Coherent light generators – Particular resonant cavity – Folded cavity
Patent
1990-12-17
1992-09-15
Epps, Georgia Y.
Coherent light generators
Particular resonant cavity
Folded cavity
372 92, 372 94, 372 99, 372107, H01S 3081
Patent
active
051484439
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
The invention relates to a laser with a beam path multiply folded by means of two cavity resonator end mirrors and with at least one reflector retroreflectively folding the laser beam and whose axis is in particular laterally displaced with respect to the axis of a further reflector.
In the case of the conventional laser, a plurality of reflectors retroreflectively folding the laser beam is constructed as a roof mirror, and two such adjacent members are axially parallely displaced relative to one another in the folding plane by approximately half their total width or approximately by half a reflecting mirror width, so that the laser beam path reciprocates and can be progressively folded. Thus, these roof mirrors are components of a so-called multipass resonator, whose folding mirrors or reflectors are used for reducing the longitudinal extension of the laser. Folding generally leads to problems in the beam guidance and quality. The beam guidance is impaired in that the beam is not completely precisely reflected in the desired direction, because the mirror adjustment is not accurate or can be undesirably influenced by the laser design. The beam quality is impaired, for example, by diffraction effects during reflection in the corner regions of roof mirrors. Generally speaking, the disadvantages increase with the number of folding actions.
A general improvement with regards to the aforementioned disadvantages is obtained through the use of retroreflective mirrors including the aforementioned roof mirrors. Such retroreflective mirrors have the property of reflecting parallel to itself an incident beam independently of the angle of incidence, so that its adjustment sensitivity is comparatively small. Such retroreflective reactors act in one plane, such as e.g. the aforementioned roof mirrors, or three-dimensionally, i.e. if three reflecting surfaces are arranged at right angles to one another. Although the adjustment sensitivity of, for example, 10 millirad is significantly reduced compared with other, non-retroreflective reflectors of, pay, 100 microrad, the beam quality still needs improvement.
An object of the present invention is to so improve a laser such that, while maintaining a comparatively low adjustment sensitivity, it has an improved beam quality.
This object is achieved by the present invention in that the beam path is folded at least twice with the retroreflective reflector.
It is an important aspect of the present invention that the influence of optical inhomogeneities on the beam quality can at least partly be removed by the special folding geometry of the retroreflective reflectors. In addition, the adjustment sensitivity is further reduced with such reflectors. This is mainly achieved in that the retroreflective reflector is utilized several times for folding the beam path. Thus, there are no optical imprecisions between individual, independent reflectors. The adjustment errors of several individual retroreflective reflectors are avoided and the stability is increased. Optical inhomogeneities are, in particular, reduced compared with conventional multipass resonators, in that spatial superimposing of individual beam path portions can be avoided.
Advantageously, the offset of the reflectors is the same or greater than the radius of the laser beam and smaller than the radial extension of the reflector mirror. As a result of this dimensioning of the offset it is ensured that there is no reciprocal overlap of beam path portions. By avoiding overlaps of parallel beam path portions of the laser beam, the best possible beam quality is obtained. The laser beam remains in the folding area of the two reflectors. In addition, the laser beam does not have to radiate into the corner area of a reflector. Such corners of two or three-dimensional retro-reflective reflectors lead to pronounced diffraction effects because the corners of the reflectors cannot be made precisely at right angles. There are instead always rounding effects and unevennesses bringing about furth
REFERENCES:
patent: 4433418 (1984-02-01), Smith
patent: 4723256 (1988-02-01), Hoag
Du Keming
Herziger Gerd
Loosen Peter
Epps Georgia Y.
Fraunhofer-Gesellschaft zur Forderung der Angewandten Forschung
LandOfFree
Laser does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Laser, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Laser will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-742502