## 1 Introduction  
The advancement of photonic technologies is increasingly driven by the need for material platforms that enable the development of photonic integrated circuits (PICs) capable of manipulating light with high precision and efficiency at the nanoscale. Among the different materials being explored, silicon carbide (SiC) has emerged as a multifunctional material platform for photonic integrated devices and circuits (PICs), based on lithographically patterned waveguides. Its attributes, such as wide bandgap (2.4-3.2 eV), high refractive index (-2.6 at 1550 nm), relatively high electro-optic coefficient (Pockels effect) (-2 pm/V at 1550 nm), and high thermal conductivity (450 W/mK), make it particularly well-suited for devices such as waveguides, ring resonators, and Pockels modulators on insulator, and position it as a versatile candidate for next-generation PICs [1; 2; 3]. Efficient operation at telecom wavelengths, specifically around 1310 and 1550 nm, is essential for various PIC applications, particularly in telecommunications and quantum information science [4]. SiC suppresses two-photon absorption at telecom wavelengths due to its large direct bandgap [5], while its linear refractive index is high, and therefore, it can facilitate the fabrication of ultra-high confinement waveguides. Moreover, SiC is unique among photonic materials due to its ability to host optically active quantum defects [6; 7; 8]. SiC has a nearly negligible magnetic moment, which is essential for supporting single-photon emitters with reduced optical decoherence [9]. This feature enables a wide range of quantum photonic applications, including quantum sensing, quantum metrology, and quantum information processing [10; 11; 12; 13]. SiC's mechanical and chemical robustness further supports applications in high-temperature and harsh environments [14; 15; 16]. Notably, among its polytypes, cubic SiC (3C-SiC) is the only one that can be grown directly on silicon. Current research on SiC for PICs primarily focuses on bulk SiC, heteroepitaxial 3C-SiC on silicon (Si) [17], homoepitaxial 4H-SiC [18], and the chemical vapor deposition of amorphous SiC (a-SiC) on Si [19]. These approaches have enabled the development of photonic devices based on suspended SiC structures, silicon carbide-on-insulator (SiCOI) thin films (e.g., 3C- and 4H-SiCOI) [20; 21; 22], and amorphous-SiCOI [23; 24], each offering distinct advantages for integration and device performance. The SiCOI platform parallels the well-established silicon-on-insulator technology in silicon photonics, offering an industry-compatible fabrication route. In contrast to the limited photonic device architectures enabled by homoepitaxial 4H-SiC and direct 3C-SiC growth on Si, which face challenges such as a lattice mismatch of \(\sim\)20% [25], SiCOI enables high-quality device fabrication through wafer bonding. This process involves flipping and transferring an epitaxially grown SiC layer onto a silicon dioxide-on-silicon substrate. Recent advances in wafer bonding [26], smart-cut, and thinning techniques have facilitated the production of high-quality 3C- and 4H-SiC on insulator (SiCOI) thin films [27; 28], resulting in platforms suitable for PICs (e.g., high-Q optical cavities and efficient nonlinear optical devices). However, wafer bonding introduces challenges, including the need for precise wafer-thickness uniformity during thinning and planarization, as well as control of material optical losses introduced by ion-cutting processes, and layer-to-layer lattice alignment [29; 30; 31]. An alternative approach to mitigate the fabrication challenges associated with the SiCOI platform through the wafer bonding process is the direct deposition of amorphous SiC on an insulator (a-SiCOI) [23; 24]. This method leverages CMOS-compatible fabrication techniques, such as plasma-enhanced chemical vapor deposition (PECVD) and inductively coupled plasma CVD (ICPCVD), which enables precise thickness control--an essential factor for wafer- and chip-scale PIC fabrication.