Fig. 1: Optical layout and working principle of miniaturized Raman system.

a Optical scheme of miniaturized Raman system, b reference sample on filter/slit, c, d CMOS sensor image that demonstrates simultaneous acquisition of main and reference Raman signals from laser excitation at 785 nm (c) and 675 nm (d); CMOS images represent Raman spectrum of water-ethanol solution (60:40) in the main channel and Raman spectrum of polystyrene in the reference channel, e, f, h, i laser stability experiment versus time that represents raw Raman spectra variation of polystyrene in the reference channel under laser excitation wavelength 785 nm (e) and 675 nm (h) and variation of raw Raman spectra of polypropylene in the main channel under laser excitation wavelength 785 nm (f) and 675 nm (i), g, j Raman spectra of polypropylene in the main channel versus time under laser excitation wavelength 785 nm (g) and 675 nm (j) after real-time (i) Raman shift, (ii) Raman intensity calibrations, (iii) anti “mode hop” deconvolution, and (iv) spectrum deblurring being applied, k, l time dependent experiment of polystyrene sample placed in the main channel that demonstrates long time calibration stability of the Raman shift (k) and Raman intensity (l), m Raman spectrum of toluene before (black curve) and after (red curve) multiple pre-processing procedures being applied, n, p three Raman spectra of polypropylene at different time points under a laser excitation wavelength of 785 nm (n) and 675 nm (p), o, q Raman spectra of polypropylene before (black curve) and after SERDS correction (red curve) under laser excitation wavelength of 785 nm (o) and 675 nm (q).