Hybrid integration of SiC has enormous potential for telecommunication applications, nonlinear photonics, sensing, and quantum photonics. Amorphous SiC (a-SiC) is particularly interesting as it has enormous potential to be deterministically integrated with most established photonic platforms. However, high-quality a-SiC photonics were missing, and compatibility with CMOS or III-V platforms requires low-temperature deposition. We have recently developed high-quality a-SiC photonics at low temperatures (⪅150°C) and demonstrated ring resonators with quality factors exceeding 5x105 (waveguide propagation loss of 0.78 dB/cm). Low-temperature deposition allowed high-performance photonic circuits by liftoff. Moreover, process compatibility made the integration of a-SiC with lithium niobate (LN) and silicon nitride (SiN) possible. On a-SiC/LN platform, we achieved electro-optical tunability of 3.4 pm/V (3mm tuning length). Furthermore, on a-SiC/SiN platform we showcase coupling efficiencies (between a-SiC and SiN), exceeding 90%, making the combination of ultralow loss (SiN) and dense (a-SiC) photonics possible.

Amorphous silicon carbide (a-SiC) has emerged as a compelling candidate for applications in integrated photonics, known for its high refractive index, high optical quality, high thermo-optic coefficient, and strong third-order nonlinearities. Furthermore, a-SiC can be easily deposited via CMOS-compatible chemical vapor deposition (CVD) techniques, allowing for precise thickness control and adjustable material properties on arbitrary substrates. Silicon nitride (SiN) is an industrially well-established and well-matured platform, which exhibits ultra-low propagation loss, but it is suboptimal for high-density reconfigurable photonics due to the large minimum bending radius and constrained tunability. In this work, we monolithically combine the a-SiC with SiN photonics, leveraging the merits of both platforms, and achieve the a-SiC/SiN heterogeneous integration with an on-chip interconnection loss of ( 0.28^+0.44_−0.28) dB and integration density increment exceeding 4444-fold. By implementing active devices on the a-SiC, we achieve 27 times higher thermo-optic tuning efficiency, with respect to the SiN photonic platform. In addition, the a-SiC/SiN platform gives the flexibility to choose the optimal fiber-to-chip coupling strategy depending on the interfacing platform, with efficient side-coupling on SiN and grating-coupling on the a-SiC platform. The proposed a-SiC/SiN photonic platform can foster versatile applications in programmable and quantum photonics, nonlinear optics, and beyond.

Superconducting nanowire single-photon detectors (SNSPDs) have emerged as essential devices that push the boundaries of photon detection with unprecedented sensitivity, ultrahigh timing precision, and broad spectral response. Recent advancements in materials engineering, superconducting electronics integration, and cryogenic system design are enabling the evolution of SNSPDs from single-pixel detectors toward scalable arrays and large-format single-photon time tagging cameras. This perspective article surveys the rapidly evolving technological landscape underpinning this transition, focusing on innovative superconducting materials, advanced multiplexed read-out schemes, and emerging cryo-compatible electronics. We highlight how these developments are set to profoundly impact diverse applications, including quantum communication networks, deep-tissue biomedical imaging, single-molecule spectroscopy, remote sensing with unprecedented resolution, and the detection of elusive dark matter signals. By critically discussing both current challenges and promising solutions, we aim to articulate a clear, coherent vision for the next generation of SNSPD-based quantum imaging systems.

In most optical waveguides employed within photonic integrated circuits, light confinement is achieved by etching the high-index layer. However, these waveguides often lack versatility in optimizing optical properties, such as mode size, shape, dispersion, and polarization. Moreover, they frequently suffer from high coupling losses and their propagation losses are significantly influenced by the quality of the etching process, especially for materials with high mechanical rigidity. Here, we present a hybrid optical waveguide concept that effectively addresses these limitations by combining a strip of easily processible low-index material (SU8) with a high-index hard-to-etch guiding layer (amorphous silicon carbide, SiC). Our approach not only eliminates the need for SiC etching but also offers flexibility in waveguide design to accommodate advanced functionalities. One of the key advancements of this hybrid configuration is its ability to suppress the transverse magnetic mode by 62 dB at 1550 nm, effectively functioning as a transverse electric pass waveguide. This simplifies the measurements by eliminating the need for polarization controllers and polarizers. Furthermore, through tailored waveguides, we achieve 2.5 times higher coupling efficiency compared to untapered hybrid SiC waveguides. We also demonstrate that thermal baking of the polymer layer reduces the scattering losses from 1.57 to 1.3 dB/cm. In essence, our hybrid approach offers a versatile way of realizing low-loss SiC-based integrated optical components with advanced features, such as excellent polarization suppression, flexible mode shapes, and dispersion control, compared to etched counterparts.

