CA1080838A - Multiline emission integral mirror laser - Google Patents
Multiline emission integral mirror laserInfo
- Publication number
- CA1080838A CA1080838A CA274,324A CA274324A CA1080838A CA 1080838 A CA1080838 A CA 1080838A CA 274324 A CA274324 A CA 274324A CA 1080838 A CA1080838 A CA 1080838A
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- Canada
- Prior art keywords
- laser
- helium
- cadmium
- discharge tube
- section
- 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
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/02—Constructional details
- H01S3/03—Constructional details of gas laser discharge tubes
- H01S3/031—Metal vapour lasers, e.g. metal vapour generation
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/02—Constructional details
- H01S3/03—Constructional details of gas laser discharge tubes
- H01S3/032—Constructional details of gas laser discharge tubes for confinement of the discharge, e.g. by special features of the discharge constricting tube
- H01S3/0323—Constructional details of gas laser discharge tubes for confinement of the discharge, e.g. by special features of the discharge constricting tube by special features of the discharge constricting tube, e.g. capillary
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/102—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling the active medium, e.g. by controlling the processes or apparatus for excitation
- H01S3/104—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling the active medium, e.g. by controlling the processes or apparatus for excitation in gas lasers
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- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Engineering & Computer Science (AREA)
- Plasma & Fusion (AREA)
- Optics & Photonics (AREA)
- Lasers (AREA)
Abstract
MULTILINE EMISSION INTEGRAL MIRROR LASER
ABSTRACT OF THE DISCLOSURE
An integral mirror type laser system which produces multiline emissions simultaneously and which is adapted for use in optical data processing systems. In particular, in a first embodiment, a unitary positive column laser comprises two sections, the first section comprising a positive column helium-cadmium laser, the second section comprising a positive column helium-neon laser, the first and second sections being coaxially aligned and having different inner diameters. Simul-taneous excitation in the two different sections provides optimum excitation for red laser light, produced by the helium-neon section and blue laser light produced by the helium-neon-cadmium section. The present system also allows separate cadmium vapor pressure control by separately controlling the varporization temperature of the cadmium and also allows con-finement of the cadmium vapor whereby the vapor does not contaminate one of the optical windows which confines the active laser medium. By proper selection of the optical cavity parameters, simultaneous red and blue laser oscilla-tions can be obtained for application in any optical data processing system that requires a red and blue laser radiation source. In a second embodiment, the helium-cadmium section is replaced by with a helium-selenium section whereby the tandem laser system is capable of producing multiline laser radiation in the red, blue and green colors.
ABSTRACT OF THE DISCLOSURE
An integral mirror type laser system which produces multiline emissions simultaneously and which is adapted for use in optical data processing systems. In particular, in a first embodiment, a unitary positive column laser comprises two sections, the first section comprising a positive column helium-cadmium laser, the second section comprising a positive column helium-neon laser, the first and second sections being coaxially aligned and having different inner diameters. Simul-taneous excitation in the two different sections provides optimum excitation for red laser light, produced by the helium-neon section and blue laser light produced by the helium-neon-cadmium section. The present system also allows separate cadmium vapor pressure control by separately controlling the varporization temperature of the cadmium and also allows con-finement of the cadmium vapor whereby the vapor does not contaminate one of the optical windows which confines the active laser medium. By proper selection of the optical cavity parameters, simultaneous red and blue laser oscilla-tions can be obtained for application in any optical data processing system that requires a red and blue laser radiation source. In a second embodiment, the helium-cadmium section is replaced by with a helium-selenium section whereby the tandem laser system is capable of producing multiline laser radiation in the red, blue and green colors.
Description
B}~CKGROUND OF TEIE: :LNVENTION
The use of lasers in optical data processing systems such as facsimile devices, digital printers and ~he like have been disclosed in the prior art. A single laser which provides light of single wavelength may be generally utilized for scanning information on a document, the reflected radiation flux being electrically transferred to a storage device or utilized to reproduce the information as a copy of the original document. A scanning laser is generally utilized to reproduce the document information (or for printing purposes only). Typically, a helium-neon laser which generates red laser light when energized has been utilized in many scanning/reproducing applications.
For example, Xerox Corporation, Stamford Connecticut, re-cently introduced a facsimile device, the Xerox Telecopier 200 (Xerox ~ and Telecopier ~ are registered trademarks of Xerox Corporation) which records on plain paper. The transceiver employs a low-energy helium-neon laser and uses the xerographic principle to receive and print messages on ordinary, unsensitized paper. Basically, when the trans-cei~er is in the transmit mode, the laser provides a small stable beam of light to raster scan the original document.
The reflected light is detected by a photosensor which translates the white and black of the document to electrical logic levels which may be transmitted by a phone line to a remote transceiver set t~ the receive mode. The receiver - transceiver directs the laser beam onto a xerographic drum .
and by electrically modulating the laser with "l" and "0"
logic levels in synchronism with the transmitter produces ~0 a copy of the oriyinal.
~.~
IJowever, it would be desirable if a single laser could be provided to produce simultaneous laser radiation of more than one wavelength to allow the accurate reproductions of documents which contain information in other than black and white form, i.e. multicolored documents.
