Compact cold-atom sensors depend on vacuum technology. One of the major limitations to miniaturizing these sensors is the active pumps—typically ion pumps—that are required to sustain the low pressure needed for laser cooling. Although passively pumped chambers have been proposed as a solution to this problem, technical challenges have prevented successful operation at the levels needed for cold-atom experiments. The authors present the first demonstration of a vacuum package successfully independent of ion pumps for more than a week; their vacuum package is capable of sustaining a cloud of cold atoms in a magneto-optical trap (MOT) for greater than 200 days using only non-evaporable getters and a rubidium dispenser. Measurements of the MOT lifetime indicate that the package maintains a pressure of better than 2×10−7 Torr. This result will significantly enable the development of compact atomic sensors, including those sensitive to magnetic fields, where the absence of an ion pump will be advantageous.
Compact cold-atom sensors depend on vacuum technology. One of the major limitations to miniaturizing these sensors is the active pumps—typically ion pumps—that are required to sustain the low pressure needed for laser cooling. Although passively pumped chambers have been proposed as a solution to this problem, technical challenges have prevented successful operation at the levels needed for cold-atom experiments. The authors present the first demonstration of a vacuum package successfully independent of ion pumps for more than a week; their vacuum package is capable of sustaining a cloud of cold atoms in a magneto-optical trap (MOT) for greater than 200 days using only non-evaporable getters and a rubidium dispenser. Measurements of the MOT lifetime indicate that the package maintains a pressure of better than 2×10−7 Torr. This result will significantly enable the development of compact atomic sensors, including those sensitive to magnetic fields, where the absence of an ion pump will be advantageous.
A glass ultrahigh vacuum chamber with rubidium alkali metal dispensers and nonevaporable getter pumps has been developed and used to create a cold atomic sample in a chamber that operates with only passive vacuum pumps. The ion-mass spectrum of evaporated gases from the alkali metal dispenser has been recorded as a function of dispenser current. The efficacy of the nonevaporable getter pumps in promoting and maintaining vacuum has been characterized by observation of the Rb vapor optical absorption on the D2 transition at 780 nm and vacuum chamber pressure rate of rise tests. The authors have demonstrated a sample of laser-cooled Rb atoms in this chamber when isolated and operating without active vacuum pumps.
Over the past decade, the cold atom sensors have transitioned gradually from laboratory-based experiments to practical field applications. The miniaturization is of great importance and needs to be achieved for this transition, especially for the vacuum system for cold atom sensors. Typically, the vacuum system is complicated and usually composed of the vacuum chamber, the optical path for the laser beam, and the magnetic field coils. The improvement of size, weight, and power (SWaP) consumption of the vacuum system has become a challenge at present. In this paper, the passive vacuum technology is proposed and overviewed to simplify the vacuum system for cold atom sensors (VSCAS). Firstly, the materials of low helium-permeability are summarized. Secondly, the key components required for the realization of the passive vacuum system (PVS) are discussed in great detail, including the getter pump and atomic source. Then, the integration of the passive vacuum system with the mentioned components is summarized, and the evaluation methods of the performance of those vacuum systems have been analyzed. Moreover, we have carried out the preliminary designs and experiments of PVS, and present some experimental results to verify its feasibility.
Compact vacuum systems are key enabling components for cold atom technologies, facilitating extremely accurate sensing applications. There has been important progress toward a truly portable compact vacuum system; however, size, weight, and power consumption can be prohibitively large, optical access may be limited, and active pumping is often required. Here, we present a centiliter-scale ceramic vacuum chamber with He-impermeable viewports and an integrated diffractive optic, enabling robust laser cooling with light from a single polarization-maintaining fiber. A cold atom demonstrator based on the vacuum cell delivers 107 laser-cooled 87Rb atoms per second, using minimal electrical power. With continuous Rb gas emission, active pumping yields a 10−7 mbar equilibrium pressure, and passive pumping stabilizes to 3×10−6 mbar with a 17 day time constant. A vacuum cell, with no Rb dispensing and only passive pumping, has currently kept a similar pressure for more than 500 days. The passive-pumping vacuum lifetime is several years, which is estimated from short-term He throughput with many foreseeable improvements. This technology enables wide-ranging mobilization of ultracold quantum metrology.
Compact ultra-high vacuum systems are key enabling components for cold atom technologies, facilitating extremely accurate sensing applications. There has been important progress towards a truly portable compact vacuum system, however size, weight and power consumption can be prohibitively large, optical access may be limited, and active pumping is often required. Here, we present a centilitre-scale ceramic vacuum chamber with He-impermeable viewports and an integrated diffractive optic, enabling robust laser cooling with light from a single polarization-maintaining fibre. A cold atom demonstrator based on the vacuum cell delivers 107 laser-cooled 87Rb atoms per second, using minimal electrical power. With continuous Rb gas emission active pumping yields a 10−7mbar equilibrium pressure, and passive pumping stabilises to 3×10−6mbar, with a 17day time constant. A passively-pumped vacuum cell, with no Rb dispensing, has currently kept a similar pressure for a year. The passive-pumping vacuum lifetime is several years, estimated from short-term He throughput, with many foreseeable improvements. This technology enables wide-ranging mobilization of ultracold quantum metrology.
We show that micro-machined non-evaporable getter pumps (NEGs) can extend the time over which laser cooled atoms can be produced in a magneto-optical trap (MOT), in the absence of other vacuum pumping mechanisms. In a first study, we incorporate a silicon-glass microfabricated ultra-high vacuum (UHV) cell with silicon etched NEG cavities and alumino-silicate glass (ASG) windows and demonstrate the observation of a repeatedly-loading MOT over a 10 min period with a single laser-activated NEG. In a second study, the capacity of passive pumping with laser activated NEG materials is further investigated in a borosilicate glass-blown cuvette cell containing five NEG tablets. In this cell, the MOT remained visible for over 4 days without any external active pumping system. This MOT observation time exceeds the one obtained in the no-NEG scenario by almost five orders of magnitude. The cell scalability and potential vacuum longevity made possible with NEG materials may enable in the future the development of miniaturized cold-atom instruments.
Quantum sensors, like optical lattice clocks, undergo a continuous development from lab-based towards mobile systems. A key aspect in the miniaturization of the experimental setups is the development of compact atom sources. Conventional atom sources for alkaline-earth-like elements consist of a high-power oven and a six-beam magneto-optical trap (MOT) inside of vacuum chamber with extensive flanges, viewports and electrical feedthroughs. Here we present a highly compact vacuum package utilizing key technologies for future quantum sensor systems: A chip-based low-power atomic oven, a planar grating MOT chip, and a miniaturized vacuum pump all held inside an additively manufactured titanium vacuum chamber, featuring custom-sized vacuum flanges. In this miniaturized setup, spanning a volume of only 750 ml, we trap up to 105 Sr atoms in a MOT, requiring an oven heating power below 1 W.