CA1207070A - Tangential flow laser apparatus - Google Patents
Tangential flow laser apparatusInfo
- Publication number
- CA1207070A CA1207070A CA000472814A CA472814A CA1207070A CA 1207070 A CA1207070 A CA 1207070A CA 000472814 A CA000472814 A CA 000472814A CA 472814 A CA472814 A CA 472814A CA 1207070 A CA1207070 A CA 1207070A
- Authority
- CA
- Canada
- Prior art keywords
- casing
- laser
- gas
- rotor
- wall
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 230000005284 excitation Effects 0.000 claims abstract description 18
- 238000001816 cooling Methods 0.000 claims description 11
- 230000032258 transport Effects 0.000 abstract description 7
- 230000010354 integration Effects 0.000 abstract 1
- 239000000203 mixture Substances 0.000 description 4
- 230000003287 optical effect Effects 0.000 description 3
- 230000005855 radiation Effects 0.000 description 3
- 230000002349 favourable effect Effects 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 230000003321 amplification Effects 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 238000007373 indentation Methods 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 230000005693 optoelectronics Effects 0.000 description 1
- 230000010355 oscillation Effects 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
Landscapes
- Lasers (AREA)
Abstract
TANGENTIAL FLOW LASER APPARATUS
ABSTRACT OF THE DISCLOSURE
In a laser device designed according to the gas trans-port or convection principle, the division into parts with different functions is replaced by complete integration of the different functions. According to the invention which covers a tangential flow laser, the gas circulation system, which consists of a rotor with radial blades arranged normal to the direction of flow of the laser gas, almost completely fills the casing. The rotor blades on one side are adjacent to the cooled wall of the casing, and on the other side are adjacent to the excitation system which extends along the wall of the casing.
ABSTRACT OF THE DISCLOSURE
In a laser device designed according to the gas trans-port or convection principle, the division into parts with different functions is replaced by complete integration of the different functions. According to the invention which covers a tangential flow laser, the gas circulation system, which consists of a rotor with radial blades arranged normal to the direction of flow of the laser gas, almost completely fills the casing. The rotor blades on one side are adjacent to the cooled wall of the casing, and on the other side are adjacent to the excitation system which extends along the wall of the casing.
Description
BACKG~OUND OF THE INVENTION
1. Field Of The Inyention The invention relates to a laser apparatus with a gas circulation and excitation system, which is designed according to the gas transport or conVection principle, and is a divisional of Application Serial No. 104,033, filed May 28, 1982.
1. Field Of The Inyention The invention relates to a laser apparatus with a gas circulation and excitation system, which is designed according to the gas transport or conVection principle, and is a divisional of Application Serial No. 104,033, filed May 28, 1982.
2. Prior Art Power, amplification and efficiency of molecular lasersj in particular CO2 lasers, decrease with increasing temperature of the laser gas. The decrease in efficiency is due to the fact that with rising temperature the line width becomes larger, the excitation energy distributes among an increasing number of rotational lines, the number of deactivating collisions increases and the population of the laser end level increases by thermal excitation, which results in a decrease in inversion o~ the individual transitions (K. G~rs, Laser 75 Optoelectronics, Conference Proceedings, pp. 30 to 37).
For this reason methods have been developed which carry off the heat together with the laser gas by ~irculating and cooling the ga~. Lasers appropriate for this method consist of an active region in which the gas is excited, with a separate (downstream) or integrated optical resonator, of the gas transport system with a built-in cooler and a pump.
~s large amounts of heat have to be carried off, large gas volumes have to be transferred by pumping. The respective lasers are large and expensive, and their applications are limited.
All of the CO2 lasers with output powers of more than 1 kW which are on the market operate according to this principle 30 of gas transport or convection laser. It was first described 7~7~
in 1969 by ~iffany, Ta~g and Foster ~Appln. Phys. Letters 15, (1969), pp. 91 to 95].
A conventional gas transport laser uses a high-power blower, e.g., a fan or a Roots pump, for rapid gas circulation.
Depending on the arrangement of the laser resonator and the direction of gas flow, a distinction is made between tangential-flow lasers and axial-flow lasers. Both of these lasers have specific advantages and drawbacks. In the case of the tangential-flow laser, the pressure loss is relatively small because of the large flow cross section. Therefore, it is possible to maintain the necessary flow rate by means of a smaller blower than in the case of the axial-flow laser. In the case of this latter laser type it is more difficult, however, to achieve homogeneous discharge and emission in the fundamental mode. For this reason the emission of the axial-flow laser can in general be better focused.
