Search Results (2)

This article reports on a millimeter-wave (MM-wave) signal down-conversion system with low phase noise for chip-scaled optical clocks. The system utilizes analog regenerative frequency division, low-noise fractional frequency division, and phase-locked frequency division techniques to down-convert a 100 GHz MM-wave signal to 100 MHz with phase noise of −117 dBc/Hz @100 Hz, −133 dBc/Hz @1 kHz, and 10 MHz with phase noise of −124 dBc/Hz @100 Hz and −143 dBc/Hz @1 kHz. The frequency stability of the signal down-converted to 100 MHz is 5.0 × 10⁻¹⁵ @ 1 s and 1.8 × 10⁻¹⁶ @ 1000 s, while the frequency stability of the 10 MHz signal is 5.7 × 10⁻¹⁴ @ 1 s and 5.9 × 10⁻¹⁶ @1000 s, both of which decrease to the 10⁻¹⁶ level at 10,000 s. This down-conversion system meets the frequency conversion requirements of state-of-the-art chip-based optical clocks and micro-cavity optical combs. Full article

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. Full article