Measuring the phase of spatially coherent polychromatic fields

Area of Science:

• Optics and Photonics
• Wave Phenomena
• Quantum Optics

Background:

• Realistic optical fields are inherently polychromatic, meaning they contain multiple frequencies.
• The concept of phase in polychromatic fields is complex and not easily defined.
• Wolf's theory suggests that under strict spatial coherence, polychromatic fields can be represented by an associated monochromatic wave.

Purpose of the Study:

• To investigate the relationship between the phase of second-order correlations and the phase of an associated monochromatic wave for polychromatic fields.
• To determine if measuring correlation phase can define the phase of a polychromatic optical field.
• To experimentally verify the theoretical prediction using a new interferometric method.

Main Methods:

• Theoretical analysis based on Wolf's work on spatial coherence.
• Development and application of a novel interferometric technique.
• Measurement of the cross-spectral density of steady-state optical fields.

Main Results:

• Demonstrated that the phase of second-order correlations directly determines the phase of the associated monochromatic wave for spatially coherent polychromatic fields.
• Successfully verified the theoretical prediction through experimental measurements.
• The novel interferometric technique proved effective for measuring the cross-spectral density.

Conclusions:

• The phase of second-order correlations provides a direct and measurable phase for spatially coherent polychromatic optical fields.
• This work simplifies the interpretation of phase in complex, realistic optical fields.
• The experimental validation opens avenues for advanced optical field characterization.