Description :: Our patents

The guessed invention falls into field of laser technique.

The known laser electrooptical blocks with a cross pumping of working gas contain a gas-discharge chamber, drawn along a gas stream, with electrode system and an optical cavity, posed perpendicularly to a gas stream [1]. The disadvantages of such electrooptical blocks consist in design conflicts at deriving high power of radiation and its simultaneously high quality concerning deriving a single-mode oscillation. In case of using stable optical resonator, providing single-mode oscillation, is restricted an opportunity of high power deriving. This takes place because of incomplete volumetric coefficient (incomplete filling of gas-discharge chamber volume with excited active medium by optical cavity volume), and also because of a high energy loading on a forward lead-out mirror, which in this case is usually transparent. In case of unstable optical resonator usage the optical cavity volume almost completely fills the volume of gas-discharge chamber with excited active medium. An energy loading on a forward lead-out mirror is substantially reduced, that allows essentially to increase power, however quality of a laser radiation, bound with its focusing, thus is aggravated, as the radiation is not single-mode.

Also is known the laser electrooptical block with cross pumping of working gas, containing the gas-discharge chamber, drawn along a gas stream, with electrode system and optical resonator, stable and unstable in two mutually orthogonal planes, transiting through an optical axis, cross a gas stream. While the plane of instability is posed perpendicularly to a gas stream [2]. In this electrooptical block to some extent are eliminated the design conflicts at deriving high power of radiation and its high quality, as volume of optical resonator unstable plane fills major volume of gas-discharge chamber with active medium at a single-mode oscillation in stable plane.

This engineering solution is most close to stated object, that is the prototype.

The disadvantage of the prototype consists in restriction of laser radiation output power, as the arrangement of electrode system on side walls of gas-discharge chamber causes small distance h between these walls. It is known, that specific energy contribution in a discharge gap is inversely proportional to distance h and h - magnification gives lowering of specific contribution and, therefore, lowering power of a laser radiation. Small distance h, necessary for security of a high specific energy contribution in a discharge gap, restricts a rate of a gas stream in the chamber, that superimposes a restriction on power of a laser radiation.

Besides, the quality of radiation in the prototype is aggravated because of a heating of a mixed gas at passage it through a discharge gap. That is a gas in a beam cross-section in optical cavity heated to different temperature and it gives a different power density in laser beam section.

Technical problems of the guessed invention are a power multiplication of a laser radiation and improvement of its quality.

The indicated problems in the guessed invention are implemented because of that the plane of instability of optical cavity is perpendicular to a gas stream. And between gas-discharge chamber walls, near to volume of the optical cavity, is posed the multisection electrode system with parallel to a gas stream arrangement of sections, intended for excitation of working gas. Thus between walls of the gas-discharge chamber the even quantity of multisection electrode systems can be posed, the optical cavity is fulfilled multipass with the same quantity of passes. And for security of passage of a laser radiation near each electrode system there are reflecting rotary blocks, converted concerning a gas stream.

The arrangement of multisection electrode system between walls of the gas-discharge chamber, near volume of optical cavity, allows to increase distance between walls of the chamber h without diminution of a specific energy contribution. As in this case specific energy contribution is defined through distance between electrode sections of multisection electrode system, which can be small. The magnification of distance between walls h and arrangement of a plane of instability perpendicularly to gas stream allows to increase volume of the optical cavity across a stream and to reduce along a stream. That gives a smaller temperature difference in the cross-section of a laser beam and, therefore, allows to greatest extent to implement virtues of stable-unstable resonator: reaching of high power at excellence of radiation. Besides at magnification h it is possible to increase gas flow rate in the gas-discharge chamber and to lower an aerodynamic drag of a contour. These both circumstances give a power multiplication of a laser radiation.

Parallel arrangement to a gas stream of sections of multisection electrode system brings to aerodynamic-drag reduction and to minimum infringement of homogeneity of a gas stream, that also ensures pinch of laser radiation power and its quality.

The arrangement between walls of gas-discharge chamber of even quantity of electrode systems in aggregate with rotary blocks, converted concerning a gas stream, allows at each subsequent pass of a laser beam through a gas-discharge gap to change on opposite an arrangement of laser beam section in relation to a gas stream. Thereof laser beam section temperature is aligned and also quality of radiation is increased.

The plan of the offered electrooptical block of the laser with working gas cross pumping and with cross discharge is shown on fig. 1. It is formed by two flat walls, posed on distance h. In gas-discharge chamber1, perpendicularly to gas stream VG , is posed the optical resonator 2, stable in a plane, parallel gas stream VG and unstable in a plane, perpendicular gas stream VG . The laser beam in the cross-section has the shape of two spots, and the distribution of a power density in each spot is close to Gaussian (fig.2). Near to volume of the optical cavity 2 is posed the multisection electrode system 3 with sections, parallel to a gas stream. Each section in this case represents a plate of electrodes, posed in parallel to each other and to a gas stream, for example, anode and cathode.

