Jinyin Wan

Scheme for a compact cold-atom clock based on diffuse laser cooling in a cylindrical cavity

We present a new scheme of compact Rubidium cold-atom clock which performs the diffuse light cooling, the microwave interrogation and the detection of the clock signal in a cylindrical microwave cavity. The diffuse light is produced by the reflection of the laser light at the inner surface of the microwave cavity. The pattern of injected laser beams is specially designed to make most of the cold atoms accumulate in the center of the microwave cavity. The microwave interrogation of cold atoms in the cavity leads to Ramsey fringes whose line-width is 24.5 Hz and the contrast of 95.6% when the free evolution time is 20 ms. The frequency stability of

Improvement in medium long-term frequency stability of the integrating sphere cold atom clock

7.3\times10^{-13}\tau^{-1/2}

Dick Effect in the Integrating Sphere Cold Atom Clock

has been achieved recently. The scheme of this physical package can largely reduce the complexity of the cold atom clock, and increase the performance of the clock.

Reaching 5.0×10-13 τ -1/2 short term frequency stability of the integrating sphere cold atom clock

The medium long-term frequency stability of the integrating sphere cold atom clock was improved. During the clock operation, Rb87 atoms were cooled and manipulated using cooling light diffusely reflected by the inner surface of a microwave cavity in the clock. This light heated the cavity and caused a frequency drift from the resonant frequency of the cavity. Power fluctuations of the cooling light led to atomic density variations in the cavity’s central area, which increased the clock frequency instability through the cavity pulling effect. We overcame these limitations with appropriate solutions. A frequency stability of 3.5×10−15 was achieved when the integrating time τ increased to 2×104 s.

A large-scale cold atom source in an integrating sphere

The Dick effect is an important factor limiting the frequency stability of sequentially-operating atomic frequency standards. Here we study the impact of the Dick effect in the integrating sphere cold atom clock (ISCAC). To reduce the impact of the Dick effect, a 5 MHz local oscillator with ultra-low phase noise is selected and a new microwave synthesizer is built in-house. Consequently, the phase noise of microwave signal is optimized. The contribution of the Dick effect is reduced to (τ is the integrating time). The frequency stability of is achieved. The development of this optimization can promote the space applications of the compact ISCAC.

Optical-plus-microwave pumping in a magnetically insensitive state of cold atoms

We present an improvement of short term frequency stability of the integrating sphere cold atom clock after increasing the intensities of clock signals and optimizing the feedback loop of the clock. A short term frequency stability of 5.0×10-13 τ -1/2 has been achieved and the limiting factors have been analyzed.

Reaching a few 10 -15 long-term stability of integrating sphere cold atom clock

An integrating sphere with a diameter of 10 cm is developed for cooling atoms. The maximum number of 2 × 1010 cold atoms is obtained from a background vapor with 220 mW cooling laser power. The cold atom number can be increased by further increasing the cooling power. Such cold atom source would have potential use for Raman–Ramsey atomic clock with good signal-to-noise ratio (SNR).