Coherent light generators – Particular resonant cavity
Reexamination Certificate
2002-07-29
2004-08-17
Leung, Quyen (Department: 2828)
Coherent light generators
Particular resonant cavity
C372S070000
Reexamination Certificate
active
06778580
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a laser amplifier system comprising a solid body having a laser-active medium, an excitation source for producing an excited state of the laser-active medium, and an amplifier radiation field which passes multiply through the solid body and from which a laser beam can be extracted.
Such a laser amplifier system is known, for example, from EP 0 632 551.
In this laser amplification system, however, the amplifier radiation field is guided, even with multiple passes through the solid body, in such a way that the individual branches are reflected back on themselves.
The disadvantage of an amplifier radiation field formed in this way is that a high number of passes of the amplifier radiation field through the solid body can be achieved only with great difficulty.
It is therefore an object of the invention to improve a laser amplifier system of the generic type in such a way that the highest possible number of passes of the amplifier radiation field through the solid body can be achieved with the simplest possible optical means.
SUMMARY OF THE INVENTION
This object is achieved according to the invention, in the case of a laser amplifier system of the type described in the introduction, by the fact that radiation field guiding optics are provided, which make the amplifier radiation field entering the solid body in the form of a plurality of incident branches with locally different trajectories and leave the solid body in the form of at least one emerging branch with a trajectory locally different from the incident branches, and that the radiation field guiding optics have at least one deviating unit which forms, from at least one of the branches emerging from the solid body, a branch which enters the solid body with a trajectory locally separate from this emerging branch.
The advantage of the solution according to the invention is that it provides a straightforward way of achieving a large number of passes of the amplifier radiation field through the solid body, and at the same time, since the incident branches and the emerging branches respectively have locally different trajectories from one another, optimum utilization of the excited laser-active medium in the solid body takes place.
It is particularly favorable for the incident branches always to enter the same solid body.
It is even more favorable for the incident branches always to enter the same volume region of the solid body.
In order not to increase the size of the cross section of the incident branches formed in turn from emerging branches by the deviating units, provision is preferably made for the radiation field guiding optics to form the incident branch from the emerging branch after intermediate focusing.
The intermediate focusing may in this case take place independently of the deviating unit. In order to configure the beam guiding optics according to the invention as compactly as possible, provision is preferably made for the intermediate focusing to take place in the vicinity of the deviating unit.
A particularly expedient solution in this case provides for an intermediate focus lying between two deviating elements of the deviating unit to be produced by the intermediate focusing, which prevents the intermediate focus from lying directly in a deviating unit.
It is particularly favorable in this case, in order to arrange both deviating elements as far away as possible from the intermediate focus, for the intermediate focus to lie approximately centrally between the two deviating elements.
Since the intensity per unit area of the cross-sectional area of the radiation field increases close to the intermediate focus, provision is preferably made for the optical path between the two deviating elements lying on either side of the intermediate focus to be greater than a spacing between an input branch entering the deviating unit and an output branch emerging from the deviating unit.
It is particularly favorable in this case for the optical path between the two deviating elements lying on either side of the intermediate focus to correspond at least to two times the spacing of the input branch and the output branch.
A particularly favorable solution provides for the deviating unit to guide the amplifier radiation field in a loop which, in relation to an input branch and an output branch of the deviating unit, has an extent in an expansion direction which is greater than the spacing between the input branch and the output branch.
This expansion of the radiation field in the expansion direction provides the opportunity to maintain a spacing which is as large as possible between the deviating elements lying on either side of the intermediate focus.
Preferably, the extent of the loop in the expansion direction is at least two times the spacing between the input branch and the output branch.
In the scope of the exemplary embodiments described so far, it has been assumed that the radiation field guiding optics convert at least one emerging branch into an incident branch by employing a deviating unit.
The solution according to the invention may, however, be refined in a particularly straightforward way if the radiation field guiding optics convert a plurality of emerging branches into a plurality of incident branches by means of at least one deviating unit.
In the scope of the description of the individual exemplary embodiments so far, the way in which the respective incident and emerging branches of the amplifier radiation field are intended to be formed has not been discussed in detail.
In principle, it would be conceivable to embody them as divergent or convergent branches, albeit with the disadvantage that the cross section of the branches would become larger as the number of passes is increased.
In order to be able to keep the cross section of the incident and emerging branches the same size, and therefore to be able to use a volume region of the solid body with excited laser-active medium optimally for amplifying the radiation field, provision is preferably made for the radiation field guiding optics to form an amplifier radiation field in which the branches entering the solid body and the branches emerging from the solid body are collimated branches.
In order respectively to form a collimated incident branch in turn from a collimated emerging branch, provision is preferably made for the radiation field guiding optics to be designed as at least singly recollimating.
In this case, “recollimating” means the conversion of a collimated radiation field via intermediate focusing into a collimated radiation field.
It is even better for the radiation field guiding optics to be designed as multiply recollimating, so that a plurality of collimated emerging branches can in turn be converted into a collimated incident branch.
During the formation of the incident branches and of the emerging branches, it is particularly favorable in terms of the formation of the amplifier radiation field for an intermediate-focused branch to be formed between the collimated emerging branch and the collimated incident branch by the radiation field guiding optics during each recollimation, that is to say when converting a collimated emerging branch into a collimated incident branch. This makes it possible to preserve the optical beam cross section in a particularly favorable way.
In terms of the interaction of the recollimation with the deviating unit, no detailed indications have been given so far. For instance, a particularly advantageous solution provides for the intermediate-focused branch required during the recollimation to pass respectively through a deviating unit according to the invention.
In principle, it would be conceivable to provide separate recollimating optics of the radiation field guiding optics for each recollimation.
Expediently, provision is made in this case for the intermediate-focused branch to travel along an optical path which corresponds to two times the focal length of the recollimation.
In terms of the design of the various recollimating optics, it would be conceivable to ca
Erhard Steffen
Giesen Adolf
Lipsitz Barry R.
McAllister Douglas M.
Universitaet Stuttgart Institut fuer Strahlwerkzeuge
Vy Hung T
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