JPS6017912Y2 - gas laser system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser, and more particularly to a closed cycle discharge gas laser device.

One of the increasingly promising types of laser systems for many commercial uses! It is a gas-excited gas flow laser.

The common basic principles of operation can be roughly classified into three categories: coaxial laser equipment (coaxial 1
asers) and orthogonal beam laser equipment (cross
beam 1 asers) and cross current laser equipment (CR
It is found in all the various forms of electrical systems, which can be divided into oss flow 1asers).

Perhaps the simplest of these categories, both to describe and to manipulate, is the coaxial type of groove, in which the flow of the gaseous working medium, the direction of the discharge, and the optical cavity are The axes are collinear within a discharge tube made of Pyrex or some similar electrically insulating material.

Orthogonal beam type laser devices have a very different physical profile than the coaxial type described above, and therefore have different operating characteristics.

In orthogonal beam devices, the working medium passes through a channel of generally rectangular cross-sectional shape and the discharge extends co-currently, but the optical axis is transverse to the gas flow discharge.

Cross-flow type geometries belonging to the third category of discharge laser geometries are also commonly constructed with gas flow channels of rectangular cross-section.

The discharge and optical axis are maintained transverse to the direction of gas flow, and the discharge can be either parallel or perpendicular to the optical axis.

This cross-flow system often requires special equipment to stabilize the discharge against gas flow effects.

For additional information on various laser device configurations,
For example, U.S. Pat. No. 3.74 by Buczek et al.
No. 7.015, title ° “Stable orthogonal magnetic field gas flow laser”
and U.S. Patent No. 3.743.9 by Bullis et al.
No. 63, entitled "Horizontal Gas Laser".

In addition to the above-mentioned shape-based differentiation, the discharge laser device also uses population inversion (thepopulation) in the working medium.
n1nversion) are often classified based on the methods used to induce them.

the working medium by a direct current discharge within itself, or by a discharge induced into the medium by suitable radio frequency radiation coupled to the working medium, or by a discharge enhanced by an intense electron beam directed into the working medium; Alternatively, devices for exciting the working medium by a discharge enhanced by photoionization techniques and various combinations of these excitation techniques have proven useful: for example, De
Maria, A. J., “Considerations on CW strong crab carbon oxide leather production”, Proceedings of
the IEEE 1973 Vol. 61 No. 6, 731~
See page 748.

Although there are inherent limitations on the power densities that such systems can induce, a coaxial discharge laser device is theoretically the simplest device, and practical considerations suggest that it is unlikely to be used in any commercial laser application. It can be easily adapted to.

The simplicity and reliability of basic coaxial laser systems with powers in the range of several kilowatts is discussed in the publication Wis.
nerXG, R6etal, “Unstable resonator of CO2 discharge convection laser device” Appl, phys, Lette
rs,] 997 Tsubo January, pp. 2284-15, which described a two-tube laser device,
The remarkable characteristics of coaxial convection lasers are revealed.

It is very simple to construct an optical resonator with its optical axis coincident with the geometrical axis of two flow tubes arranged end-to-end in the cavity.

Each tube has an auxiliary extension with an offset axis through which the working medium is injected, flows along the optical axis, and exits through a common exhaust space.

A discharge is maintained within each tube between each of the two cathodes located in the offset axial extension of each tube and a common anode located in the discharge chamber.

A special truss structure connects the optical surface devices forming the optical cavity.

This coaxial laser system evolved into the development of the 12-tube amplifier, in which stable output from a low-power master oscillator is fed into multi-pass power amplifier optics within the 12-tube configuration. be directed.

This is discussed in Burwell W, G, “Considerations on CW strong laser technology” (The Proceed
ings of the Th1rd Worksho
p onLaser Interaction a
nd Re1ated PlasmaPhenom
Please refer to ena (scheduled to be announced).

Although this system provides a relatively large amount of output from the coaxial forming device, the overall device is somewhat impractical for manufacturing operations.

The primary objective of the present invention is to provide a high quality laser radiation beam in the nominal power range of 1 to 10 kilowatts with equipment designed to operate within a standard commercial environment.

Based on the invention, a coaxial laser system with an unstable cavity and a power amplifier generates an annular beam of high-quality laser radiation within a structure designed to function within a production environment: the laser gas is in the optical region. through two inlet manifolds that direct the gas flow to a central outlet fill chamber through a plurality of discharge tubes where the gas is electrically excited and which are optically excited. are in series and electrically in parallel.

