We demonstrate an integrated laser system for the mobile integrating sphere cold atom clock. Three distributed Bragg reflector diode lasers (780 nm) with custom drive circuits are used for the cooling, repumping, pumping, and probe lights. Automatic frequency-locking and relocking of the laser are presented. All of the optical elements are integrated on two sides of an aluminum base plate. The mechanical structure is simulated and optimized to minimize the deformation of the base plate. We optimize, measure, and discuss the frequency and intensity noises of the laser system. The techniques and designs used in this laser system can also be used in other mobile platforms for quantum sensing experiments.
We demonstrate an integrated laser system for the mobile integrating sphere cold atom clock. Three distributed Bragg reflector diode lasers (780 nm) with custom drive circuits are used for the cooling, repumping, pumping, and probe lights. Automatic frequency-locking and relocking of the laser are presented. All of the optical elements are integrated on two sides of an aluminum base plate. The mechanical structure is simulated and optimized to minimize the deformation of the base plate. We optimize, measure, and discuss the frequency and intensity noises of the laser system. The techniques and designs used in this laser system can also be used in other mobile platforms for quantum sensing experiments.
The free-fall atomic clock has shown considerable potential for long-term stability and mobility, yet reports on its design and implementation remain limited. Herein, we introduce a simple integrated optical system for free-fall cold Rb atomic clocks. A distributed feedback (DFB), frequency-doubled fiber laser, and a 780 nm DFB laser diode are utilized as the cooling and repumping light source, respectively. Both lasers feature a broad mode-hop-free tuning range and reduced sensitivity to acoustic noise. Benefiting from a high signal-to-noise ratio of modulation transfer spectroscopy (MTS), the linewidth of the fiber laser is measured to be 42 kHz. The power and frequency management of the cooling beams is implemented by two 110-MHz acousto-optic modulators (AOMs), enabling a frequency detuning as large as −92 MHz. The power-frequency management module is integrated into a single side bench of 316 mm × 270 mm × 52 mm. The power fluctuation of the probe beam is measured to be 0.8% (RMS) over 24 hours measurement. Using an ultra-high vacuum system, the functionality of the optical system is preliminarily verified by the time-of-flight (TOF) signal of the cold atom cloud.
SummaryDiffuse laser cooling provides a compact cold atom system for quantum precision measurement processes, especially for the integrating sphere cold atom clock. However, the laser cooling system of current integrating sphere cold atom clock is bulky and complex, which is not conductive to the miniaturization of cold atom clock. In order to make a less complex diffuse laser cooling system, we adopt the scheme to combine the fiber mirrors and the diffuse laser cooling technique. The incident laser beams are reflected by the fiber mirrors and teflon, and the atoms can be successfully cooled and detected in the miniaturized zone. The preparation of fiber mirrors and the realization of diffuse laser cooling system with a simple optical system can lay a solid foundation for further miniaturization of the overall system of integrating sphere cold atom clock in the future.
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.
Quantum technologies are nowadays emerging as enabling tools for practical applications, such as quantum sensing, quantum computing and quantum metrology. Lasers play a central role in many of these technological platforms, e.g. for atomic clocks, ion-based or neutral atom-based quantum computers or atom interferometers. Here we present a complete laser system to cool, trap and control strontium atoms in an optical lattice or in tweezer arrays. A sub-Hz linewidth master laser, locked to a high-finesse optical cavity provides the frequency reference for an ultra-low noise comb. The rack-mounted laser system consists of all cooling, repumping, and clock lasers stabilized to the optical frequency comb. Each of the involved laser frequencies can therefore be tuned and mapped in the frequency domain with a high degree of stability. The system is controlled via a software interface, allowing to operate the cold-atom-based physics package autonomously. The system is tailored for the operation of 88Sr or 87Sr optical lattice clocks, or for quantum computing applications, but other sub-Hz lasers could be obtained by phase locking additional clock laser frequencies to the ultra-stable comb, enabling convenient and accurate optical frequency ratio measurements. The laser system architecture and the relevant characterization measurements will be presented, proposing some user-cases such as quantum computing and atom interferometry on strontium atoms. This represents a technological leap for quantum optics, allowing to explore further applications of quantum sensors outside a traditional lab.
We demonstrate an optical frequency standard by locking the output frequency of an external cavity diode laser to the 780 nm D2 transition of diffuse laser cooled 87Rb atoms using frequency modulation spectroscopy (FMS). A 50-cm-long cold atomic cloud is obtained within a ϕ 2 cm ×l 50 cm vacuum glass tube, featuring greater simplicity and reliability. By analyzing the impact of power and detuning of cooling and repumping lasers, and power of frequency-modulated laser on FMS based on cold atoms, we choose the optimal parameter and lock the laser frequency to the 87Rb 52S1/2 (F = 2) → 52P3/2 (F′ = 3) cycling transition. The cold-atom-based optical frequency standard achieves an in-loop frequency stability of 3.3 × 10−15 at 1 s, with peak-to-peak frequency fluctuations being less than 50 Hz within 6000 s. This represents the integration of cold atoms into an optical frequency standard utilizing FMS for frequency stabilization. In contrast to the common cold-atom optical frequency standards, our approach requires fewer lasers and eliminates the need for a complex and expensive Pound–Drever–Hall (PDH) system. Its low complexity makes it a promising candidate for development into a space cold-atom clock, promoting advancements in space science and navigational positioning. Additionally, it possesses great potential to serve as an absolute wavelength standard.
We discuss the characterization and specifications of a home-built external cavity diode laser system that is suitable for frequency-domain cold-atom velocimetry and measurements of gravitational acceleration. The laser system is frequency stabilized using a modulation-free technique that lowers the temperature of a magneto-optical trap (MOT) in comparison with a MOT realized using a laser that relies on lock-in spectroscopy. The laser system also incorporates a feedback loop involving an acousto-optic modulator for intensity stabilization, which reduces the effect of low frequency vibrations. By integrating this laser with a home-built, dual-output radio frequency synthesizer, we are able to derive two laser beams with a precisely controlled relative detuning for frequency domain interferometry using laser-cooled atoms. The detuning can range from the mHz to the MHz level with a stability of 10 μHz.