NARROW BRIGHT LINE WIDTH BBO OPTICAL PARAMETRIC OSCILLATOR UTILIZING ABNORMAL RESONANCE

摘要

PURPOSE: To provide an optical parametric oscillator which utilizes nonlinear crystals that are cut so as to cause type I mutual action. ;CONSTITUTION: The oscillator has abnormal excitation beams which generate normal signals and idler beams. In order to rotate the signal beams, optical elements are used. However, before transmitting the signal beams to a grating element 16, the diffusion plane of the element 16 is made parallel to the abnormal plane of a nonlinear crystal 12. Having the above means, the decrease in the aperture angle of the parametric gain of the abnormal plane reduces the bright line width of the generated output so far as the crystal 12 having a relatively narrow allowable angle such as a BBO(β-BaB₂O₄) crystal is concerned. The diffraction grating 16 converts an angular variation to a wave length variation. If a rotor is not used in an optical parametric oscillator 10, the diffusion plane of the grating 16 should be perpendicular with respect to the abnormal plane of the crystal 12 in order to obtain a maximum efficiency of the grating 16 and as a result, the narrow allowable angle of the crystal 12 is not related to the reduction in the output bright line width.;COPYRIGHT: (C)1997,JPO