Effects of carrier-induced modal intermodulation on dynamic spectral characteristics of multimode Fabry-Pérot lasers

The physical mechanism attributed to producing 'rabbit-ears' on the chirped multimode optical spectra of gain-switched Fabry-Pérot semiconductor lasers is investigated thoroughly. It has been observed experimentally that the short-wavelength rabbit-ears are dominant in the short-wavelength longitudinal modes. However, the long-wavelength rabbit-ears are dominant in the modes near the lasing wavelength, while the short-wavelength rabbit-ears are again dominant in the longest-wavelength modes. In this paper, the unequal rabbit-ears of each mode and the asymmetric chirped spectrum are shown to be a result of the dynamic power transfer between the modes during the gain-switched optical pulse due to carrier-induced modal intermodulation. Such an understanding, and the ability to model accurately this characteristic, is also shown to be essential for designing Fabry-Pérot laser systems, for short-haul applications such as fibre-to-the-home.