DE102004038307A1 - Solid polymer laser medium production method, involves heating and deforming structure so that structure is combined along corresponding side surfaces to form cylindrical body, and structure is bonded to body along sides - Google Patents

Abstract

The method involves forming a laminated structure consisting of a solid doped polymer (1) and a transparent polymer (2), where the boundary layer between the polymers is evenly formed. The structure is heated and deformed so that the structure is combined along corresponding side surfaces (4) to form a cylindrical body, where the polymers form the exterior surface of the body. The structure is bonded to the body along the sides.

Description

The The invention relates to a process for producing a solid polymer laser medium according to the generic term of claim 1.

The The principle of doping a polymer matrix with dye molecules was Developed at the end of the seventies.

Since then, several examples of solid state polymer dye lasers have been developed, in most cases using an embodiment that operates in a longitudinally-pumped configuration ( US 5,136,596 ).

This configuration makes it possible to produce an output laser beam having a quality identical to the pump beam quality, since the cross section of the excitation region is defined by the cross section of the pump laser beam. In the case that one works with a high pulse power with a simultaneously low pulse repetition rate (repetition rate) (for example: with the aid of an Nd: YAG laser in the low-frequency Q-switching mode (Q-switch mode), a conversion efficiency of 50-70% can be achieved. be achieved with a reasonable lifetime of the gain medium. On the other hand, the laser threshold is relatively high, about 100 to 200 kW / cm ² for commercial plastics, which are impregnated with dyes.

For pump sources with high repetition rates, e.g. Copper steam laser, you have to For this reason, the pumping beam on a surface with a relatively small Focus diameter to achieve reasonable conversion efficiency. this leads to to a recognizable photodegradation of the laser dye, namely after just a single laser pulse, and in some cases even too damage the polymer matrix.

The operating time of the gain medium may be increased by periodically changing the position at which the excitation occurs by either moving and / or rotating the gain medium with respect to the pumping beam. To achieve this goal, the gain medium has become a thin strip ( US 5,136,596 ) or to a disk (A. Costella et al., "High repetition rate solid state dye laser pumped by a copper vapor laser", Appl. Physics Letter, v.79, N.4, p.452-454). The longest operating time was 30 minutes.

A another approach to increase the operating time (stability) of the dye-doped Polymer-reinforcing medium can be on the "threshold-like" dependency the photodegradation rate of the dye as a function of pump power density be based. (L.K. Denisov et al. "Service life of dye-impregnated polymer active elements at various energy densities and pump powers ", Quantum Electronics 1997, Vol. 27 (2) p. 115-117).

The Photodegradation rate decreases significantly when the pump power density falls below a certain value. However, this value is too low, to ensure adequate output efficiency in the longitudinal Pump Configuration but is high enough for effective lasing in the transversal Pump configuration.

Of the substantial disadvantage of the transversal pump configuration lies in the deficient one quality the output beam and leads as a result, too big optical losses within the resonator.

Out RU 21 05 401 It is known to substantially improve the quality of the output beam by employing a gain medium consisting of a "sandwich" structure with a dye-doped layer and a transparent layer of comparable polymer material, both layers having approximately the same refractive index. It will be in RU 21 05 401 proposed to realize such a reinforcing medium by polymerizing the transparent layer, followed by a Aufpolymerisierung the dye-doped layer. A disadvantage of the proposed method, however, is the high technical complexity for the formation of non-planar layers, which is associated with a considerable cost disadvantage. In this case, a non-planar, preferably a cylindrical amplification medium is desirable in order to be able to realize a periodic change in the position at which the excitation takes place (for example by rotation of the cylindrical amplification medium).

Out DE 102 43 845.5 For example, a method of making a reinforcing medium is known by joining a dye-doped polymer and a transparent polymer having a nearly equal refractive index to a disk-shaped reinforcing medium such that the transparent polymer forms an outer ring and the dye-doped polymer forms an inner surface by forming the dye-doped polymer cooled introduced into the transparent polymer and both polymers joined together in a special form and there are heat treated so that an optimal optical contact is made between the two polymers, and then that the joined together into a body polymers in a known manner, for example by Turning mechanically machined and polished.

