CA1187926A - Multiple pulse tea laser - Google Patents
Multiple pulse tea laserInfo
- Publication number
- CA1187926A CA1187926A CA000414365A CA414365A CA1187926A CA 1187926 A CA1187926 A CA 1187926A CA 000414365 A CA000414365 A CA 000414365A CA 414365 A CA414365 A CA 414365A CA 1187926 A CA1187926 A CA 1187926A
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- Prior art keywords
- discharge
- resonator
- pulse
- regions
- pulses
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Classifications
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- 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
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/06—Construction or shape of active medium
- H01S3/07—Construction or shape of active medium consisting of a plurality of parts, e.g. segments
- H01S3/073—Gas lasers comprising separate discharge sections in one cavity, e.g. hybrid lasers
- H01S3/076—Folded-path lasers
-
- 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
-
- 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
- H01S3/09—Processes or apparatus for excitation, e.g. pumping
- H01S3/097—Processes or apparatus for excitation, e.g. pumping by gas discharge of a gas laser
- H01S3/0971—Processes or apparatus for excitation, e.g. pumping by gas discharge of a gas laser transversely excited
- H01S3/09713—Processes or apparatus for excitation, e.g. pumping by gas discharge of a gas laser transversely excited with auxiliary ionisation, e.g. double discharge excitation
- H01S3/09716—Processes or apparatus for excitation, e.g. pumping by gas discharge of a gas laser transversely excited with auxiliary ionisation, e.g. double discharge excitation by ionising radiation
-
- 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)
- Health & Medical Sciences (AREA)
- Toxicology (AREA)
Abstract
MULTIPLE PULSE TEA LASER
Abstract A laser system capable of producing multiple pulses comprising a single optical resonator having multiple dis-change regions and multiple sets of electrodes and preion-izers. The optical resonator is folded and the beam passes through all of the discharge regions. Since the multiple discharges occur within the same resonator, multiple ident-ical pulses are produced and since the discharge regions are separated, the shock wave and medium inhomogeneity produced by a discharge in one discharge region will not disturb the others. The overall mirror separation and electrode spacing define a Fresnel number suited for single transverse mode operation.
Abstract A laser system capable of producing multiple pulses comprising a single optical resonator having multiple dis-change regions and multiple sets of electrodes and preion-izers. The optical resonator is folded and the beam passes through all of the discharge regions. Since the multiple discharges occur within the same resonator, multiple ident-ical pulses are produced and since the discharge regions are separated, the shock wave and medium inhomogeneity produced by a discharge in one discharge region will not disturb the others. The overall mirror separation and electrode spacing define a Fresnel number suited for single transverse mode operation.
Description
Back rcund of the Invention This invention relates to laser systems capable of multiple pulse operation.
There is a need for a laser system which can produce multiple pulses having a controllable separation between pulsesO For instance, such a system i5 useul in systems performing averaged cross-wind velocity measurements by using a correlation technique, and in incoherent designator systems~
lQ One technique that may be used is to employ two separate lasers pulsing consecutively. The multiple pulses are then transmitted along the same optical axis~ The problem is that the mode from the diferent lasers are not exactly the same, thus cau~ing problems in applications requiring correlation between the pulses. ~dditionally, it is extremely difficult to maintain ~he required alignment s~ability between the two lasers. Another technique which may be used consists of pulsing a standard laser a~ the required interval to produce the multiple pulses~ A problem with ~his is ~hat it requires a power supply with a high enough current capability to recharge the energy storage capacitors in less than tha minimum interval required.
~nother problem is that when the laser is pulsed with a short interval between pulses, as required in certain appli-cations, the shock waves and the medium inhomogeneities produced by a first discharge do not substantially dissipate, prior to subsequent discharge, thus creating problems by interfering with the subsequent di~charge.
7~
Summary of the Invention These and o-ther problems are solved by -the present invention which provides for a laser system capable of produc-ing mul-tiple pulses without the problems encoun-tered with presently known techniques. This is achieved by using multipl.e discharge regions within a common resonator. The advantage of this system is that the overall mirror separa-tion and the electrode spacingdefine a Fresnel number which is almos-t ideal for single transverse mode operation. By folding the resona-tor, as in the present invention, a more compact structureis achieved. Additionally, since the separa-te discharge re--gions can have -their own pulse forming network and trigger c:ircui-t, the multiple discharges can be fired simultaneously for maximum output, or they can be fired sequenti.ally separa-ted by a delay for producing multiple discharge ou-tput that is useful in the applications men-tioned herein. Another ad-vantage of this system is that since the discharge regions are inside -the same resonator, the multiple pulses generate an identical output beam. Additionally, in the folded resona-tor design of the present invention, the multiple dischargesare separate and isolated from each other, thus the di.scharge in a first region will not disturb the medium in a second region.
The present invention may be summarized~ according to a first broad aspec-t, as comprising in combination: an optical resonator; a gain medium disposed in said resonator;
a plurality of discharge regions disposed in said gain medium;
and means for producing a first discharge pulse in a firs-t one of said regions in response to a first con-trol pulse and -for producing a second, time delayed, discharge pulse in a second one of said regions in response to a second, time de-' :~
layedl con-trol pulse, and wherein said optical resonator in-cludes meansl responsive to the first and time delayed second discharge pulses, for generating correspondingly time delayed pulses of resonant optical energy in the resonatorl such time delayed resonant optical energy pulses being coupled along a common path to an output of the resonator.
