Abstract: Example apparatuses and methods are provided that improve laser performance or decrease the frequency or severity of the occurrence of Stimulated Brillouin scattering. One example is a laser device that may include a seed laser configured to generate an optical output, a pattern generator configured to generate a modulation pattern, and a phase modulator configured to apply a modulation scheme to the optical output based on the modulation pattern. The modulation pattern may include a digital sequence and the modulation pattern may be applied to modulate a phase or an amplitude of the optical output.

Abstract: The output of an optical device which involves a stimulated brillouin scattering (SBS) gain medium is enhanced over a range of input beam intensities by providing a gain medium which has a given SBS gain for a given input beam intensity, and modifying the gain medium to reduce its SBS gain coefficient. By lowering the SBS gain coefficient, SBS dominance and suppression of stimulated Raman scattering (SRS) can be mitigated, and the output fidelity of a phase conjugation system with respect to its input can be significantly enhanced. Mechanisms for reducing the SBS gain coefficient include increasing the medium viscosity, thermal conductivity and/or diffusion coefficient, or causing the medium relaxation zone to coincide with the frequency of the phonons involved in the SBS process. Two different media can be mixed together in varying proportions to progressively modify the overall medium SBS gain as the input beam intsnsity is progressively changed.

Abstract: A passive (self-pumped) phase conjugate mirror uses a third-order nonlinear polarization medium, either of the refractive type (effective nonlinear) or the actual nonlinear type, with an optical system of one or more mirrors to reflect back through the medium a coherent incident beam diffracted by the medium. With two mirrors, they may be aligned to form a linear optical cavity containing the nonlinear medium, or they may be so oriented on one side of the medium that the incident beam transmitted through the medium is reflected back through the medium at an angle with the incident beam, and diffracted light from the incident beam is reflected back through the medium in the opposite direction coincident with the incident beam. A passive phase conjugate mirror may replace an end mirror of an optical cavity for a laser gain medium. Phase distortions of the laser beam in the laser cavity are corrected by the passive phase conjugate mirror.