Although lasers have been produced in the prior art which are capable of producing multiline emissions simultane-ously, such as an argon laser, these lasers are generally expensive and large in size, making them impractical for use in commercial systems, such as the Telecopier 200 transceiver described hereinabove.
An article in the Proceedings of the IEEE, He-Ne-Cd Laser With Two Color Output, S. A. Ahmed et al, November, 1969, pages 2084-2085, describes, inter alia, a helium-neon-cadmium laser which produces simulataneous lasing at 4416A and ~ -- 6328A. However, the laser discharge essentially occurs through a single discharge tube of a single diameter making o o ~ ~ ~
optimum/adjustment of the blue (4416A~ and red (6328A) laser light extemely difficult~
2n Therefore, a simplified and relatively inexpensive laser which can produce multiline emissions simultaneously and which can be adapted for commercial utilization would satisfy an apparent need in optical data processing technology.
SUMMARY OF THE PRESENT INVENTION
~ .
The present invention provides an integral mirror type laser system which produces multiline emissions simultane~
ously and which is adapted for use in optical data processing systems. In particular, in a first embodiment, a unitary positive column laser comprises two sections, the ~ 4 ~
:.' .: ; ~ , . ` : ' :
first section comprising a positive column helium-cadmiurn laser, the second section comprising a positive column helium-neon laser, the first and second sections being coaxially aligned and having diEferent inner diameters~
Simultaneous excitation of each section provides optimum excitation for red laser light, produced by the helium-neon section, and blue laser light, produced by the helium-neon-cadmium section. The present system also allows separate cadmium vapor pressure control by separately controlling the vaporization temperat~re of the cadmium and also allows confinement of the cadmium vapor whereby the ~apor does not contaminate one of the optical windows which confines the active laser medium. By proper selection of the optical cavity parameters, simultaneous red and blue laser oscillations can be obtained for application in any optical data processing system that requires a red and blue laser radiation source. In a second emhodiment, the helium-cadmium section is replaced by with a helium-selenium section whereby the tandem laser system is capable of producing multiline laser radiation in the red, blue and green colors.
It is an object of an aspect of the present invention to provide an integral mirror type laser system which is capable of producing multiline laser radiation.
It is an object of an aspect of the present invention to provide an integral mirror type laser system for producing multiline radiation, said system inc~uding positive column laser sections coaxially arranged and having different discharge bore diameters, each section having different active media incorporated therein.
~ 5 ~
.
, , It ls an object o~ an aspect of the present invention to provide an integral mirror type mul-tiline laser device whi.ch incorporates two coaxially aligrled positive column sections of different inner diameters, each section incorporat-ing a different active medium therein, the active medium in the first section comprising a gas, the active medium in the second section comprising a gas mixtuxe which includes a metal vapor.
It is an object of an aspect of the present invention ; 10 to provide an integral mirror type laser system comprising two positive column sections coaxially arranged and having different discharge bore diameters for producing red and blue : laser radiation in a first embodiment and red, blue and green in a second embodiment.
In accordance with one aspect of this invention there is provided a laser discharge tube for producing an out-put laser beam having a plurality of wavelengths comprising~
~ a tube envelope for enclosing first and second active lasing .~ mediums, said tube envelope including end members for hermetic-ally sealing said envelope, a first discharge tube having an inner diameter and supported within said envelope, a second discharge tube having an inner diameter and supported within said envelope and coaxially aligned with said first discharge tube, said first and second discharge tubes being operative to produce said output laser beam, a first electrode positioned . .
adjacent one e~d of said first discharge tube, a second electrode ~ :
operatively positioned with respect to one end of said second discharge tube, and means for applying an electrostatic potential between said first and second electrodes of a potential to main-- 30 tain the same discharge current between said electrodes through said first and second discharge tubes whereby said first active ~ - 6 -..... . . .
. :
,. . .
: . . . -lasing medium produces a first laser beam of at least one wavelength and said second active lasing medium produces a second laser beam comprising at least one wavelength, said first and second laser beams being combined into a laser out-put beam having a plurality of wavelengths, the inner diameters of said first and second dischargle tubes being different and selected to optimize the output of said first and second '~ laser beams.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the invention as well as other objects and further features thereof, reference is made to the following description which is to be read in conjunction with the following wherein:
Figure l shows a first embodiment of the present invention which simultaneously generates red and blue laser light; and Figure 2 shows a second embodiment of the present invention which simultaneously generates red, green and blue (white) laser light.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
' Referring now to the figure, a first embodiment of the laser assembly 10 of the present invention is illustrated.
Laser ass*mbly 10 comprises an outer tube envelope 12, made of~x glass for example, and an -~ braclc ~a~
.' .
, . .
' ' -., ~ 6a -~.~. . . .
.