According to another broad aspectl the invention provides a laser system comprising in combination: a plurality of discharge regions having a gain medium disposed -therein;
means for producing time delayed discharge pulses in said discharge regions; and an optical resonator having said plur-ality of discharge regions disposed thereinl said op-tical resonator comprising: means for generatingl in response to said time delayed discharge pulsesl correspondingly time delay-ed pulses of resonant optical energy in the resonator; andl means for directing said time delayed pulses of resonant op-tical energy along a common path to an output of the resonator, a portion of said path passing through the gain medium in each of the plurality of discharge regions.
Preferably, each of said discharge regions comprises a different predetermined portion of said resonator. Said discharge pulse producing means may comprise means for switch-ing an electric pulse across the pair of electrodes associated with a predetermined one of said plurality of discharge regions.
Brief Descriptlon of_the D awing A better understanding oE the features oE the preferred embodiment may be obtained from the accompanying detailed description used in conjunction with the drawing which shows a block dlagram of a laser system of ~he presen~ invention.
Description of the Preferred E odiment Referring now to the drawing, there i5 shown a transverse electric field laser 10 comprising a folded op-tical resonator defined hy mirrors 30, 32, 34 and 36. Mirrors 30 and 36 are the end mlrrors tha~ define the oppo~ite extremes of khe optical cavity, and mirrors 32 and 34 are used to fold or turn around a resonating heam in order ~o llmit the length of the device. The mixture of a lasing gas is confined within the resonator structure by a folded laser envelope, not shown.
For example, an appropriate mixture comprising carbon dioxide, nitrogen and helium, as is known in the art, may be used.
One se~ of main electrodes is placed between each region defined by one of the end mirrors and a ~urn-around mirror.
Thus, electrodes 12 and 14 are placed between reflector 30 and 32 symmetrically about a center line of the folded laser and electrodes 16 and 18 are similarly placed between mirrors 36 and 34 symmetrically about a corresponding center line~ A
preionizing flash board is also placed adjacent ~o each of the two regions thus definedO Each flashboard 21 and 23 comprises a support plate 20 and 22, respectively, and a plurality of auxiliary electrodes 24 dispose!d on a first surface of each ~upport plate facing a respective main discharge region de-fined by the volume between a pair of main electrodes. The two preionizing flash boards are placed back~o-back and thus can share a common conductive member 26~ The center auxiliary e].ectrode of each flashboard is electrically coupled to t:he conductive member 26 which is electrically grounded. ~he two end auxiliary electrodes of each flash-board are electrically coupled ~o an output terminal of a respective pulse forming network. The operation of each flashboard is as followsO Upon application oE a high voltage pulse between the two end auxiliary electrode and ground, a discharge will be produced bel,ween the end electrodes and their adjacent neighbors~ resulting in a transfer Gf charge to these neighbors since the auxiliary electrode in combi-nation with the backing plate and the conductive member form a plurality of spaced capacitors. The charge is then trans-ferred ~y consecutive discharges from the two end electrodes to the grounded center electrode. The preionizing flash-boards are located so that the chain of discharges between the auxiliary electrodes o each flash board 21 and 23 illum-ina~es a respective main discharge region between a pair of two main electrodes. This is because the flash board converts a fraction of the stored energy into a pulse of ultraviolet radiation which in turn produces free electrons which when accelerated by an electric field promote uniform ionization of the gas in the interaction spa~e between the main electrodes~ ThiS is necessary to preclude the occurence of arcing, which would dump all the energy otherwise needed for pumping the gas mix.
The curvature and spacing of mirrors 30 and 36 and the size of the defining aperture determine the mode in which the optical resonator will o~cillate. The fundamental or low~st order radially symmetric mode7 (TEMoo mode), is desired since it has the least beam divergence and no nodes or gaps in the far field. Mirrors 30 and 36 have a concave surface of similar radius of curvature to define a resonator having a mode volume with a waist in the center line of the folded resona~or between the two turn-around mirrorsO
When the t~o sets of electrodes are placed symmetrically ~7~
about the center, the mode volume contained between one pair of electrodes is the same as the otherO This is im-portant to make sure that bot:h pulses are the same. Although the emitted beam might be sli.ghtly diveryent, due to the curvature of the mirrors, this divergence may be compensated for by using an output mirror 36 with a curved rear surface, not shown in the fiyure, to effectively act as a lensO The aperturing is effected by making the mirrors slightly larger than the region between the main electrodes. An aperture i5 then placed somewhere in the resonator, typically at the output mirror. The diameter of the aperture is approximately equal to the electrode spacing. Using the main electrode spacing for defining the size of beam aperture insures optimum use of the gain medium, since most of the gas excited by the discharge i5 used to contribute to the formation of a laser pulse~ Alternatively, aperturing may be effected by placing an aperture stop 33 between the two folding mirrors 32 and The operation of a laser system of the present invention is as follows~ A timer 50 supplies a timing pulse at a pre-determined repetition rate, for example 20 ~Iz~ The timing pulses are used by trigger 60 to trigger pulse forming net-work 70 to supply a pulse of voltage to one of the flash-boards, flashboard 21 for example, in order to preionize the laser Medium, in this case in the region adjacent main elec-trQdes 12 and 14 t as described hereinahovel Preferably, the duration oE the preionizing pulse is a few nanoseconds to 150 nanoseconds and has an amplitude of a Eew thousand volts.
