Table 1 Summary of Raman spectroscopy techniques

Spontaneous Raman spectroscopy

Detects intrinsic Raman scattering of molecules. Can be combined with fibre probes or microscopy to give spatial and biochemical information

Label free, non-invasive and non-destructive, no sample preparation required

Diagnostics, guided surgery,^{53, 54} molecular pathology,^{82, 83, 97} stem cell research,^{24, 65, 67,68,69, 98} tissue engineering^70,71,72,73

RRS

Particular bands enhanced by matching the excitation wavelength with electronic resonance of molecules, can be coupled with SERS

10³–10⁵-fold increase in signal-to-noise, chromophores can be investigated

Characterising specific biomolecules e.g., carotenoids, cytochrome^{25, 26, 99}

SERS

Raman signal is enhanced using roughened metal surface e.g., nanoparticles, metal coated slide

10⁶-fold increase in signal-to-noise, functionalised nanoparticles

pH and redox measurements,^{33, 34} cell-based assays,^{100, 101} immunoassays¹⁰²

SORS

Raman signal measured at site offset from point of excitation, to collect diffusely scattered photons

Allows greater penetration into sample, more depth information in thicker tissues

Potential detection of calcifications and cancer margins in breast tissue^{41, 43}

SRS/CARS

Non-linear variants requiring pulsed, synchronised laser source.

Video rate, label free biomolecular imaging, 5× increase in signal-to-noise

Imaging specific molecules of interest e.g., hydroxyapatite, lipids, drugs^{47, 62, 84}