Raman-Assisted Multiband Nonlinear Frequency-Conversion Network in a High- Q LTOI Microdisk

On-chip nonlinear frequency conversion offers a key route to broadband coherent light sources, but spanning telecom, visible, and ultraviolet wavelengths within a single resonator remains challenging. Lithium tantalate-on-insulator, which has recently emerged as a promising material platform for integrated photonics, combines strong Raman activity, a large second-order nonlinearity, broad optical transparency and high resistance to photorefractive damage, thereby attracting increasing attention for on-chip nonlinear frequency conversion. Here, we experimentally demonstrate a Raman-assisted multiband frequency-conversion network in a high-Q lithium tantalate-on-insulator microdisk with a loaded quality factor of 2.48 × 106. Under separately optimized operating conditions, the device produces high-purity single-mode Raman lasing with a threshold of 3.14 mW, a slope efficiency of 32.44%, and a side-mode suppression ratio of 29.5 dB, as well as multiple Stokes lines and an anti-Stokes line. Together, the directly observed Raman fields and the intermediate Stokes fields inferred from energy conservation define a network of cascaded χ(2) pathways that generates near-infrared and visible emission and extends to 312.6 nm in the ultraviolet. These results demonstrate cooperative Raman and second-order nonlinear interactions across widely separated spectral bands in a single microcavity, providing a route to integrated multiband sources and a platform for studying coupled nonlinear dynamics.