Trigger 60 is preferably formed by a spark gap having a trigger elec.rode connected to timer 50~ The spark gap is
There is a need for a laser system which can produce multiple pulses having a controllable separation between pulsesO For instance, such a system i5 useul in systems performing averaged cross-wind velocity measurements by using a correlation technique, and in incoherent designator systems~
lQ One technique that may be used is to employ two separate lasers pulsing consecutively. The multiple pulses are then transmitted along the same optical axis~ The problem is that the mode from the diferent lasers are not exactly the same, thus cau~ing problems in applications requiring correlation between the pulses. ~dditionally, it is extremely difficult to maintain ~he required alignment s~ability between the two lasers. Another technique which may be used consists of pulsing a standard laser a~ the required interval to produce the multiple pulses~ A problem with ~his is ~hat it requires a power supply with a high enough current capability to recharge the energy storage capacitors in less than tha minimum interval required.
~nother problem is that when the laser is pulsed with a short interval between pulses, as required in certain appli-cations, the shock waves and the medium inhomogeneities produced by a first discharge do not substantially dissipate, prior to subsequent discharge, thus creating problems by interfering with the subsequent di~charge.
7~
Summary of the Invention These and o-ther problems are solved by -the present invention which provides for a laser system capable of produc-ing mul-tiple pulses without the problems encoun-tered with presently known techniques. This is achieved by using multipl.e discharge regions within a common resonator. The advantage of this system is that the overall mirror separa-tion and the electrode spacingdefine a Fresnel number which is almos-t ideal for single transverse mode operation. By folding the resona-tor, as in the present invention, a more compact structureis achieved. Additionally, since the separa-te discharge re--gions can have -their own pulse forming network and trigger c:ircui-t, the multiple discharges can be fired simultaneously for maximum output, or they can be fired sequenti.ally separa-ted by a delay for producing multiple discharge ou-tput that is useful in the applications men-tioned herein. Another ad-vantage of this system is that since the discharge regions are inside -the same resonator, the multiple pulses generate an identical output beam. Additionally, in the folded resona-tor design of the present invention, the multiple dischargesare separate and isolated from each other, thus the di.scharge in a first region will not disturb the medium in a second region.
The present invention may be summarized~ according to a first broad aspec-t, as comprising in combination: an optical resonator; a gain medium disposed in said resonator;
a plurality of discharge regions disposed in said gain medium;
and means for producing a first discharge pulse in a firs-t one of said regions in response to a first con-trol pulse and -for producing a second, time delayed, discharge pulse in a second one of said regions in response to a second, time de-' :~
layedl con-trol pulse, and wherein said optical resonator in-cludes meansl responsive to the first and time delayed second discharge pulses, for generating correspondingly time delayed pulses of resonant optical energy in the resonatorl such time delayed resonant optical energy pulses being coupled along a common path to an output of the resonator.
According to another broad aspectl the invention provides a laser system comprising in combination: a plurality of discharge regions having a gain medium disposed -therein;
means for producing time delayed discharge pulses in said discharge regions; and an optical resonator having said plur-ality of discharge regions disposed thereinl said op-tical resonator comprising: means for generatingl in response to said time delayed discharge pulsesl correspondingly time delay-ed pulses of resonant optical energy in the resonator; andl means for directing said time delayed pulses of resonant op-tical energy along a common path to an output of the resonator, a portion of said path passing through the gain medium in each of the plurality of discharge regions.
Preferably, each of said discharge regions comprises a different predetermined portion of said resonator. Said discharge pulse producing means may comprise means for switch-ing an electric pulse across the pair of electrodes associated with a predetermined one of said plurality of discharge regions.
Brief Descriptlon of_the D awing A better understanding oE the features oE the preferred embodiment may be obtained from the accompanying detailed description used in conjunction with the drawing which shows a block dlagram of a laser system of ~he presen~ invention.
Description of the Preferred E odiment Referring now to the drawing, there i5 shown a transverse electric field laser 10 comprising a folded op-tical resonator defined hy mirrors 30, 32, 34 and 36. Mirrors 30 and 36 are the end mlrrors tha~ define the oppo~ite extremes of khe optical cavity, and mirrors 32 and 34 are used to fold or turn around a resonating heam in order ~o llmit the length of the device. The mixture of a lasing gas is confined within the resonator structure by a folded laser envelope, not shown.
For example, an appropriate mixture comprising carbon dioxide, nitrogen and helium, as is known in the art, may be used.
One se~ of main electrodes is placed between each region defined by one of the end mirrors and a ~urn-around mirror.
