Ultrashort Laser Pulse Phenomena, 2nd Edition

Fiber Lasers 379

as self-standing units or as compact seed sources for high-power fs amplifier

systems.

6.9.2. Raman Soliton Fiber Lasers

SRS is associated with intense pulse propagation in optical fibers. A review of

this topic can be found in Rudolph and Wilhelmi [140] for example. The broad

Raman gain profile for the Stokes pulse extends up to the frequency of the pump

pulse. An overlap region exists because of the broad pump pulse spectrum. The

lower frequency components of the pulse can experience gain at the expense of

attenuation of the higher frequency components. In addition, the amplification of

spontaneously scattered light is possible. Either process leads to the formation

of a Stokes pulse which separates from the pump pulse after the walk-off distance

because of GVD. These processes can be utilized for femtosecond Raman soliton

generation in fibers and fiber lasers [141–143]. An implementation of this idea

is shown in Figure 6.15. The pulses from a cw mode-locked Nd:YAG laser

CW mode-locked

Nd: YAG

Fiber

BS

P

L

1

L

1

M

2

M

2

Figure 6.15 Experimental configuration of a synchronously pumped fiber ring Raman laser.

(Adapted from Gouveia-Neto [143].)