Microfabricated vapor cell sensors are used in chip-scale atomic clocks and magnetometers. The most common architecture of the cell body is a silicon body with a cavity for the vapor, such as alkali metal vapor, extending through the silicon body, sandwiched by glass windows, sealing the cavity. Optical signals are transmitted through one of the windows and received through the other window. The glass/silicon/glass structure is amenable to wafer scale production in microelectronic fabrication facilities, which keeps fabrication costs lower than building sensors individually.
Demands for higher performance have generated a need for microfabricated vapor cell sensors that support two perpendicular signal paths, which is difficult to achieve in a small package using the glass/silicon/glass structure. Other designs for microfabricated vapor cell sensors that support perpendicular signal paths have been proposed, but are not readily fabricated on a wafer scale, or in typical microelectronic fabrication facilities.