We designed, fabricated, and measured quantum silicon nanophotonic spatial-polarization controlled-phase gate. The experimental truth table for polarization basis shows an average gate fidelity of 95.31%.

Impedance discontinuity at coaxial through-silicon-via (CTSV)–redistribution layer (RDL) transitions degrades high-frequency transmission in 3-D chiplet interconnects. This work proposes an analytical impedance-matching method for coaxial TSV–RDL transitions and establishes surrogate models for compensation-capacitance selection and interdigital capacitor (IDC) dimension design. An admittance-extracted N-stage π-equivalent model is utilized to evaluate transition impedances. The required compensation capacitance is determined from a response surrogate, and an IDC capacitance surrogate further maps this capacitance to practical IDC dimensions. For an 85 GHz target operating band, the selected nominal 12 fF capacitors improve |S21| by 0.51 dB and reduce |S11| by 16.92 dB at 85 GHz. The overall port reflection coefficient decreases from 0.354 to 0.0505, corresponding to a reflected-power reduction from 12.56% to 0.255%, while the average improvements over 0–85 GHz reach 0.218 dB for |S21| and 20.54 dB for |S11|. The proposed method connects transition impedance analysis, capacitance selection, and IDC geometry design, providing an efficient approach for broadband TSV–RDL matching.

Large-scale quantum computers possess the capacity to effectively tackle practical problems that can be insurmountable for classical computers. The main challenge in building these quantum computers is to realize scalable modules for remote qubits and entanglement. By assembling small, specialized parts into a larger architecture, the modular approach mitigates complexity and uncertainty. Such a distributed architecture requires non-local quantum gate operations between remote qubits. An essential method for implementing such operations, known as quantum gate teleportation, requires only local operations, classical communication, and shared entanglement. Till today, the quantum gate teleportation using a photonic chip has remained elusive. Here we experimentally demonstrate the quantum teleportation of an on-chip controlled-NOT (CNOT) gate, assisted with the scalable silicon chip platform, high-fidelity local quantum logic gates, linear optical components, post-selected entanglement, and coincidence measurements from photonic qubits. First, we measure and characterize our teleported chip-scale CNOT gate with an average truth table fidelity of 93.1 +- 0.3

Waveguide crossing is the indispensable building block for large-scale photonic integrated circuits. However, current existing silicon waveguide crossing still suffers from excessive insertion loss, limited bandwidth, and large footprint, which severely restricts on-chip photonic circuit scalability. Here, we propose an ultra-compact waveguide crossing that achieves a 400-nm bandwidth (1250-1650 nm) with average insertion loss below 0.19 dB and crosstalk below -17 dB, using a novel, to the best of our knowledge, root-mean-square transmittance figure of merit (RMS-FOM) methodology. Meanwhile, the device maintains an ultra-compact footprint of 4 × 4 μm2. Comprehensive tolerance analysis reveals that the optimized devices sustain insertion losses below 0.4 dB at 1310 nm and 0.35 dB at 1550 nm across manufacturing deviations of up to ±100 nm, confirming the robustness and reliability of our device under realistic fabrication. Large-scale experimental validation demonstrates that the fabricated device exhibits low crosstalk of below -18.8 dB and -20 dB and insertion losses of 0.32 dB and 0.35 dB in two operating bands (1250-1350 nm and 1500-1600 nm). We believe the device establishes a new benchmark for silicon waveguide crossings by integrating optimized overall performance with an ultra-compact footprint, broadband, and fabrication tolerance, thereby enabling high-density on-chip optical interconnects in communication, data centers, and quantum technologies.

We observe the formation of thermally stable Kerr solitons arising from periodically modulated waveforms, without chaotic behavior, in a strongly coupled dispersion-managed microresonator driven by a single pump laser. A broad range for soliton existence and deterministic transitions are observed.

