A high-power, continuous-wave laser was designed for use in power transmission and energy-collecting systems, and for producing incoherent light for pumping a laser material. The laser has a high repetitive pulsing rate per unit time, resulting in a high-power density beam. The laser is composed of xenon flash tubes powered by fast-charging capacitors flashed in succession by a high-speed motor connected to an automobile-type distributor

Brandhorst, H. W., Jr.

Evans, J. C., Jr.

English

NASA Technical Reports Server

REPLY TO
ATTN OF: GP
TO:
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
WASHINGTON. O.C. 20546
JUL 2 8 1975
KSI/Scientific & Technical Information Division
Attn: Miss Winnie M. Morgan
FROM: GP/Office of Assistant General
Counsel for Patent Matters
<*•»
Iin
SUBJECT: Announcement of NASA-Owned U.S* Patents in STAR
; /
KJ,.! In accordance with, the procedures agreed upon by Code GP
HO; and/Code KSI, the attached NASA-owned U.S. Patent is being
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vo The following information is provided:
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3 U.S. Patent No. : -
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Government or
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NASA Patent Case No.
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,NOTE - If this patent covers an invention made by a corporate
employee of a NASA Contractor, the following is applicable:
YES /—/ NO
Pursuant to Section 305(a) of the National Aeronautics and
Space Act, the name of the Administrator of NASA appears on
the first page of the patent; however, the name of -the actual
inventor (author) appears at the heading of column No. 1 of
the Specification, following the words "...with respect to
an invention of
C
'^Bonnie L. Woerner
Enclosure
https://ntrs.nasa.gov/search.jsp?R=19750019292 2020-03-19T21:05:46+00:00Z
United States Patent
Evans, Jr. et al.
[in 3,894,289
[45] July 8, 1975
[54] HIGH POWER LASER APPARATUS AND
SYSTEM
[75] Inventors: John C. Evans, Jr.; Henry W.
Brandhorst, Jr., both of Berea, Ohio
[73] Assignee: The United States of America as
represented by the United States
National Aeronautics and Space
Administration, Office of General
Counsel-Code GP, Washington,
D.C.
[22] Filed: July 29, 1968
[21] Appl. No.: 848,403
Related U.S. Application Data
[62] Division of Ser. No. 487,929, Sept. 16, 1965,
abandoned.
[52] U.S. Cl 330/4.3; 331/94.5 A; 240/41 B
[51] Int. Cl HOls 3/09
[58] Field of Search 331/94.5; 250/238;
240/41.35 R; 60/26; 126/270; 244/1 SS;
330/4.3
[56] References Cited
UNITED STATES PATENTS
1,928,002 9/1933 Berg 240/41.35
2,402,662 6/1946
3,174,705 3/1965
3,434,678 3/1969
3,569,881 3/1971
Ohl 250/238 X
Schiff et al 244/1
Brown et al 244/1
Tucker 331/94.5
FOREIGN PATENTS OR APPLICATIONS
966,455 8/1964 United Kingdom 331/94.5
OTHER PUBLICATIONS
Hogg et al., Masers & Lasers, TK 7872 M 45, 1962,
pp. 171-173.
Primary Examiner—Maynard R. Wilbur
Assistant Examiner—N. Moskowitz
Attorney, Agent, or Firm—N. T. Musial; Gene E.
Shook; John R. Manning
[57] ABSTRACT
Increasing the power output of a laser beam by in-
creasing the flashing rate of a source of coherent light.
Power is transmitted by using a laser as a transmitter
of coherent light.
1 Claim, 3 Drawing Figures
177
PATENTED JtlL 81975
SHEET
3.894,289
27
FIG. I
INVENTORS
JOHN C. EVANS, J*«
HENRY W. BRANDHORST JR.
BY
ATTORNEYS
PATErltEOJUl 81975
SHEET
3.894,289
177
nnn
FIG. 3 INVENTORSJOHN C. EVANS JR.
HENRY W. BRANDHORST JR.
BY q
-m.
ATTORNEYS
3,894,289
1 2
HIGH POWER LASER APPARATUS AND SYSTEM It is yet still another object of the instant invention to
The invention described herein may be manufac- provide for a laser apparatus wherein the size of the ca-
tured and used by or for the Government of the United pacitor banks or the power supply are relatively small.
States of America for governmental purposes without It is another object of the instant invention to provide
the payment of any royalties thereon or therefor. 5 for a new power transmission system utilizing a laser
STATEMENT OF COPENDENCV TO-t^ ^W^^U*. ,o
This is a division of application Ser. No. 487,929, provide for a new and improved arrangement for pro-
filed Sept. 16, 1965 now abandoned. ducing incoherent light for use in pumping a laser ma-
The instant invention relates to lasers. More particu- 10 terial.
larly, the instant invention relates to apparatus for use It is another object of the instant invention to provide
in producing a source of incoherent light capable of ini- a source of high intensity light having a high pulsing
tiating laser action in a laser material and a system uti- rate.
lizing the coherent light emitting from the laser mate- The aforesaid objects of the instant invention and
rial. 15 other objects which will become apparent as the de-
The word laser is an acronym for the phrase "light scription proceeds are achieved by increasing the flash-
amplification by stimulated emission of radiation." ing rate of the source of incoherent light, or in other
The instant invention is intended for particular use words, firing the laser more times per unit time interval,
with lasers utilizing a solid laser material such as ruby Increasing the flashing rate or firing rate of the source
to produce a narrow beam of coherent light. 20
 of incoherent light results in a series of low amplitude
The operation of the laser is based on the fact that output pulses. The time integration of the energy con-
the atomic systems represented by the molecules of the tent of these pulses yields a higher average power than
laser material can exist in any series of discreet energy a single giant pulse which in turn results in an increased
levels or states. These systems absorb energy when laser output. This method of firing the laser more times
going to a higher state and emit energy when going to 25 per unit, that is, repetitive pulsing, is achieved in the