Thus, electrodes 12 and 14 are placed between reflector 30 and 32 symmetrically about a center line of the folded laser and electrodes 16 and 18 are similarly placed between mirrors 36 and 34 symmetrically about a corresponding center line~ A
preionizing flash board is also placed adjacent ~o each of the two regions thus definedO Each flashboard 21 and 23 comprises a support plate 20 and 22, respectively, and a plurality of auxiliary electrodes 24 dispose!d on a first surface of each ~upport plate facing a respective main discharge region de-fined by the volume between a pair of main electrodes. The two preionizing flash boards are placed back~o-back and thus can share a common conductive member 26~ The center auxiliary e].ectrode of each flashboard is electrically coupled to t:he conductive member 26 which is electrically grounded. ~he two end auxiliary electrodes of each flash-board are electrically coupled ~o an output terminal of a respective pulse forming network. The operation of each flashboard is as followsO Upon application oE a high voltage pulse between the two end auxiliary electrode and ground, a discharge will be produced bel,ween the end electrodes and their adjacent neighbors~ resulting in a transfer Gf charge to these neighbors since the auxiliary electrode in combi-nation with the backing plate and the conductive member form a plurality of spaced capacitors. The charge is then trans-ferred ~y consecutive discharges from the two end electrodes to the grounded center electrode. The preionizing flash-boards are located so that the chain of discharges between the auxiliary electrodes o each flash board 21 and 23 illum-ina~es a respective main discharge region between a pair of two main electrodes. This is because the flash board converts a fraction of the stored energy into a pulse of ultraviolet radiation which in turn produces free electrons which when accelerated by an electric field promote uniform ionization of the gas in the interaction spa~e between the main electrodes~ ThiS is necessary to preclude the occurence of arcing, which would dump all the energy otherwise needed for pumping the gas mix.
The curvature and spacing of mirrors 30 and 36 and the size of the defining aperture determine the mode in which the optical resonator will o~cillate. The fundamental or low~st order radially symmetric mode7 (TEMoo mode), is desired since it has the least beam divergence and no nodes or gaps in the far field. Mirrors 30 and 36 have a concave surface of similar radius of curvature to define a resonator having a mode volume with a waist in the center line of the folded resona~or between the two turn-around mirrorsO
When the t~o sets of electrodes are placed symmetrically ~7~
about the center, the mode volume contained between one pair of electrodes is the same as the otherO This is im-portant to make sure that bot:h pulses are the same. Although the emitted beam might be sli.ghtly diveryent, due to the curvature of the mirrors, this divergence may be compensated for by using an output mirror 36 with a curved rear surface, not shown in the fiyure, to effectively act as a lensO The aperturing is effected by making the mirrors slightly larger than the region between the main electrodes. An aperture i5 then placed somewhere in the resonator, typically at the output mirror. The diameter of the aperture is approximately equal to the electrode spacing. Using the main electrode spacing for defining the size of beam aperture insures optimum use of the gain medium, since most of the gas excited by the discharge i5 used to contribute to the formation of a laser pulse~ Alternatively, aperturing may be effected by placing an aperture stop 33 between the two folding mirrors 32 and The operation of a laser system of the present invention is as follows~ A timer 50 supplies a timing pulse at a pre-determined repetition rate, for example 20 ~Iz~ The timing pulses are used by trigger 60 to trigger pulse forming net-work 70 to supply a pulse of voltage to one of the flash-boards, flashboard 21 for example, in order to preionize the laser Medium, in this case in the region adjacent main elec-trQdes 12 and 14 t as described hereinahovel Preferably, the duration oE the preionizing pulse is a few nanoseconds to 150 nanoseconds and has an amplitude of a Eew thousand volts.
Trigger 60 is preferably formed by a spark gap having a trigger elec.rode connected to timer 50~ The spark gap is
2~
used ~o electrically connect suitable energy storage capac-itors, which are part of pulse forming network 70/ across the required points on the auxiliary electrodes. The energy storage capacitQrs in pulse forming network 70 are charged to their required level by high power voltage supply 80n A
main laser discharge pul~e is applied by pulse forming network 70 ~o main electrod~s 12 and 14 approximately after the cessation of the preionizing discharge be~ween the auxiliary ele~tro~es o the fla~hboard.
The same timing pulses applied ~o trigger 60 are also applied by timer 50 to delay 90. Delay 90 is used to provide a sui~ably delayed timing pulse to trigger lO0, which in turn is used to trigger pulse forming network llO to supply a voltage pulse to the second flashboard, flashboard 23 for example, to preionize the laser medium adjacent main elec-trodes 16 and 18. At the end of this preionizing pulse, pulse forming network llO also applies a main discharge pulse across the second set of main electrodes 16 and 18. Thus, the system just described produce~ a first laser pulse at ~0 time to defined by each timing pulse from timer S0 and a second laser pulse at a subsequent tirne tl determined by the amount of delay selected in delay 90.
It should be understood that even though a specific im-plementation for a preionizing flashboard has been described to produce a preionization pulse to uniformly ionize the gas mix, other methods of producing the required level of ion-ization for proper operation of the laser may be used.
It should be appreciated that since there are provided two separate discharge regions that can be fired off indepen-dentlyr the laser system can be used to generate a larger ~37~
laser pulse by setting the delay in delay ~0 to zero~ thus causing simultaneous discharges in the two sets o electrodesO
Alternatively, any amount of delay may be set by delay 90 to generate two discharges that are separated in time by any predetermined amount less tha:n the timing pulse repetition rate.