:. .
inner capillar~ disch~rge tube 14. C~pillary discharge tube 14 comprlses two coaxial]y aliyned positive column sections 16 and 18, each made of glass, section 16 including a flared end portion 20 which forms a reservoir 15 with glass disc support member 19 `for the active laser medium, typicalIy a metal. Capillary dis-charge tube 18 coaxially extend~s into the reservoir 15, as shown. A cathode electrode 21 is disposed in a side arm - 23 of tube envelope 12. The outer tube envelope 12 has a typical diameter of 45 millimeters and a length of 60 centi-meters (from mirror to mirror) whereas discharge tube section 16 has a typical length (including flared portion 20) of 20 centimeters, an inner diameter ~non-flared portion) of 4 millimeters and an outer diameter (non-flared port1on) o~
7 millimeters. Discharge tube section 18 has a typical length of ~0 centimeters and inner diameter of 1 millimeter and an outer diameter of 7 millimeters. The ends of tube envelope ~
12 are sealed by end mirror assemblies 32 and 34 as shown. ~ ~ -- The mirror assembly 32 comprises a metal flange 36 sealed to the tube envelope and an apertured metal flange 38 joined thereto. A fully reflecting mirror 40 may be sealed to metal flange 38 by standard techniques or by the technique described in copending application serial no. 244,017, filed January ! 21, 1976. Mirror 40 typically comprises a glass substrate upon which is coated a reflecting layer comprising a plurality ` dielectric layers, the reflecting layer facing inward (within ; the tube envelope). End mirror assembly 34 comprises a metal flange 42 sealed to the tube envelope and an apertured metal flange 44 joined thereto. A partially transmissive mirror 46 is sealed to apertured flange 44 by standard techniques or in a manner as described in the aforementioned copending patent application. Mirror 46 comprises .~, .. - 7 -;: - . . . .
. ~
3~
a glass substra-t~ upon which is coate~ a partially trans-missive layer of dielectric material, the transmissive layer being positioned within t~e envelope 12. As will be set forth hereinafter, mirrors 40 and 46 are appro-priately coated with layers of dielectric material such that only a laser beam 50 of a desired wavelength is transmitted by mirror 46, beam 50 being ùtilized by external apparatus such as for the scanning purposes as set forth hereinabove.
Anode pin 52 is inserted into the space within envelope 12 as shown and are glass sealed to the envelope using standard glass sealing techniques.
Variable voltage source 54 is connected between anode pin 52 and cathode 21 as shown.
In a first embodiment, a helium-neon gas mixture is filled within envelope 12 by standard techniques well known in the art, to a predetermined helium-neon total pressure. In a first embodiment, a few grams, typically 10 grams, of cadmium metal 70 is placed within reservoir 15 of envelope12. A heater 72 may be provided to - vaporize the cadmium to a preselected pressure as described hereinbelow.
Although laser assembly 10 functions as a single, unitary device, for purposes of e~planation, both sections of the tube will be described separately. The left hand section of the assembly operates as a positive column helium-neon laser tube would operate. That is~ the helium-neon gas is introduced into envelope 12 at a preselected pressure (helium at 3.0 Torr and neon at 0.3 Torr) and a discharge is initiated between anode pin 52 and cathode 24, by maintaining a voltage of approximately lKv therebetween by adjusting source 54 and adjustable ballast resistor 55.
Ballast resistor 55 functions to limit the laser tube dis-charge current. The electrical discharge (from anode 52, - through tubes 16 and 18 and to cathode 21), excites the helium atoms to a metastable state which, due to inelastic collisions of the second kind, transfers energy to the neon atoms which are elevated to the population inversion state. The neon atoms, in falling to a lower energy state, emit a laser light of a frequency corresponding to the two different energy levels as is well known in the art. For helium-neon lasers, a red 10 light of a wavelength of 6328A is generated. Glass disc , - support member 19 supports tube 18 within envelope 12 and also serves to confine the discharge through tube 18 in a manner well known in the art.
A solid cadmium charge 70 is deposited in the right ; hand section of the laser assembly 10 prior to laser tube ~ !
operation. Heater 72 is energized and the cadmium metal is -vaporized, the preferred vapor pressure being attained by con-trolling the cadmium temperature. In particular, the cadmium temperature is maintained at approximately 280C by appropriate control of heater 72. Also confined within the section is gaseous helium and neon at a pressure as set forth hereinabove with reference to the left hand section. When a dischaxge is initiated between electrode 21 and anode pin 52 via voltage source 54 and ballast resistor 55, it excites the helium atoms to a metastable excited state from which energy is imparted to the vaporized cadmium atoms. This causes the cadmium atoms to ionize to an excited state required for lasing action. The ionized cadmium atoms are then transported along the length of the discharge confining bore tube 18 to cathode 21 via the process of cataphoresis in a manner well known in the art.
When the excited ionized cadmium atoms return towards a lower g _ .,.. ,. . . - .
:: .
~, energy state, laser radiation at 4416A (blue) is produced.
The vapor cadmium condenses - 9a - :
~ . ~
l~B08~38 ~.s condensa-te 74 d~e to the cooler tube opera-tion at those regions of the tube as shown.