The task of the outer ring made of the transparent polymer in the transverse pumping mode is to greatly reduce the negative influence of the polymer / air interface on the light generation. To DE 102 43 845.5 can be a cost-effective production of reinforcing medium for given requirements on the beam quality by using a transparent outer ring than without a transparent outer ring with a correspondingly high optical quality of the surface of the dye-doped polymer. Despite these advantages, the in DE 102 43 845.5 described light amplifier medium, the transparent and dye-doped polymer layer by relatively weak Wan-der-Vaals forces interconnected. That is why the mechanical and optical stability of the in DE 102 43,845.5 described light amplifier medium substantially lower than that in RU 21 05 401 described light amplifier medium.

It It is therefore an object of the invention to provide a process for the preparation of a Specify solid polymer laser medium, with which a solid polymer laser medium can be produced, which has a better stability, which is a much higher Output power with the same good quality of the laser beam and the same high conversion efficiency is achieved.

These The object is achieved by a Method solved with the features of claim 1.

One particular advantage of the method consists in the direct chemical bond between the dye-doped Polymer and the transparent polymer resulting in high stability at the same time high output power and beam quality leads.

By virtue of the fact that at least one layer structure consisting of a spatially limited layer of a dye-doped polymer and a layer of a transparent polymer arranged thereon is produced with essentially the same refractive index, wherein the boundary layer between the polymers is planar and then the layer structure is heated according to the invention and is deformed so that the at least one layer structure can be joined along corresponding side surfaces, whereby a substantially hollow cylindrical body is formed and the layer of the dye-doped polymer, the inner surface and the layer of the transparent polymer form the outer surface of the substantially hollow cylindrical body, wherein the boundary layer of Polymers forming a cylinder or truncated cone, a solid polymer laser medium for the transverse pumping operation with a stability comparable to the solid Po lymer laser medium described in ( RU 21 05 401 ) getting produced.

After the deformation of the at least one layer structure whose side surfaces are optionally mechanically processed in order to prepare them for bonding. Subsequently, the at least one layer structure is glued along the corresponding side surfaces to form a substantially hollow cylindrical body. As a result, according to the invention, it is possible to produce a substantially hollow-cylindrical solid-polymer laser medium which can be rotatably arranged in a structure for light amplification and / or light generation. Due to the rotatable applicability of the laser medium, it can be ensured that this is claimed by rotation at respectively different locations, whereby a reduction of the degradation rate can be achieved. Furthermore, the at RU 2105401 occurring technical problems in the polymerization of non-planar surfaces avoided. As a result, a quality and stability for the boundary layer between the polymers required for laser operation in the transverse pumping mode can be realized, preferably by polymerizing or polymerizing the dye-doped polymer onto the transparent polymer, wherein according to the invention the initially formed layer structure is deformed.

In a particularly preferred embodiment becomes the merged and bonded, substantially hollow cylindrical body heated, whereby a hardening of the used adhesive is achieved. The finished laser medium is in a further preferred embodiment for use in a light amplification structure machined and / or polished. A mechanical processing the laser medium according to the invention is preferably done by means of a lathe.

In a further preferred embodiment, the dye-doped polymer of the laser medium according to the invention is slightly conical, for example formed with a cone angle of 3 ° degrees, to prevent the generation of interference effects by unwanted reflections at the end faces. Preferably, the planar layer structure used, consisting of a layer of a dye-doped polymer and an overlying layer of a transparent polymer, has a substantially rectangular shape. The conical shape of the laser medium according to the invention can be realized by mechanical processing of a planar layer structure. Alternatively, the conical shape but also directly in the Polymerisati On the transparent laser medium with the dye-doped laser medium can be achieved by a suitable form.

Further expedient embodiments of the Invention are in the subclaims described.

