| 摘要 |
<p>A phase-conjugation apparatus comprises a photo-refractive crystal and means for directing one beam Iin of light in a self-pumped configuration (or a plurality of beams of light in a mutually-pumped configuration) into the crystal so that a phase-conjugation process takes place and a phase-conjugated beam Ipc is returned along the same path as the input beam. In order to enable improvements to be made in the range of input beam positions and/or beam orientations, and/or being the time to reach stability, and/or overall stability, and/or the phase-conjugation efficiency, the input beam is incident on the crystal at an obtuse angle to the direction in which a beam of any orientation would ultimately tend to bend in the crystal, which in the case of a barium titanate crystal equates to the so-called +C direction.</p> |