The gas mixture of helium and neon fills the entire laser tube structure. The cadmium vapor is distributed in capillary tube 18 near cathode 21 by cataph~retic pumping. Cataphoresis also confines the cadmium to the portion of the capillary tube 18 near cathode 21. Thus, the helium-neon gas mixture is the only active medium in capillary tube 16 adjacent anode ~ 10 52 while the gas and vapor mixture of helium, neon and - cadmium is the active medium in the portion of capillary tube 18 adjacent cathode 21. It should be noted that section 16, in addition to providing path for the helium-ne~n discharge, also provides for the cataphoretic confinement of the cadmium vapor atoms which may diffuse towards mirror 40. This prevents cadmium vapor from condensing on the reflecting surface of mirror 40. The ; discharge current, in essence, forms a continuous ~ilament ~- passing through both capillary tubes 16 and 18. The inner ; 20 diameter of capillary tube 16 adjacent anode 52 is chosen ~;
to optimize the 6328A output resulting from the excitation ; reaction of the discharge on the helium-neon gas, the diameter (in millimeters) being approximately equal to i /10 wherein io is the discharge current in milliamps (ma).
Typically, io is selected to be 40 ma providing an inner diameter of 4 millimeters. The inner diameter of the capillary tube near cathode 21 is chosen to optimize the ` 4416A output resulting ~rom the helium-neon-cadmium dis-charge and is equal to io/40~ For an io f 40 ma, the diameter is therefor 1 millimeter.
The use of two coaxial discharge tubes having different inner diameters selected to optimize the output ~ ' ` -10-.~ , . " - ,, , , l338 therefrom allows the output laser beam 50 to be corres-pondinqly opti~lzed for external utilization.
n summary, after the discharge is initiated and the cadmium vaporized, voltage source 54 causes lasing action to occur. The left hand section in essence provides red laser light~ the right hand section in essence providing the - blue laser light component of light beam 50 notwithstanding the presence of helium-neon gas therein (helium-cadmium interaction predominates over the helium-neon interaction).
The dielectric coatings on integral mirrors 40 and 46 are selected so that only red and blue light (combined in one beam) is transmitted by mirror 46 as beam 50O Typical dielectric coatings include alternate layers of titanium and silicon dioxide, each layer having a predetermined thickness.
It shoul~ be noted that the temperature applied to the cadmium charge 70 determines its vapor pressure (and thus the intensity of the light produced) the cadmium pressure essentially not being affected by the helium-neon pressure.
Although not shown in Figure 1, the simultaneous generation of red and blue light as a single beam 50 can be dispersed into its separate component colors by using a prism or appropriate light filters.
Referring now to Figure 2, a second embodiment of the present invention is illustrated. The embodiment shown is substantially identical to that shown in Figure 1, the only difference being a charge of selenium metal 80 is utilized in the right hand section instead of cadmium.
Selenium vapor, when maintained at a predetermined temperature of approximately 270C by heater 72 interacts with the helium-neon gas wherein the helium ions and/or metastable atoms causes ,, ~, ~ - - ~ , ^ . . , ' 1~8~il3~3 the selenium atoms to be positively ionized and excited to a higher energy state. When the excited selenium atoms return to its initial or ground state, multili 3 emissions, including blue and green laser light is produced. The blue and green laser light emissions include -the following wavelengths: ~604A (blue), ~97~A (blue-green), 5069A
O O
(green), 5176A (green), and 5306A (green)~ The confinement of the selenium vapor is identical to the process described with reference to Figure 1 hereinabove and the inner diameters of capillary discharge tube sections 16 and 18 are substantially identical to the helium-cadmium embodi-ment described with reference to Figure 1. The laser mirrors, in this embodiment, are coated for broadband re-flectance (from about 4800A to about 6500A).
In operation, after vaporizing the selenium to the appropriate vapor pressure and initiating the discharge in both sections, voltage source 54 and ballast resistor 55 act to maintain the discharge for lasing action, red, blue and green (white) light being simultaneously transmitted as beam 50. As set forth hereinabove with reference to Figure 1, the separate color components of beam 50 can be obtained if desired by utilizing a prism to disperse each color component or by providing appropriate color filters.
The laser assembly described witn reference to Figures 1 and 2 hereinabove provides a multiline laser source for many applications, such as laser scanning as described hereinabove.
; The laser structure described hereinabove is simple, compact and low cost, the low cost feature arising from the fact that only one set of laser mirrors, one power ; supply and one unitary structure are necessary. Further, --1~
. ,~ .
1~8~338 no alignmant Eixturing is required to ensure coaxiality of the multiple color laser beams.
While the invention has been described with reference to its preferred embodiment, it will be under-stood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teaching of the invention without departing from its essential teachings.
..
~' .
.~ ' il ' ' ' ~ ' .
.:
. .
The use of lasers in optical data processing systems such as facsimile devices, digital printers and ~he like have been disclosed in the prior art. A single laser which provides light of single wavelength may be generally utilized for scanning information on a document, the reflected radiation flux being electrically transferred to a storage device or utilized to reproduce the information as a copy of the original document. A scanning laser is generally utilized to reproduce the document information (or for printing purposes only). Typically, a helium-neon laser which generates red laser light when energized has been utilized in many scanning/reproducing applications.