Significance With the acceleration of global informatization, the volume of communication data has been growing exponentially, which puts forward higher requirements for the characteristics of high speed, large capacity, and low cost of information networks. However, the bottleneck of integrated circuits is gradually emerging with the slowdown of Moore's law. Compared with electronic integrated circuits, photonic integrated circuits (PICs) can significantly reduce the system's size, weight, operating power, and cost (SWaP-c). A PIC is a miniaturized platform that monolithically combines diverse optical functionalities, including photodetection, signal modulation, spectral filtering, optical routing, and nonlinear optical processes, within a precisely fabricated chip-scale architecture. Its submicron-scale waveguide structures enable deterministic control of light propagation characteristics, while standardized semiconductor manufacturing processes enable cost-effective mass production. While silicon maintains near-total dominance in microelectronics fabrication, PICs demonstrate the versatility of material systems through heterogeneous integration. This is mainly because different material platforms offer various advantages and disadvantages, and therefore, there is no single dominant material platform in the field of integrated photonics. Heterogeneous integration technology can make full use of the advantages brought by multiple materials and structures to realize "complementary material advantages" and "synergistic enhancement of functions", which can further improve the performance of the device and expand its functions, making it useful in optical communications, computing, lidar, microwave photonics, and other applications. Research in this field not only advances fundamental science but also supports the development of related industries, paving the way for next-generation communication technologies and high-performance computing devices. Progress In this paper, we focus on an overview of commonly used materials, integration techniques, and application examples in heterogeneous integrated photonics for multi-material systems. In the first section of the review, we briefly describe current bottlenecks in conventional single-material system photonic integration technology. Then, to solve this, heterogeneous integrated photonics technology based on multi-material systems has emerged. To better understand the properties of various photonic integrated materials, we summarize their physicochemical properties as well as material characteristics in the second section, which includes group IV materials (Si, Ge), group III-V compound semiconductors, silicon nitride, lithium niobate, two-dimensional materials, and phase change materials. The relevant material parameters are summarized in Table 1. In the third section, we present four heterogeneous integration technology tools, namely inter-chip hybrid integration, wafer bonding, micro-transfer printing, and monolithic integration. The process flow diagram is shown in Fig. 5. The comparison of the four technologies is presented in Table 2. The focus of this review is on the fourth section. During the last decade, heterogeneous integrated photonics for multi-material systems has been applied in various types of photonic devices: 1) Waveguide and passive devices: On-chip optical waveguides and passive components are among the most important components of devices and systems in integrated optics. They are used for device interconnections and information multiplexing and processing, and the overall system performance greatly depends on their basic characteristics. Some recent research on on-chip heterogeneous integrated optical waveguides and passive devices is summarized in Figs. 9 and 10. Heterogeneous integration reduces the complexity of the etching process while expanding the functionality of optical waveguides and passive devices. 2) On-chip lasers: Materials such as silicon, silicon nitride, and lithium niobate lack efficient light sources due to their indirect bandgap. Therefore, to realize integrated on-chip lasers, it is often necessary to introduce other semiconductor materials with a direct bandgap, such as III-V compound semiconductors, as a gain medium. Several schemes for integrated lasers have been demonstrated, including hybrid integration based on advanced packaging, heterogeneous integration based on wafer bonding, micro-transfer printing, and monolithic integration (Fig. 11). 3) On-chip electro-optic modulators: Electro-optic (EO) modulators play a crucial role in converting high-speed signals from the electrical domain to the optical domain, serving as essential components in long-haul optical communication, microwave photonics, and lidar. By introducing heterogeneous materials with various advantageous properties, the heterogeneous integration approach is worth considering for improving the performance of conventional modulators. For example, integrating germanium or two-dimensional materials on silicon-on-insulator (SOI) platforms enables modulators with high bandwidth [Fig. 12(a)], high linearity [Fig. 12(b)], and low power consumption by utilizing the electro-absorption effect. Pockels modulators, which change the refractive index of the waveguide through an applied voltage, are more suitable for signal modulation in higher-order modulation formats. Lithium niobate wafers can be bonded to planarized optical waveguides via wafer bonding, achieving excellent performance with an EO bandwidth greater than 110 GHz and a half-wave voltage of 3.1 Vcm [Fig. 12(e)]. 4) On-chip photodetectors: An on-chip photodetector (PD) plays a pivotal role in PICs by converting optical signals into electrical ones. The indirect bandgaps of silicon (1.12 eV), silicon nitride (5 eV), and lithium niobate (3.9 eV) are not sufficient for direct absorption and detection in the near-and mid-infrared wavelength ranges. To address this issue, various alternative materials such as germanium, III-V compound semiconductors, and two-dimensional materials (Fig. 13) are introduced via heterogeneous integration to enable effective absorption at the desired wavelengths. 5) On-chip photonic integrated systems: Optical phased arrays (OPA), microwave photonic systems (MWP), optical frequency combs (OFCs), optical neural networks (ONN), and other function-specific photonic devices or systems can be classified as on-chip photonic integrated systems. These systems are realized by integrating multiple optical functional components (e.g., lasers, modulators, waveguides, passive devices, detectors, etc.) onto a single chip. Heterogeneous integration promotes the evolution of photonic integrated systems toward multifunctionality, high integration, wide bandwidth, and low cost. Conclusions and Prospects In summary, compared to existing single-material photonic integration technology, heterogeneous integration based on multi-material systems can significantly improve device performance and broaden system functionality by making full use of the advantages of different materials. However, several critical issues remain to be addressed. Future development of heterogeneous integrated photonics based on multi-material systems will require careful trade-offs between fabrication cost, device performance, process compatibility, and device size. We believe that multi-material heterogeneous integrated photonics is poised to drive rapid advancements in optical communication, computing, microwave photonics, and lidar.

