Shot-Noise Limited Time-Encoded Raman Spectroscopy

Figure 4

The result of averaging on the TICO-Raman spectrum of benzene. The lower, blue spectrum is the nonaveraged spectrum. The signal (3060 cm⁻¹ peak) is 34 times higher than the standard deviation of the areas in I or II. Averaging leads to much increased Raman spectra and new spectral features become visible. The different spectra were vertically offset for clarity. The increase in signal-to-noise ratio (SNR) over the amount of averaging is plotted on the right, where two different regions of the spectrum were used to calculate the noise. Region I shows a higher standard deviation due to the contribution of an additional effect—we assume cross-phase modulation (XPM, see text). In region II, this effect is constant and does not enter the standard deviation, leading to an almost optimal square root increase in SNR.