For example, Xerox Corporation, Stamford Connecticut, re-cently introduced a facsimile device, the Xerox Telecopier 200 (Xerox ~ and Telecopier ~ are registered trademarks of Xerox Corporation) which records on plain paper. The transceiver employs a low-energy helium-neon laser and uses the xerographic principle to receive and print messages on ordinary, unsensitized paper. Basically, when the trans-cei~er is in the transmit mode, the laser provides a small stable beam of light to raster scan the original document.
The reflected light is detected by a photosensor which translates the white and black of the document to electrical logic levels which may be transmitted by a phone line to a remote transceiver set t~ the receive mode. The receiver - transceiver directs the laser beam onto a xerographic drum .
and by electrically modulating the laser with "l" and "0"
logic levels in synchronism with the transmitter produces ~0 a copy of the oriyinal.
~.~
IJowever, it would be desirable if a single laser could be provided to produce simultaneous laser radiation of more than one wavelength to allow the accurate reproductions of documents which contain information in other than black and white form, i.e. multicolored documents.
Although lasers have been produced in the prior art which are capable of producing multiline emissions simultane-ously, such as an argon laser, these lasers are generally expensive and large in size, making them impractical for use in commercial systems, such as the Telecopier 200 transceiver described hereinabove.
An article in the Proceedings of the IEEE, He-Ne-Cd Laser With Two Color Output, S. A. Ahmed et al, November, 1969, pages 2084-2085, describes, inter alia, a helium-neon-cadmium laser which produces simulataneous lasing at 4416A and ~ -- 6328A. However, the laser discharge essentially occurs through a single discharge tube of a single diameter making o o ~ ~ ~
optimum/adjustment of the blue (4416A~ and red (6328A) laser light extemely difficult~
2n Therefore, a simplified and relatively inexpensive laser which can produce multiline emissions simultaneously and which can be adapted for commercial utilization would satisfy an apparent need in optical data processing technology.
SUMMARY OF THE PRESENT INVENTION
~ .
The present invention provides an integral mirror type laser system which produces multiline emissions simultane~
ously and which is adapted for use in optical data processing systems. In particular, in a first embodiment, a unitary positive column laser comprises two sections, the ~ 4 ~
:.' .: ; ~ , . ` : ' :
first section comprising a positive column helium-cadmiurn laser, the second section comprising a positive column helium-neon laser, the first and second sections being coaxially aligned and having diEferent inner diameters~
Simultaneous excitation of each section provides optimum excitation for red laser light, produced by the helium-neon section, and blue laser light, produced by the helium-neon-cadmium section. The present system also allows separate cadmium vapor pressure control by separately controlling the vaporization temperat~re of the cadmium and also allows confinement of the cadmium vapor whereby the ~apor does not contaminate one of the optical windows which confines the active laser medium. By proper selection of the optical cavity parameters, simultaneous red and blue laser oscillations can be obtained for application in any optical data processing system that requires a red and blue laser radiation source. In a second emhodiment, the helium-cadmium section is replaced by with a helium-selenium section whereby the tandem laser system is capable of producing multiline laser radiation in the red, blue and green colors.
It is an object of an aspect of the present invention to provide an integral mirror type laser system which is capable of producing multiline laser radiation.
It is an object of an aspect of the present invention to provide an integral mirror type laser system for producing multiline radiation, said system inc~uding positive column laser sections coaxially arranged and having different discharge bore diameters, each section having different active media incorporated therein.
~ 5 ~
.
, , It ls an object o~ an aspect of the present invention to provide an integral mirror type mul-tiline laser device whi.ch incorporates two coaxially aligrled positive column sections of different inner diameters, each section incorporat-ing a different active medium therein, the active medium in the first section comprising a gas, the active medium in the second section comprising a gas mixtuxe which includes a metal vapor.
It is an object of an aspect of the present invention ; 10 to provide an integral mirror type laser system comprising two positive column sections coaxially arranged and having different discharge bore diameters for producing red and blue : laser radiation in a first embodiment and red, blue and green in a second embodiment.
In accordance with one aspect of this invention there is provided a laser discharge tube for producing an out-put laser beam having a plurality of wavelengths comprising~
~ a tube envelope for enclosing first and second active lasing .~ mediums, said tube envelope including end members for hermetic-ally sealing said envelope, a first discharge tube having an inner diameter and supported within said envelope, a second discharge tube having an inner diameter and supported within said envelope and coaxially aligned with said first discharge tube, said first and second discharge tubes being operative to produce said output laser beam, a first electrode positioned . .
adjacent one e~d of said first discharge tube, a second electrode ~ :
operatively positioned with respect to one end of said second discharge tube, and means for applying an electrostatic potential between said first and second electrodes of a potential to main-- 30 tain the same discharge current between said electrodes through said first and second discharge tubes whereby said first active ~ - 6 -..... . . .
. :
,. . .
