Coherent light generators – Particular resonant cavity – Folded cavity
Reexamination Certificate
2002-08-06
2004-07-20
Davie, James W. (Department: 2828)
Coherent light generators
Particular resonant cavity
Folded cavity
C372S009000, C372S070000, C372S108000
Reexamination Certificate
active
06765947
ABSTRACT:
The invention relates to a laser amplifying system with a solid-state member having a laser-active medium and with a radiation field system determined by an optical guide means for the radiation field and an actively switchable optical switching element arranged in the radiation field system for influencing the losses in the radiation field system.
Laser amplifying systems of this type are known from the state of the art, wherein during a pass through the radiation field system not only the optical switching element but also the solid-state member having the laser-amplifying medium are normally passed through once.
Since an optical switching element can never be switched free from losses but always has a minimum loss for laser radiation passing through it, this design for laser amplifying systems with a low-amplification laser-active medium is a problem.
The object underlying the invention is therefore to improve a laser amplifying system of the generic type in such a manner that this is suitable for low-amplification laser-active media.
This object is accomplished in accordance with the invention, in a laser amplifying system of the type described at the outset, in that the solid-state member is designed like a thin plate, that the radiation field system comprises an incoming branch and an outgoing branch which are, on the one hand, coupled to one another and between which, on the other hand, an amplifying radiation field is provided which is formed from a plurality of intermediate branches which extend between two optical beam reversing elements and, for their part, all penetrate the solid-state member in a direction transverse to its flat sides and within a volume area, wherein the active volume area has, in directions transverse to beam axes of the intermediate branches, an extension which corresponds at the most to three times the average extension of the radiation field cross sections of the volume sections of the intermediate branches located in the active volume area.
The advantage of the inventive solution is, therefore, to be seen in the fact that due to the provision of the amplifying radiation field with the intermediate branches a high amplification is possible with a multiple pass through the solid-state member designed like a thin plate without the respective losses of the actively switchable optical element having a negative effect on the amplification and without the beam quality suffering.
In addition, the advantage of the inventive solution is also to be seen in the fact that, with it, a large optical path length of the amplifying radiation field can be realized between the respective passes through the switching element and so, as a result, it is possible to use a switching element which operates slowly, for example, in the microsecond range with switching flanks in the range of more than ten nanoseconds.
A solid-state member which is designed like a thin plate is to be understood in accordance with the invention as a solid-state member, the flat sides of which have an extension which is at least ten times, even better one hundred times, the thickness thereof.
Solid-state members which are designed like thin plates and can customarily be used are described, for example, in European patent application No. 0 632 551.
With respect to the arrangement of the actively switchable optical switching element, the most varied of possibilities are conceivable. For example, it would, in principle, be conceivable to arrange the actively switchable optical switching element in one of the intermediate branches of the amplifying radiation field.
It is particularly favorable when the actively switchable optical switching element is arranged outside the amplifying radiation field.
One advantageous solution provides, in this respect, for the actively switchable optical switching element to be arranged in the incoming or outgoing branch of the radiation field system.
In principle, it is sufficient in the inventive solution to provide an amplifying radiation field with a plurality of intermediate branches. If, however, the optical path length of the radiation field system is intended to be maximized, it is also conceivable for the radiation field system to have at least two amplifying radiation fields and for two beam reversing elements to be associated with each amplifying radiation field, wherein both amplifying radiation fields can also extend between the same beam deflecting elements.
With respect to the number of volume areas having a laser-active medium, it is likewise advantageous when providing several amplifying radiation fields when different volume areas having a laser-active medium are associated with the different amplifying radiation fields.
With respect to the construction of the radiation field optical guide means for determining the amplifying radiation field, the most varied of possibilities are conceivable. A particularly favorable solution, in particular, with respect to the transfer properties from intermediate branch to intermediate branch provides for at least one transfer element arranged between the beam reversing elements to be associated with each amplifying radiation field, this transfer element preferably bringing the beam axes of the intermediate branches together in an area of intersection, in which they overlap with their radiation field cross sections at least by half.
It is even better when the intermediate branches overlap with their radiation field cross sections in the area of intersection by at least two thirds, even better overlap for the most part.
The transfer element may, in this respect, be a transfer element operating in transmission. It is, however, particularly favorable when the transfer element is designed to reflect the intermediate branches since such a transfer element allows operations with small losses.
A particularly advantageous variation of a transfer element designed to be reflecting provides for this to be designed as a reflector with a curved reflection surface and, therefore, represent at the same time a folding element for the intermediate branches.
The transfer element may, in principle, have different imaging properties. One particularly advantageous solution provides for the transfer element to be designed as a transfer element acting in a collimating manner for the beam axes of the intermediate branches, i.e., allowing intermediate branches proceeding from an area of intersection to extend parallel to one another following the imaging.
An alternative development likewise preferred within the scope of the inventive solution provides for the transfer element to be designed as a transfer element bringing the beam axes of the intermediate branches together twice in an area of intersection, i.e., the transfer element causes intermediate branches proceeding from an area of intersection to run together again in an area of intersection due to imaging.
The provision of one transfer element acting on the intermediate branches between the beam reversing elements is, in this respect, not a final determination; within the scope of the inventive solution it is also conceivable to provide several transfer elements, depending on the transfer to be carried out.
In the same way, the determination of two beam reversing elements is merely a minimum condition for the determination of the respective amplifying radiation field. It is also conceivable within the scope of the invention to provide additional deflecting elements, for example, multiple deflection elements.
With respect to the beam reversing elements, no further details have been given in conjunction with the preceding explanations concerning the individual embodiments.
The beam reversing elements are preferably designed such that at least some of the intermediate branches extend in the amplifying radiation field, to a great extent, spatially separated.
A favorable variation provides for intermediate branches to extend essentially spatially separate from one another.
Another solution provides for two respective intermediate branches to coincide geometrically but to extend wit
Davie James W.
Lipsitz Barry R.
TRUMPF Laser GmbH + Co. KG
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