Optical cavity characterization with a mode-matched heterodyne sensing scheme

Area of Science:

• Optics and Photonics
• Laser Physics
• Cavity Quantum Electrodynamics

Background:

• Optical cavities are fundamental components in various laser systems and scientific experiments.
• Precisely characterizing cavity parameters like mirror transmissivity and optical losses is crucial for optimizing performance.
• Existing methods may suffer from spatial coupling dependencies or require ex-situ measurements.

Purpose of the Study:

• To present a novel, in-situ technique for measuring the complex reflectivity of optical cavities.
• To enable precise determination of individual mirror transmissivities and round-trip optical losses.
• To demonstrate the technique's independence from laser coupling configurations.

Main Methods:

• Utilizing a resonant local oscillator laser and an auxiliary probe laser coupled to opposite ends of the optical cavity.
• Employing a heterodyne sensing scheme to analyze the interference beat-note between reflected and transmitted fields.
• Leveraging the local oscillator's passage through the cavity to ensure in-situ eigenmode measurements.

Main Results:

• Demonstrated the technique on a 19-meter optical cavity.
• Achieved accurate measurements of individual mirror transmissivities.
• Quantified round-trip optical losses with an accuracy of several parts per million.

Conclusions:

• The developed technique offers a robust and accurate method for in-situ optical cavity characterization.
• This approach overcomes limitations of previous methods by being independent of spatial laser coupling.
• The high accuracy achieved opens possibilities for advanced optical system design and metrology.