Retarders, also called wave plates, are optical devices that alter the phase difference between two perpendicular polarization components of a light wave.
How They Work:
- Made from birefringent materials (like quartz or mica) that have different refractive indices for different polarization directions.
- When linearly polarized light enters a wave plate, its perpendicular components travel at different speeds, creating a phase shift.
- This phase shift changes the polarization state of light (e.g., from linear to elliptical or circular).
Common Types:
- Quarter-wave plate: Introduces a 90° (π/2) phase shift — converts linearly polarized light to circular or elliptical polarization.
- Half-wave plate: Introduces a 180° (π) phase shift — rotates the polarization direction of linearly polarized light.
Applications:
- Used in polarization microscopy, optical communication, quantum optics, and laser systems to manipulate and analyze the polarization of light.
Wave plates are essential for precise control of light polarization in advanced optical systems.