We miniaturized the complex optical system responsible for the cooling, pumping, and imaging of an on-chip-based cold-atom inertial sensor. This optical bench uses bonded miniature optics and includes all the necessary optical functions. The bench has a volume of 35×25×5cm 3 . We developed a laser frequency lock adapted to the optical bench using saturated absorption in a rubidium cell. The entire laser source based on frequency doubling of 1.56 µm fiber lasers, including the control system and the saturated absorption module, fits in a 5 U rack. Using the miniaturized bench, we realized two- and three-dimensional magneto-optical traps for rubidium 87 atoms.
We miniaturized the complex optical system responsible for the cooling, pumping, and imaging of an on-chip-based cold-atom inertial sensor. This optical bench uses bonded miniature optics and includes all the necessary optical functions. The bench has a volume of 35×25×5cm 3 . We developed a laser frequency lock adapted to the optical bench using saturated absorption in a rubidium cell. The entire laser source based on frequency doubling of 1.56 µm fiber lasers, including the control system and the saturated absorption module, fits in a 5 U rack. Using the miniaturized bench, we realized two- and three-dimensional magneto-optical traps for rubidium 87 atoms.
In this study, a miniature laser frequency stabilization module for cold atom sensing applications was designed and realized.The module can lock the laser frequency to the saturated absorption spectrum of the D2 line of rubidium (Rb) atoms using the frequency modulation spectroscopy method.The module core is a tiny Rb cell, co-packaged with the saturation absorption optical setup, temperature control circuit, and detection circuit through a joint optical-mechanical-electrical design for a total volume of only 40 mm × 15 mm × 30 mm.The frequency fluctuation of the 780 nm laser after frequency stabilization by the module was within 1 MHz over 1000 s, which is adequate for magneto-optical trap experiments.The results verify the feasibility of the module as a frequency reference and provide a light source for portable cold atom sensing devices.
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.
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.
To simplify applications that rely on optical trapping of cold and ultracold atoms, ColdQuanta is developing techniques to incorporate miniature optical components onto in-vacuum atom chips. The result is a hybrid atom chip that combines an in-vacuum micro-optical bench for optical control with an atom chip for magnetic control. Placing optical components on a chip inside of the vacuum system produces a compact system that can be targeted to specific experiments, in this case the generation of optical lattices. Applications that can benefit from this technology include timekeeping, inertial sensing, gravimetry, quantum information, and emulation of quantum many-body systems. ColdQuanta’s GlasSi atom chip technology incorporates glass windows in the plane of a silicon atom chip. In conjunction with the in-vacuum micro-optical bench, optical lattices can be generated within a few hundred microns of an atom chip window through which single atomic lattice sites can be imaged with sub-micron spatial resolution. The result is a quantum gas microscope that allows optical lattices to be studied at the level of single lattice sites. Similar to what ColdQuanta has achieved with magneto-optical traps (MOTs) in its miniMOT system and with Bose- Einstein condensates (BECs) in its RuBECi(R) system, ColdQuanta seeks to apply the on-chip optical bench technology to studies of optical lattices in a commercially available, turnkey system. These techniques are currently being considered for lattice experiments in NASA’s Cold Atom Laboratory (CAL) slated for flight on the International Space Station.
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.