Stability analysis of high power, octave spanning, continuous-wave supercontinuum sources based on cascaded Raman scattering in standard telecom fibers

Abstract

Long term spectral and temporal stability of a recently proposed high power, continuous-wave, supercontinuum source has been characterized. The supercontinuum laser, based on telecom fibers as the nonlinear medium and delivering >35W of CW power over an octave spanning bandwidth (880 to >1900nm), was operated continuously for extended periods of time to investigate its spectral stability. The dependence of stability on various parameters such as the wavelength of pumping and output power was studied by pumping the supercontinuum at 3 different wavelengths and at 3 different output power levels. The RMS value of the difference spectrum (spectral change) was used as the metric for comparison. The spectrum was stable with <1 dB variation over a duration of 60 minutes of continuous operation. This small variation is attributed to heating of the fiber and can be further reduced by properly heat sinking the fiber. When the fiber was cooled down to ambient temperature during power cycling tests, the change in spectrum was ~0.4dB. The supercontinuum output power fluctuations were characterized using a fast photo detector and was measured to be within ± 3% in nanosecond time-scales. The stability measured by these experiments demonstrates the efficacy of the source for a variety of applications.