Low threshold cascaded Raman random fiber laser with hybrid Erbium-Raman gain

A low-threshold cascaded Raman random fiber laser is proposed based on the hybrid Erbium-Raman gain in a 90 m-long ultra-high numerical aperture fiber cascaded with a 25 m-long erbium-doped fiber pump with a 1480 nm laser diode. Experimental results show that the threshold pump power is only 67 mW. Under a low pump power of 500 mW, five orders of Raman Stokes are achieved with center wavelengths of 1565, 1681, 1810, 1966 and 2153 nm, respectively. Time domain characteristics measurements indicates that Q-switched laser pulses are produced and it should be the high peak power of these laser pulse that gives rise to the generation of high order Raman stokes components.