Biomedical subjects
Publications and source records attributed to Stéphane Coen.
We experimentally demonstrate the operation of a passively mode-locked Raman fiber ring laser with an ultrahigh repetition rate of 100 GHz and up to 430 mW of average output power. This laser constitutes a simple wavelength versatile pulsed optical source. Stable mode locking is based on dissipative four-wave mixing with a single fiber Bragg grating acting as the mode-locking element.
We experimentally demonstrate that continuous-wave supercontinuum generation in optical fibers can be significantly enhanced by using both multiwavelength pumping and dispersion management. We show by detailed spectral analysis that continuum enhancement is achieved mainly through a combination of Raman-assisted modulation instabilities, soliton compression, and dispersive wave generation. With this technique, an 800 nm wide (from 1.2 to 2.0 microm) 2 W supercontinuum source is reported that uses a three-wavelength pump and a dispersion-tailored four-optical fibers arrangement.
We present a new numerical model of cascaded Raman fiber lasers that takes into account the chromatic dispersion of the fiber and includes the full spectrum of the intracavity field. This model explains and describes remarkably well a new operating regime found experimentally and reveals that chromatic dispersion is truly a new degree of freedom in the design of cascaded Raman lasers.
We study experimentally the influence of chromatic dispersion and Rayleigh backscattering on cascaded Raman generation in silica optical fibers. Effects ranging from enhanced spectral broadening of the Stokes orders to generation of higher Stokes order at unexpected wavelengths are observed. Additionally, we show that four-wave-mixing processes can quench the noisy Rayleigh lasing lines generated in power Raman amplifiers. Our observations are confirmed by numerical simulations.
Modulation instability at high frequencies has been demonstrated in the normal dispersion regime by use of a photonic crystal fiber. This fiber-optic parametric generator provides efficient conversion of red pump light into blue and near-infrared light.
We present what is to our knowledge the first complete measurement of the dependence of Raman gain on chromatic dispersion, fully revealing the influence of parametric four-wave mixing on stimulated Raman scattering. In particular, a threefold increase of the Raman gain is observed under phase-matching conditions, in excellent agreement with theoretical predictions. Our experiments, which were performed in a photonic crystal fiber, demonstrate that these unique fibers can be exploited to boost the performances of fiber Raman amplifiers.
The coupling between a resonant excitation and a nonresonant parametric process in a nonlinear system is studied experimentally under non-phase-matched conditions. Our study performed in the context of anti-Stokes stimulated Raman scattering provides a clear observation of the self-induced phase matching of a parametric process. A close agreement with theoretical predictions is observed.