Intensity statistics in a long random fiber Raman laser.

Area of Science:

• Nonlinear Optics
• Laser Physics
• Fiber Optics

Background:

• Raman fiber lasers exhibit complex output emission statistics.
• Understanding signal evolution requires analyzing nonlinear effects like Kerr nonlinearity.
• Deviations from standard statistical models need characterization.

Purpose of the Study:

• To investigate the output emission statistics of a continuous-wave Raman fiber laser.
• To analytically characterize deviations from Rayleigh statistics caused by Kerr nonlinearity.
• To validate theoretical findings with experimental data and numerical calculations.

Main Methods:

• Modeling signal evolution using a generalized nonlinear Schrödinger equation (NLSE) with gain.
• Applying kinetic theory to analytically derive the mean of the squared output signal intensity.
• Performing numerical simulations to supplement analytical results.

Main Results:

• Output statistics closely resemble Rayleigh distributions, with deviations attributed to Kerr nonlinearity.
• Analytical derivation of the mean squared intensity shows good qualitative agreement with experimental data.
• Kinetic theory provides finite results for small gain and nonlinearity, consistent with NLSE integrability.

Conclusions:

• Kerr nonlinearity introduces quantifiable deviations in Raman fiber laser output statistics.
• The developed kinetic theory offers a robust method for analyzing these statistical deviations.
• The findings are applicable to generalized NLSE systems with effectively small inserted terms.