: . . . -lasing medium produces a first laser beam of at least one wavelength and said second active lasing medium produces a second laser beam comprising at least one wavelength, said first and second laser beams being combined into a laser out-put beam having a plurality of wavelengths, the inner diameters of said first and second dischargle tubes being different and selected to optimize the output of said first and second '~ laser beams.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the invention as well as other objects and further features thereof, reference is made to the following description which is to be read in conjunction with the following wherein:
Figure l shows a first embodiment of the present invention which simultaneously generates red and blue laser light; and Figure 2 shows a second embodiment of the present invention which simultaneously generates red, green and blue (white) laser light.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
' Referring now to the figure, a first embodiment of the laser assembly 10 of the present invention is illustrated.
Laser ass*mbly 10 comprises an outer tube envelope 12, made of~x glass for example, and an -~ braclc ~a~
.' .
, . .
' ' -., ~ 6a -~.~. . . .
.
:. .
inner capillar~ disch~rge tube 14. C~pillary discharge tube 14 comprlses two coaxial]y aliyned positive column sections 16 and 18, each made of glass, section 16 including a flared end portion 20 which forms a reservoir 15 with glass disc support member 19 `for the active laser medium, typicalIy a metal. Capillary dis-charge tube 18 coaxially extend~s into the reservoir 15, as shown. A cathode electrode 21 is disposed in a side arm - 23 of tube envelope 12. The outer tube envelope 12 has a typical diameter of 45 millimeters and a length of 60 centi-meters (from mirror to mirror) whereas discharge tube section 16 has a typical length (including flared portion 20) of 20 centimeters, an inner diameter ~non-flared portion) of 4 millimeters and an outer diameter (non-flared port1on) o~
7 millimeters. Discharge tube section 18 has a typical length of ~0 centimeters and inner diameter of 1 millimeter and an outer diameter of 7 millimeters. The ends of tube envelope ~
12 are sealed by end mirror assemblies 32 and 34 as shown. ~ ~ -- The mirror assembly 32 comprises a metal flange 36 sealed to the tube envelope and an apertured metal flange 38 joined thereto. A fully reflecting mirror 40 may be sealed to metal flange 38 by standard techniques or by the technique described in copending application serial no. 244,017, filed January ! 21, 1976. Mirror 40 typically comprises a glass substrate upon which is coated a reflecting layer comprising a plurality ` dielectric layers, the reflecting layer facing inward (within ; the tube envelope). End mirror assembly 34 comprises a metal flange 42 sealed to the tube envelope and an apertured metal flange 44 joined thereto. A partially transmissive mirror 46 is sealed to apertured flange 44 by standard techniques or in a manner as described in the aforementioned copending patent application. Mirror 46 comprises .~, .. - 7 -;: - . . . .
. ~
3~
a glass substra-t~ upon which is coate~ a partially trans-missive layer of dielectric material, the transmissive layer being positioned within t~e envelope 12. As will be set forth hereinafter, mirrors 40 and 46 are appro-priately coated with layers of dielectric material such that only a laser beam 50 of a desired wavelength is transmitted by mirror 46, beam 50 being ùtilized by external apparatus such as for the scanning purposes as set forth hereinabove.
Anode pin 52 is inserted into the space within envelope 12 as shown and are glass sealed to the envelope using standard glass sealing techniques.
Variable voltage source 54 is connected between anode pin 52 and cathode 21 as shown.
In a first embodiment, a helium-neon gas mixture is filled within envelope 12 by standard techniques well known in the art, to a predetermined helium-neon total pressure. In a first embodiment, a few grams, typically 10 grams, of cadmium metal 70 is placed within reservoir 15 of envelope12. A heater 72 may be provided to - vaporize the cadmium to a preselected pressure as described hereinbelow.
Although laser assembly 10 functions as a single, unitary device, for purposes of e~planation, both sections of the tube will be described separately. The left hand section of the assembly operates as a positive column helium-neon laser tube would operate. That is~ the helium-neon gas is introduced into envelope 12 at a preselected pressure (helium at 3.0 Torr and neon at 0.3 Torr) and a discharge is initiated between anode pin 52 and cathode 24, by maintaining a voltage of approximately lKv therebetween by adjusting source 54 and adjustable ballast resistor 55.
Ballast resistor 55 functions to limit the laser tube dis-charge current. The electrical discharge (from anode 52, - through tubes 16 and 18 and to cathode 21), excites the helium atoms to a metastable state which, due to inelastic collisions of the second kind, transfers energy to the neon atoms which are elevated to the population inversion state. The neon atoms, in falling to a lower energy state, emit a laser light of a frequency corresponding to the two different energy levels as is well known in the art. For helium-neon lasers, a red 10 light of a wavelength of 6328A is generated. Glass disc , - support member 19 supports tube 18 within envelope 12 and also serves to confine the discharge through tube 18 in a manner well known in the art.
A solid cadmium charge 70 is deposited in the right ; hand section of the laser assembly 10 prior to laser tube ~ !
operation. Heater 72 is energized and the cadmium metal is -vaporized, the preferred vapor pressure being attained by con-trolling the cadmium temperature. In particular, the cadmium temperature is maintained at approximately 280C by appropriate control of heater 72. Also confined within the section is gaseous helium and neon at a pressure as set forth hereinabove with reference to the left hand section. When a dischaxge is initiated between electrode 21 and anode pin 52 via voltage source 54 and ballast resistor 55, it excites the helium atoms to a metastable excited state from which energy is imparted to the vaporized cadmium atoms. This causes the cadmium atoms to ionize to an excited state required for lasing action. The ionized cadmium atoms are then transported along the length of the discharge confining bore tube 18 to cathode 21 via the process of cataphoresis in a manner well known in the art.
