Cold atom microwave clock based on intracavity cooling in China space station.

Atomic clocks with higher frequency stability and accuracy than traditional space-borne atomic clocks are the cornerstone of long-term autonomous operation of space-time-frequency systems. We proposed a space cold atoms clock based on an intracavity cooling scheme, which captures cold atoms at the center of a microwave cavity and then executes in situ interactions between the cold atoms and microwaves. As a result of the microgravity environment in space, the cold atoms can interact with the microwaves for a longer time, which aids in realizing a high-precision atomic clock in space. This paper presents the overall design, operational characteristics, and reliability test results of the space atomic clock based on the intracavity cooling scheme designed for the operation onboard the China space station. In addition, the engineering prototype performance of the space cold atoms microwave clock is also presented. The ground test results for the clock show a fractional frequency stability of 1.1 × 10-12 τ-1/2 reaching 2.5 × 10-15 at 200,000 s, providing solid technical and data support for its future operation in orbit.

Infrared imaging of polydimethylsiloxane-doped upconversion particle composites.

Short-wave infrared imaging is playing an increasingly important role in present scientific research. However, the high experimental cost limits its application. Based on the upconversion fluorescence effect, we prepared a low-cost composite film for short-wave infrared imaging using upconversion particles and polydimethylsiloxane. The imaging quality and stability of the prepared composite films are examined using an infrared laser. The fluorescence density fluctuation of the composite films at 100 is only 1.2%, and the maximum value of the fluorescence power percentage error caused by the inhomogeneity is only 4.5%. Due to the affordable and easy accessibility, a typical optical laboratory can prepare and use the aforementioned technique in experiments in a short time.

An integrated laser system for the cold atom clock.

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.