Source: European Space Agency

The Role of Reference Cavities in Optical Frequency Standards

Introduction

A reference cavity is a passive optical resonator used in optical frequency standards to stabilize the optical frequency of a laser. This stabilization is essential for achieving high-frequency stability in various applications.

Frequency Stabilization Mechanism

The optical frequency of a laser can be stabilized to the frequency of a resonance of the reference cavity. This process, known as frequency locking, involves using electronic feedback systems based on methods like the Pound–Drever–Hall or Hänsch–Couillaud method.

Advantages of Reference Cavities

Compared to laser resonators, passive reference cavities offer higher stability as they lack the disturbances introduced by laser gain media. They can have a high finesse and Q factor, leading to precise determination of resonance frequencies. Various measures, such as rugged construction, low thermal expansion spacer materials, thermal isolation, and power level control, contribute to achieving extraordinary stability.

High Frequency Stability

By implementing stringent measures in frequency metrology laboratories, reference cavities can provide stability to lasers with short-term linewidths below 1 Hz. This level of stability is crucial for applications requiring high precision and accuracy.

Future Developments

Ongoing research aims to further improve the stability and performance of reference cavities, paving the way for advancements in optical frequency standards and related technologies.

Conclusion

Reference cavities play a vital role in ensuring the high-frequency stability of lasers in optical frequency standards. Their ability to provide precise frequency references is essential for a wide range of scientific and technological applications.

Source: ResearchGate
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