Convection lasexs, in which the gas flow is passed in axial direction through glass tubes serving as discharge vessels, have a better radiation quality which is partly due to the radially symmetric discharge conditions, their radiation can be better focused. A sufficiently high ~low rate can, however, only ~e maintained by means of a relatively high pressure gradient within the laser tube. As a result, the discharge conditions are not uniform along the tube. A strong and heavy circulation blower (~oots pump) is necessary.
~ n improvement of the axial convection laser is described in German OS 29 16 408. This design provides for helical circulation of the gas mixture within the discharge tube by suitably designed, water-cooled baffle plates. Its passages ~z~7n70 through the actiye zone of the laser are only of short duration; between the passages, there is sufficient time for the heat absorbed to be dissipated. ~he helical baffle plates are provided with bores lying on a line parallel to the axis.
5 Through these bores the gas discharge burns to excite the laser mixture. This arrangement has the advantages that only a relatively low circulation rate is necessary and that the longitudinal arrangement of the laser resonator ensures a high mode quality. It is difficult, however, to keep the gas discharge in place, as it is easily blown out of the resonator by the gas flow. Favorable operating conditions can be maintained only with specifically defined discharge parameters, so the intensity of this laser type cannot be satisfactorily controlled.
BROAD DESCRIPTION OF THE INVENTION
The object of the invention is to provide a gas transport or convection laser for generating high-power la~er radiation, in which the temperature rise in the laser gas is effectively suppressed and the necessary flow rate can be maintained without sophisticated structural components.
It has been found that the object of the invention can be reached by means of a laser device (designed according to the gas transport or convection principle with a casing enclosing the gas circulation and excitation systems) in which 25 the division of the laser into parts with defined functions has been abandoned and the various functions are fully integrated.
_~_ ~Z1~7~70 The invention refers to tangential flow lasers. In the tangential flow laser the gas circulation system consists of a ro~or with radial blades arranged normal to the direction of flow of the laser gas and largely fills the casing. The rotor blades are adjacent on one side to the cooled wall of the casing and on the other side to the excitation system which extends along the wall of the casing.
Preferably cooling fins for cooling the laser gas are arranged normal to the rotor axis and extend in the direction of flow of the laser gas. The excitation system advantageously consists of one or several rows of discharge chambers which are mounted by means of a holder attached to the wall of the casing. The two ends of the holder and the excitation system are preferably shaped such that their resistance to the flow of the laser gas is minimized, Also, preferably two rows of discharge chambers are mounted on opposite sides of the wall of the casing and the rotor is mounted between the two rows of discharge chambers.
Advantageously the casing has an elliptic cross section and the discharge chambers are arranged on opposite sides of the main axis of the elliptic casing. The rotor is preferably hollow, the rotor cylinder and the wall of the casing are preferably provided with openings and the laser gas preferably can be recirculated from the casing axially into the rotor.
The proposed laser devices according to the invention permit the circulation rate of the laser gas to be substan-tially increased. As correspondingly more heat can be carried off with the laser gas, the power of a laser of 7~7(~
corresponding size can be increased proportional to the circulation rate. Power per unit volume and power per flow rate are reduced by a factor of 3 to 5. In the device according to the invention, the components moving the gas, for example, can no longer be identified as a pump. This means that the requirements of laser design are for the first time fully satisfied and that modern technolgoy has been introduced.
DETAILED DESCRIP~ION OF THE INVENTION
In the following invention is described in greater detail on the basis of schematic drawings which only illustrate one embodiment. In the drawings:
Figure 1 is a cross section of a design of the laser device according to the invention operating according to the tangential flow principle; and Figure 2 is a longitudinal section of the emhodiment shown in Figure 1.
In the case of the embodiment shown in Figure 1, the gas in the laser is set in motion by rotor part 22 with radial blades 230 Rotor 22 largely fills the interior of casing 24. Rotor blades 23 are on one side adjacent to the wall of the casing and on the other side to excitation system 25 which extends along the wall of the casing.
The wall of the casing is cooled on outside 26 which carries cooling fins 27 to achieve cooling of the laser gas. Cooling fins 27 are arranged normal to the rotor axis and extend in the direction of flow of the laser gas.
