The Fabry–Pérot interferometer is an optical device that uses multiple reflections between two parallel, highly reflective surfaces (mirrors) to produce interference fringes. Unlike simpler two-beam setups, it enhances interference by allowing light to bounce many times between the mirrors, leading to sharp and high-contrast fringes.
How It Works:
- A light wave enters the cavity between the two mirrors.
- It reflects back and forth multiple times, and each partially transmitted wave interferes with the others.
- Constructive interference occurs only for specific wavelengths that satisfy the resonance condition, producing bright fringes.
Key Features:
- High resolution: Because of multiple reflections, it can distinguish very small differences in wavelength, making it ideal for spectroscopy.
- Adjustability: By changing the mirror spacing or angle of incidence, the interferometer can be tuned to different wavelengths or frequencies.
Applications:
- Spectral analysis of light from stars or lasers.
- Refractive index measurements in materials.
- Laser cavity design and telecommunications.
The Fabry–Pérot interferometer is a cornerstone of modern optics, enabling highly accurate measurements of wavelength, frequency, and other optical properties.