Loop phase-conjugate mirror for depolarized beams

摘要

A loop phase conjugator comprises: (a) a nonlinear optical medium; (b) a polarisation separator to separate a signal beam (E1) and two orthogonal polarised components (E11) and (E12) and directing them through the medium where they emerge as a loop beam (E2) with polarised components (E21 and (E22); (c) a polarisation mixer receiving the loop beam and mixing the components (E21) and (E22) to output loop beam components (E51) and (E52); (d) relay optics directing the loop beam (E2) back to the medium so that (E51) and (E52) intersect and optically interfere with (E11) and (E12) respectively to form gratings, the relay optics and gratings forming an optical loop; (e) an optical diode in the loop producing a non-reciprocal optical loss in the loop that is greater for beams propagating along the direction the loop than in the opposite direction; and (f) an optical gain medium in the loop to form a ring laser resonator. The diode and gain medium are positioned so that an oscillation beam (E3) with components (E31) and (E32) builds up from optical noise and oscillates in a direction counter to the propagation direction at loop beam (E2), with a proportion of (E3) transmitted by the gratings and exiting the loop as phase conjugate beam (E4).