Morphology and statistics of wide-spectrum speckles.

Although the theory of scattered speckles was initially established via idealization of treating the incident light as monochromatic, phenomenon and regulations of wide-spectrum speckles are yet urgent to be studied, with immense growing applications of broadband source such as femtosecond laser, light-emitting-diode and sunlight illumination. Here we quantitatively analyze the morphology and statistics of speckles produced by a point-like source with wide-spectrum, using a phase plate model to describe the scattering layer. Due to differences in induced phase related to wavelength, wide-spectrum speckle patterns appear radial divergence in intensity distribution, as well as in visibility of both speckles and that of the second-order coherence. This is significantly different from the translation-invariance of monochromatic speckles. The spatially-varying morphology and statistics of the speckles contain spatial and spectral information of the incidence, thus can be used as an indicator to achieve optical metrology or sensing with a wide-spectrum source in the scattering environment.