FBAR Oscillator and MEMS Tunable VCSEL to Generate the Probe Lasers for Microfabricated Atomic Clock

In this paper, we describe several new approaches to cost reduction for the realization of ultraminiaturized atomic clocks. One is the development of a wavelength tuner for vertical-cavity surface-emitting lasers (VCSELs) for the atomic clocks. Our VCSEL is designed so that an electrostatic actuator can control the length of the laser cavity, eliminating the offset from the desired central wavelength even in postprocessing. This is effective in reducing the screening cost, which is the main factor driving up the cost of laser chips for coherent population trapping (CPT) atomic clocks. In another approach, we used a thin film bulk acoustic resonator (FBAR) for the atomic clock oscillator to significantly reduce the circuit scale and added a balun circuit and a gain adjustment circuit. This oscillator was manufactured using a legacy process with a line width of 180 nm, and good oscillation was successfully confirmed in the 3 GHz band.