As result from Figure 2, the excitation syste~ in this case consists of a row of discharge chambers 28, each of which is provided with one center electrode 29 and one ~LZ{?7~
annular outside electrode 30. After excitation, the laser gas moved and cooled by rotor 22 flows into the optical resonator where it releases its energy to the laser oscillation. It is also possible to use mirror systems for a folded optical path instead of simple spherical laser mirrors 31.
The discharge chambers arranged in one row are attached to holder 32 (or direct to the wall of the casing) whose ends are shaped according to aerodymanic principles in order to ensure that any potential turbulence of the flowing laser gas is prevented.
Rotor blades 23 are provided with indentations or recesses which permit them to grip between the cooling fins and set the laser gas in motion so that effective cooling of the laser gas is ensured. One design of the rotor blades is shown in Figure 2.
The flow conditions and the cooling can be further improved by providing hollow rotor 22 and by permitting the laser gas to penetrate into the interior of the casing through small openings 33 in the rotor depicted in Figure 5 and to leave the casing through small openings 34 in the wall of the casing. The laser gas thus leaving the casing is then returned axially into rotor 22. This circulation is maintained by-centrifugual force. A pump is not necessary.
A variation of the laser device according to the invention consists in the arrangement of the discharge chambers so as to form excitation system 25 in two or more rows. In the case of two rows of discharge chambers, they can be provided, for example, on opposite sides of the ~2~7Q7C~
wall of the casing such that the rotor rotates between these two rows. In such an embodiment it is preferable to use a casing of elliptical cross section. The discharge chambers can then be arranged on opposite sides of the main axis of the casing so that the rotor blades can still be adjacent to the cooled wall of the casing on the sides of the secondary axis.
The laser device according to the invention has, for example, a length of 1 m. The cross-sectional area of the discharge chambers then totals 0.05 m . The flow rate in the discharge chambers can be up to 160 m~s. This means that a gas volume of 8 m3/s flows through the discharge chambers. An appropriate gas mixture has the composition C02 : N2 : He = 1 : 7 : 3. A favorable pressure range is between 50 and several hundred torr.
Under these conditions, the device having an inner casing of 1 mm length has a power output of 8 kW. Higher powers can be achieved if two rows of discharge chambers are provided or if the dimensions of the device are increased or if several devices are connected in series.
i 25
For this reason methods have been developed which carry off the heat together with the laser gas by ~irculating and cooling the ga~. Lasers appropriate for this method consist of an active region in which the gas is excited, with a separate (downstream) or integrated optical resonator, of the gas transport system with a built-in cooler and a pump.
~s large amounts of heat have to be carried off, large gas volumes have to be transferred by pumping. The respective lasers are large and expensive, and their applications are limited.
All of the CO2 lasers with output powers of more than 1 kW which are on the market operate according to this principle 30 of gas transport or convection laser. It was first described 7~7~
in 1969 by ~iffany, Ta~g and Foster ~Appln. Phys. Letters 15, (1969), pp. 91 to 95].
A conventional gas transport laser uses a high-power blower, e.g., a fan or a Roots pump, for rapid gas circulation.
Depending on the arrangement of the laser resonator and the direction of gas flow, a distinction is made between tangential-flow lasers and axial-flow lasers. Both of these lasers have specific advantages and drawbacks. In the case of the tangential-flow laser, the pressure loss is relatively small because of the large flow cross section. Therefore, it is possible to maintain the necessary flow rate by means of a smaller blower than in the case of the axial-flow laser. In the case of this latter laser type it is more difficult, however, to achieve homogeneous discharge and emission in the fundamental mode. For this reason the emission of the axial-flow laser can in general be better focused.
Convection lasexs, in which the gas flow is passed in axial direction through glass tubes serving as discharge vessels, have a better radiation quality which is partly due to the radially symmetric discharge conditions, their radiation can be better focused. A sufficiently high ~low rate can, however, only ~e maintained by means of a relatively high pressure gradient within the laser tube. As a result, the discharge conditions are not uniform along the tube. A strong and heavy circulation blower (~oots pump) is necessary.
~ n improvement of the axial convection laser is described in German OS 29 16 408. This design provides for helical circulation of the gas mixture within the discharge tube by suitably designed, water-cooled baffle plates. Its passages ~z~7n70 through the actiye zone of the laser are only of short duration; between the passages, there is sufficient time for the heat absorbed to be dissipated. ~he helical baffle plates are provided with bores lying on a line parallel to the axis.
