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arXiv · 2607.11186

Leveraging Raman response in X-cut thin-film lithium tantalate for ultrabroadband combs and polychromatic visible light

Xin Wang·Mingkun Xiao·Min Sun·Ronghong Gao·Yuqi Chen·Zhengshun Lei·Xun Zhang·Wenfeng Zhou·Jintian Lin·Yikai Su·Xingchen Ji·Yong Zhang
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Abstract

X-cut thin-film lithium tantalate (TFLT) offers a unique combination of third nonlinearity, electro-optic effects, and a high optical damage threshold. However, its strong Raman response has historically hindered broadband Kerr comb generation. Here, we leverage this inherent Raman response by engineering coupling-defined dissipation. This allows us to reconfigure the relative thresholds of Raman and Kerr processes without modifying the intrinsic microresonator dispersion. Through this coupling-engineered threshold control, we can deliberately access distinct comb states, ranging from pure Kerr combs to Raman-Kerr synergistic broadband combs. We demonstrate a Kerr comb spanning 450 nm and a Raman-Kerr comb spanning 650 nm, representing the broadest combs reported to date on X-cut TFLT platforms. Moreover, in strongly coupled devices, we show that a single near-infrared pump can generate visible emission across multiple bands (from violet to red) via cascaded second sum-frequency processes. Our work demonstrates that a strong Raman response can be transformed from a parasitic competitor into an enabling mechanism for achieving broader comb spectra and generating polychromatic visible light. This work establishes X-cut TFLT as a powerful monolithic platform for nonlinear light sources, electro-optic functions, and complex photonic systems.

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Xin Wang, Mingkun Xiao, Min Sun, Ronghong Gao, Yuqi Chen, Zhengshun Lei, Xun Zhang, Wenfeng Zhou, Jintian Lin, Yikai Su, Xingchen Ji, Yong Zhang. 2026-07-13. Leveraging Raman response in X-cut thin-film lithium tantalate for ultrabroadband combs and polychromatic visible light. https://arxiv.org/abs/2607.11186

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