When the excited ionized cadmium atoms return towards a lower g _ .,.. ,. . . - .
:: .
~, energy state, laser radiation at 4416A (blue) is produced.
The vapor cadmium condenses - 9a - :
~ . ~
l~B08~38 ~.s condensa-te 74 d~e to the cooler tube opera-tion at those regions of the tube as shown.
The gas mixture of helium and neon fills the entire laser tube structure. The cadmium vapor is distributed in capillary tube 18 near cathode 21 by cataph~retic pumping. Cataphoresis also confines the cadmium to the portion of the capillary tube 18 near cathode 21. Thus, the helium-neon gas mixture is the only active medium in capillary tube 16 adjacent anode ~ 10 52 while the gas and vapor mixture of helium, neon and - cadmium is the active medium in the portion of capillary tube 18 adjacent cathode 21. It should be noted that section 16, in addition to providing path for the helium-ne~n discharge, also provides for the cataphoretic confinement of the cadmium vapor atoms which may diffuse towards mirror 40. This prevents cadmium vapor from condensing on the reflecting surface of mirror 40. The ; discharge current, in essence, forms a continuous ~ilament ~- passing through both capillary tubes 16 and 18. The inner ; 20 diameter of capillary tube 16 adjacent anode 52 is chosen ~;
to optimize the 6328A output resulting from the excitation ; reaction of the discharge on the helium-neon gas, the diameter (in millimeters) being approximately equal to i /10 wherein io is the discharge current in milliamps (ma).
Typically, io is selected to be 40 ma providing an inner diameter of 4 millimeters. The inner diameter of the capillary tube near cathode 21 is chosen to optimize the ` 4416A output resulting ~rom the helium-neon-cadmium dis-charge and is equal to io/40~ For an io f 40 ma, the diameter is therefor 1 millimeter.
The use of two coaxial discharge tubes having different inner diameters selected to optimize the output ~ ' ` -10-.~ , . " - ,, , , l338 therefrom allows the output laser beam 50 to be corres-pondinqly opti~lzed for external utilization.
n summary, after the discharge is initiated and the cadmium vaporized, voltage source 54 causes lasing action to occur. The left hand section in essence provides red laser light~ the right hand section in essence providing the - blue laser light component of light beam 50 notwithstanding the presence of helium-neon gas therein (helium-cadmium interaction predominates over the helium-neon interaction).
The dielectric coatings on integral mirrors 40 and 46 are selected so that only red and blue light (combined in one beam) is transmitted by mirror 46 as beam 50O Typical dielectric coatings include alternate layers of titanium and silicon dioxide, each layer having a predetermined thickness.
It shoul~ be noted that the temperature applied to the cadmium charge 70 determines its vapor pressure (and thus the intensity of the light produced) the cadmium pressure essentially not being affected by the helium-neon pressure.
Although not shown in Figure 1, the simultaneous generation of red and blue light as a single beam 50 can be dispersed into its separate component colors by using a prism or appropriate light filters.
Referring now to Figure 2, a second embodiment of the present invention is illustrated. The embodiment shown is substantially identical to that shown in Figure 1, the only difference being a charge of selenium metal 80 is utilized in the right hand section instead of cadmium.
Selenium vapor, when maintained at a predetermined temperature of approximately 270C by heater 72 interacts with the helium-neon gas wherein the helium ions and/or metastable atoms causes ,, ~, ~ - - ~ , ^ . . , ' 1~8~il3~3 the selenium atoms to be positively ionized and excited to a higher energy state. When the excited selenium atoms return to its initial or ground state, multili 3 emissions, including blue and green laser light is produced. The blue and green laser light emissions include -the following wavelengths: ~604A (blue), ~97~A (blue-green), 5069A
O O
(green), 5176A (green), and 5306A (green)~ The confinement of the selenium vapor is identical to the process described with reference to Figure 1 hereinabove and the inner diameters of capillary discharge tube sections 16 and 18 are substantially identical to the helium-cadmium embodi-ment described with reference to Figure 1. The laser mirrors, in this embodiment, are coated for broadband re-flectance (from about 4800A to about 6500A).
In operation, after vaporizing the selenium to the appropriate vapor pressure and initiating the discharge in both sections, voltage source 54 and ballast resistor 55 act to maintain the discharge for lasing action, red, blue and green (white) light being simultaneously transmitted as beam 50. As set forth hereinabove with reference to Figure 1, the separate color components of beam 50 can be obtained if desired by utilizing a prism to disperse each color component or by providing appropriate color filters.
The laser assembly described witn reference to Figures 1 and 2 hereinabove provides a multiline laser source for many applications, such as laser scanning as described hereinabove.
; The laser structure described hereinabove is simple, compact and low cost, the low cost feature arising from the fact that only one set of laser mirrors, one power ; supply and one unitary structure are necessary. Further, --1~
. ,~ .
