Ring cavity optical parametric apparatus

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION The parametric process takes place when all three beams are propagating within the crystal approximately along the same path, in the same direction.
The ring oscillator of the present invention forces unidirectional propagation of the parametric beams.
The parametric photons travel, during the entire process, in the direction of the pump beam, and continuously contribute to the amplification.
In the present invention, the signal (and/or idler) beam is retro-reflected twice within a ring oscillator.
The parametric beams are folded by corner reflectors (a right angle prism, or any combination of optical components which will reflect the beams in a direction parallel to their original direction).
The beam(s) propagate in a single direction within the crystals.
This direction coincides with the direction of the pump beam which is folded once within the cavity by one of the retroreflectors.
Therefore, the overall interaction time (or the effective gain length) is increased significantly.
The design does not compromise the cavity length which is kept to a minimum.
Forcing the signal and idler beams to propagate in the same direction as the pump beam without compromising the cavity length maximizes the optical conversion efficiency.
Tunability is achieved by varying the temperature of the crystal, by applying variable voltage or by rotating the crystal (or pairs of crystals) with respect to the direction of the pump beam, in a manner similar to known linear cavity designs.
Shown in FIG.
1 is a unidirectional OPO cavity C.
In cavity C, pump beam 10 and parametric beams 12 are always propagating in the same direction as each other as these beams move through the cavity.
Even if the beams are turned, they are turned together whereby all beams propagate in a common direction at any one time during the process.
Specifically, cavity C includes two right angle prisms 14 and 28 that are oriented to face each other to form a ring oscillator shaped in the form of a rectangle