The Invention will be described below in an embodiment for the production according to the invention closer to a laser medium explained. In the corresponding Show drawing:

1 a planar layer structure consisting of a dye-doped polymer and an overlying transparent polymer in a schematic, cut along the longitudinal axis representation;

2 a planar layer structure consisting of a dye-doped polymer and an overlying transparent polymer in a schematic, cut along the transverse axis representation (along the line A-A ');

3 the schematic representation of the essential manufacturing steps for a solid polymer laser medium according to the invention;

4 the schematic representation of the essential manufacturing steps for a solid polymer laser medium according to the invention;

5 a mold for deforming the planar layer structure acc. of the 1 and 2 in plan view;

6 a mold for deforming the planar layer structure acc. of the 1 and 2 in a sectional view (along the line B-B ');

7 a mold in plan view;

8th a die in a sectional view (along the line C-C ');

9 a solid polymer laser medium produced by the method according to the invention in plan view,

10 a schematic, sectional view of the solid polymer laser medium according to the invention along the line EE 'and

11 the schematic representation of the device configuration for light amplification by means of the laser medium after the 9 and 10 in plan view.

A particular advantage of the method according to the invention is that for the production of a solid polymer laser medium plane and thus inexpensive to produce polymer layers, as in 1 and 2 is shown schematically, can be used. In this case, the layer structure in the exemplary embodiment has a planar dye-doped polymer 1 as well as a flat transparent polymer 2 on. The dye-doped polymer 1 consists of MMA + 10% MAA and is impregnated with Rhodamine-B. The concentration of Rhodamine B is 8 · 10 ^-4 mol / l. For the transparent polymer 2 Commercially available PMMA is used. In this case, the boundary layer of the two polymers 1 . 2 and the outer surface at an angle α = 3 ° to each other, as in 2 is shown schematically. This planar layer structure is achieved by grafting the dye-doped polymer layer 1 on the transparent polymer layer 2 produced.

The 3 and 4 show a schematic representation of the essential manufacturing steps of a laser medium according to the inventive method. First of all, a flat layer structure (corresponding to 1 and 2 ) consisting of a layer of a dye-doped polymer 1 and an overlying layer of a transparent polymer 2 went out. This layer structure 1 . 2 is first heated and then deformed. This can be done according to 4 be realized, for example, that the layer structure 1 . 2 in the middle with the form 13 connected and heated to 130 ± 5 ° C. Thereafter, the heated layer structure 1 . 2 by means of the form 13 deformed in such a way that it has a substantially part-circular formation in sectional view, which covers at least (something) more than a semicircle. This means that the layer structure 1 . 2 forms a hollow cylinder in which a segment is cut out. After cooling to room temperature, the structure becomes 1 . 2 with shape 13 in compression 14 clamped and heated again to 130 ± 5 ° C and then under tightening the screws 15 deformed. After deformation, the structure 1 . 2 cooled. Then, the end faces of the structure are cut off so as to form a halved cylinder cut along its longitudinal axis. Thereafter, the corresponding end surfaces 4 coated with adhesive and with a semi-circular layer structure of the same shape between mold 13 and mold 14 clamped and held at 110 ° C for 10 minutes to allow the adhesive to cure.

The adhesive used in the exemplary embodiment was a monomer solution from Polymer-Optica Ltd. (Dzerzhinsk, Russia). Form 13 is in the 5 and 6 , form 14 in the 7 and 8th shown schematically.

Subsequently, the laser medium (consisting of 1 and 2 ) machined and polished by means of a lathe. The laser medium produced by the method according to the invention is in the 9 and 10 shown. The surfaces a, b are polished with optical quality. The area c requires a lower quality level when polishing.

The thickness k of the transparent polymer 2 ( 9 and 10 ) must be sufficiently large to avoid the generation of spurious effects (parasitic modes) caused by reflections from surface c. The thickness k is, for example, 2 mm.

The gain medium has a certain by the angle α slightly conical shape to the influence of the surface c on the laser activity to minimize.

The final mechanical treatment, for example, machining by a lathe and polishing of the surfaces a, b and c leads to the reinforcing medium according to FIG 9 and 10 ,

Would the outer ring 2 in 9 not be present from the transparent polymer in a transverse pumping mode, the main laser activity at the surface of the dye-doped polymer 1 due to scattering on the free surface lead to a greatly reduced conversion efficiency. Furthermore, a very high mechanical stability must be ensured between the two layers. Errors at the boundary layers can lead to mechanical cracks and / or material changes already after short laser operation, which leads to a strong reduction of the laser activity.

