DE3013301A1 - Reflection system for ring laser - has partially and totally reflecting mirrors at ends of parallel paths between electrode pairs - Google Patents

Abstract

The ring laser with two outputs having different wavelengths has a housing (2) forming a resonance chamber (5) with a set of four parallel electrodes (10 to 14). These are arranged in pairs (10,11; 13,14) so as to form two parallel paths, and do not extend for the full length of the housing. In the space remaining at their ends, are four mirrors (18 to 21) arranged at four corners, and diagonal to the two paths. Two mirrors (18,19) for one path are totally reflecting, and the other two (20,21) are partially reflective, forming the two outputs. Where one output is required, only one mirror is partially reflective. Where four outputs are required, all four mirrors are partially reflective. In another form, two totally reflecting mirrors are located at one end, and two plane and partially reflective mirrors are at the other end. The angles of the first two mirrors can be varied, and the plane mirrors can be moved in the direction of the two paths. Another design has a triangular optical element.

Description

The invention relates to a laser arrangement consisting of one of

a housing surrounded resonator chamber with an electrode system, the one serving in a center electrode with at least two of the electrical discharge Surfaces and at least two outer electrodes opposite these surfaces is broken down, with on the inside housing front sides in the amount of one of the Clearances between the electrodes each point the laser beam in the direction of the other Side deflecting optical element and at least at the level of the other free space a partially transparent optical element on one side for coupling out the laser beam is provided, of which the deflecting optical elements of one end face are arranged at an angle to the beam path.

Such a laser arrangement is dealt with in DE-OS 27 53 304, for example. In principle, each of the optical elements - with the appropriate training - be used to decouple the laser beam. For example, it becomes more wavelength-selective Mirror formed, each mirror can couple out a laser beam that is in the wavelength of the laser beams coupled out at the other mirrors is. The preferred shape of the ring laser, however, is a so-called unstable resonator " with only one output mirror, as described in JOURNAL OF APPLIED PHYSICS, Vol. 42/8 from July 1971, pages 3133 to 3137, in the technical article CO2 Regenerative Ring Power Amplifiers "illustrated and described by C.J. Buczek, R.J. Freiberg and M.L. Skolnick is. Also the trade journal ELEKTRONIK 1978, issue 1 pages 85 ff., In the article "The ring laser - a new concept for dye lasers" by Günter Hummelt are closer Information on ring lasers can be found.

The object of the invention is to increase the performance of the generic Laser for at least one wavelength.

This object is achieved according to the invention in that all four optical Elements facing each other and arranged at angles to the beam path optical surfaces the laser beam in the manner of a ring laser on each of them opposite steer optical elements. Due to the favorable utilization of the active medium a rapid increase in gain and when trained as an unstable resonator a high energy yield in mono-mode operation, i.e. a relatively high degree of efficiency, achieved. Although the arrangement of the optical deflection elements at 45 ° to the Ray path is the rule, so that the ray path is externally rectangular in shape possesses, in principle, other angles can also be used, provided that the Decoupling mechanism requires this. For example, it is conceivable that the in the diagonal opposite optical elements with the beam path enclose the same angle.

A further development of the invention provides that? for one use of two or more wavelengths and with appropriately subdivided electrodes the optical elements around an axis perpendicular to the main horizontal plane of the device are pivotably arranged in such a way that any free space between the electrodes assigned to a different wavelength. In this way you get a two- or multi-wavelength lasers with wave trains generated synchronously with one another. The breaking down of the electrodes is to be understood here in such a way that by reducing the width of the electrodes with the same discharge volume and therefore almost unchanged Power of the resonator chamber in practically any number of parallel beam paths can be fanned out. The simplest fanning is the one with two beam paths, the one through a center electrode and its opposite on two effective surfaces External electrodes results. Both these and more complicated fanning are in of the laid-open specification cited at the outset.

In the upcoming context it can be far apart Wavelengths are useful, the area assigned to the respective wavelengths or to form surface areas of the optical elements as grids and with different To provide lattice constants.