5 Through these bores the gas discharge burns to excite the laser mixture. This arrangement has the advantages that only a relatively low circulation rate is necessary and that the longitudinal arrangement of the laser resonator ensures a high mode quality. It is difficult, however, to keep the gas discharge in place, as it is easily blown out of the resonator by the gas flow. Favorable operating conditions can be maintained only with specifically defined discharge parameters, so the intensity of this laser type cannot be satisfactorily controlled.
BROAD DESCRIPTION OF THE INVENTION
The object of the invention is to provide a gas transport or convection laser for generating high-power la~er radiation, in which the temperature rise in the laser gas is effectively suppressed and the necessary flow rate can be maintained without sophisticated structural components.
It has been found that the object of the invention can be reached by means of a laser device (designed according to the gas transport or convection principle with a casing enclosing the gas circulation and excitation systems) in which 25 the division of the laser into parts with defined functions has been abandoned and the various functions are fully integrated.
_~_ ~Z1~7~70 The invention refers to tangential flow lasers. In the tangential flow laser the gas circulation system consists of a ro~or with radial blades arranged normal to the direction of flow of the laser gas and largely fills the casing. The rotor blades are adjacent on one side to the cooled wall of the casing and on the other side to the excitation system which extends along the wall of the casing.
Preferably cooling fins for cooling the laser gas are arranged normal to the rotor axis and extend in the direction of flow of the laser gas. The excitation system advantageously consists of one or several rows of discharge chambers which are mounted by means of a holder attached to the wall of the casing. The two ends of the holder and the excitation system are preferably shaped such that their resistance to the flow of the laser gas is minimized, Also, preferably two rows of discharge chambers are mounted on opposite sides of the wall of the casing and the rotor is mounted between the two rows of discharge chambers.
Advantageously the casing has an elliptic cross section and the discharge chambers are arranged on opposite sides of the main axis of the elliptic casing. The rotor is preferably hollow, the rotor cylinder and the wall of the casing are preferably provided with openings and the laser gas preferably can be recirculated from the casing axially into the rotor.
The proposed laser devices according to the invention permit the circulation rate of the laser gas to be substan-tially increased. As correspondingly more heat can be carried off with the laser gas, the power of a laser of 7~7(~
corresponding size can be increased proportional to the circulation rate. Power per unit volume and power per flow rate are reduced by a factor of 3 to 5. In the device according to the invention, the components moving the gas, for example, can no longer be identified as a pump. This means that the requirements of laser design are for the first time fully satisfied and that modern technolgoy has been introduced.
DETAILED DESCRIP~ION OF THE INVENTION
In the following invention is described in greater detail on the basis of schematic drawings which only illustrate one embodiment. In the drawings:
Figure 1 is a cross section of a design of the laser device according to the invention operating according to the tangential flow principle; and Figure 2 is a longitudinal section of the emhodiment shown in Figure 1.
In the case of the embodiment shown in Figure 1, the gas in the laser is set in motion by rotor part 22 with radial blades 230 Rotor 22 largely fills the interior of casing 24. Rotor blades 23 are on one side adjacent to the wall of the casing and on the other side to excitation system 25 which extends along the wall of the casing.
The wall of the casing is cooled on outside 26 which carries cooling fins 27 to achieve cooling of the laser gas. Cooling fins 27 are arranged normal to the rotor axis and extend in the direction of flow of the laser gas.
As result from Figure 2, the excitation syste~ in this case consists of a row of discharge chambers 28, each of which is provided with one center electrode 29 and one ~LZ{?7~
annular outside electrode 30. After excitation, the laser gas moved and cooled by rotor 22 flows into the optical resonator where it releases its energy to the laser oscillation. It is also possible to use mirror systems for a folded optical path instead of simple spherical laser mirrors 31.
The discharge chambers arranged in one row are attached to holder 32 (or direct to the wall of the casing) whose ends are shaped according to aerodymanic principles in order to ensure that any potential turbulence of the flowing laser gas is prevented.
Rotor blades 23 are provided with indentations or recesses which permit them to grip between the cooling fins and set the laser gas in motion so that effective cooling of the laser gas is ensured. One design of the rotor blades is shown in Figure 2.
