Fabry-Perot based short pulsed laser linewidth measurement with enhanced spectral resolution

A method to accurately measure the linewidth of short laser pulses at a low repetition rate is demonstrated. Based on the principle of parallel plate equal inclination interference, the linewidth of a short-pulse laser with a low repetition rate is measured by using a Fabry-Pe ' rot (F-P) etalon combined with a CMOS beam profiler. The center of the recorded interference pattern is precisely identified using Hough transformation, and a pixel rotation algorithm is applied to maximise the data collected, transforming two-dimensional image information into onedimensional spectral information. This algorithm significantly increases the number of data points, improves the spectral resolution, and reduces the error caused by the size of the CMOS pixel size to less than 1 MHz. The influence of the transmission spectrum width (TSW) of the F-P etalon on the measurement results is analyzed, and we demonstrate a reduction in the error introduced by the TSW of the F-P etalon is through deconvolution. This further improves the measurement quality and provides a means by which etalons with a wide TSW can be applied to the measurement of the linewidth of lasers with low pulse energy.