Design and performance of the ALPS II regeneration cavity

Area of Science:

• Experimental Physics
• Particle Physics
• Optics and Photonics

Background:

• The regeneration cavity (RC) is essential for the Any Light Particle Search II (ALPS II) experiment, amplifying signals from axions and axion-like particles.
• Minimizing optical losses in the RC is vital for maximizing resonant enhancement and improving the experiment's figure of merit.

Purpose of the Study:

• To minimize optical losses in the ALPS II regeneration cavity.
• To achieve the longest possible storage time for a two-mirror optical cavity.

Main Methods:

• Constructed a 123-meter long, two-mirror optical cavity for the ALPS II experiment.
• Measured the round-trip optical losses and storage time of the regeneration cavity.

Main Results:

• Demonstrated the longest storage time for a two-mirror optical cavity at 7.17 ± 0.01 ms.
• Achieved a cavity linewidth of 44.4 Hz and a finesse of 27,500 at a 1064 nm wavelength.

Conclusions:

• The achieved storage time and low optical losses are critical for the ALPS II experiment's sensitivity to axion-like particles.
• The results represent a significant advancement in optical cavity technology for high-sensitivity particle physics experiments.