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Diffraction filtered large mode laser resonator
| Details |
Inventors: Pax, Paul H.;
Assignee: Continuum Electro-Optics, Inc. (Santa Clara, CA)
Primary Examiner: Sikes; William L.
Assistant Examiner: Morse; Susan S.
Attorney, Agent or Firm: Majestic, Parsons, Siebert & Hsue
A laser resonator that is geometrically stable by classical definition is provided with beneficial characteristics of an unstable type through the use of a novel implementation of spatial filtering. A pinhole aperture is provided as part of, or on conjunction with, a mirror at one end of the cavity to cause light reflected from the mirror to diverge as it is directed toward the other end of the cavity. A spot focus of light, as usually found in spatial filters, is not utilized. The result is a laser cavity structure which provides a large mode beam within the cavity, a good quality output beam having a smoothly varying intensity distribution across it and which is easy to align. |
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DETAILED DESCRIPTION These and additional objects are accomplished by the present invention wherein, briefly and generally, edge diffraction effects of a small limiting aperture at one end of the resonator are utilized to substantially entirely control the divergence of the resonator beam travelling away from the aperture, without the necessity for any particular mirror curvature at that end of the resonator to control that divergence.
This aperture controlled divergence, along with utilizing a defined curvature of the mirror and a cooperating large aperture at an opposite end of the resonator, results in making efficient use of the amplifying media by filling it.
The two apertures cooperate to form a spatial filter without the disadvantage of forming a point focus.
This eliminates undesirable concentrations of energy that can limit the amount of power at which the resonator can be operated in order to avoid damage.
The limiting aperture can alternatively take the form of a pinhole in front of a larger mirror, as close to its surface as practical, or a small mirror with non-reflecting areas around it.
Since the limiting aperture is illuminated by a beam having a crosssectional area that is many times that of the aperture, there is a significant energy loss at the aperture.
Therefore, this structure has an application where some limitation must be provided on peak power in order to avoid damaging elements within the resonator.
Further, the length of the resonator and other parameters have fewer constraints than the SFUR design, without sacrificing the quality of the intensity profile of the output beam.
The resonator configuration according to the present invention has a wide application, including use in a laser source or regenerative amplifier, particularly a laser source utilizing a dye cell positioned between a pinhole aperture and its associated end mirror where the beam intensity profile is highly uniform.
The classical definitions for stable and unstable types of resonators do not adequately characterize the resonator structure according to the present invention
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