Recent efforts in quantum photonics emphasize on-chip generation, manipulation, and detection of single photons for quantum computing and quantum communication. In quantum photonic chips, single photons are often generated using parametric down-conversion and quantum dots. Quantum dots are particularly attractive due to their on-demand generation of high-purity single photons. Different photonic platforms are used to manipulate the states of the photons. Nevertheless, no single platform satisfies all the requirements of quantum photonics, as each platform has its merits and shortcomings. For example, the thin-film silicon nitride (SiN) platform provides ultra-low loss on the order of 0.1 dB m−1, but is incompatible with dense integration , requiring large bending radii. On the other hand, silicon on insulator offers a high refractive index contrast for dense integration but has a high absorption coefficient at the emission wavelengths (800–970 nm) of state-of-the-art QDs. Amorphous silicon carbide (a-SiC) has emerged as an alternative with a high refractive index (higher than SiN), an extended transparency window compared to Silicon, and a thermo-optic coefficient three times higher than that of SiN, which is crucial for tuning photonic devices on a chip. With the vision of realizing a quantum photonic integrated circuit, we explore the hybrid integration of SiN/a-SiC photonic platform with quantum dots and superconducting nanowire single-photon detectors. We validate our hybrid platform using a brief literature study, proof-of-principle experiments, and complementary simulations. As a proof-of-principle, we show a quantum dot embedded in nanowires (for deterministic micro-transfer and better integration) that emits single photons at 885 nm with a purity of 0.011 and a lifetime of 0.98 ns. Furthermore, we design and simulate an adiabatic coupler between two photonic platforms, a-SiC and SiN, by aiming to use the benefits of both platforms, i.e. dense integration and low losses, respectively. Our design couples the light from SiN waveguide to a-SiC waveguide with 96% efficiency at 885 nm wavelength. Our hybrid platform can be used to demonstrate on-chip quantum experiments such as Hong–Ou–Mandel, where we can design a large optical delay line in SiN and an interference circuit in a-SiC.

Since their first demonstration in 2001 [Gol’tsman et al., Appl. Phys. Lett. 79, 705-707 (2001)], superconducting-nanowire single-photon detectors (SNSPDs) have witnessed two decades of great developments. SNSPDs are the detector of choice in most modern quantum optics experiments and are slowly finding their way into other photon-starved fields of optics. Until now, however, in nearly all experiments, SNSPDs were used as “binary” detectors, meaning that they could only distinguish between 0 and > = 1 photons, and photon number information was lost. Recent research has demonstrated proof-of-principle photon-number resolution (PNR) SNSPDs counting 2-5 photons. The photon-number-resolving capability is highly demanded in various quantum-optics experiments, including Hong-Ou-Mandel interference, photonic quantum computing, quantum communication, and non-Gaussian quantum state preparation. In particular, PNR detectors at the wavelength range of 850-950 nm are of great interest due to the availability of high-quality semiconductor quantum dots (QDs) [Heindel et al., Adv. Opt. Photonics 15, 613-738 (2023)] and high-performance cesium-based quantum memories [Ma et al., J. Opt. 19, 043001 (2017)]. In this paper, we demonstrate NbTiN-based SNSPDs with >94% system detection efficiency, sub-11 ps timing jitter for one photon, and sub-7 ps for 2 photons. More importantly, our detectors resolve up to 7 photons using conventional cryogenic electric readout circuitry. Through theoretical analysis, we show that the PNR performance of demonstrated detectors can be further improved by enhancing the signal-to-noise ratio and bandwidth of our readout circuitry. Our results are promising for the future of optical quantum computing and quantum communication.

