Abstract: This invention relates to increasing the power output of a broadband Raman amplifier by angle-tuned phase matching of either multiple individual pump lines or a continuous spectra in a pump beam 1 relative to their corresponding Stokes lines or Stokes spectra in the Stokes seed beam 2 so that energy can transfer from the pump lines to the Stokes lines more efficiently. The invention can work in any solid or fluid Raman medium. The Raman cell could be in a length of optical fiber using the internal reflections in the optical fibers as mirrors 8. By using angle tuning, enhancement of the Raman gain is produced which allows the Raman amplifier to achieve high power output with much larger pump bandwidths than were previously possible. The input pump beam 1 is fanned by diffraction grating 3 so that the pump lines are at the proper angle to be phase matched with the Stokes seed beam 2 which may also be fanned.

Abstract: A method for creating population inversions for use in stimulated emission devices which beam combine, beam clean-up, or frequency up-convert electromagnetic radiation. The invention comprises near resonantly enhanced multiphoton pumping of a multilevel quantum medium with pump beams of appropriate intensities and frequencies detuned from the transition frequencies of the medium. The intensities are orders of magnitude lower than those required for non-resonantly enhanced multiphoton pumping. The detuning is smaller for the maximum multiphoton resonance than for the single photon resonances. Appropriate medium decay constants are required for creating a population inversion between energy levels of the quantum medium. The population inversion exists between energy levels of the medium whose energy difference may exceed the energy of any single pump photon energy.

Abstract: To provide a solution of the problem of medium dispersion in a two-line Raman amplifier which may increase the intensity-length product requirement and limit the conversion efficiency. By adjusting the angles between the input beams, the four-wave mixing phase mismatch due to medium dispersion may be eliminated. This couples together the Raman gains of the two lines so that the effective pump intensity for each is the total pump intensity. Since both lines convert in about the same amplifier length, independent of the relative power in each, the conversion efficiency is not limited by the inability to optimize the length for both lines simultaneously.