研究目的
Developing a new clock laser system with a frequency stability below 10-16 for rapid evaluation of ytterbium lattice clocks.
研究成果
The new clock laser system shows promising results with a thermal noise limit of 4.8×10-17 at room temperature. The frequency stability of the new clock laser is much better than the old clock laser, as indicated by the beating signal analysis. Further measurements with an additional identical clock laser will provide exact frequency stability and linewidth data.
研究不足
The frequency stability of the beating signal between the new clock laser and the old clock laser was limited by the latter, indicating that the exact frequency stability and the linewidth of the new clock laser need further measurement.
The new clock laser system is based on second harmonic generation for the 578 nm laser for the Yb clock transition. It uses a tapered amplifier laser system at 1156 nm and a ridge-type waveguide periodically-poled lithium niobate crystal. The optical cavity for the new clock laser is made of a 30-cm-long cuboid-shaped ULE spacer, fused silica mirror substrates, and ULE compensation rings. Crystalline mirror coatings at 1156 nm were used to reduce the thermal noise. The cavity is mounted horizontally by Viton pads at the points with minimum vibration sensitivity, and the temperature of the cavity was stabilized using one aluminum layer for the active temperature control and two passive thermal shields. The 1156 nm laser light was sent to the cavity using a phase-stabilized single-mode polarization maintaining fiber, and the frequency of this laser was stabilized to the resonance of the cavity using the Pound-Drever-Hall method.
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