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▣ 주   제: Wafer-Level Microfabrication Technologies for Alkali Vapor Cells Toward MEMS Atomic Clocks

▣ 연   사: Prof. Yoshikazu Hirai

▣ 소   속: Kyoto University

▣ 일   시: 2026. 7. 31.(금) 17:00

▣ 장   소: 제4공학관 D601호

▣ 초   청: 김종백 교수

▣ 초   록

Microfabricated alkali vapor cells are essential components of coherent population trapping (CPT) atomic clocks and play a central role in achieving miniaturized timing devices. In this seminar, I will present our recent progress in wafer-level microfabrication technologies for alkali vapor cells, with a particular focus on improving both manufacturability and device performance. The first topic is an integrated vapor-cell structure that combines a CPT optical cavity with Si three-dimensional microstructures [1, 2]. This structure was designed to facilitate the low-temperature thermal decomposition of RbN3, allowing efficient Rb generation under a reduced thermal budget. As a result, the Rb sourcing process inside the cell can be significantly shortened while maintaining stable Rb generation. The second topic is wafer-level, cell-by-cell control of N2 buffer-gas pressure in microfabricated vapor cells [3]. RbN3 was patterned by inkjet deposition and decomposed after wafer-level sealing using laser irradiation, generating both Rb vapor and N₂ buffer gas inside each cell. The generated N₂ pressure exhibited a linear relationship with the deposited RbN₃ amount, with a coefficient of variation (CV) of 5.0%. CPT characterization showed that, in the low-pressure regime below approximately 5 kPa, CPT-based laser stabilization can enhance the CPT resonance amplitude by improving spectral selectivity. Overall, these wafer-level approaches provide practical routes toward scalable fabrication and performance optimization of alkali vapor cells, which are critical for future MEMS atomic clocks and high-precision timing devices.