Injection power and wavelength dependence of an external-seeded gain-switched Fabry-Perot laser

We experimentally investigate a gain-switched Fabry-Perot semiconductor laser externally injection seeded with a narrow linewidth continuous wave laser. We determine the dependence of pulse width, side-mode suppression ratio, and timing jitter on seeding power and seeding wavelength. As external seeding power is increased up to a certain value, we observe negligible change in pulse width, a linear increase in side-mode suppression ratio, and a linear decrease in timing jitter. Exceeding a certain value leads to substantial pulse broadening. By tuning the seeding wavelength across a chirped mode of the laser, we observe the lowest timing jitter and the largest side-mode suppression when the seed wavelength is aligned with the center of the chirped spectrum of a desired mode.