The flow conditions and the cooling can be further improved by providing hollow rotor 22 and by permitting the laser gas to penetrate into the interior of the casing through small openings 33 in the rotor depicted in Figure 5 and to leave the casing through small openings 34 in the wall of the casing. The laser gas thus leaving the casing is then returned axially into rotor 22. This circulation is maintained by-centrifugual force. A pump is not necessary.
A variation of the laser device according to the invention consists in the arrangement of the discharge chambers so as to form excitation system 25 in two or more rows. In the case of two rows of discharge chambers, they can be provided, for example, on opposite sides of the ~2~7Q7C~
wall of the casing such that the rotor rotates between these two rows. In such an embodiment it is preferable to use a casing of elliptical cross section. The discharge chambers can then be arranged on opposite sides of the main axis of the casing so that the rotor blades can still be adjacent to the cooled wall of the casing on the sides of the secondary axis.
The laser device according to the invention has, for example, a length of 1 m. The cross-sectional area of the discharge chambers then totals 0.05 m . The flow rate in the discharge chambers can be up to 160 m~s. This means that a gas volume of 8 m3/s flows through the discharge chambers. An appropriate gas mixture has the composition C02 : N2 : He = 1 : 7 : 3. A favorable pressure range is between 50 and several hundred torr.
Under these conditions, the device having an inner casing of 1 mm length has a power output of 8 kW. Higher powers can be achieved if two rows of discharge chambers are provided or if the dimensions of the device are increased or if several devices are connected in series.
i 25
Claims (7)
1. Laser apparatus based on gas transport principle, in which laser gas flows through a laser resonator inside a casing, said casing enclosing both gas circulation and excitation systems, the gas circulation system being equipped with a rotor having radial blades which are arranged essentially normal to the direction of flow of the laser gas and the excitation system through which the laser gas flows being arranged at the wall of the casing, the rotor filling the casing substantially excluding the space of excitation system or systems such that the rotor blades extend either towards the wall of the casing or towards the excitation system whereby the laser gas is moved in the space between the blades and the cooled wall of the casing.
2. The laser apparatus as claimed in claim 1 wherein cooling fins for cooling the laser gas are arranged normal to the rotor axis and extend in the direction of flow of the laser gas.
3. The laser apparatus as claimed in claim 1 wherein the excitation system consists of one or several rows of discharge chambers which are mounted by means of a holder attached to the wall of the casing.
4. The laser apparatus as claimed in claim 3 wherein the two ends of the holder and the excitation system are shaped such that their resistance to the flow of the laser gas is minimized.
5. The laser apparatus as claimed in claim 4 wherein two rows of discharge chambers are mounted on opposite sides of the wall of the casing and wherein the rotor is mounted between the two rows of discharge chambers.
6. The laser apparatus as claimed in claim 5 wherein the casing has an elliptic cross section and wherein the discharge chambers are arranged on opposite sides of the main axis of the elliptic casing.
7. The laser apparatus as claimed in claim 1, 2 or 3 wherein the rotor is hollow, wherein the rotor cyclinder and the wall of the casing are provided with openings and wherein the laser gas can be recirculated from the casing axially into the rotor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000472814A CA1207070A (en) | 1981-05-29 | 1985-01-24 | Tangential flow laser apparatus |
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3121372.3 | 1981-05-29 | ||
| DE19813121372 DE3121372A1 (en) | 1981-05-29 | 1981-05-29 | Laser arrangement |
| DEP3138622.9 | 1981-09-29 | ||
| DE19813138622 DE3138622A1 (en) | 1981-09-29 | 1981-09-29 | "LASER ARRANGEMENT" |
| CA000404033A CA1188782A (en) | 1981-05-29 | 1982-05-28 | Axial flow laser apparatus |
| CA000472814A CA1207070A (en) | 1981-05-29 | 1985-01-24 | Tangential flow laser apparatus |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000404033A Division CA1188782A (en) | 1981-05-29 | 1982-05-28 | Axial flow laser apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1207070A true CA1207070A (en) | 1986-07-02 |
Family
ID=27167243
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000472814A Expired CA1207070A (en) | 1981-05-29 | 1985-01-24 | Tangential flow laser apparatus |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1207070A (en) |
-
1985
- 1985-01-24 CA CA000472814A patent/CA1207070A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |