Source: Site du groupe Calva

Understanding Resonant Mode Cleaners in Photonics

Introduction

A resonant mode cleaner is a device used in photonics to improve the beam quality of high-power laser beams by transmitting only the fundamental (Gaussian) mode while attenuating higher-order modes. This process helps in achieving a cleaner beam profile and spectral filtering.

Working Principle

When a laser beam with a single optical frequency is passed through an optical cavity (resonator), the frequencies of the higher-order resonator modes do not align with the fundamental mode frequencies due to the Gouy phase shift. By locking the laser frequency to a fundamental mode resonance, higher-order modes are strongly attenuated, resulting in an improved beam quality and spectral cleanup.

Applications

Resonant mode cleaner cavities are commonly used in large-scale interferometers for gravitational wave detection where high beam quality is crucial. These cavities can provide superior beam cleanup and spectral filtering compared to nonresonant mode cleaners, especially at high optical powers.

Design Considerations

Optimizing the mode matching of the input beam to the fundamental mode of the resonator is essential for high power efficiency. While resonant mode cleaners offer significant advantages, they require precise mode matching and are more complex to design and set up compared to nonresonant alternatives.

Conclusion

Resonant mode cleaners play a vital role in enhancing beam quality and spectral purity in high-power laser systems. Their ability to selectively transmit the fundamental mode while attenuating higher-order modes makes them indispensable in applications requiring precise beam control and spectral filtering.

Source: Advanced LIGO
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