Further, in accordance with the present invention, the internal optics are isolated from ambient vibrations and mechanical disturbances, insulated to prevent electrical short circuits, cooled to minimize actuation temperature fluctuations, and provided with a robust structure. A single truss structure, which is not in contact with the laser working medium, integrates the mirror array system and other optical devices.

One advantage of the present invention is that it provides a beam of laser radiation that can be reliably directed to a variety of locations over a wide range of areas of interest in a typical commercial production facility.

The invention can operate for an indefinite period of time as a closed cycle system requiring very little gas replenishment.

Moreover, the system positive branch parfocal unstable resonator can be configured for either maximum brightness or maximum power.

The main feature of the invention is the folded optical path, which allows the installation of a resonator with a relatively long optical path installed in a relatively short system envelope.

An annular mirror couples energy from the unstable resonator to the amplifier, and the optical device is directionally stable to better than 10 microradians.

The folded path optical device is a modular dimensioned structure whose length and relative proportions of oscillator and amplifier can be varied very easily.

The main gas circulation piping system is formed into a rigid connecting loop, which is flexibly installed in the laser section of the system.

Moreover, a platform supporting the internal optics of the laser device is flexibly mounted from the platform housing and vertically connected to each other by a rigid optical platform.

The laser gas is excited by a DC discharge maintained within a plurality of discharge tubes.

The above-mentioned and other quantitative features and advantages of the present invention will become more apparent by reference to the following detailed description of the preferred embodiments illustrated in the accompanying drawings.

With reference to the drawings, the simplified inverted view shown in FIG. 1 includes a gas laser 10 having support legs 12 mounted on the ground 14.

The optical box 16 has collapsed into the main part of the laser device.

The gaseous working medium is distributed through a gas supply pipe 18 to both ends of the laser device, exits the laser device through a discharge plenum 20 and is carried away to a gas discharge pipe 22 .

Optical platform truss 24 is suspended by a plurality of vibratory mounting devices 26 that are rigidly attached to optical platform devices 28 at each end of the optical box.

An alignment device 30 is rigidly attached to the truss, and an outer optical device 32 is positioned by an outer support member 34 extending from the platform truss.

A pair of end inlet manifolds 36, one of which is shown in FIG. 2, are coupled to a plurality of discharge tubes 38 extending through the optical box.

At each end of the optical box is an optical platform housing 40 that communicates with the discharge plenum through the discharge tube as shown in FIG.

The platform housing has a connecting rod 42 extending therethrough, and a flexible seal 44 forms a gas seal at the point where the connecting rod passes through the housing, such as the lower housing plate 46.

The optical platform assembly 28 includes an upper platform plate 64 and a lower platform plate 66; each platform housing has an internal bench 68 that is connected to an upper bench plate 70, a lower bench plate 72, and a lower bench plate 72; It includes a reflective device 74 rigidly attached to a backing plate 76 connecting the upper and lower bench plates.

The same upper and lower plates from each optical platform device are rigidly attached to the optical platform truss, and the vibratory mounting device is also rigidly attached to the optical platform housing, thereby allowing the platform truss and platform device to are mechanically floating relative to the platform housing and their supporting structures connected to the ground.

One of the main concerns in the structure of the present invention is that
The objective was to isolate the optical equipment of the system from torsional effects in the various auxiliary support members due to unstable conditions such as thermal cycling phenomena; Both isolation against vibrations present in the environment and the electrical isolation of the reflective surface device itself are necessary.

The rigid optical structure unit basically includes the optical platform truss 24 and the two optical platform devices 28 rigidly attached to this truss, but with provision for mechanical and electrical isolation. has.

The internal benches 68 are constructed of a metal such as Imphal and are at a higher potential than ground due to the surrounding ionized gases, which are mounted on the connecting rods of an insulating material such as alumina. ing.

These rods are also constructed from an insulating material such as fiberglass material.
0 by a flexible sealing device 44.

Additionally, because the rigid optical structure is supported from the optical platform housing by a vibratory mounting device 26, the structure remains mechanically floating relative to the support device.

For further details on the mechanical and electrical isolation of the present optical system, see “C0ruO10 et al.
See related invention described in Stable Platform Structure for Gas Laser °', U.S. Pat.

Additional details related to gas circulation and discharge are shown in FIG.