To correct an inhomogeneous energy distribution in the beam or homogeneously to be able to make, the optical elements are interchangeable and have one of the flat surface deviating and adapted to the respective needs -z-.B. cylindrical or aspherical - shape.

As a rule, the optical surfaces cannot be entered from the outset specify, but each one can be specifically selected as well as tested in the system and be determined. The application is, for example, conceivable with a laser in which a partial beam is coupled out and checked for its optical quality, i.e.

essentially checked for its homogeneous intensity distribution as well as is regulated by means of adaptive optical elements. This process leaves also automate.

Another development of the invention provides that the two Front sides of the housing itself as totally and / or (partially) reflective carrier plates are formed, the carrier plates made of quartz glass, (glass) ceramic, germanium, Cadmium telluride or zinc selenide can exist. Such a coupling of mirrors is only slightly subject to temperature influences and has no mutual influence Adjustment problems. It is useful that at least one totally reflective Area and a sufficiently permeable area on the area facing the resonator Side of the carrier plate is provided or incorporated in the carrier plate. Total or Partial transparency requires a corresponding remuneration: In practice it has proved to be advantageous, the totally reflective area in the form of e.g. consisting of a metallic layer (gold) or a dielectric layer Evaporate reflective layer and transparent material for the permeable area to choose or the latter at least partially through a through hole to replace. Such formed plates can be by limiting the also use the reflective area as a mode diaphragm. In this case it results the The advantage of having an element serving to limit the radiation that would otherwise be required would save. One equipped with optical surfaces that are rigidly adjusted to one another Plate is also suitable for other lasers such as solid-state, pulsed gas, continuous wave lasers etc. usable, so that element protection is desired for this.

As for the totally reflecting mirrors, they can if they are on the same face, by a prism block or a Triple mirror to be replaced. In the case of the triple mirror, it is advantageous if he face with flat areas exposed to the beam path and from the Beam path kept out-edges angeordllei; is. For tuning the resonator length it also makes sense that the optical elements and / or their holder Serving end faces are formed adjustable with the aid of a piezo drive. The direction of adjustment runs perpendicular to the plane of the elements or pages.

Another feature of the invention provides that in the beam path two decoupled beams with a wavelength of less than 3 light R 1 7 2, if necessary a common optical crystal - e.g.

Germanium or CdTe - to generate another beam with different Wavelength 2 3 can be coupled.

In the following, exemplary embodiments (the Invention explained in more detail, the corresponding in the individual figures Parts have the same reference numbers. It shows Fig. 1 the longitudinal section through a Ring laser with two beam paths, deflection means arranged at 45 ° to them and two decoupling points, 2 shows the longitudinal section through a laser with one wavelength per beam path, FIG. 3 with a ring laser according to FIG. 1 four beam paths and a corresponding number of decoupling points.

4 shows a ring laser according to FIG. 1 with two different ones Arranged angles, causing the beam path in the manner of a parallelogram Deflection means, Fig. 5a the two end faces of the housing (carrier plate and prism block) with one another each rigidly adjusted mirrors - in side view, Fig. 5b the Carrier plate according to FIG. 5a - in plan view, FIG. 6 shows an end face of the housing, in which the totally reflecting mirrors are replaced by a triple mirror and FIG. 7 shows a laser roughly in accordance with FIG. 2, in which the coupled-out radiation is different Wavelength is guided through a germanium crystal.

The basic arrangement according to FIG. 1 shows the laser 1, its housing 2 surrounds the resonator or discharge space 5, in which the electrode system 10 to 14 is arranged.

The two end walls 8 and 9 of the housing essentially serve the holder of the mirrors 17 to 21. The one after outside leading The electrode system 10 to 14 provided with a voltage supply consists of the one in the longitudinal axis of the housing 2 arranged center electrode 11, the two in opposite directions facing discharge surfaces 12 and 13, respectively with an electrode opposite it in the area of the inner longitudinal wall of the housing 10 and 14 or their discharge surfaces 3 and 4 interact.