In general, each time that a discharge takes place, a portion of the gas mixture in the discharge breaks down and decomposes into different compounds. In the case where CO2 is used as the active species, the breakdown produces CO and 2 Under normal conditions, the disassociated components will recombine, and catalysts may be used to aid the recom~
bination process. However, a problem occurs in applications requiring multiple puls~s separated by a time duration shorter than the recombination timer The disassociated gas causes a smaller amount of active molecules to be available in the discharge region, and thus it provides less gain, possibly less than the minimum required, for the generation of a laser pulse. In addition to producing a decomposition o the gain medium, each discharge produces a shock wave which heats the medium in the vicinity of the discharge~ The rise in temperature reduces the gain of the medium further, thus pre-cluding the successive generation of substanti.ally identical laser pulses if each discharge takes place before the heat dissipates. An importan~ advantage of the laser system of the present invention is that these problems are eliminated by providing multiple discharge regions separated from each other and effectively having independent gas volumes, thus enabling the firing of successive discharges in different regions, each utilizing a substantially stable ac-tive volume _ g _ ~7~
of the gain medium. It should also be appreciated that since the two discharges are separated and are isolated from each other the shock wave from one discharge should not signifi cantly disturb the other discharge.
It has been found that if a delay time of approximately lO0 microseconds is used, there is no measurable interference in the two laser pulses thus generated. This is because the shock wave has been sufficiently dlssipated within that period of time~ Smaller intervals may be achieved by placing around the discharge regions materials that absorb the shock wave and prevent it from bouneing off the walls of the envelope and return to disturb the optical cavity.
An advantage of the present laser 5y5tem i5 that since the two discharge regions are within the same optical resonator pulsing either one of them produces substantially iden~ical output pulses. Additionally, the overall mirror separation in the electrode spacing define a Fresnel number which is almost ideal for single tranverse mode operatio~.
The Fresnel number is proportional to the radius square of ~he beam divided by the operating wavelength times the length o the optical resonator, A Fresnel number approximately equal to 2 i5 found to easily ~atisfy the single transverse mode requirementsn The folded design makes possible the building of such a resonator in a very compac~ structure.
~his may be achieved by having a main electrode separation of 0.85 centimeters and having a single discharge region length of 25 centimeter for an operating wavelength of 10.6 microns for a CO2 TEA laser.
It is understood that the above described embodimen~s of the invention are illustrative only and that modifications thereof may occur ~o ~hose skilled in the artD Accordingly, it is desired that this invention is not ~o be limited ~o the embodiments disclosed herein but is to be limited only as defined by the appended claims.
used ~o electrically connect suitable energy storage capac-itors, which are part of pulse forming network 70/ across the required points on the auxiliary electrodes. The energy storage capacitQrs in pulse forming network 70 are charged to their required level by high power voltage supply 80n A
main laser discharge pul~e is applied by pulse forming network 70 ~o main electrod~s 12 and 14 approximately after the cessation of the preionizing discharge be~ween the auxiliary ele~tro~es o the fla~hboard.
The same timing pulses applied ~o trigger 60 are also applied by timer 50 to delay 90. Delay 90 is used to provide a sui~ably delayed timing pulse to trigger lO0, which in turn is used to trigger pulse forming network llO to supply a voltage pulse to the second flashboard, flashboard 23 for example, to preionize the laser medium adjacent main elec-trodes 16 and 18. At the end of this preionizing pulse, pulse forming network llO also applies a main discharge pulse across the second set of main electrodes 16 and 18. Thus, the system just described produce~ a first laser pulse at ~0 time to defined by each timing pulse from timer S0 and a second laser pulse at a subsequent tirne tl determined by the amount of delay selected in delay 90.
It should be understood that even though a specific im-plementation for a preionizing flashboard has been described to produce a preionization pulse to uniformly ionize the gas mix, other methods of producing the required level of ion-ization for proper operation of the laser may be used.
It should be appreciated that since there are provided two separate discharge regions that can be fired off indepen-dentlyr the laser system can be used to generate a larger ~37~
laser pulse by setting the delay in delay ~0 to zero~ thus causing simultaneous discharges in the two sets o electrodesO
Alternatively, any amount of delay may be set by delay 90 to generate two discharges that are separated in time by any predetermined amount less tha:n the timing pulse repetition rate.
In general, each time that a discharge takes place, a portion of the gas mixture in the discharge breaks down and decomposes into different compounds. In the case where CO2 is used as the active species, the breakdown produces CO and 2 Under normal conditions, the disassociated components will recombine, and catalysts may be used to aid the recom~
bination process. However, a problem occurs in applications requiring multiple puls~s separated by a time duration shorter than the recombination timer The disassociated gas causes a smaller amount of active molecules to be available in the discharge region, and thus it provides less gain, possibly less than the minimum required, for the generation of a laser pulse. In addition to producing a decomposition o the gain medium, each discharge produces a shock wave which heats the medium in the vicinity of the discharge~ The rise in temperature reduces the gain of the medium further, thus pre-cluding the successive generation of substanti.ally identical laser pulses if each discharge takes place before the heat dissipates. An importan~ advantage of the laser system of the present invention is that these problems are eliminated by providing multiple discharge regions separated from each other and effectively having independent gas volumes, thus enabling the firing of successive discharges in different regions, each utilizing a substantially stable ac-tive volume _ g _ ~7~
of the gain medium. It should also be appreciated that since the two discharges are separated and are isolated from each other the shock wave from one discharge should not signifi cantly disturb the other discharge.