A gas supply pipe carries the working medium to each end of the inlet manifold 3
Connected to the top surface of each manifold are four insulating tubes that supply the working medium to the discharge tubes 6 and lift the working medium to the horizontal position of the discharge tubes and allow it to flow into the discharge plenum.

Each tube has an annular cathode ring 78 with a thick walled copper orifice for long operating life.

The tubes all pass through a discharge manifold 80 which serves as a common anode that is maintained at ground potential.

The top, bottom and sides of the horizontal section of the discharge tube are covered by a rectangular tube encapsulation device 82, which is rigidly connected to the optical platform housing.

A tube encapsulator cooler 84 includes a heat absorption loop 86 to cool the interior of the tube encapsulator.

This particular system being described is an 8-tube coaxial discharge laser.

The eight tubes are arranged optically in series and electrically and flow-wise in parallel.

These tubes are grouped in parallel pairs in a single horizontal plane, six of which are located in the oscillator section and two in the amplifier section of the laser device.

The working medium is a mixture of carbon dioxide, helium, and nitrogen, and the working medium is 300-400 ft/Sec (91,4-1
A flow rate of 21.9 m/5 ec) passes through the laser device and is maintained at a nominal hydrostatic pressure of 3 Qtorr.

The path lengths of the oscillator and amplifier above are each approximately 30ft (
9,14m, ) and 10ft (3,0577L) T:
The mode diameter of the beam in the 3-inch (7,62 cm) diameter discharge tube is approximately 2-' (6,2 cm)
98cm).

12000ft3/min (3407re/min
) provides an output beam containing 7 kilowatts of useful laser power when 50 kilowatts of direct current energy is applied to the working medium in the eight discharge tubes.

For the laser shaping apparatus described here, the entire system has been found to have very good gas-tight integrity, resulting in low flow rates of make-up gas required while retaining gas removal. Cleaning will be carried out.

In many circulating gas laser systems, a fraction of the flow rate through the main circulator is required to maintain a steady output state of the new gas in the output beam, i.e. to ensure efficient operation.
It is not uncommon for it to occur that more than % must be added to the flow system.

For the present invention that operates with the parameters listed above, two
For operation over 413G, only 5% of the flow rate of the working medium is required.
A nominal make-up gas flow rate of /100 was required.

The system described herein is an essentially sealed closed loop system resulting in minimal leakage from the surrounding atmosphere into the near vacuum conditions of the low pressure working medium.

If air-containing water vapor or other contaminants were to leak into the circulation loop of the working medium, extremely complex plasma chemistry would occur, especially within the discharge region of the laser device.
This can occur and laser performance can be significantly degraded.

The entire system constituting a closed cycle gas laser according to the invention is schematically shown in FIG.

A gaseous working medium flows into the discharge laser device 10, which generates the alignment laser.
ser) 30, Enclosing equipment cooler (the encl
osurecooler) f 36 , a power supply 88 and a controller 90 , and the laser device generates radiation that interacts with the outer optics 32 .

The working medium leaves the laser section and enters the discharge plenum chamber (t
It is cooled in an exhaust heat exchanger 92 located in the discharge plenum.

A make-up gas supply system 94 supplies the fresh working medium in the amount described above to the main stream and the mixture flows through a main circulator 96 which provides the working medium with the pressure changes necessary to operate the closed cycle. .

A gas removal system 98 connected to the high pressure side loop of the circulator provides the necessary control of system pressure.

From the circulator, the working medium flows through a circulatory system heat exchanger 100, which removes the work heat absorbed by the working medium by compression, and flows back into the laser device.

A mirror surface arrangement forming an optical cavity according to a preferred embodiment of the present invention is shown in FIG.

Concave end mirror 1 combined with four rotating plane mirrors 104
02 and an end convex mirror 106 form the resonator part of this cavity; the end mirrors
ive branch), forming a parfocal unstable resonator.

An annular plane mirror 108 extracts a radiation beam with an annular cross-section from this resonator and directs it to an amplifier plane mirror 110;
The amplifier plane mirror redirects this annular beam into the amplifier section of the cavity.

A nominally 30 ft (9,14 rrL) long planar stable resonator can be implemented with carefully prepared concave mirrors with radii of curvature ranging from 100 ft (30,4877 L) to 150 ft (45,72 rn,).

This has made structures consisting of concave mirrors with long radii of curvature impractical for commercial applications.