At the level of the free spaces between the electrodes are on the end walls 8 and 9 - in the case of the solid line ray of wavelength R 1 - the three totally reflective optical elements 18 to 20, e.g. mirrors, and the partially transparent optical element 21, which is likewise designed accordingly Mirror can be attached. The mirror surfaces are facing each other and each arranged at 46 ° to the beam path. Will the gas in the resonator excited, a line corresponding to the solid line arises after the emission so-called ring laser, which is coupled out through the partially transparent mirror 21. In the case of a ring laser with two wavelengths and 1 and l 2, the Off-1 and coupling another totally reflecting mirror, e.g. the mirror 20, can be replaced by a partially transparent mirror.

An embodiment with four different wavelengths that can be coupled out 21 to 24 is shown in FIG. The transmission here is 85% and the reflection 15%.

Of course, the percentages of transmission and Reflection also different in other exemplary embodiments - e.g. in the case of the four optical ones Elements also differing from one another - be formed.

In Fig. 2, compared to Fig. 1, the mirrors 19 'and 20' are inclusive their grid designed to be rotatable in the direction of the double arrows. Mirror 19 '. became - in the manner shown here - rotated by approx. 45 °, like this that the mirrors 19 'and 20' now only in one direction, namely parallel to one another and to the longitudinal direction of the housing 2 on the transparent or assigned to them Partially transparent mirrors 18 'and 21' reflect in the direction of the double arrows are arranged displaceably and can replace the wall at this point. on In this way it is possible to tune the length of the resonator and on the other hand to operate the laser with two synchronous pulse wavelengths 2 1 and # 2 and thereby coupling out the corresponding radiation separately through the mirrors 18 'and 21'. Instead of the grating, other wave-selective optical elements, e.g. prisms, be used. The lattice constants can also be used for the individual wavelengths design assigned mirrors differently. Adjusting the optical elements and / or the side walls carrying them takes place with the aid of the piezo drive 23, and each perpendicular to the plane of these elements or pages.

In the exemplary embodiment in FIG. 4, the beam path forms a Parallelogram. This comes about because in each case only those in the diagonal are each other opposing mirrors 18 and 20 as well as 19 and 21 or their grids with the beam path form the same angle. Here is laser radiation with different wavelengths 1 and 2 2 are coupled out via the mirrors 18 and 20, which in this case are 80% transparent.

Fig. 5a and 5b show the end walls 8 and 9 drawn separately.

You can choose from glass, (glass) ceramic, quartz, plastic, germanium, CdTe, or zinc selenide. In the present embodiment, the two are Mirrors 18 'and 21' attached rigidly adjusted to one another on their surface. While the mirror 18 'is designed to be totally reflective, the mirror 21' is in his outer area partially permeable and in its center due to the continuous Hole 7 'fully permeable.

Depending on the type of laser, about 10 to 90% of the area can be on the recess omitted. In another exemplary embodiment, not shown in the drawing, there is none Recess provided; in this case the "mirror" has to be transparent and only have low absorption. It is also conceivable to have the entire front wall made of transparent To manufacture material and only the point where total reflection is desired, to be trained accordingly. The attachment of this totally reflective point can e.g. by vapor deposition of a gold layer. The totally reflective ones can do just as well Mirror and the (partially) permeable layers should be embedded in the wall. One A plate formed in this way can be used as a mode diaphragm.

In another embodiment, the totally reflective Mirror of the end wall 9 also through to NEN prism block 15 (Fig. 5a) or a triple mirror 16 (Fig. 6) is replaced by -n, the latter being inserted into the beam path in such a way that that only its flat areas 16 ', but not its prism edges 16 "optically are effective.

As can be seen from FIG. 7, the decoupled according to FIG. 2 can be Radiations of different wavelengths 21 and # 2 through a wavelength mixer 22, which can consist of a germanium crystal, for example, to a wavelength r2 Mix 3 = 2Rç 2.

