Micro-spatially offset Raman spectroscopy

Similarly to SORS technique, micro-SORS is able to preferentially collect the Raman photons generated under the surface in turbid (diffusely scattering) media.

Micro-SORS is particularly useful when dealing with precious or unique objects as for Cultural Heritage field and Forensic Science or in biomedical applications, where a non-destructive molecular characterization constitute a great advantage.

This more sophisticated micro-SORS variant provides a complete separation of laser excitation and collection zones (Δx offset) that requires a hardware or a software modification to a conventional Raman microscope.

The separation can be achieved by using an external probe or fibre optics to deliver the laser,[13] by displacing the laser spot by moving the beam-steer alignment mirrors,[5][6] by using a spatially resolved CCD,[4] by using a digital micro-mirror device (DMD),[14] by moving the tip of the Raman detection fibre to perform an off-confocal detection of the signal[15] or by combining hyperspectral SORS and defocusing micro-SORS.

[16] Full micro-SORS was proven to be more effective in terms of both penetration depth into the sample and relative enhancement of sublayer signal[13] To reconstruct the micro-layer succession it is required to collect a conventional Raman spectrum and at least a one micro-SORS spectrum; the acquisition of several spectra at gradually increasing defocusing distances or spatial offsets is usually the best way to approach unknown materials.