A Cold-Atom Interferometer with Microfabricated Gratings and a Single Seed Laser

Abstract

The extreme miniaturization of a cold-atom interferometer accelerometer requires the development of novel technologies and architectures for the interferometer subsystems. We describe several component technologies and a laser system architecture to enable a path to such miniaturization. We developed a custom, compact titanium vacuum package containing a microfabricated grating chip for a tetrahedral grating magneto-optical trap (GMOT) using a single cooling beam. The vacuum package is integrated into the optomechanical design of a compact cold-atom sensor head with fixed optical components. In addition, a multichannel laser system driven by a single seed laser has been implemented with time-multiplexed frequency shifting using single sideband modulators, reducing the number of optical channels connected to the sensor head. This laser system architecture is compatible with a highly miniaturized photonic integrated circuit approach, and by demonstrating atom-interferometer operation with this laser system, we show feasibility for the integrated photonic approach. In the compact sensor head, sub-Doppler cooling in the GMOT produces 15 μK temperatures, which can operate at a 20 Hz data rate for the atom interferometer sequence. After validating atomic coherence with Ramsey interferometry, we demonstrate a light-pulse atom interferometer in a gravimeter configuration without vibration isolation for 10 Hz measurement cycle rate and T = 0 - 4.5 ms interrogation time, resulting in Δg/g = 2.0e-6. All these efforts demonstrate progress towards deployable cold-atom inertial sensors under large amplitude motional dynamics.

Cold atom inertial sensors for navigation applications

“…Sensors that use multiple atom clouds are being developed [15,25] to remove the dead time and increase the duty cycle. Other developments are focussed on reducing the size, weight and power ("SWaP") requirements of the sensors through better design [9], integration of optical and laser technologies with the vacuum systems [26], and more complex laser pulse sequences [27]. However, the current technology does have potential uses in navigation.…”

$Λ$-enhanced gray molasses in a tetrahedral laser beam geometry

“…One promising approach to MOT miniaturization is the grating MOT, which replaces most of the magnetooptical trap's expansive optical layout with a compact set of diffraction gratings [3,4]. Grating MOTs are being integrated into a variety of quantum instruments and sensors, including atomic clocks [5], atom interferometers [6], electron-beam sources [7], magnetometers [8], and vacuum gauges [8,9]. Both the diffraction gratings [10,11] and beam launch optics [12] of a grating MOT are amenable to nanofabrication.…”