The industrialization in the fields of telecommunications, artificial intelligence, and the Internet of Things has steadily progressed. With the increasing demand for information transmission and data processing in these fields, it is not sustainable anymore to optimize processing speed only via increase in integration density and miniaturization of transistors, which are limited by the laws of physics, design complexity, and cost. Therefore, complementing the current lack of processing speed by other novel technologies is being widely discussed. Integrated photonics, which uses photons as information carriers, can be an alternative to meet the aforementioned requirements. Compared with traditional electrical circuits, photon integrated circuits leverage micro and nanoscale optical components to realize light transmission, which offer several prominent features such as high bandwidth, low power consumption, and ultrahigh transmission speed. Specifically, on-chip photonic systems can be used to host high-Q resonant cavities for enhancing light-matter interaction owing to the unique physical characteristics of photons and advanced manufacturing techniques. This in turn paves the way for applications in nonlinear photonics and quantum photonics.

Thus far, many manufacturing processes have been established for integrated photonics on various material platforms such as silica, Ⅲ-Ⅴ compound semiconductors, silicon, silicon nitride, and lithium niobate. Of these platforms, silicon-integrated photonics has remarkably progressed owing to mature manufacturing techniques for Si-based integrated circuits, whereas the absence of photoelectric characteristics and the high propagation loss are not beneficial for establishment of configurable photonic systems. Lithium niobate, which is considered a promising platform for integrated photonics, has been applied in ultrafast optical modulation and microwave photonics because of its remarkable attributes of second- and third-order nonlinearities and low optical loss; however, one must consider that its incompatibility with complementary metal-oxide-semiconductor (CMOS) and its photorefractive effect impede the commercialization of lithium niobate photonics. As direct bandgap semiconductors, the high-efficiency electroluminescence of Ⅲ-Ⅴ materials makes on-chip laser a plausible technique for large-scale photonic circuits; however, the relatively high propagation loss and narrow transparency window are still detrimental factors.

The development of silicon carbide-integrated photonics is in its infancy stage. Silicon carbide has attracted considerable research interest in the recent years owing to its remarkable material and optical properties, and it has gradually emerged as a candidate for industrialization of integrated photonics on account of its CMOS compatibility. Benefiting from the high nonlinear coefficients and low optical loss, silicon carbide has been extensively used to realize many nonlinear optical effects for fabrication of compact and scalable integrated photonic circuits. These effects include efficient second-harmonic generation, rapid electro-optical modulation, and silicon optical frequency comb generation, among others. Meanwhile, similar to diamond, there exist numerous spin defects in silicon carbide materials, and they have been proven to be impressive quantum light sources in optical resonators for study of cavity quantum electrodynamics effects.

Currently, novel research works have confirmed the potential of silicon carbide photonics as an ideal candidate, but they are still plagued by several problems related to micromachining limitation and inefficient modulation. To further explore the industrial feasibility of photonics chips, the extra innovations in fabrication and device design are still required to attain a monolithic photonic system based on silicon carbide with linear modulating methods and configurable nonlinear effects. Therefore, one must comprehensively present the latest research progress on silicon carbide-integrated photonics, while relevant prominent performance should be indicated to emphasize the prospective of silicon carbide as a universal platform for integrated photonics.

For achieving sufficient reliability and high density of integration, silicon-carbide-on-insulator (SiCOI) structures can be used to confine a light field within the functional layer without suspension. Preparations, including thin film preparation for 3C-SiCOI (see Fig.1), smart-cut technology (see Fig.2), and grinding thinning (see Fig.3) for 4H-SiCOI, are introduced with specific process flow and material characterization. Among them, the research groups from Columbia University, Shanghai Institute of Microsystems and Information Technology, Stanford University, respectively, have prepared SiCOI with low surface roughness and low cost. The SiCOI platforms prepared using the aforementioned methods exhibit relatively low optical loss (see Table 2), which enable different nonlinear frequency conversions to be implemented on high-Q microcavities based on SiCOI. In terms of second-harmonic generation (see Fig.4) and electro-optical modulation (Fig.5), various devices such as waveguides, photonic crystals, and microrings in SiCOIs, as well as their fundamental principles and performance merits, are listed. Considering the generation of wide optical frequency combs, a comb spectrum with stable silicon states based on high-Q microcavities has been yielded in 4H-SiCOI (see Fig.6); additionally, second-harmonic generation is favorable for broadening the comb spectrum by accomplishing the frequency conversion between the midinfrared and visible bands (see Fig.7). Abundant color centers with attractive properties in silicon carbide allow for integration of color centers and microcavities (see Fig.9) and coherent manipulation over nuclear spin qubits (see Fig.10). Additionally, issues regarding precisely locating the color centers in 4H-SiCOI are considered vis-a-vis some recent studies (see Fig.11). The challenges and prospects of silicon carbide photonics are discussed, including its commercialization requirements, application in quantum networks, heterogeneous integration for monolithic all-optical systems, and on-chip multiphysical field coupling.

Silicon carbide-integrated photonics has attracted considerable research interest in the recent years. On account of its salient nonlinearity and CMOS compatibility, silicon carbide has gradually emerged as a candidate material for integrated photonic circuits. With a view to fully benefiting from the impressive material and optical properties of silicon carbide, advanced fabrication methods and on-chip device designs must be explored for large-scale application of integrated photonics based on SiCOI. Moreover, in conjunction with CMOS electronic devices and acoustic devices, integrated photonics based on SiCOI will be capable of making silicon carbide as a promising material platform for achieving multiphysical field coupling in monolithically integrated photonics.