Second-order correlated interference with multi-wavelength thermal-light beams

A method for correlating thermal light over a wide spectral range is proposed. A multi-wavelength pseudothermal source, prepared by projecting laser beams of multiple wavelengths (650 nm, 635 nm, 532 nm, and 473 nm) onto a moving thin ground glass plate, is employed in a double-slit interference experiment. The ground glass plate induces random phase differences between light beams of different wavelengths passing through it. This initial random phase difference significantly influences the high-order intensity correlation functions of multi-wavelength thermal beams. Experimentally, second-order correlated interference patterns, including subwavelength interference, of pseudothermal beams with different wavelengths are observed in the intensity correlation measurements. This method facilitates applications of correlated thermal photons in quantum information processing and quantum imaging.