Ultraviolet-C to mid-infrared supercontinuum generation in periodically poled lithium tantalate waveguides

Supercontinuum generation makes use of the nonlinear optical effects arising from the interaction of light with the bound electronic states in crystal lattices and has many applications, especially in the ultraviolet for the direct probing of large-energy electronic transitions. However, supercontinuum from integrated waveguides has been limited to >330 nm in the ultraviolet-A band because of material dispersion and absorption. Here, we demonstrate unprecedented ultraviolet-C-to-mid-infrared supercontinuum on a chip, leveraging the exceptional transparency window and second-order nonlinearity of lithium tantalate (LT). A key innovation is the introduction of chirped periodically poled LT with submicron ferroelectric domains. Utilizing 3-wave-mixing processes under quasi-phase-matching conditions, we created the shortest ultraviolet wavelength ever reported from a chip-below 270 nm-while reaching 2400 nm in the mid-infrared, covering more than three octaves with just 100 pJ pulse energy on a chip for the first time. It's the first on-chip supercontinuum fully covering the ultraviolet-A/B bands while extending into the ultraviolet-C band. This work establishes thin-film LT as a versatile platform for full-spectrum nonlinear photonics, opening new possibilities for integrated ultraviolet sources.