On fig. 3 the plan of laser electrooptical block with a cross pumping of working gas and with longitudinal discharge is shown. In this case each section of multisection electrode system 3 represents sequentially posed to each other and in parallel to a gas stream knife or pin electrodes, in particular, anodes and cathodes.

Distance between cathodes and anodes h can not be less than 1,5 sizes of basic cavity mode in a plane of stability (in a plane, parallel gas stream) on a level

1/e², e = 2,81828.... Otherwise tails of basic Gaussian mode will be cut off by electrodes, that, first, reduces quality of radiation, and, secondly, can destroy electrodes. Considerable magnification of a discharge gap, when it is more, than in 2 times exceeds the size of a Gaussian mode, will give an occurrence of high Gaussian modes, that essentially will lower quality of radiation, and at presence of additional selection by diaphragms will give laser efficiency lowering. Thus, the optimum requirements are implemented at 1,5w _1/e² < h < 2w _1/e².

We shall mark, that the different configurations of electrodes are possible, for example, the cathodes can be dowels, anodes - knives with an independent lead of electrical energy and inversely.

The construction of the discharge chamber is sharply simplified, if each of electrodes represents a set of parallel plates, and planes of these plates oriented perpendicularly for opposite electrodes. In this case is implemented a discharge chamber of a cross configuration. The quantity of electrodes in such discharge chamber is many times less, than in a pin one. If number of cathodes - M and number of anodes - N, number of crosses, that is “ the effective number of electrodes ” is equal NM. Thus, the quantity of discharge gaps exceeds the quantity of electrodes in (N M) / (N+M) times. If, for example, N=60; M=10, (60 x10) / (60+10) = 8.6.

The quantity of independent current sources or ballast devices is also less in such times. To the discharge chamber of such configuration most effectively is to apply reactive ballast devices, such as inductivities and capacities or current sources.

On fig. 4 the plan of the electrooptical block of the laser with a cross pumping of working gas and with the cross discharge is shown, in which between walls of the gas-discharge chamber 1 two multisection electrode systems 3 are posed. For security of passage of a laser radiation near each system 3 there is a rotary block 4, converted concerning a gas stream, representing two mirrors, set angular 45⁰ to a laser beam in two gaps with active medium and angular 90⁰ to each other (fig. 5). The quantity of multisection electrode systems 3 can be enlarged up to even quantity, thus there will be an odd quantity of rotary blocks 4.

The offered electrooptical block of the laser with a cross pumping of working gas operates as follows. After insert of a pumping system the working gas moves between walls of the gas-discharge chamber1 with velocity VG . On electrodes of multisection electrode system 3 supply a high voltage for an ignition of a glow discharge and making active medium in working gas. In case of cross discharge active medium forms between sections of multielectrode system 3 across a gas stream, and also on some distance from this system on a gas stream (fig. 1). In case of longitudinal discharge active medium forms between pin electrodes of multisection electrode system 3, posed on both sides from volume of optical cavity 2 (fig. 3). Photons, formed in active medium, are organized in a laser beam at a multiple reflection in stable-unstable resonator 2, in which the plane of instability is posed perpendicularly to gas stream VG . It ensures complete filling of volume of gas-discharge chamber 1 with laser beam. In a plane, parallel to a gas stream VG , the optical resonator is stable, that ensures a single-mode oscillation of laser beam in two spots (fig. 2). At suitable setting of optical cavity mirrors the oscillation of radiation only in one spot is possible. In cross-section a volume of optical cavity 2 has the shape, drawn across a gas stream, that allows to greatest extent to implement virtues of stable-unstable resonator.

At presence between walls of gas-discharge chamber 1 two electrode systems 3 a laser beam transits near to each electrode system, being reflected between passes from mirrors of converted rotary block 4 (fig. 4, 5). After reflection from mirrors of converted rotary block 4 section of a laser beam is turned concerning a gas stream VG on 180⁰, that are hotter streams of a beam are located in more cold part of a gas stream and inversely.

What is claimed is:

An electrooptical block of a laser with cross pumping of working gas, comprising: a gas-discharge chamber, drawn along a gas stream, and optical resonator, stable and unstable in two mutually orthogonal planes, passing through an optical axis cross a gas stream, a plane of instability of this optical resonator being perpendicular to a gas stream; characterized in that a gas-discharge chamber consists of two multisection electrode systems of an opposite sign, and a discharge is carried out between two electrode systems of an opposite sign longitudinal to a gas stream, volume of optical resonator is posed between these electrode systems, and distance between them h is selected in an interval 1,5 W_{1 / e}² < h < 2 W_{1 / e}² where W_{1 / e}²- size of a basic mode in a plane of stability on a level 1 / e², where e = 2.81828.
The electrooptical block according to claim1, wherein anodes and cathodes represent parallel plates, drawn across a stream, while planes of anodes oriented perpendicularly to planes of cathodes.
The electrooptical block according to each of claims 1, 2, wherein between walls of gas-discharge chamber is posed even quantity of multisection electrode systems; the optical resonator is fulfilled with the same quantity of passes, and for security of passage of a laser radiation near each electrode system there are reflecting rotary blocks, converted concerning a gas stream.