We demonstrate an integrated photonics infrastructure for atomic laser cooling. We trap 5 x 106 87Rb atoms in a magneto-optical trap using free-space cooling beams emitted from a SiN photonic integrated circuit.
Abstract Cold atoms are important for precision atomic applications including timekeeping and sensing. The 3D magneto-optical trap (3D-MOT), used to produce cold atoms, will benefit from photonic integration to improve reliability and reduce size, weight, and cost. These traps require the delivery of multiple, large area, collimated laser beams to an atomic vacuum cell. Yet, to date, beam delivery using an integrated waveguide approach has remained elusive. Here we report the demonstration of a 87 Rb 3D-MOT using a fiber-coupled photonic integrated circuit to deliver all beams to cool and trap > 1 ×10 6 atoms to near 200 μK. The silicon nitride photonic circuit transforms fiber-coupled 780 nm cooling and repump light via waveguides to three mm-width non-diverging free-space cooling and repump beams directly to the rubidium cell. This planar, CMOS foundry-compatible integrated beam delivery is compatible with other components, such as lasers and modulators, promising system-on-chip solutions for cold atom applications.
The creation of cold atoms underpins quantum sensing and precision metrology, computing, timekeeping, and fundamental science experiments. Miniaturizing the lasers and optical infrastructure, which occupy over 80% of the volume of these experiments, through photonic integration could improve robustness, reliability, and manufacturability while reducing cost and enabling portable space-based precision measurements and quantum tools for non-experts. Yet, there has been limited progress towards integration of the laser and optical infrastructure required to generate cold atoms onto a single chip. We demonstrate a photonic engine that generates, controls, and delivers precision light to create cold atoms in a rubidium 3-dimensional magneto-optical trap (3D-MOT). We integrate on a single chip two frequency-agile self-injection-locked lasers, laser frequency and intensity control, passive beam combining and splitting, signal monitoring, and high-efficiency beam delivery to a rubidium vapor cell. The integrated engine is shown to support multiple functions required for generating cold atoms including stable generation of low-noise cooling and repump light, frequency control for atom spectroscopy and stabilization, real-time laser monitoring, routing for laser offset locking, optical power modulation, and large-area three-beam delivery of 3 mW to the physics package. Fully electrically controlled, the engine enables sustained 3D-MOT operation, trapping more than 1 million atoms at an average temperature of 350 uK and supporting atom-number and temperature measurements. These results demonstrate the first single-chip integration of light generation, control, and delivery for cold-atom generation, offering a path toward smaller, more robust, and manufacturable cold-atom systems for applications including cold-atom clocks and sensors.
Magneto-optical traps (MOTs), indispensable to cold-atom-based quantum computing and quantum precision measurement, are increasingly desired in compact and stable form. Particularly, the six-beam 3D-MOT, distinguished by symmetric geometry and superior trapping performance, finds particularly broad applications. Conventional implementations, however, rely on complex and bulky free-space optics, hindering miniaturization, practical assembly, and long-term stability. Here, we demonstrate a compact six-beam 3D-MOT system that employs two multifunctional optical metasurface chips to implement the optical-field functionalities required for cooling and trapping atoms. By combining two metasurface chips and a vacuum cell, a photonic-integrated cell module (PICM) is implemented as the core assembly and the volume is only" 73*73*107 mm^3" . In success, 1.3 * 10^3 Rb atoms are trapped and cooled to the temperature of ~183 μK. It should be noticed that the laser beam is guided to the metasurface through optical fiber, thus such fully fiber-coupled architecture enables straightforward and stable operations. We believe that this work would pave a practical route toward compact and portable 3D-MOT.
Cold atoms play an important role in fundamental physics, precision timekeeping, quantum and gravitational sensing, precision metrology, and quantum computing. The three-dimensional magneto-optical trap (3D-MOT) is a fundamental tool used to create large populations of cold atoms and serves as an integral component for a wide range of quantum and atomic experiments. The 3D-MOT employs laboratory-scale laser systems to trap, cool, manipulate, and interrogate atoms and quantum states. Photonic integration has reached a point where it is possible to generate, control, and deliver light to atomic transitions and provides a path to integrated 3D-MOTs. We review progress and discuss potential paths toward integration of 3D-MOT lasers and optics with focus on the ultra-low loss silicon nitride photonic integration platform. We review 3D-MOT technology, building blocks and components, and discuss characteristics of the lasers, optics, and atomic physics package. We discuss how the silicon nitride platform can be used to perform MOT functions including cooling, trapping, and spectroscopy. An illustrative example of a rubidium photonic integrated MOT (PICMOT) is used to describe possible paths forward to integration. We also discuss how photonic integration can support lower temperatures and atom trapping and manipulation in integrated cold-atom platforms for quantum sensing and computing.
The high-precision gravity measurements of cold atom experiments puts highly demands on the design and qualification of magneto-optical trap. We present a new modular magneto-optical trap for the cooling and manipulation of rubidium atom interferometry based on free space optical bench technology, which has been developed for a portable atomic inertial sensor. The setup consists of an integrated cooling laser injecting module, a free space bench module, an integrated Raman laser injecting module and a reflecting mirror attached to a single tri-axial accelerometer. The traditional magneto-optical trap includes 3 pairs of commercial cooling laser injecting lens, which are hard to assembled together in 3 mutually perpendicular directions and intersected at a common point. This paper introduces a new free space bench method to meet the angle and position requirements of magneto-optical trap. The vertical angle error of each pair of Cooling beams and intersection coincidence distance can be controlled in a small range. And the free space bench module is easy to control the parameters of laser beams, such as power and polarization. Theoretical analysis and experimental results show that the new modular magneto-optical trap is more reliable and robust in comparison with traditional MOT.