DON26BZ01-NV037 — Synthetic Alkali Atom Vapor Density for Atom-Based Sensors
Award Maximum: $140,000 (Base) / $100,000 (Option) Period of Performance: 6 months (Base) + 6 months (Option) Phase Type: Phase I
OBJECTIVE: Simplify the thermal management of practical atom-based quantum sensors based on alkali atoms by creating a passive atom source operated at thermal equilibrium based on a synthetic alkali vapor density for rubidium or cesium atoms.
DESCRIPTION: Quantum sensors based on atoms offer the opportunity to produce measurements with excellent sensitivity or long-term stability, making them attractive for use in atomic clocks, magnetometers, or inertial sensors. In these sensors, the atomic vapor represents the sensing media where variations in signal magnitude from fluctuations in atom number can lead to instability or loss of sensitivity.
Many atom-based sensors rely on heavy alkali atoms, specifically rubidium and cesium. This is because of the simplified, hydrogen-like energy level structure, the availability of narrow-linewidth semiconductor diode lasers on the relevant D1 (795/895 nm) and D2 (780/852 nm) transitions, the accessibility of commercial microwave electronics at the 3-10 GHz hyperfine splittings, and the ease of production of vapor phase atoms at modest temperatures.
Active approaches to alkali regulation have been demonstrated to manipulate the vapor to a non-equilibrium state. These approaches involve forced chemical reactions, intercalated graphite, alkali impregnated materials glasses. In each case, a feedback loop must respond to measurements of the vapor density, leading to extra sensor complexity.
An equilibrium vapor density represents the simplest atom source which can be synthetically adjusted to an elevated temperature through a mixture. Here, a primary species mixed with a secondary species reduces the equilibrium vapor density of both species by the mixing ratio following Raoult's Law. Such an approach can be applied to laser-cooled systems in addition to vapor cells to enable equilibrium operation at elevated system temperature, providing tight thermal regulation at low power.
PHASE I: Develop and demonstrate a method to produce a predetermined mixture of primary and secondary alkali species allowing for reduction of equilibrium vapor density of the primary species. Mixtures consistent with supporting laser cooling at elevated temperatures from 30-85°C should be demonstrated corresponding to ~10-10,000× reductions in the primary species. Spectroscopic determinations of the primary species density in the mixture should be evaluated against unmixed samples of the primary alkali species. In the Phase I Option, if exercised, stability of the mixtures against thermal cycling should be demonstrated.
PHASE II: Produce mixtures capable of supporting laser cooling and trapping at elevated temperatures over the 30-85°C range. Mixtures will be produced in or transferred into chambers that support optical access, magnetic fields, and ultra-high vacuum conditions compatible with atom trapping for evaluation. In addition, atom trapping performance will be evaluated to determine number of atoms and loading time constant at a range of temperatures around the target temperature. Deliver at a minimum three (3) samples (containing > 1 mg each) of the atom-trapping material in a proposed delivery mechanism to the Navy at the conclusion of Phase II.
PHASE III DUAL USE APPLICATIONS: Based on the demonstrations and continual advancement of laser cooling technologies, the atom source should lead to dramatic improvements in the SWaP of cold atom systems. Support the Navy in transitioning the technology to Navy use. The end product technology could be leveraged to adapt atom-based sensors to a variety of thermal environments to support biomedical, communications, and navigation applications.
KEYWORDS: Quantum sensing, magneto-optical trap, atom source, atomic clock, atom interferometer, atomic magnetometer