The first demonstration of free-space terabits coherent data transmission link with microresonator frequency comb is reported over a 160 m atmospheric horizontal free-space field trial under log-normal turbulent conditions using 16-QAM together with polarization multiplexing.

We report the first quantum gate teleportation with a CMOS-integrated silicon nanophotonic chip, experimentally demonstrating non-local entangling gate operation with high fidelity, and establishing a distributed quantum computation network.

This paper presents the design, fabrication, and characterization of a high-performance heterogeneous silicon on insulator (SOI)/thin film lithium niobate (TFLN) electro-optical modulator based on wafer-scale direct bonding followed by ion-cut technology. The SOI wafer has been processed by an 8 inch standard fabrication line and cut into 6 inch for direct bonding with TFLN. The hybrid SOI/LN electro-optical modulator operated at the wavelength of 1.55 μm is composed of couplers on the Si layer and a Mach–Zehnder interferometer (MZI) structure on the LN layer. The fabricated device exhibits a stable value of the product of half-wave voltage and length (V π L) of around 2.9 V·cm. It shows a good low-frequency electro-optic response flatness and supports 96 Gbit/s data transmission for the NRZ format and 192 Gbit/s data transmission for the PAM-4 format.

Heterogeneous integration solutions for photonics circuits exploit the advantages of different platforms. Here, the design, fabrication, and characterization of a high‐performance heterogeneous silicon nitride (SiN)/thin film lithium niobate (TFLN) electro‐optic Mach–Zehnder modulator are shown. This work is based on wafer‐scale direct bonding, followed by ion‐cut technology and wafer‐scale fabrication. All the optical control is achieved in SiN layer, and the lithium niobate is etchless. Edge couplers (ECs) are integrated as input and output ports, and the modulator shows a total insertion loss of 11.6 dB, a broadband electro‐optic response with 3 dB bandwidth beyond 110 GHz at C‐band, and supports 180 Gbit/s data transmission for NRZ format and 260 Gbit/s data transmission for PAM‐4 format. The device also shows a good modulation capability from 1260 to 1640 nm due to the wavelength insensitivity of the hybrid ECs. Such high‐performance integrated EOMs based on fully wafer‐scale fabrication may lay the foundations for the mass production of a multi‐material integration platform in the future.

Laser frequency microcombs provide a series of equidistant, coherent frequency markers across a broad spectrum, enabling advancements in laser spectroscopy, dense optical communications, precision distance metrology, and astronomy. Here, we design and fabricate silicon nitride, dispersion-managed microresonators that effectively suppress avoided-mode crossings and achieve close-to-zero averaged dispersion. Both the stochastic noise and mode-locking dynamics of the resonator are numerically and experimentally investigated. First, we experimentally demonstrate thermally stabilized microcomb formation in the microresonator across different mode-locked states, showing negligible center frequency shifts and a broad frequency bandwidth. Next, we characterize the femtosecond timing jitter of the microcombs, supported by precise metrology of the timing phase and relative intensity noise. For the single-soliton state, we report a relative intensity noise of -153.2 dB/Hz, close to the shot-noise limit, and a quantum-noise-limited timing jitter power spectral density of 0.4 as(2)/Hz at a 100 kHz offset frequency, measured using a self-heterodyne linear interferometer. In addition, we achieve an integrated timing jitter of 1.7 fs +/- 0.07 fs, measured from 10 kHz to 1 MHz. Measuring and understanding these fundamental noise parameters in high clock rate frequency microcombs is critical for advancing soliton physics and enabling new applications in precision metrology.

