Fig. 2: Demonstration of sensitivity and quantification performance of miniaturized Raman system.

a, b Image on CMOS sensor of the SERS spectrum of BPE deposited on nano pillars based SERS substrate at a concentration of 100 µM; signal measured alaser spot size on the sample of 10 µm (a) and 100 µm (b), c SERS spectrum of BPE obtained after the averaging of 3 rows on CMOS image in Fig. 1a, d SERS spectrum of BPE obtained after the averaging of 20 rows on CMOS image in Fig. 1b, e illustration of dynamic QE variation of pixels on CMOS sensor, f, g fluorescence spectrum from glass cover slide excited by laser with excitation wavelength 785 nm obtained after averaging of 10 repetitions without pixel averaging method (f) and with pixel averaging method (g) demonstrating improved SNR ratio, h SORS like sample illumination layout with off-axis laser beam delivery and on-axis Raman beam collection that serves dual purpose: avoiding back reflections to diode laser and minimization of fluorescence impact on the out of focus signals, i photograph of miniaturized Raman spectrometer measuring whiskey content through the glass bottle, j Raman spectrum of whiskey measured by miniaturized Raman system through the glass bottle with on-axis (black curve) and off-axis (red curve) laser beam delivery that demonstrates SORS benefit to avoid the contribution of fluorescence from glass bottle (upper right image is a screen shot from CMOS sensor in the case of off-axis laser beam delivery), k, n Raman spectra of water-ethanol solution (40% of ethanol) with different concentrations of methanol (variation between 0–40%) in the range 400–2300 cm⁻¹ (k) and 2750–4000 cm⁻¹ (n), l, m result of PLS calibration for methanol quantification based on the Raman data in the range 400–2300 cm⁻¹, o, p result of PLS calibration for methanol quantification based on the Raman data in the range 2750–4000 cm⁻¹.