Integrated photonic circuits have transformed data communication, biosensing, and light detection and ranging and hold wide-ranging potential for optical computing, optical imaging, and signal processing. These applications often require tunable and reconfigurable photonic components, most commonly accomplished through the thermo-optic effect. However, the resulting tuning window is limited for standard optical materials, such as silicon dioxide and silicon nitride. Most importantly, bidirectional thermal tuning on a single platform has not been realized. For the first time, we show that by tuning and optimizing the deposition conditions in inductively coupled plasma chemical vapor deposition (ICPCVD) of silicon dioxide, this material can be used to deterministically tune the thermo-optic properties of optical devices without introducing significant losses. We demonstrate that we can deterministically integrate positive and negative wavelength shifts on a single chip, validated on amorphous silicon carbide (a-SiC), silicon nitride (SiN), and silicon-on-insulator (SOI) platforms. This enables the fabrication of a novel tunable coupled ring optical waveguide (CROW) requiring only a single heater. In addition, we observe up to a 10-fold improvement of the thermo-optic tunability and demonstrate athermal ring resonators with shifts as low as 1.5 pm/°C. The low-temperature deposition of our silicon dioxide cladding can be combined with lift-off to isolate the optical devices, resulting in a decrease in thermal crosstalk by at least 2 orders of magnitude. Our method paves the way for novel photonic architectures incorporating bidirectional thermo-optic tunability.@en

In the past decade, lithium niobate (LiNbO₃ or LN) photonics, thanks to its heat-free and fast electro-optical modulation, second-order non-linearities, and low-loss, has been extensively investigated. Despite numerous demonstrations of high-performance LN photonics, processing lithium niobate remains challenging and suffers from incompatibilities with standard complementary metal-oxide-semiconductor (CMOS) fabrication lines, limiting its scalability. Silicon carbide (SiC) is an emerging material platform with a high refractive index, a large non-linear Kerr coefficient, and a promising candidate for heterogeneous integration with LN photonics. Current approaches of SiC/LN integration require transfer-bonding techniques, which are time-consuming, expensive, and lack precision in layer thickness. Here, we show that amorphous silicon carbide (a-SiC), deposited using inductively coupled plasma enhanced chemical vapor deposition at low temperatures (<165 °C), can be conveniently integrated with LiNbO₃ and processed to form high-performance photonics. Most importantly, the fabrication only involves a standard, silicon-compatible, reactive ion etching step and leaves the LiNbO₃ intact, hence its compatibility with standard foundry processes. As a proof-of-principle, we fabricated waveguides and ring resonators on the developed a-SiC/LN platform and achieved intrinsic quality factors higher than 1.06 × 10⁵ and a resonance electro-optic tunability of 3.4 pm/V with a 3 mm tuning length. We showcase the possibility of dense integration by fabricating and testing ring resonators with a 40 μm radius without a noticeable loss penalty. Our platform offers a CMOS-compatible and scalable approach for the implementation of future fast electro-optic modulators and reconfigurable photonic circuits, as well as nonlinear processes that can benefit from involving both second- and third-order nonlinearities.

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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.@en

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.

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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.@en

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.

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In order to improve the light extraction of AlGaN-based short wavelength ultraviolet light emitting diodes (DUC-LEDs), a type of microstructure with high aspect ratio is introduced and optimized on the AlN substrate surface. And, particle swarm optimization (PSO) algorithm is used to inverse design of the surface microstructure to maximize the light extraction efficiency (LEE). Considering that the propagation characteristics of TM-polarized light are different from that of TE-polarized light, the optical field distribution and LEE is analyzed for the UVC-LEDs with different TE-polarized component when the optimized surface microstructure is applied. Furthermore, the preparation process tolerance of the high aspect ratio structure is discussed by calculating the LED's LEE when the structural deviation occurs or morphology changes. Simulation results show that, by using the optimized surface microstructure based on parabola cone array, the LEDs' LEE is increased from 4.4% to 8.7% and from 0.4% to 3.7% for TE-polarized and TM-polarized emission, respectively. In addition, it is demonstrated that the light extraction improvement by the surface microstructure has a good tolerance to the structural deviation and morphology. The results are significant for improving light extraction and realizing high efficient short wavelength AlGaN-based UVC-LEDs by designing surface microstructures.

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