The proposed gain medium (consisting of 1 . 2 ) is designed for operation in a dye laser. The laser medium according to the 9 and 10 For example, it can be used in a light amplification structure as in 11 is shown schematically. In this case, excitation light of a pump source 5 via an optical system 12 on the laser medium (out 1 . 2 ), whereby the laser medium is excited transversely. The resonator is through the mirror 6 and 7 as well as the prism 8th educated. The laser medium is rotatably mounted and during operation reduces the degradation by means of the motor 10 turned. The (light) chopper 9 interrupts the excitation by the pump source 5 at selected intervals to the degradation of the laser medium (out 1 . 2 ) continue to decrease. As a pump source 5 comes into consideration a copper vapor laser (repetition rate v = 16 kHz, laser pulse length 20 ns, average output power 10 W, wavelengths 510.6 nm and 578.2 nm) or any other pulsed laser. The reflection of the output mirror 7 was 60%. The width of the excited region in the laser medium was 0, 8 mm.

The Radiation of the dye laser with the tested and introduced gain medium was tunable in the range 605 nm - 635 nm with a spectral bandwidth of 2.5 nm.

1

dye-doped polymer

2

transparent polymer

4

side surface

5

pump laser

6

mirror

7

mirror

8th

prism

9

Chopper (Chopper)

10

engine

12

optical system

13

shape

14

mold

15

screw

a

area

b

area

c

area

d

thickness of the light amplifier medium

D

Except diameter of the light amplifier medium

α

angle

k

thickness of the transparent polymer

Claims (11)

Process for the production of a solid-polymer laser medium for a high-performance solid-state dye laser with high repetition rate, characterized by the following process steps: - producing at least one layer structure ( 1 . 2 ) consisting of a spatially limited layer of a dye-doped polymer ( 1 ) and a layer of a transparent polymer ( 2 ) with the same or almost the same refractive index, the boundary layer between the polymers ( 1 . 2 ) is formed, - heating and deformation of the at least one layer structure ( 1 . 2 ) such that the at least one layer structure ( 1 . 2 ) along corresponding side surfaces ( 4 ), whereby a hollow-cylindrical or nearly hollow-cylindrical body can be formed, wherein the layer of the dye-doped polymer ( 1 ) the inner surface and the layer of the transparent polymer ( 2 ) form the outer surface of the hollow cylindrical or nearly hollow cylindrical body, - if appropriate, mechanical machining of the corresponding side surfaces ( 4 ) of the at least one layer structure ( 1 . 2 ) for a gluing and Bonding the at least one layer structure ( 1 . 2 ) along the corresponding side surfaces ( 4 ) to a hollow cylindrical or nearly hollow cylindrical body. Method according to claim 1, characterized in that that the hollow cylindrical or almost hollow cylindrical body heated becomes. Method according to claim 1 or 2, characterized that the hollow cylindrical or almost hollow cylindrical body mechanically processed and / or polished. Method according to one of the preceding claims, characterized in that a layer structure ( 1 . 2 ) is used with rectangular or nearly rectangular shape. Method according to one of the preceding claims, characterized in that a layer structure ( 1 . 2 ) is used with flat surfaces. Method according to claim 5, characterized in that a layer structure ( 1 . 2 ), in which the dye-doped polymer ( 1 ) formed a finite angle to the interface of the polymers ( 1 . 2 ) having. Method according to one of the preceding claims, characterized in that the layer of the transparent polymer ( 2 ) is prepared by polymerization. Method according to claim 7, characterized in that the layer structure ( 1 . 2 ) by Aufpolymerisierung the dye-doped polymer ( 1 ) on the layer of the transparent polymer ( 2 ) will be produced. Method according to one of the preceding claims, characterized characterized in that the layer structure before deformation on a temperature between 125 ° C and 135 ° C heated becomes. Method according to one of claims 2 to 11, characterized that the hollow cylindrical or almost hollow cylindrical body for 10 Is heated to a temperature of 110 C for a few minutes. Method according to one of the preceding claims, characterized characterized in that the hollow cylindrical or nearly hollow cylindrical body two layer structures is assembled, which with respect to their Semicircular cross section or almost semicircular are formed.