Raman fiber laser with random distributed feedback based on a twin-core fiber

Abstract

An operation of a linearly polarized Raman fiber laser with random distributed feedback based on a polarization-maintaining twin-core fiber (TCF) is demonstrated for the first time, to the best of our knowledge. The results indicate that the TCF allows one to obtain laser generation with a linewidth that is about five times smaller than that for the random laser based on a conventional fiber with similar parameters. The reasons for narrowing include both the weakening of nonlinear effects due to the power density reduction and the spectrally selective properties of the TCF.

Random Raman fiber laser based on a twin-core fiber with FBGs inscribed by femtosecond radiation

“…Reflectivity R r is equal to 0 for the half-open cavity configuration with an angled cleaved output fiber end. The Raman gain coefficient is taken to be 0.95 W −1 km −1 , which is within the experimental range for this TCF [18].…”

“…An additional possibility of line narrowing consists in the reduction of power density in the fiber core, thus reducing nonlinear effects. In particular, one can use large-mode-area [17], multicore [18], or tapered [19] passive fibers. For example, in a random laser based on a twin-core PM fiber with a half-open cavity involving a broadband fiber loop mirror (FLM) [18], the linewidth is five times smaller than that for a random laser based on a conventional single-mode fiber (SMF) with similar parameters [10].…”

“…In particular, one can use large-mode-area [17], multicore [18], or tapered [19] passive fibers. For example, in a random laser based on a twin-core PM fiber with a half-open cavity involving a broadband fiber loop mirror (FLM) [18], the linewidth is five times smaller than that for a random laser based on a conventional single-mode fiber (SMF) with similar parameters [10]. The reasons for the line narrowing include not only the weakening of nonlinear effects due to the power density reduction, but also the spectrally selective properties of the twin-core fiber itself (with a quasi-periodic wavelength transmission function).…”

“…The reasons for the line narrowing include not only the weakening of nonlinear effects due to the power density reduction, but also the spectrally selective properties of the twin-core fiber itself (with a quasi-periodic wavelength transmission function). As a result, the linewidth of RDFB lasers using a twin-core fiber in combination with a broadband FLM amounts to about 0.5 nm at ∼7 W output power [18].…”

“…A PM TCF has been developed and manufactured in FORC RAS (Moscow). The radius of the cores is 3 0.3 μm, and the average distance between the core centers is 17.1 0.3 μm; the propagation loss coefficient at 1.06 μm is measured to be 2.2 dB/km, and the Raman gain coefficient is 0.85-0.95 W −1 km −1 [18]. The general scheme of the investigated RDFB laser configurations is shown in Fig.…”