Low-SWaP, tunable, and narrow-linewidth laser systems for deployable quantum technologies
Mateus Corato‐Zanarella, Matthias Lommel, Dimitri Mayzlin, Emilio Lopes, Jovana Nojić, Alexander Eras, Christian Nölleke, Björn Globisch, Chris Haimberger
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.
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.
As quantum technologies transition from laboratories to the world, their successful deployment critically relies on the size, weight, and power (SWaP) of the laser sources fueling them. Due to the stringent optical requirements of most of these systems, they still predominantly use bulky lasers made of free-space components. With the emergence of high-performance, chip-scale lasers based on photonic integrated circuits (PICs) [1], practical quantum systems that are compact and scalable are now within reach. However, to successfully realize a PIC-based laser module that meets both optical and functional requirements, a system-level approach for co-designing the optical source (gain medium and PIC), the driver electronics, and the control software needs to be adopted.
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.
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.
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.
Quantum information processing (QIP) approach based on trapped ions is a promising technology that exploits different ion species as individual qubits and qubit gates, while featuring long coherence times, high fidelity of operations, fast readout, and ion-ion gate entanglement. The practical usefulness of trapped-ion quantum computer depends on its further scaling to a large number of qubits. Meanwhile, trapped-ion quantum computer relies on a set of single-frequency lasers, utilizing them for different functions such as photoionization, atom cooling, optical pumping and qubit operations. Thus, a combination of narrow linewidth lasers is required, with the emission wavelengths precisely defined by the corresponding electronic transitions of the selected ion species. Further development, scalability and commercialization of quantum information technologies is interwind with the availability of affordable and robust single-frequency lasers on a variety of application-specific wavelengths. QIP manifests strict requirements posed to lasers in terms of central wavelength, linewidth, long-term stability, beam quality, polarization extinction ratio, side-mode suppression ratio, etc. In this work we present the development and characterization of multiwavelength narrow linewidth system designed for the Ba+ trapped ion computing. The laser system emits single-frequency, sub-MHz emission at 553 nm, 493 nm and 614 nm based on second-harmonic generation of two separate semiconductor laser platforms. Two-step photoionization of neutral Ba is implemented resonantly through 6s2 1S0 → 6s6p 1P1 transition corresponding to 553 nm wavelength, whereas Ba ion is Doppler cooled on 6S1/2 →6P1/2 transition corresponding to 493 nm. Such single-frequency greenyellow and cyan lasers are based on intracavity frequency doubled vertical-external-cavity surface-emitting laser (VECSEL), serving as an effective replacement of the legacy dye laser, previously used to address these Ba transition. On the other hand, frequency doubled external cavity diode laser (ECDL) is employed to generate 614 nm orange emission needed for 5D5/2→ 6P3/2 transition. The laser system incorporates modular laser engines together with low-noise driving electronics, mechanical and acoustic concealment and provide laser locking interfaces to high-finesse optical cavity or a wavemeter.