
238 Handbook of Biomedical Optics
scattering can be performed at any excitation wavelength.
Tuning the excitation wavelength will shi all of the Raman
peaks, while uorescence features remain at xed positions. is
phenomenon can be exploited to discriminate between the two
types of emission; taking the dierence between two such spec-
tra suppresses the uorescence and highlights Raman-related
features. is technique is called shied-excitation Raman dif-
ference spectroscopy (Shreve et al. 1992).
12.3.2 Near-Infrared Absorption
As just noted, the tunability of Raman excitation means that it
can be performed at whatever wavelengt ...