Investigation of the low power stage of an 1178nm Raman system

An 1178 nm seeded and 1069 nm pumped Raman laser system where the second Stokes is amplified in a 1121 nm resonator defined by high reflector fiber Bragg gratings (FBGs) has the potential of producing high output power of narrow linewidth 1178 nm. However, 1121 nm power leakage out of the resonator cavity around the gratings was found to impact the performance of the laser and needs to be dealt with in order to obtain high 1178 nm output power levels. In order to address this problem, the causes of linewidth broadening must be understood. A fully nonlinear model has been built which involves propagation of the spectral wave shape via the nonlinear Schrödinger equation in addition to the Raman processes. It was found that increases in 1121 nm cavity power, fiber Bragg grating bandwidth, and the nonlinear index of refraction n2, as well as a decrease in group velocity dispersion β 2 leads to an increase in linewidth broadening. It is concluded that the magnitude of linewidth broadening seen experimentally can only be explained if the spectral components outside the bandwidth of the FBGs are being amplified. Experimentally, 1121 nm power leakage can be handled by using a three wavelength WDM on either side of the rare earth doped amplifier. In addition, usage of a fiber having a high value for group velocity dispersion and/or a low value for nonlinear index of refraction n2 in addition to narrower bandwidth fiber Bragg gratings may help reduce the amount of linewidth broadening.

[1]  T. Kato,et al.  Estimation of nonlinear refractive index in various silica-based glasses for optical fibers. , 1995, Optics letters.

[2]  Bera Palsdottir,et al.  Cascaded Raman fiber laser at 1480 nm with output power of 104 W , 2012, Other Conferences.

[3]  K. Okamoto Fundamentals of Optical Waveguides , 2000 .

[4]  J W Nicholson,et al.  Raman fiber laser with 81 W output power at 1480 nm. , 2010, Optics letters.

[5]  T. M. Shay,et al.  1121 nm resonator properties and impact on the design of a 1178 nm sodium guidestar laser , 2012, LASE.

[6]  D. Milam Review and assessment of measured values of the nonlinear refractive-index coefficient of fused silica. , 1998, Applied optics.

[7]  Yan Feng,et al.  Multiwatts narrow linewidth fiber Raman amplifiers. , 2008, Optics express.

[8]  Ronald Holzlöhner,et al.  39 W narrow linewidth Raman fiber amplifier with frequency doubling to 26.5 W at 589 nm , 2009 .

[9]  Iyad Dajani,et al.  Investigations of single-frequency Raman fiber amplifiers operating at 1178 nm. , 2013, Optics express.

[10]  Yan Feng,et al.  Stimulated-Brillouin-scattering-suppressed high-power single-frequency polarization-maintaining Raman fiber amplifier with longitudinally varied strain for laser guide star. , 2012, Optics letters.

[11]  Yan Feng,et al.  50W CW visible laser source at 589nm obtained via frequency doubling of three coherently combined narrow-band Raman fibre amplifiers. , 2010, Optics express.

[12]  Luke R. Taylor,et al.  25 W Raman-fiber-amplifier-based 589 nm laser for laser guide star. , 2009, Optics express.

[13]  Robert Q. Fugate,et al.  Studies of a mesospheric sodium guidestar pumped by continuous-wave sum-frequency mixing of two Nd:YAG laser lines in lithium triborate , 2006, SPIE Defense + Commercial Sensing.

[14]  ルーク アール. テイラー,et al.  Narrow-band fiber Raman optical amplifier , 2009 .