Space-time coherence of polychromatic propagation-invariant fields

Area of Science:

• Optics and Photonics
• Wave Phenomena
• Coherence Theory

Background:

• Propagation-invariant fields maintain their transverse shape during propagation.
• Polychromatic fields consist of multiple frequencies.
• Spatial coherence describes the correlation of wave disturbances across space.

Purpose of the Study:

• To analyze the spatial coherence properties of polychromatic stationary propagation-invariant fields in the space-time domain.
• To investigate the influence of spectral bandwidth on coherence for specific field types (X waves).

Main Methods:

• Theoretical analysis of polychromatic stationary propagation-invariant fields.
• Examination of space-frequency and space-time domain coherence.
• Focus on fields with frequency-independent cone angles (X waves).

Main Results:

• These fields are generally partially coherent in the space-time domain.
• Transversely achromatic fields with complete transverse coherence are an exception.
• For X waves, space-time coherence radius critically depends on spectral bandwidth.

Conclusions:

• The spectral bandwidth significantly impacts the spatial coherence of X waves.
• Coherence area radius can be comparable to the monochromatic component's central lobe radius.
• Understanding these coherence properties is crucial for applications involving complex light fields.