Integrated High‐Q Fabry‐Pérot Cavity at 780 nm with Ultrabroad Operating Bandwidth and High Fabrication Tolerance

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Fabry‐Pérot (F‐P) cavities are highly desirable for atom cooling and narrow‐linewidth generation. However, there are few studies on integrated F‐P cavities with high‐quality factors in the visible and near‐visible wavelength ranges, particularly at 780 nm, which corresponds to the energy transition of rubidium atoms. In this work, an integrated F‐P cavity design based on silicon nitride is demonstrated achieving an intrinsic quality factor of 6.1 × 105 at 780 nm without thermal annealing, along with a broad operating bandwidth of 500 nm and high fabrication tolerance. To the best of the knowledge, this quality factor represents the highest reported value in these wavelength ranges, accompanied by the largest operating bandwidth. These results offer significant potential for advancing on‐chip atom cooling and contribute to the broader development of photonic integrated circuits and quantum optics.