Jinc-trap resonator

DETAILED DESCRIPTION The present invention provides a Fourier transform resonator employing a Jinc-trap spatial filter which is designed to satisfy the aforementioned needs.
The resonator creates extremely flat, broad modes which efficiently fill the gain medium of a laser, such as the oxygen-iodine laser that is currently under development by the U.
S.
Air Force.
An improved stable resonator is thereby provided having modes which more efficiently extract power from the laser gain medium and form smaller focal spots than conventional stable resonators.
This improved resonator construction avoids the requirement for beam-center fill-in optics which are typically employed in conventional unstable resonators.
Further, the spatial filter used in this improved resonator is fully compatible with employment of a phase conjugate mirror therein.
Accordingly, the present invention is directed to a Jinc-trap resonator, which comprises the combination of: (a) a Fourier transform lens defining an optical axis with right and left transform planes disposed along the axis one focal length from either side of the center of the lens; (b) a laser gain medium located between the lens and a first one of the right and left transform planes; (c) reflecting means disposed at the first one of the transform planes; and (d) a Jinc-trap spatial filter disposed at the second one of the transform plane.
A near Jinclike field distribution, J.
sub.
1 (X)/X), is effectively trapped at the second transform plane, while the corresponding transform mode at the opposite first transform plane, adjacent to where the gain medium is located, is nearly constant in amplitude and flat in phase.