits. The SiN layer provides 200-300 nm thick waveguides with <1 dB/m loss and a mature passive photonics ecosystem, while III-V materials provide large χ(2) and χ(3) nonlinearities for parametric gain, frequency conversion and quantum light generation. Adiabatic interlayer couplers yield <25 mdB loss to InGaP waveguides and resonators with intrinsic quality factors exceeding 106, enabling 15× brighter entanglement sources and efficient nonlinear conversion on SiN. Integrated components--including low-loss beam splitters, waveguide crossers, and tunable interferometers--are complemented by III-V lasers and InP photodetectors with amplifiers achieving up to 99−12+1% quantum efficiency and 3 GHz bandwidth. This architecture unites ultra-efficient sources, nonlinear elements and detectors on a wafer-scale, low-loss platform, establishing a path toward large-scale, low-noise quantum photonic systems.