Optical frequency microcombs generate a series of equidistant, coherent frequency references over a broad spectrum, advancing spectroscopy, communications, metrology, and astronomy. Here, we design and fabricate a silicon nitride adiabatic ring microresonator that achieves low average dispersion with negligible avoided mode crossings. We explore the soliton microcomb bifurcation diagram for various mode-locking states in the microresonator, and investigate the stochastic linewidth through both numerical simulations and experimental measurements. The fabricated microresonator exhibits a loaded quality factor of 1.8 million, a measured group velocity dispersion of -3 ± 1.1 fs 2 /mm, and a free spectral range of 88 GHz, characterized using swept-wavelength interferometry. We experimentally demonstrate thermally stabilized microcomb formation in the device using a dual-polarization-driven method, enabling access to single soliton, double soliton, and soliton crystal microcombs with forward and backward pump wavelength tuning. A short-time delayed linear interferometer is developed to examine the linewidths of individual comb teeth and the soliton microcomb linewidth distributions. The measured interferometric envelopes for the single-soliton, double-soliton, and soliton crystal microcombs show linewidths of 2.3 kHz, 3.0 kHz, and 2.4 kHz, respectively. The linewidth distribution broadens slightly away from the pump towards shorter wavelengths, exhibiting increased fluctuations due to the structured optical spectrum. Understanding the fundamental linewidths in high-clock-rate frequency microcombs is essential for unlocking new applications.

Large-scale quantum computers possess the capacity to effectively tackle practical problems that can be insurmountable for classical computers. The main challenge in building these quantum computers is to realize scalable modules for remote qubits and entanglement. By assembling small, specialized parts into a larger architecture, the modular approach mitigates complexity and uncertainty. Such a distributed architecture requires non-local quantum gate operations between remote qubits. An essential method for implementing such operations, known as quantum gate teleportation, requires only local operations, classical communication, and shared entanglement. Till today, the quantum gate teleportation using a photonic chip has remained elusive. Here, we experimentally demonstrate the quantum teleportation of an on-chip controlled-NOT (CNOT) gate, implemented via a silicon polarization directional coupler. Assisted with the scalable silicon chip platform, high-fidelity local quantum logic gates, linear optical components, post-selected entanglement, and coincidence measurements from photonic qubits, we first measure and characterize our teleported chip-scale CNOT gate with an average truth table fidelity of 93.1 +/- 0.3%. Second, for different input polarization states, we obtain an average quantum state fidelity of 87.0 +/- 2.2% with our teleported on-chip CNOT gate. Third, we use our non-local CNOT gate for remote entanglement creation of four Bell states, with an average quantum state fidelity of 86.2 +/- 0.8%. Fourth, we fully characterize our teleported on-chip CNOT gate with a quantum process fidelity of 83.1 +/- 2.0%, and an average non-local CNOT gate fidelity of 86.5 +/- 2.2%. Our teleported photonic on-chip quantum logic gate could be extended both to multiple qubits and chip-scale modules towards fault-tolerant and large-scale distributed quantum computation. (c) 2025 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.

We demonstrate a hybrid SiN/TFLN electro-optic Mach–Zehnder modulator with 3 dB bandwidth beyond 110 GHz and 67 GHz operating at C-band and O-band. Ion-cut wafer-level bonding was employed and the lithium niobate is etchless.