Shutter 114, beam catcher (beamcat)
cher) 116, an output window chamber containing an output window 118;
l l 2 is attached to an optical platform housing with an outer optic as shown in FIG.

This window is placed in the path of the output beam and its planar surface arrangements are offset by a small angle α, so that
Radiation reflected by these surfaces is not reflected back along the axis of the laser device.

The beam catcher is placed in the path of the radiation reflected from the surface to capture this energy, thereby eliminating damage or other deleterious effects on the structure.

A shutter is movably mounted inside this output passage chamber: this allows this output passage to be changed without destroying the vacuum of the optical platform housing.

Typically, laser devices are operated continuously, although the output beam may be delivered to the operating area intermittently.

During radiation cessation, the beam is diverted from its normal path by a diverting mirror 120 which directs the full power beam to a calorimeter 122 shown in FIG.

The deflecting mirror has a sharp straight edge and slides across the output beam.

In this manner, the output beam can be directed either to the target area or to the calorimeter without causing any reflections to the general environment when the deflecting mirror is rotated into the path of the output beam. Ru.

The position of this deflecting mirror is controlled by a pneumatic cylinder in combination with an electric solenoid in the anti-tamper safety system; no suitable air pressure is distributed to this pneumatic cylinder and a controlled electrical potential is distributed to this solenoid. Otherwise, the deflecting mirror remains in the path of the laser output beam, thereby deflecting the beam to the calorimeter.

The inside of the calorimeter is painted black to increase its absorption, so that virtually all of the deflected beam is absorbed onto the inside of the calorimeter.

The calorimeter is calibrated to measure the output from the laser device.

This result is typically obtained by temperature measurement using a suitable thermocouple.

Particular attention has been paid to the design of the gas supply pipes and discharge pipes, especially in the vicinity of the discharge plenum, where these pipes are placed in isolated and insulated arrangements from the ground.
off device) 124; the device includes a first bolting plate 126 and a second bolting plate 128 interconnected by a plurality of standoff rods 130, as shown in FIG. It includes.

A fill pipe (pl) connecting the discharge fill chamber to a discharge pipe
enum pipe) l 32 is the dividing pipe (s
The splitting pipe connects the suction pipe to the inlet manifold to eliminate side loads on the laser system as a result of pressure differentials across these pipes. It has become.

Furthermore, the pipes 132, 134 are connected to a flexible bellows device 136.
is flexibly connected to this standoff device to isolate the laser device from vibrations in the main circulation system.

An important structural requirement of this standoff device is that the cross-sections of the inlet and outlet vibrators are equal and perpendicular to a common axis passing through the geometric center of the cross-sections to load the discharge plenum with torsional moments. The goal is to remove the

Additionally, the main circulator, its drive motor, and the circulatory system heat exchanger are mounted on a support pad separate from the optical system to minimize the amount of vibration transmitted to the laser system.

Cooling is required in several parts of this system.

It is at the exhaust heat exchanger 92 that the greatest amount of heat is removed from the system.

This unit uses a two-conventional water-cooled fan-tube structure in which substantially the entire discharge power is not converted into laser radiation, but is removed from the working medium.

Another place where relatively large amounts of heat are removed from the working medium is in the circulatory system heat exchanger 100, which is also a water-cooled fan-tube arrangement and pumps absorbed by the flowing gas during the compression process. Get rid of work.

The mirror devices in the oscillator and amplifier are also cooled.

The amount of heat absorbed by these mirror devices is not as large as in the devices described above, however, this mirror cooling is essential to prevent distortion and damage to the mirror surface due to the intense radiation flux exerted on the same surface. It is something like that.

These mirrors are specially designed with intricate fluid passages behind the reflective surface to enable water cooling of the mirrors.

This technique is well known in the art and is summarized in U.S. Pat. No. 3,645,608, Cooling Apparatus for Reflective Apparatus, by Tanley et al.

This cooling is performed using distilled water since the mirror surface is at a potential higher than ground.

While the exact cooler design is not critical, removing excess heat from the interior of the rectangular tube enclosure 82 is.

A large amount of heat is normally generated within the working volume discharge tube, some of which is expressed through the upper portion of the optical platform truss, causing vibration and optical misalignment within the same.