1~8~338 no alignmant Eixturing is required to ensure coaxiality of the multiple color laser beams.
While the invention has been described with reference to its preferred embodiment, it will be under-stood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teaching of the invention without departing from its essential teachings.
..
~' .
.~ ' il ' ' ' ~ ' .
.:
. .
Claims (5)
1. A laser discharge tube for producing an output laser beam having a plurality of wavelengths comprising:
a tube envelope for enclosing first and second active lasing mediums, said tube envelope including end members for hermetically sealing said envelope, a first discharge tube having an inner diameter and supported within said envelope, a second discharge tube having an inner diameter and supported within said envelope and coaxially aligned with said first discharge tube, said first and second discharge tubes being operative to produce said output laser beam, a first electrode positioned adjacent one end of said first discharge tube, a second electrode operatively positioned with respect to one end of said second discharge tube, and means for applying an electrostatic potential between said first and second electrodes of a potential to maintain the same discharge current between said electrodes through said first and second discharge tubes whereby said first active lasing medium produces a first laser beam of at least one wavelength and said second active lasing medium produces a second laser beam comprising at least one wavelength, said first and second laser beams being combined into a laser out-put beam having a plurality of wavelengths, the inner diameters of said first and second discharge tubes being different and selected to optimize the output of said first and second laser beams.
a tube envelope for enclosing first and second active lasing mediums, said tube envelope including end members for hermetically sealing said envelope, a first discharge tube having an inner diameter and supported within said envelope, a second discharge tube having an inner diameter and supported within said envelope and coaxially aligned with said first discharge tube, said first and second discharge tubes being operative to produce said output laser beam, a first electrode positioned adjacent one end of said first discharge tube, a second electrode operatively positioned with respect to one end of said second discharge tube, and means for applying an electrostatic potential between said first and second electrodes of a potential to maintain the same discharge current between said electrodes through said first and second discharge tubes whereby said first active lasing medium produces a first laser beam of at least one wavelength and said second active lasing medium produces a second laser beam comprising at least one wavelength, said first and second laser beams being combined into a laser out-put beam having a plurality of wavelengths, the inner diameters of said first and second discharge tubes being different and selected to optimize the output of said first and second laser beams.
2. The laser discharge tube as defined in Claim 1 wherein said first active lasing medium comprises a gas and said second active lasing medium comprises a vaporized metal.
3. The laser discharge tube as defined in Claim 2 wherein said gas comprises a mixture of helium and neon and said metal comprises cadmium, said first laser beam compris-ing red laser light and said second laser beam comprising blue laser light.
4. The laser discharge tube as defined in Claim 2 wherein said gas comprises a mixture of helium and neon gas and said metal comprises selenium, said first laser beam com-prising red laser light and said second laser beam comprising blue and green laser light.
5. The laser discharge tube as defined in Claim 1 wherein said end members comprise optical mirrors sealed to an apertured flange member, said apertured flange member being affixed to the ends of said tube envelope, one of said optical mirrors being reflective of said first and second laser beams and the other of said optical mirrors partially transmitting said first and second laser beams as said combined laser out-put beam.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US68055977A | 1977-01-13 | 1977-01-13 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1080838A true CA1080838A (en) | 1980-07-01 |
Family
ID=24731594
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA274,324A Expired CA1080838A (en) | 1977-01-13 | 1977-03-18 | Multiline emission integral mirror laser |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS5388597A (en) |
| CA (1) | CA1080838A (en) |
| FR (1) | FR2377720B1 (en) |
| GB (1) | GB1573275A (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3036112C2 (en) * | 1980-09-25 | 1984-02-09 | W.C. Heraeus Gmbh, 6450 Hanau | Metal vapor laser with cataphoretic vapor transport |
| GB2200241A (en) * | 1986-09-22 | 1988-07-27 | Gen Electric Plc | Optical resonators |
| GB8711212D0 (en) * | 1987-05-12 | 1987-06-17 | English Electric Valve Co Ltd | Laser apparatus |
| EP0575324A1 (en) * | 1990-07-27 | 1993-12-29 | Ion Laser Technology | Mixed gas ion laser |
| JPH04215716A (en) * | 1990-12-17 | 1992-08-06 | Matsushita Electric Ind Co Ltd | Hot water feeder |
| JPH0767776A (en) * | 1994-06-24 | 1995-03-14 | Matsushita Electric Ind Co Ltd | Hot-water supply system |
-
1977
- 1977-03-18 CA CA274,324A patent/CA1080838A/en not_active Expired
- 1977-04-26 GB GB1733677A patent/GB1573275A/en not_active Expired
- 1977-04-29 FR FR7713076A patent/FR2377720B1/fr not_active Expired
- 1977-07-20 JP JP8618777A patent/JPS5388597A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| GB1573275A (en) | 1980-08-20 |
| FR2377720B1 (en) | 1981-09-18 |
| FR2377720A1 (en) | 1978-08-11 |
| JPS6130438B2 (en) | 1986-07-14 |
| JPS5388597A (en) | 1978-08-04 |
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