Filtering the spectrum of multi-longitudinal lasers by using optical retarders

Design and practical realization of photonic filters using segments of polarization maintaining optical fibers (PMF) are reported in this work. These photonic filters can modify the spectrum of wide-band optical sources (multi-longitudinal laser or broadband LED). An optical delay, when introduced on the emission of a wide-band optical source, modify its optical autocorrelation and hence its optical spectrum. Optical delays can be generated by optical retarders such as segments of PMF´s or birefringent crystals. In the frequency domain, the optical retarders act as photonic filters. The selective optical filtering of multi-longitudinal laser modes, when matching the photonic filters to the laser spectrum is demonstrated in this paper.