Fig. 2

a Schematic diagram of a Raman spectrometer adapted from Butler et al.²⁰ (Permission obtained from Nature Publishing Group). Excitation light is represented by a blue line, while the green line represents scattered light. Excitation light travels from the laser source, through narrow band pass filters, beam expander and a dichroic mirror. It is then reflected off a mirror into a system of optics where it is directed onto the sample. Light scattered from the sample is collected by the optics and is directed by focusing mirror and long pass filters onto a grating through which it is dispersed. This dispersed light is finally focused onto the detector. b Raman spectrum of phenylalanine crystals using a 532 nm laser at 30 mW power and 1 s exposure using a 50× air objective. Spectral resolution of the system is 0.5 cm⁻¹