Fig. 2: Excess noise autocorrelation can characterize spectrometers.

a Excess noise autocorrelation matrix from a previously reported visible light OCT spectrometer²⁰. The zoom-ins of the autocorrelation matrix show a thinner quasi-diagonal at central wavelengths than at peripheral wavelengths in the spectrum. b The spectral resolution measured from this autocorrelation matrix with the proposed method agrees well with the conventional interferometry and narrowband laser calibration method results. c Vertical shifting of the sensor (as depicted in Fig. 1a), relative to the optimal position, mainly changes the intensity measured by the pixels (dots). Shift 1 denotes the smallest shift, while shift 3 denotes the largest shift from the optimal position. Due to the small magnitude of the shift relative to the translation stage screw pitch, the shifts were not precisely measured. d Axial shifting of the sensor (as depicted in Fig. 1a) towards the focusing lens, relative to the optimal position, mainly changes the spectral resolution. The subplot shows the summed total spectrum intensity for each shift normalized to the total spectrum intensity at the optimal position