It has been found that if a delay time of approximately lO0 microseconds is used, there is no measurable interference in the two laser pulses thus generated. This is because the shock wave has been sufficiently dlssipated within that period of time~ Smaller intervals may be achieved by placing around the discharge regions materials that absorb the shock wave and prevent it from bouneing off the walls of the envelope and return to disturb the optical cavity.
An advantage of the present laser 5y5tem i5 that since the two discharge regions are within the same optical resonator pulsing either one of them produces substantially iden~ical output pulses. Additionally, the overall mirror separation in the electrode spacing define a Fresnel number which is almost ideal for single tranverse mode operatio~.
The Fresnel number is proportional to the radius square of ~he beam divided by the operating wavelength times the length o the optical resonator, A Fresnel number approximately equal to 2 i5 found to easily ~atisfy the single transverse mode requirementsn The folded design makes possible the building of such a resonator in a very compac~ structure.
~his may be achieved by having a main electrode separation of 0.85 centimeters and having a single discharge region length of 25 centimeter for an operating wavelength of 10.6 microns for a CO2 TEA laser.
It is understood that the above described embodimen~s of the invention are illustrative only and that modifications thereof may occur ~o ~hose skilled in the artD Accordingly, it is desired that this invention is not ~o be limited ~o the embodiments disclosed herein but is to be limited only as defined by the appended claims.
Claims (18)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In combination:
an optical resonator;
a gain medium disposed in said resonator;
a plurality of discharge regions disposed in said gain medium; and means for producing a first discharge pulse in a first one of said regions in response to a first control pulse and for producing a second, time delayed, discharge pulse in a second one of said regions in response to a second, time delayed, control pulse, and wherein said optical resonator includes means, respon-sive to the first and time delayed second discharge pulses, for generating correspondingly time delayed pulses of resonant optical energy in the resonator, such time delayed resonant optical energy pulses being coupled along a common path to an output of the resonator.
an optical resonator;
a gain medium disposed in said resonator;
a plurality of discharge regions disposed in said gain medium; and means for producing a first discharge pulse in a first one of said regions in response to a first control pulse and for producing a second, time delayed, discharge pulse in a second one of said regions in response to a second, time delayed, control pulse, and wherein said optical resonator includes means, respon-sive to the first and time delayed second discharge pulses, for generating correspondingly time delayed pulses of resonant optical energy in the resonator, such time delayed resonant optical energy pulses being coupled along a common path to an output of the resonator.
2. In combination:
an optical resonator;
a gain medium disposed in said resonator;
a plurality of discharge regions disposed in said gain medium; and means for producing a first discharge pulse in a first one of said regions in response to a first control pulse and for producing a second, time delayed, discharge pulse in a second one of said regions in response to a second, time delayed, control pulse, and wherein said optical resonator includes means, respon-sive to the first and time delayed second discharge pulses, for generating correspondingly time delayed pulses of resonant optical energy in the resonator, such time delayed resonant optical energy pulses being directed along a common path to an output of the resonator, said path passing through the gain medium and the plurality of discharge regions.
an optical resonator;
a gain medium disposed in said resonator;
a plurality of discharge regions disposed in said gain medium; and means for producing a first discharge pulse in a first one of said regions in response to a first control pulse and for producing a second, time delayed, discharge pulse in a second one of said regions in response to a second, time delayed, control pulse, and wherein said optical resonator includes means, respon-sive to the first and time delayed second discharge pulses, for generating correspondingly time delayed pulses of resonant optical energy in the resonator, such time delayed resonant optical energy pulses being directed along a common path to an output of the resonator, said path passing through the gain medium and the plurality of discharge regions.
3. The combination of claim 2 wherein:
the first discharge pulse produced in the first dis-charge region in response to the first control. pulse generates a turbulence in the optical resonator and wherein the time delay of the second control pulse is greater than the duration of turbulence generated in the resonator by the first discharge pulse in the first discharge region.
the first discharge pulse produced in the first dis-charge region in response to the first control. pulse generates a turbulence in the optical resonator and wherein the time delay of the second control pulse is greater than the duration of turbulence generated in the resonator by the first discharge pulse in the first discharge region.
4. The combination of claim 2 wherein:
the time delay of the second control pulse is greater than 100 microseconds.
the time delay of the second control pulse is greater than 100 microseconds.
5. A laser system comprising in combination:
a plurality of discharge regions having a gain medium disposed therein;
means for producing time delayed discharge pulses in said discharge regions; and an optical resonator having said plurality of discharge regions disposed therein, said optical resonator comprising:
means for generating, in response to said time delayed dis-charge pulses, correspondingly time delayed pulses of resonant optical energy in the resonator; and, means for directing said time delayed pulses of resonant optical energy along a common path to an output of the resonator, a portion of said path passing through the gain medium in each of the plurality of discharge regions.
a plurality of discharge regions having a gain medium disposed therein;
means for producing time delayed discharge pulses in said discharge regions; and an optical resonator having said plurality of discharge regions disposed therein, said optical resonator comprising:
means for generating, in response to said time delayed dis-charge pulses, correspondingly time delayed pulses of resonant optical energy in the resonator; and, means for directing said time delayed pulses of resonant optical energy along a common path to an output of the resonator, a portion of said path passing through the gain medium in each of the plurality of discharge regions.
