Chip-Scale Packages for a Tunable Wavelength Reference and Laser Cooling Platform

We demonstrate a tunable, chip-scale wavelength reference to greatly reduce the complexity and volume of cold-atom sensors. A 1-mm optical path length microfabricated cell provides an atomic wavelength reference, with dynamic frequency control enabled by Zeeman-shifting the atomic transition through the magnetic field generated by the printed-circuit-board coils. The dynamic range of the laser frequency stabilization system is evaluated and used in conjunction with an improved generation of chip-scale cold-atom platforms that traps 4 million ${}^{87}\mathrm{Rb}$ atoms. The scalability and component consolidation provide a key step forward in the miniaturization of cold-atom sensors.

Figure 1

A schematic diagram overview of the chip-scale wavelength and cooling platforms. (a) A MEMS cell-based wavelength reference using saturated absorption spectroscopy. Solid/dashed lines indicates the incident/retro-reflected beam. PD: photodiode. PCB HC: printed-circuit-board Helmholtz coils. PBS: polarizing beam splitter. SMR: surface-mounted resistor. (b) MEMS cell GMOT incorporated laser cooling platform with planar coils. GMOT: grating magneto-optical trap. PCB AHC: printed-circuit-board anti-Helmholtz coils. (c) Microscope image of the MEMS cell in the wavelength reference package. (d) Layer structure for the wavelength reference MEMS cell stack. BSG: borosilicate glass. (e) Layer structure for the UHV-MEMS cell stack. ASG: aluminosilicate glass. (f) Example image of the cold-atom sample formed from the combined chip-scale platforms.

Figure 2

(a) Printed-circuit-board generated Helmholtz magnetic field orientation through the MEMS spectroscopy cell. (b) Measured frequency shift as a function of the coil current, where blue circles (red squares) represent a positive (negative) applied magnetic field magnitude. The black lines highlight a $\pm 1.4$ MHz/G frequency shift. (c) The Zeeman-shifted error signal measured with a single shot at 12 MHz detuning (red), on resonance (black) and at 66 MHz detuning (blue).

Figure 3

(a) Printed-circuit-board-generated anti-Helmholtz magnetic field orientation through the 6-mm-thick cold-atom cell. (b) Measured atom number as a function of laser lock frequency, provided by the MEMS wavelength reference. (c) Overlapping Allan deviation of the beat-note signal when the VBR laser is stabilized to the tunable wavelength reference and a 7-cm reference cell, shown in red squares and blue circles, respectively. (d) Simultaneously measured atom number stability from the cold-atom platform.