Novel L-band multiwavelength raman fiber laser based on three-stage mixed-cascaded phosphor-silicate Raman process

We experimentally demonstrate an L-band multiwavelength Raman fiber laser based on the three-mixed-cascaded stimulated Raman scattering (SRS) of both P
2
O
5
and SiO
2
/GeO
2
in a phosphosilicate fiber. A 1064 nm Yb
³⁺
-doped double-clad fiber laser (YDCFL) is used to pump a spool of 1-km phosphosilicate fiber. The three-stage mixed-cascaded Raman cavity is arranged as: 1) the 1st- and 2nd-order Raman cavities use the SRS of P
2
O
5
and are formed by the two pairs of highly-reflective fiber Bragg gratings at 1239 and 1484 nm, respectively; 2) the 3rd-order Raman cavity uses the SRS of SiO
2
/GeO
2
and is completed by a polarization-maintaining fiber (PMF) Sagnac comb filter and a broadband fiber loop mirror. When the injected pump power from YDCFL is 4.8 W, up to 12-wavelength stable oscillation around 1601 nm has been obtained with wavelength spacing of 0.58 nm and extinction ratio of >30 dB.