6. The combination of Claim 5 wherein:
each of said discharge regions comprises a different predetermined portion of said resonator.
each of said discharge regions comprises a different predetermined portion of said resonator.
7. The combination of Claim 5 wherein:
the laser system comprises a plurality of pairs of opposing electrodes and wherein each one of said plurality of discharge regions is associated with one of the plurality of pairs of opposing electrodes, each pair of electrodes having disposed therebetween the gain medium in the discharge region associated therewith and each pair of electrodes having sur-faces disposed transversely to the portion of the path passing through the discharge region associated with such pair of electrodes.
the laser system comprises a plurality of pairs of opposing electrodes and wherein each one of said plurality of discharge regions is associated with one of the plurality of pairs of opposing electrodes, each pair of electrodes having disposed therebetween the gain medium in the discharge region associated therewith and each pair of electrodes having sur-faces disposed transversely to the portion of the path passing through the discharge region associated with such pair of electrodes.
8. The combination of claim 7 wherein:
said discharge pulse producing means comprises means for switching an electric pulse across the pair of electrodes associated with a predetermined one of said plurality of discharge regions.
said discharge pulse producing means comprises means for switching an electric pulse across the pair of electrodes associated with a predetermined one of said plurality of discharge regions.
9. The combination of claim 8 wherein:
said pulses of resonant optical energy form optical beams having a predetermined diameter, and wherein the opposing electrodes are spaced a predetermined distance, said distance defining the diameter of the optical beams.
said pulses of resonant optical energy form optical beams having a predetermined diameter, and wherein the opposing electrodes are spaced a predetermined distance, said distance defining the diameter of the optical beams.
10. The combination of claim 9 wherein:
said optical resonator has a predetermined length, and wherein the distance between the pair of opposing electrodes and the length of the resonator are selected to provide for single transverse mode operation.
said optical resonator has a predetermined length, and wherein the distance between the pair of opposing electrodes and the length of the resonator are selected to provide for single transverse mode operation.
11. The combination of claim 5 wherein:
said common path is folded about a fold region and wherein said fold region is disposed between a first one of said plurality of discharge regions and a second one of said plurality of discharge regions.
said common path is folded about a fold region and wherein said fold region is disposed between a first one of said plurality of discharge regions and a second one of said plurality of discharge regions.
12. In combination:
an optical resonator;
a gain medium disposed within the resonator;
a plurality of discharge regions disposed within said optical resonator, said discharge regions having corresponding portions of the gain medium disposed therein; and pulse forming means for producing a first discharge pulse in a first one of said discharge regions and for producing a second, time delayed, discharge pulse in a second one of said discharge regions, and wherein said optical resonator includes means, respon-sive to the first and time delayed second discharge pulses, for generating correspondingly time delayed pulses of resonant optical energy in the resonator, such time delayed resonant optical energy pulses being directed along a common path to an output of the resonator, said path passing through the portions of the gain medium disposed within the plurality of discharge regions.
an optical resonator;
a gain medium disposed within the resonator;
a plurality of discharge regions disposed within said optical resonator, said discharge regions having corresponding portions of the gain medium disposed therein; and pulse forming means for producing a first discharge pulse in a first one of said discharge regions and for producing a second, time delayed, discharge pulse in a second one of said discharge regions, and wherein said optical resonator includes means, respon-sive to the first and time delayed second discharge pulses, for generating correspondingly time delayed pulses of resonant optical energy in the resonator, such time delayed resonant optical energy pulses being directed along a common path to an output of the resonator, said path passing through the portions of the gain medium disposed within the plurality of discharge regions.
13. The combination of claim 12 wherein:
said common path is folded about a fold region and wherein said fold region is disposed between the first one of said plurality of discharge regions and the second one of said plurality of discharge regions.
said common path is folded about a fold region and wherein said fold region is disposed between the first one of said plurality of discharge regions and the second one of said plurality of discharge regions.
14. The combination of claim 12 wherein:
the optical resonator further comprises a plurality of pairs of opposing, spaced electrodes coupled to said pulse forming means and wherein each one of said plurality of dis-charge regions is associated with one of the plurality of pairs of opposing, spaced electrodes, each pair of electrodes having a portion of the gain medium disposed therebetween and each pair of electrodes having surfaces disposed transversely to the portion of the path for the time delayed pulses of resonant optical energy passing through said gain medium.
the optical resonator further comprises a plurality of pairs of opposing, spaced electrodes coupled to said pulse forming means and wherein each one of said plurality of dis-charge regions is associated with one of the plurality of pairs of opposing, spaced electrodes, each pair of electrodes having a portion of the gain medium disposed therebetween and each pair of electrodes having surfaces disposed transversely to the portion of the path for the time delayed pulses of resonant optical energy passing through said gain medium.
