  Optical metasurfaces revolutionized the approach to moulding the propagation
of light by enabling simultaneous control of the light phase, momentum,
amplitude and polarization. Thus, instantaneous spectropolarimetry became
possible by conducting parallel intensity measurements of differently
diffracted optical beams. Various implementations of this very important
functionality have one feature in common - the determination of wavelength
utilizes dispersion of the diffraction angle, requiring tracking the diffracted
beams in space. Realization of on-chip spectropolarimetry calls thereby for
conceptually different approaches. In this work, we demonstrate that random
nanoparticle arrays on metal surfaces, enabling strong multiple scattering of
surface plasmon polaritons (SPPs), produce upon illumination complicated SPP
scattered patterns, whose angular spectra are uniquely determined by the
polarization and wavelength of light, representing thereby spectropolarimetric
fingerprints. Using um-sized circular arrays of randomly distributed
{\mu}m-sized gold nanoparticles (density ~ 75 {\mu}m$^-$$^2$}) fabricated on
gold films, we measure angular distributions of scattered SPP waves using the
leakage radiation microscopy and find that the angular SPP spectra obtained for
normally incident light beams different in wavelength and/or polarization are
distinctly different. Our approach allows one to realize on-chip
spectropolarimetry by fingerprinting using surface nanostructures fabricated
with simple one-step electron-beam lithography.
