Actively Mode Locked Raman Fiber Laser with Multimode LD Pumping

We present our recent experimental results on the pulsed regimes of Raman conversion highly multimode laser diode (LD) pump radiation into 1st and higher order Stokes in graded-index fibers. Three different linear cavities fiber with modulation losses (by acousto-optic modulator, AOM) or gain LD current) are explored compared. An wavelength 976 nm is used for pumping enabling lasing at (1018 nm) 2nd (1064 orders. At ~27.2-kHz repetition rate corresponding to cavity round-trip frequency (i.e., mode-locking regime), nanosecond pulses have been observed both orders having highest peak power ~300 W scheme bulk AOM shortest duration 5–7 ns fiber-pigtailed AOM. same time, beam quality generated greatly improved as compared that (M2 > 20) reaching best value = 2.05) demonstrating also most stable regime.