Detecting objects deep within scattering media via multi-wavelength intensity interferometry

Normally, two wavefronts interfere, if they are coherent. With the help of a scattering medium, though, an interferometric signal can be artificially generated by any two wavefronts, as long as they are within the memory effect range of the medium. Here, we exploit this phenomenon to gain information about objects hidden deep within scattering media. Conventional memory effect protocols require the object to be within the memory effect range, which necessitates thin media. Moreover, they usually require the medium to interact with the far field pattern of the object. Both conditions are violated, if the object is immersed in an extended scattering medium. Here, we demonstrate that we can retrieve object information in such a scenario with the help of intensity interferometric measurements: We illuminate the scene with two wavelengths, which are within the spectral memory effect of the medium. By calculating the correlation coefficient of the resulting speckle patterns at several lateral positions, we are able to retrieve the diffraction pattern of the object in the difference wavelength and hence gain information about the object. 28 erferometrie T nder Bielke