Wave Guide Laser With Frustration Element

The invention relates to a laser system consisting substantially of a folded beam path located in an amplifying medium and terminated by at least partially transmitting and/or totally reflecting optical elements. A system of this type is treated in detail, for example, in the German Offenlegungsschrift No. 27 53 304, which is hereby incorporated by reference.

The object of the invention is considered to be the provision of a Q-switch that operates abruptly, i.e. with very short time constants, and which can be used to modulate the laser beam. This object is attained, according to the invention, in that the folding of the beam and any necessary coupling out of the beam is performed by a frustration element consisting of two deviating elements made of optically refracting material, e.g., two prisms, which face each other across a variable gap. A laser of this type may be constructed with commercially available parts so that, from the viewpoint of both manufacture and function, relatively simple elements are available to influence the laser beam in such a way that its resonator preferably does not oscillate. In connection with the foregoing, it is suitable that the variable gap is defined between the oblique side of the larger prism and the long side of the smaller prism and further that the long side of the larger prism faces the endface of the laser that lies opposite the optical elements, with or without spacing.

The variation of the gap between the two ridge prisms may be obtained with the aid of piezo-electric drive means. If desired, the beam may be extracted from the cavity via the side of the frustration element defining the width of the gap, depending on whether only one of the ends of the beam path is terminated by a totally reflecting mirror and the other by an at least partially transmitting window, or, on the other hand, both ends are terminated by totally reflecting elements. In the latter case, the resonator oscillates until the pulse has built up and the gap is closed, whereafter the beam leaves the cavity at right angles to the long axis thereof, or, in the other case, through the window.

An advantageous further development of the invention provides for the use of the proposed apparatus in gas lasers, semiconductor lasers or solid state lasers. For gas lasers, it may be advantageous if the beam passages and the folding region in the frustration element are integral with a block of material, in the form of a continuous channel. In that case, excitation and discharge take place via electrodes or series of electrodes entering the channel on opposite sides thereof. Many materials can be used; they must have electrically insulating properties, so that for example, glass, ceramics, glass-ceramic compositions, quartz or plastic are usable in principle. The gas channels in the material have diameters in the millimeter range.

Two exemplary embodiments of the invention will be explained in detail with the aid of the drawing, the two figures of which exhibit the same reference characters for similar elements.

FIG. 1 is an illustration of the apparatus of the invention wherein the beam may be disposed in any suitable laser medium; and

FIG. 2 is an illustration of the apparatus of the invention when used for a gas laser.

In FIG. 1, two mutually parallel beam paths 2 and 3 of a laser 1 are shown to be disposed in any suitable medium, for example, a solid state medium. On one side 8, the upper channel 2, as seen in the figure, is terminated by a totally reflecting optical element 6, for example, a mirror, while the channel 3 is terminated by a transmitting element 7, i.e., a window, for extracting the beam out of the cavity, indicated schematically by the solid-line arrow 16. The other endface 9 of the laser faces a deviating element 10 made of an optically refracting material, in particular, the long side 10" of, for example, a ridge prism, across a separating space. The deviating element deviates the laser beam by 2.times.90.degree. from one discharge channel into the other. However, the prism may also be in contact with the endface of the laser as shown, for example, in FIG. 2. Its oblique side 10' faces, across a small gap, the long side 11' of a further ridge prism 11, the length of the side 11' being made equal to the length of the oblique side 10'. The ridge prism 11 may be displaced in the directions of the double arrow by means of a piezo-electric drive 12, thereby changing the width of the gap and hence affecting the oscillation of the laser beam. A system of prisms with a variable gap is also described as a frustration element.

In another embodiment of the invention, the at least partially transmissive mirror 7 may be replaced by a totally reflecting mirror. In that case, the beam is extracted from the cavity at the other side, i.e., across the face 10' of the frustration element, which is reflecting when the element is open, and departs in the direction of the dashed arrow 17. The angle the departing beam makes with the axis of the cavity need not be 90.degree. but depends on the material being used and is, for example, 106.degree. for quartz.

In yet another embodiment of the invention, the optical element 7 may have a transmission factor of only 70% or thereabout. In that case, time-shifted pulses may be coupled out along both arrows.

FIG. 2 illustrates an embodiment especially suited to the requirements of gas lasers, also having two mutually parallel channels 2 and 3, disposed in the direction of the longitudinal axis. Their diameters lie in the millimeter range and they are either cast into the compact block of material 4 or may be bored into such a block after casting. Passages or recesses 5, perpendicular to the channels, extend toward the outside and are produced in the material in the same way as the channels themselves. They serve to receive two opposing rows of electrodes, in the present example sets of three electrodes 13 and 13'.