Raman Emission (also Spontaneous Raman Emission) can be used to identify specific chemical bonds, which can be translated to identifying specific chemical species. For more complex samples, that would mean identifying between different types of objects (for instance, the material of a particle, or the type of bacteria).
However, Raman emission tends to be very weak, which forces the adoption of high-NA objectives, long exposure times, and sensitive detectors. Moreover, the spectral shifts can be relatively small, which adds a spectra resolution requirement to the instruments.
Enhanced Raman Emission emerged as a series of tools tailored to increase the emission. Common approaches include surface enhancement, or field enhancement near tips, for example near constrictions created by nanoparticles.
Compressive Raman sits on the other side, increasing the sensitivity of the detection. Instead of acquiring a full spectrum, a spatial light modulator directs only some wavelengths to a very sensitive SPAD (detector or array).