The rectangular tube encapsulation device protects the discharge tube from physical damage and prevents heat transfer by conduction to the truss; moreover, the tube encapsulation device greatly strengthens the entire optical box and protects it from physical damage. This contributes to reducing torsional phenomena, i.e. torsions that might otherwise exert undesirable forces on the truss.

The tube encapsulation device cooler maintains the temperature of the gas outside the discharge tube at approximately room temperature.The circulation fan placed inside the rectangular tube encapsulation device recirculates the gas throughout the tube encapsulation device. provides a more uniform temperature distribution over the temperature range.

In addition to the cooling described above, the calorimeter, deflection mirror, and beam catcher each require cooling appropriate to the amount of operation of the system.

Although the invention has been illustrated and described in connection with a preferred embodiment thereof, it will be recognized by those skilled in the art that various modifications and omissions in form and detail may be made without departing from the scope of the invention. should be understood.

[Brief explanation of the drawing]

FIG. 1 is a simplified inverted view of the present invention, showing various structural details of some of the main structural units of the system. 2 is a simplified end chamber view of the apparatus shown in FIG. 1; FIG. FIG. 3 is a simplified schematic inverted view of the optical encapsulation device and main support structure. FIG. 4 is a simplified schematic inverted view showing additional details of the gas flow system and cooling device within the optical box. FIG. 5 is a simplified schematic diaphragm of a fully closed cycle system according to the present invention. FIG. 6 is a simplified plan view of the optical device forming the laser oscillator and amplifier. FIG. 7 is a simplified illustrative view of the output penetration chamber. 10... Gas laser, 12... Support leg, 14... Ground, 16... Optical box, 18... Gas supply pipe, 20...
...Discharge filling chamber, 22... Gas discharge pipe, 2
4...Optical platform truss, 26...
... Vibratory mounting device, 28 ... Optical platform, 32 ... Outer optical device, 34 ...
...Outer support member, 36...End inlet manifold, 38...Discharge tube, 40...
・Optical platform housing, 42...Connecting rod, 44...Sealing device, 68...
・Optical bench, 74...Reflection device, 82...
... Packaging device, 86 ... Packaging device cooler, 92 ... Exhaust heat exchanger 94 ... Makeup gas supply device, 96 ...・・Main circulatory system, 98・・
... Gas removal system, 102 ... Concave mirror, 104 ... Plane mirror, 106 ... Convex mirror, 108 ... Annular plane mirror, 110 ...・
・Amplifier plane mirror, 112... Output penetration chamber, 12
4...Standoff device.

Claims (1)

[Claims for Utility Model Registration] A closed cycle laser system generating laser radiation by means of a gaseous working medium circulated in one loop, having a gas inlet, a gas outlet and a bent passage; an unstable resonator formed between two curved reflective surfaces having a common optical axis and having a plurality of discharge tubes arranged around the optical axis; means for generating an electrical discharge along said optical axis to generate an electrical discharge; a planar reflective surface disposed on said optical axis for extracting laser radiation from said unstable resonator as an output beam having an annular cross section; a gas laser device comprising means for cooling a surface and a part for amplifying the laser radiation extracted from said unstable resonator; a first heat exchanger providing a cooling effect on said working medium; and said gas outlet. passage means connecting the heat exchanger to the heat exchanger; a forced circulation device for continuously circulating the working medium through the loop; passage means connecting the heat exchanger and the forced circulation device, the passage means connecting the heat exchanger and the forced circulation device; passage means including means for isolating the first heat exchanger from vibrations occurring in the circulation forcing means; a second heat exchanger that provides a cooling effect to the working medium exiting the circulation forcing means; passage means connecting a heat exchanger to the forced circulation device; and passage means connecting the second heat exchanger to the gas inlet of the gas laser device, the gas inlet being connected to the second heat exchanger. passage means having a means for insulating against vibrations occurring in the loop; a replenishment gas supply device connected to any one of the passage means for replenishing new working fluid to the working fluid flowing through the loop; and the circulation forcing device. a gas removal device connected to a passage means connecting the second heat exchanger and removing a portion of the working medium in the loop to maintain a stable pressure in the loop; A passage means connecting the second heat exchanger and a passage means connecting the second heat exchanger to the gas inlet of the gas laser apparatus are interconnected, and a pressure difference between the inside and outside of these passage means causes the passage means to be connected to the gas inlet of the gas laser device. A closed cycle laser system comprising: a standoff device for avoiding lateral forces acting on the gas laser device;