15. The combination of claim 14 wherein:
said time delayed pulses of resonant optical energy form optical beams, and further comprising means for aperturing said optical beams to a size approximately equal to the spacing between the pair of opposing electrodes associated with each one of said plurality of discharge regions.
said time delayed pulses of resonant optical energy form optical beams, and further comprising means for aperturing said optical beams to a size approximately equal to the spacing between the pair of opposing electrodes associated with each one of said plurality of discharge regions.
16. The combination of claim 15 wherein:
said optical resonator has a predetermined length, said length being selected to provide for single transverse-mode operation.
said optical resonator has a predetermined length, said length being selected to provide for single transverse-mode operation.
17. The combination of claim 12 further comprising:
means for preionizing the gain medium in a selected one of said plurality of discharge regions prior to the discharge pulse in the selected region.
means for preionizing the gain medium in a selected one of said plurality of discharge regions prior to the discharge pulse in the selected region.
18. The combination of 13 further comprising:
means for preionizing the gain medium in the first discharge region prior to the discharge pulse in said first region and for preionizing, after a preionlzation time delay, the gain medium in the second discharge region prior to the discharge pulse in said second region, said preionization time delay corresponding to the time delay between the dis-charge pulse in the first region and the discharge pulse in the second region; and wherein turbulence is produced in the resonator with each discharge pulse and wherein said preionizing means is disposed adjacent the first discharge region and the second discharge region to inhibit turbulence associated with one of such discharge pulses from entering the discharge region wherein the other one of the discharge pulses is produced.
means for preionizing the gain medium in the first discharge region prior to the discharge pulse in said first region and for preionizing, after a preionlzation time delay, the gain medium in the second discharge region prior to the discharge pulse in said second region, said preionization time delay corresponding to the time delay between the dis-charge pulse in the first region and the discharge pulse in the second region; and wherein turbulence is produced in the resonator with each discharge pulse and wherein said preionizing means is disposed adjacent the first discharge region and the second discharge region to inhibit turbulence associated with one of such discharge pulses from entering the discharge region wherein the other one of the discharge pulses is produced.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US31767481A | 1981-11-02 | 1981-11-02 | |
| US317,674 | 1981-11-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1187926A true CA1187926A (en) | 1985-05-28 |
Family
ID=23234767
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000414365A Expired CA1187926A (en) | 1981-11-02 | 1982-10-28 | Multiple pulse tea laser |
Country Status (4)
| Country | Link |
|---|---|
| CA (1) | CA1187926A (en) |
| DE (1) | DE3240413C2 (en) |
| FR (1) | FR2515884B1 (en) |
| GB (1) | GB2108752B (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3314157A1 (en) * | 1982-04-19 | 1983-12-08 | Kraftwerk Union AG, 4330 Mülheim | Excitation circuit for laser systems, especially for TE high-energy lasers, with adjustment of the pre-ionisation |
| EP0183023B1 (en) * | 1984-11-24 | 1991-02-20 | Trumpf GmbH & Co | Gas laser with transversal coupling of high-frequency energy |
| JPS61280499A (en) * | 1985-06-05 | 1986-12-11 | Sumitomo Chem Co Ltd | Amine adduct compound of aluminum phosphinate and plant blight controlling agent containing said compound as active component |
| US4833686A (en) * | 1987-06-29 | 1989-05-23 | Hughes Aircraft Company | Electrodes for transversely excited gas lasers |
| DE10303620A1 (en) * | 2003-01-30 | 2004-08-19 | Rofin-Sinar Laser Gmbh | Stripline laser |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BE788846A (en) * | 1971-09-24 | 1973-03-15 | D Comp Gen | LASER GENERATOR DEVICE |
| FR2216699B1 (en) * | 1973-02-01 | 1978-03-03 | Comp Generale Electricite | |
| US4288756A (en) * | 1977-06-17 | 1981-09-08 | United Kingdom Atomic Energy Authority | CO2 Laser |
| DE2753304C2 (en) * | 1977-11-30 | 1984-11-08 | Eltro GmbH, Gesellschaft für Strahlungstechnik, 6900 Heidelberg | Transversely excited gas laser (TEA laser) operating at atmospheric pressure |
| FR2464583A1 (en) * | 1979-08-31 | 1981-03-06 | Comp Generale Electricite | LASER GAS DEVICE CAPABLE OF PULSED EMITTING STABILIZED FREQUENCY RADIATION |
| US4499582A (en) * | 1980-04-05 | 1985-02-12 | Heinrich Karning | Laser system |
-
1982
- 1982-10-20 GB GB08229902A patent/GB2108752B/en not_active Expired
- 1982-10-28 CA CA000414365A patent/CA1187926A/en not_active Expired
- 1982-11-02 FR FR8218338A patent/FR2515884B1/en not_active Expired
- 1982-11-02 DE DE19823240413 patent/DE3240413C2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| GB2108752B (en) | 1986-04-09 |
| DE3240413A1 (en) | 1983-05-19 |
| DE3240413C2 (en) | 1994-09-01 |
| GB2108752A (en) | 1983-05-18 |
| FR2515884B1 (en) | 1986-11-21 |
| FR2515884A1 (en) | 1983-05-06 |
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