Quantum SiN Photonic Circuits Achieve 94.7% Yield with Integrated, Tunable InGaAs Emitters

Scalable photonic technologies, essential for future quantum devices, demand the seamless integration of diverse components with minimal signal loss. Jasper De Witte, Atefeh Shadmani, and Zhe Liu, alongside Andraz Debevc, Tom Vandekerckove, and Marcus Albrechtsen, address this challenge by demonstrating a method for integrating mature indium gallium arsenide emitters into silicon nitride photonic circuits. The team achieves a remarkably high processing yield of 94. 7% using established micro-transfer printing techniques, creating integrated devices that suppress noise and operate with exceptional stability. Crucially, these emitters exhibit electrical wavelength tunability compatible with standard CMOS circuitry, representing a significant step towards building complex, scalable photonic systems on a single chip.

Gallium Arsenide Quantum Dots on Silicon Nitride

Researchers have created a scalable platform for building advanced quantum technologies by successfully integrating gallium arsenide (GaAs) quantum dots with silicon nitride (SiN) photonics. This achievement represents a significant step towards creating practical, plug-and-play quantum photonic circuits, essential for applications like secure communication and powerful quantum computers. The team demonstrated the fabrication and characterization of a fully integrated quantum emitter on a SiN chip, achieving high efficiency and paving the way for scalable production. The technology combines GaAs quantum dots, which serve as highly efficient light emitters generating single photons, with silicon nitride, providing a low-loss waveguide material ideal for building complex photonic circuits.

Micro-transfer printing precisely places the GaAs quantum dots onto the SiN chip, enabling integration of these dissimilar materials, and the system is optimized for low-temperature operation to further enhance performance and minimize noise. The team achieved remarkably high coupling efficiency between the quantum dot and the SiN waveguide, demonstrating the potential for efficient light transmission. This integrated platform combines the quantum dot emitter with the photonic circuit on a single chip, streamlining device fabrication, and the generated photons exhibit characteristics crucial for quantum applications, including single-photon emission and indistinguishability. Furthermore, the SiN waveguides exhibit low optical loss, ensuring signal integrity, and researchers demonstrated the ability to tune the wavelength of the emitted photons, adding another layer of control.

The fabrication process begins with growing GaAs membranes containing the quantum dots using molecular beam epitaxy, while SiN waveguides are fabricated on a silicon wafer using standard lithographic techniques. These GaAs membranes are then processed into small coupons containing the quantum dots, and micro-transfer printing precisely places these coupons onto the SiN chip. Grating couplers efficiently couple light into and out of the SiN waveguides, and the integrated chip is mounted in a cryostat for low-temperature operation. This technology holds immense promise for various quantum applications, including secure quantum communication networks, unlocking computational power far beyond today’s machines, and developing highly sensitive quantum sensors for medical imaging and environmental monitoring. The demonstrated platform provides a clear pathway towards building large-scale quantum photonic circuits, bringing these futuristic technologies closer to reality, and future work will focus on improving scalability, increasing efficiency, and exploring new applications.

Quantum Dots Transferred to Silicon Nitride Platform

Scientists have engineered a scalable photonic integration platform by precisely transferring indium gallium arsenide (InGaAs) quantum dot emitters embedded in gallium arsenide (GaAs) waveguides onto a silicon nitride (SiN) platform, achieving a high processing yield of 94. 7% using commercially available micro-transfer printing tools. This method addresses the challenge of integrating diverse photonic components with minimal optical loss, a critical requirement for next-generation single-photon level technologies. The process begins with pre-processing the GaAs nanobeams, including fabrication of ohmic contacts, using established GaAs fabrication techniques.

These nanobeams incorporate a vertical p-i-n heterostructure, essential for suppressing noise and enabling wavelength tunability through electrical biasing. To overcome the fragility of the exceptionally thin GaAs nanobeams, the team embedded each nanobeam within a larger rectangular photoresist coupon, providing mechanical robustness during the transfer and release processes, and allowing for the integration of diverse GaAs device geometries, including those with grating couplers for fiber interfacing and tapered mode couplers for evanescent coupling to SiN waveguides. Photoresist tethers, anchored to the GaAs substrate, hold the coupons in place during subsequent release steps, and the team repurposed an existing sacrificial layer within the GaAs process flow to define these free-standing photoresist coupons. The micro-transfer printing process utilizes a commercially available tool, enabling high-throughput fabrication, while adaptations in design accommodate limitations in objective magnification and positional alignment, preserving coupling efficiency from the GaAs to the SiN waveguides.

Electrical control is achieved through the p-i-n heterostructure, allowing active control of the emitter’s charge environment with bias voltages below 0. 6V, compatible with complementary metal-oxide-semiconductor (CMOS) technologies. The resulting integrated emitters demonstrate high purity and exhibit no long-timescale blinking after transfer, signifying a robust and reliable integration process.

InGaAs Quantum Dots Integrated on Silicon Nitride

Scientists have achieved a high processing yield of 94. 7% in the scalable integration of indium gallium arsenide (InGaAs) quantum dots embedded in gallium arsenide (GaAs) waveguides onto silicon nitride (SiN) photonic platforms, utilizing commercially available micro-transfer printing tools. This work demonstrates a pathway toward heterogeneous integration of diverse photonic devices on a single chip, avoiding the optical losses associated with current modular systems that rely on multiple fiber-to-chip couplings. The team successfully integrated mature emitters into a p-i-n heterostructure, enabling noise suppression, near-blinking-free operation, and wavelength tunability through electrical biasing with voltages below 0.

6V, compatible with complementary metal-oxide-semiconductor (CMOS) technologies. The research centers on transferring fragile, 160-nanometer thick and 300-nanometer wide GaAs nanobeams, each containing InGaAs quantum dots, onto SiN waveguides. To protect these delicate structures during processing, each nanobeam is embedded within a larger rectangular photoresist coupon, ensuring mechanical robustness throughout the transfer process. The resulting devices consist of a GaAs nanobeam integrated directly onto a SiN waveguide, with the InGaAs quantum dots positioned within a vertical p-i-n structure designed to lock charge states and suppress noise.

Experiments reveal that the integrated emitters retain high purity and exhibit no long-timescale blinking after transfer onto the SiN interposer, demonstrating the effectiveness of the integration process. The team addressed limitations in objective magnification and positional alignment inherent in scalable micro-transfer printing tools through adaptations in device design, successfully preserving high coupling efficiency from the GaAs to the SiN waveguides. This achievement paves the way for future scaling to high-throughput integration, potentially co-integrating single photon detectors and high-speed modulators alongside the emitters on a single chip.

Quantum Emitters Integrated on Silicon Nitride

This work demonstrates a scalable micro-transfer printing procedure for integrating quantum emitters onto a silicon nitride platform using commercially available tools, representing a significant advance in photonic integration. Researchers successfully transferred indium gallium arsenide dots embedded in gallium arsenide waveguides onto the.