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Microfabricated Vapor Cells with Reflective Sidewalls for Chip Scale Atomic Sensors

1,2,3, 1,2,3,*, 1,2,3, 4 and 1,2,3,*
1
Collaborative Innovation Center for Micro/Nano Fabrication, Device and System, Tsinghua University, Beijing 100084, China
2
State Key Laboratory of Precision Measurement Technology and Instrument, Tsinghua University, Beijing 100084, China
3
Department of Precision Instrument, Tsinghua University, Beijing 100084, China
4
State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing 100190, China
*
Authors to whom correspondence should be addressed.
Micromachines 2018, 9(4), 175; https://doi.org/10.3390/mi9040175
Received: 13 December 2017 / Revised: 1 April 2018 / Accepted: 9 April 2018 / Published: 11 April 2018
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Abstract

We investigate the architecture of microfabricated vapor cells with reflective sidewalls for applications in chip scale atomic sensors. The optical configuration in operation is suitable for both one-beam and two-beam (pump & probe) schemes. In the miniaturized vapor cells, the laser beam is reflected twice by the aluminum reflectors on the wet etched 54.7° sidewalls to prolong the optical length significantly, thus resulting in a return reflectance that is three times that of bare silicon sidewalls. To avoid limitations faced in the fabrication process, a simpler, more universal and less constrained fabrication process of microfabricated vapor cells for chip scale atomic sensors with uncompromised performance is implemented, which also decreases the fabrication costs and procedures. Characterization measurements show that with effective sidewall reflectors, mm3 level volume and feasible hermeticity, the elongated miniature vapor cells demonstrate a linear absorption contrast improvement by 10 times over the conventional micro-electro-mechanical system (MEMS) vapor cells at ~50 °C in the rubidium D1 absorption spectroscopy experiments. At the operating temperature of ~90 °C for chip scale atomic sensors, a 50% linear absorption contrast enhancement is obtained with the reflective cell architecture. This leads to a potential improvement in the clock stability and magnetometer sensitivity. Besides, the coherent population trapping spectroscopy is applied to characterize the microfabricated vacuum cells with 46.3 kHz linewidth in the through cell configuration, demonstrating the effectiveness in chip scale atomic sensors. View Full-Text
Keywords: MEMS fabrication; rubidium vapor cells; reflectance; linear absorption contrast; coherent population trapping (CPT) spectroscopy; chip scale atomic sensors MEMS fabrication; rubidium vapor cells; reflectance; linear absorption contrast; coherent population trapping (CPT) spectroscopy; chip scale atomic sensors
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Han, R.; You, Z.; Zhang, F.; Xue, H.; Ruan, Y. Microfabricated Vapor Cells with Reflective Sidewalls for Chip Scale Atomic Sensors. Micromachines 2018, 9, 175.

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