Cross-spectral purity-a fundamental property of light: tutorial

Area of Science:

• Optics and Photonics
• Coherence Theory

Background:

• Cross-spectral purity is a fundamental concept in coherence research.
• Its connection to spatiotemporal separability generalizes field separability to correlation functions.

Purpose of the Study:

• To introduce cross-spectral purity to the wider optics community.
• To discuss its definitions, properties, generation, and detection.
• To highlight its experimental significance.

Main Methods:

• Review of theoretical definitions and properties of cross-spectral purity.
• Discussion of methods for generating and detecting cross-spectral purity.
• Analysis of experimental implications.

Main Results:

• Cross-spectral purity is intimately linked to spatiotemporal separability.
• The concept is implicitly assumed in many optical experiments.
• It has observable effects across diverse applications.

Conclusions:

• Cross-spectral purity is a crucial, yet under-recognized, concept in optics.
• Understanding and utilizing cross-spectral purity can advance fields like quantum optics and ghost imaging.