Coherent frequency microcombs, generated in nonlinear high-Q microresonators and driven by a single continuous-wave laser, have enabled several scientific breakthroughs in the past decade, thanks to their high intrinsic phase coherence and individual comb line powers. Here, we report terabit-per-second-scale coherent data communications over a free-space atmospheric link, using a platicon frequency microcomb, employing wavelength- and polarization-division multiplexing for next-generation optical wireless networks. Spanning more than 55 optical carriers with 115 GHz channel spacing, we report the first free-space coherent communication link using a frequency microcomb, achieving up to 8.21 Tbit/s aggregate data transmission at a 20 Gbaud symbol rate per carrier over 160 m, even under log-normal turbulent conditions. Utilizing 16-state quadrature amplitude modulation, we demonstrate retrieved constellation maps across the broad microcomb spectrum, achieving bit-error rates below both hard- and soft-decision thresholds for forward-error correction. Next, we examine a wavelength-division multiplexing free-space passive optical network as a baseline for free-space fronthaul, achieving an aggregate data rate of up to 5.21 Tbit/s and a field-tested spectral efficiency of 1.29 bit/s/Hz in the microcomb-based atmospheric link. We also quantify experimental power penalties of ≈ 3.8 dB at the error-correction threshold, relative to the theoretical additive white Gaussian noise limit. Furthermore, we introduce the first-ever demonstration of master–slave free-space carrier phase retrieval with frequency microcombs, and the compensation for turbulence-induced intensity scintillation and pointing error fluctuations, to improve end-to-end symbol error rates. This work provides a foundational platform for broadband vertical heterogeneous connectivity, terrestrial backbone links, and ground-satellite communication.

Light detection and ranging (LiDAR) is widely used in scenarios such as autonomous driving, imaging, remote sensing surveying, and space communication due to its advantages of high ranging accuracy and large scanning angle. Optical phased array (OPA) has been studied as an important solution for achieving all-solid-state scanning. In this work, the recent research progress in improving the beam steering performance of the OPA based on silicon photonic integrated chips was reviewed. An optimization scheme for aperiodic OPA is proposed.

This paper presents the test results for high-performance and high-uniformity waveguide silicon-based germanium (Ge) photodetectors (PDs) for the O band and C band. Both wafer-scale and chip-scale test results are provided. The fabricated lateral p − i − n (LPIN) PDs exhibit a responsivity of 0.97 A/W at a bias of −2V, a bandwidth of 60 GHz, and a no-return-to-zero (NRZ) eye diagram rate of 53.125 Gb/s. Additionally, an average dark current of 22.4 nA was obtained in the vertical p − i − n (VPIN) PDs at −2V by optimizing the doping process. The device can reach an average responsivity of 0.9 A/W in the O band. The standard deviation in a wafer with a dark current and responsivity is as low as 7.77 nA and 0.03 A/W at −2V, respectively.

We demonstrate the Mach-Zehnder interferometer (MZI) silicon-based electro-optic modulators in the short-wave mid-infrared 2 μm band. The waveguide structure and doping position of the devices are optimized by simulation. The devices are manufactured on a 220 nm silicon-on-insulator (SOI) platform, and are measured through self-built short-wave mid-infrared measurement platform. The device with the length of 3.5 mm has a measured modulation efficiency of 1.853 V·cm at 3 V reverse bias. The highspeed characterization is also performed, and the device with the length of 3.5mm has a data rate of over 20 Gb/s at the voltage swing of 2.8 Vpp with on-off keying (OOK) modulation formats. The modulation speed of the 2 mm device can reach over 40 Gb/s with 4-level pulse amplitude modulation (PAM-4) formats at a voltage swing of 2.5 Vpp.

Frequency microcombs with microwave and millimeter-wave repetition rates provide a compact solution for coherent communication and information processing. The implementation of these microcombs using a CMOS-compatible platform further paves the way for large-scale photonic integration and modularity. Here, we demonstrate free-running soliton microcombs with K-band repetition rates with very low phase noise over a 4 GHz pump detuning range reaching −117 (−123) dBc/Hz at 10 kHz offset for a 19.7 (10) GHz carrier without active pump stabilization, exceeding commercial electronic microwave oscillators at frequency offsets above 40 kHz. The minimum laser noise to soliton microwave signal transduction factor observed is −73 dB. This noise performance is achieved using a hybridized dual-mode for soliton generation to achieve passive thermal stabilization and minimal soliton spectrum shift from prior Raman scattering and dispersive wave formation. We further examine the locking of the repetition rate to an external ultrastable photonic oscillator to illustrate the feasibility of phase noise suppression below the thermorefractive noise limits of microresonator frequency combs.