Deconvolutional Suppression of Resolution Degradation in Coherent Optical Spectrum Analyzer

Optical spectral analysis is essential to demonstrate the light-matter interactions from the frequency domain. Although the existing coherent spectrum analyzers (COSA) have already achieved resolutions of similar to 50 fm, the mirror effect limits the further improvement in spectral resolution and thus the detection of low-concentration, small-scale analytes. Focusing on this problem, we first formulate the resolution degradation of COSA caused by the mirror effect, indicating the tuning nonlinearity of the local oscillator could introduce a non-stationary disturbance to the spectral data sampled at equal time intervals. Subsequent theoretical and experimental works have proved that the combination of dynamic wavelength calibration and spectral deconvolution can suppress the non-stationary disturbance. And the spectral resolution could reach 8 fm without extra compressions. This deconvolution-based scheme also avoids the long fibers used in scattering compressed schemes, improving the system's environmental stability.