Distributed Feedback Raman and Brillouin Fiber Lasers

Distributed feedback Raman and Brillouin lasers use intrinsic gain mechanisms in optical waveguides to produce compact, narrow-linewidth sources in arbitrary spectral bands determined only by the available pump wavelengths. In this chapter, we begin with a theoretical description of Raman DFB lasers. We show how they can be modeled using a set of nonlinear coupled-mode equations. In agreement with a closed-form approximation to the threshold gain, time domain simulations reveal the dependence of threshold and slope efficiency on cavity parameters such as gain, loss, specifics of the grating profile, and nonlinear effects such as two photon absorption. We then review the realizations of narrow-linewidth Raman fiber lasers. We show how different pump schemes and cavities affect the performance and discuss possibilities for improvements. Finally, we describe the Brillouin DFB laser and compare its performance with that of a Raman DFB laser made with the same cavity.