Photonic integrated circuits (PICs) are enabling breakthroughs in several areas, including quantum computing, neuromorphic processors, wearable devices, and more. Nevertheless, existing PIC measurement methods lack the spectral precision, speed, and sensitivity required for refining current applications and exploring new frontiers such as point-of-care or wearable biosensors. Here, the “sweeping optical frequency mixing method (SOHO)” is presented, surpassing traditional PIC measurement methods with real-time operation, 30 dB higher sensitivity, and over 100 times better spectral resolution. Leveraging the frequency mixing process with a sweeping laser, SOHO excels in simplicity, eliminating the need for advanced optical components and additional calibration procedures. Its superior performance is demonstrated on ultrahigh-quality factor (Q) fiber-loop resonators (Q = 46 × 10⁶), as well as microresonators, realized on a new optical waveguide platform. An experimental spectral resolution of 19.1 femtometers is demonstrated using an 85-meter-long unbalanced fiber Mach Zehnder Interferometer, constrained by noise resulting from the extended fiber length, while the theoretical resolution is calculated to be 6.2 femtometers, limited by the linewidth of the reference laser. With its excellent performance metrics, SOHO has the potential to become a vital measurement tool in photonics, excelling in high-speed and high-resolution measurements of weak optical signals.

We present the first observations of laser synchronised relaxation oscillations in superconducting nanowire single photon detectors. Understanding the thermal feedback behind these oscillations aids the development of photon number resolving and higher count rate detectors.

Achieving high degree of tunability in photonic devices has been a focal point in the field of integrated photonics for several decades, enabling a wide range of applications from telecommunication and biochemical sensing to fundamental quantum photonic experiments. We introduce a novel technique to engineer the thermal response of photonic devices resulting in large and deterministic wavelength shifts across various photonic platforms, such as amorphous Silicon Carbide (a-SiC), Silicon Nitride (SiN) and Silicon-On-Insulator (SOI). In this paper, we demonstrate bi-directional thermal tuning of photonic devices fabricated on a single chip. Our method can be used to design high-sensitivity photonic temperature sensors, low-power Mach-Zehnder interferometers and more complex photonics circuits.

Measuring superconducting materials near absolute zero Kelvin poses challenges due to low output voltage. This study presents a cryogenic amplifier for ultra-low temperatures, fabricable on the same chip as the material, replacing noisy room temperature setups.

At the core of quantum photonic information processing and sensing, two major building pillars are single-photon emitters and single-photon detectors. In this review, we systematically summarize the working theory, material platform, fabrication process, and game-changing applications enabled by state-of-the-art quantum dots in nanowire emitters and superconducting nanowire single-photon detectors. Such nanowire-based quantum hardware offers promising properties for modern quantum optics experiments. We highlight several burgeoning quantum photonics applications using nanowires and discuss development trends of integrated quantum photonics. Also, we propose quantum information processing and sensing experiments for the quantum optics community, and future interdisciplinary applications.

In this work, we fabricate and characterize ring resonators on ICPCVD-deposited a-SiC films at a low temperature of 150°C, demonstrating exceptional intrinsic quality factors and low waveguide propagation losses, thus highlighting the potential for a-SiC as a valuable platform for future hybrid photonic technologies.

Integrated photonic platforms have proliferated in recent years, each demonstrating its unique strengths and shortcomings. Given the processing incompatibilities of different platforms, a formidable challenge in the field of integrated photonics still remains for combining the strengths of different optical materials in one hybrid integrated platform. Silicon carbide is a material of great interest because of its high refractive index, strong second- and third-order nonlinearities, and broad transparency window in the visible and near-infrared range. However, integrating silicon carbide (SiC) has been difficult, and current approaches rely on transfer bonding techniques that are time-consuming, expensive, and lacking precision in layer thickness. Here, we demonstrate high-index amorphous silicon carbide (a-SiC) films deposited at 150 °C and verify the high performance of the platform by fabricating standard photonic waveguides and ring resonators. The intrinsic quality factors of single-mode ring resonators were in the range of Q_int = (4.7-5.7) × 10⁵ corresponding to optical losses between 0.78 and 1.06 dB/cm. We then demonstrate the potential of this platform for future heterogeneous integration with ultralow-loss thin SiN and LiNbO₃ platforms.