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Claims (15)

Ring laser PATENT CLAIMS Laser arrangement consisting of one of a housing surrounded resonator chamber with an electrode system, which is in a center electrode with at least two surfaces serving for electrical discharge and at least two outer electrodes opposite these surfaces is subdivided, with an the inside end faces of the housing at the level of one of the free spaces between the electrodes one optical element each deflecting the laser beam in the direction of the other side and, at least at the level of the other free space, a partially transparent optical one on one side Element for decoupling the laser beam is provided, of which the deflecting optical elements of one end face arranged at an angle to the beam path are that all four optical elements (18 to 21) facing each other and arranged at angles to the beam path optical surfaces the laser beam in the manner of a ring laser on each of them steer opposing optical elements. 2. Laser arrangement according to claim 1, d a d u r c h g e k e n n z e i c h -n e t that in each case the diagonally opposite optical Elements (18; 20 or 19; 21) enclose the same angle with the beam path (Fig. 6). 3. Laser arrangement according to claim 1 and 2, d a d u r c h g e k e n n -z e i c h n e t that for a use of two or more wavelengths and with correspondingly subdivided electrodes (10 to 14), the optical elements (18 'to 21') about an axis perpendicular to the main horizontal plane of the device are pivotably arranged that each space between the electrodes one is assigned to another wavelength 2 (Fig. 2). 4. Laser arrangement according to one of the preceding claims, d a d u r c h e k e n n n z e i c h n e t that the assigned to the respective wavelengths R. Areas or surface areas of the optical elements (19 '; 20') at comparatively widely spaced wavelengths designed as a grating and with different Lattice constants (17) are provided (Fig. 2) .. 5. Laser arrangement according to one of the preceding claims, d a d u r c h e k e n n n n z e i c h n e t that the optical elements (18 'to 21') are interchangeable are arranged and one of the flat surface according to the respective needs have a different - e.g. cylindrical or aspherical - shape. 6. Laser arrangement according to one of the preceding claims, d a d u r c h e k e n n n z e i c h n e t that the two end faces (8; 9) of the housing (2) are themselves designed as totally and / or (partially) reflective carrier plates. 7. Laser arrangement according to claim 6, d a d u r c h g e k e n n -z e i c h n e t that the carrier plates (8; 9) made of quartz, glass, (glass) ceramic, plastic, Germanium, cadmium telluride or zinc selenide exist. 8. Laser arrangement according to claim 6 and 7, d a d u r c h g e k e n n -z e i c h n e t that at least one totally reflective area (6) and one sufficiently permeable area (7) on the side facing the resonator (5) the carrier plate (8) are provided or incorporated in the carrier plate. 9. Laser arrangement according to claim 8, d a d u r c h g e k e n n -z e i c h n e t that the totally reflective area (6) is in the form of a reflective layer vapor-deposited and the permeable area (7) made of a transparent material less Absorption and / or a through hole (7 ') consists (Fig. 5b). 10. Laser arrangement according to claim 9, d a d u r e h g e k e n n -z e i c h n e t that the reflective layer consists of a metallic layer - e.g. gold - Or a dielectric layer. 11. Laser arrangement according to one of claims 6 to 10, d a d u r c h g e k e n n n z e i c h n e t that the carrier plate (8) by limiting the reflective Area is designed as a mode diaphragm. 12. Laser arrangement according to one of the preceding claims, d a d u r c h g e k e n n n z e i c h n e t that the totally reflecting mirror (19; 20 or 19 '; 20 ') of one end face (9) as a prism block (15) or triple mirror (16) are formed (Fig. 5a and 6). 13. Laser arrangement according to claim 12, d a d u r c h g e k e n n -z e i c h n e t that the front side of the corner cube is exposed to the beam path flat areas (16 ') and edges (16 ") kept out of the beam path is arranged (Fig. 6). 14. Laser arrangement according to one of the preceding claims, d a d u r c h e k e n n n z e i c h n e t that the optical elements (18 to 21 ') and / or the end faces (8; 9) serving to hold them with the aid of a piezo drive (23) are adjustable (Fig. 1). 15. Laser arrangement according to one of the preceding claims, d a d u r c h e k e n n n z e i c h n e t that in the beam path of two decoupled Rays of different wavelengths »2 2 a common, another ray optical crystal (22) generating different wavelengths R3 - e.g. germanium or CdTe - coupled (Fig. 7).