Wavelength-dependent speckle multiplexing for imaging through opacity

Abstract Memory-effect-based speckle-correlated imaging through opacity has been exploited widely in recent years. Generally, spatially incoherent light sources are required to provide effective illumination that can eliminate the interference noise. Here, the wavelength-dependent speckle multiplexing (WDSM) technique is first proposed and demonstrated as an effective method to suppress the interference noise, thereby facilitating the use of partially spatially coherent light as an alternative promising illuminating source. In contrast to the conventional decoherent approach which often employs a rapidly rotating diffuser to reduce the spatial coherence of a spatially coherent light, the WDSM shows greatly enhanced structural robustness by combining a tunable laser and the speckle illumination using a multimode fibre. The proposed WDSM not only expands the scope of candidate light sources for speckle-correlated imaging based on the classical phase-retrieval algorithm, but also enables the multi-channel detection determined by the speckle spectral decorrelation, which would further facilitate the waveband selective light-matter detection through opacity. This work also combines the advantages of fibre optics and laser technology and enriches the potential applications of speckle-correlated imaging.