a lower state. The atomic systems are raised from the following manner. In one embodiment a plurality of six
lower or ground level to the higher of the three levels xenon flash tubes which are circumferentially disposed
by irradiation from a strong light source which need not around a laser rod are fired repetitively in succession
be coherent but should preferably have a high concen- by the use of a high speed motor connected to an au-
tration of energy in the shorter wave length. The opera- 30 tomobile-type distributor which triggers a suitable fir-
tion of raising the energy level of the laser to produce ing circuit. The flash tubes are powered through a bank
the desired photon emission is referred to in the art as of fast charging capacitors. The apparatus is arranged
optical pumping. so that while one of the capacitors is discharging into
Optical pumping may be achieved by, for example, one of the flash tubes and causing it to fire the other
discharging a conventional capacitor into a xenon- 35 five are being charged. Another embodiment involves
filled flash lamp. The light output of the lamp is then an exploding wire mounted on a reel which is moved by
sufficient to promote laser action. At the present time a high speed driving motor.
the light output of flash lamps is rated generally be- The wire is mounted so as to pass through one of two
tween 100-100,000 joules depending upon construe- electrodes and is movable toward the other electrode,
tion and design details. Conversion of this light into 40 When the wire comes into contact with the other elec-
laser output is around 4 percent efficient and hence, trode a circuit is closed, producing thereby a high in-
laser beams up to 4000 joules can be obtained. Simulta- tensity flash of light,
neous flashing of several lamps is also in use. Repetitive pulsing or increasing the output pulses per
Certain desired uses for lasers such as point to point unit time results in a high power density beam for an
power transmission, welding, rock drilling, and materi- extended period of time. For example, a repetition rate
als cutting would appear to require high energy density of 20 pulses per second for a 50 joule pulse will issue
in the laser beam. a kilowatt of laser power; however, a flashing rate of
It has been proposed to increase the power output of 1000 per second will result in a power output of 50
a laser beam by increasing the power density of a single kilowatts.
pulse laser. However, it would appear to be difficult to Other objects and many of the attendant advantages
handle the giant pulse thus produced, and hence, such of this invention will be readily appreciated as the same
an arrangement would have very limited application. becomes better understood by reference to the follow-
It is therefore an object of the instant invention to ing description when considered in connection with the
produce a laser output having a high average power accompanying drawings and wherein like reference nu-
density. merals designate like parts throughout the figures
It is another object of the instant invention to pro- thereof and wherein
duce a laser having an essentially continuous wave out- FIG. 1 -is a combination pictorial and schematic view
put. of one embodiment of a laser-type energy transmitter;
It is another object of the instant invention to provide
 6Q FIG. 2 is a pictorial representation of a power trans-
fer a laser output that is easily controllable. It is yet still mission system using the energy transmitter of FIG. 1
another object of the instant invention to provide for a and;
laser apparatus wherein the energy storage require- FIG. 3 is a view in elevation of another embodiment
ments are modest. of a laser-type energy transmitter.
It is another object of the instant invention to provide
 &g Referring now to FIGS. 1 and 2 there is shown in
for a laser apparatus wherein the capacitors that form FIG. 2 a cylindrically formed crystal or rod 11 of laser
part of the power supply for the light source are capa- material such as ruby. The crystal or rod 11 of laser ma-
ble of operation at higher frequencies. terial is activated by means of a rapid pulsing light
3,894,289
3 4
source. In the embodiment shown, the light source in- tion coil triggering circuit is connected through the au-
cludes a plurality of six xenon discharge lamps 21 tomobile-type distributor switch 71 to trigger coij,.84
through 26, circumferentially surrounding the laser rod which 'is connected to xenon discharge lamp 24. The
11 and mounted on a common lamp bank 27. In the gas in the lamp 24 is ionized providing an electrical
embodiment shown, the six xenon discharge lamps 21 5 path and causing the capacitor 34 connected across
through 26 are each rated at 3000 watt seconds. The said lamp 24 to discharge and the lamp 24 to thereby
xenon discharge lamps 21 through 26 are arranged by flash brightly. During this flashing time all the other ca-
a mechanical switching means so as to repetitively fire pacitors, i.e. 31, 32, 33, 35 and 36 are charging and as
in succession. the distributor shaft 91 rotates, another trigger coil is
The xenon discharge lamps 21 through 26 are ener- 10 energized and another lamp is fired.
gized by means of a capacitive-type discharge circuit [n FIG. 2 is shown in simplified form an entire system f<
and are triggered by means of an induction coil circuit. for transmitting power utilizing the laser apparatus of I
The capacitor-type energizing circuit and the induction FIG. 1. It should be noted however, that the laser appa- ,
coil triggering circuit are mechanically coupled to the
 ratus of FIG. 3 could also be employed. Although not
xenon discharge lamps 21 through 26 so as to provide 15
 shown in FIG 2 the distributors and attendant power
for repetitive firing in succession. supplies are physically located in the center of the ca-
The capacitor energizing circuit includes six capaci-
 pacitor bank. The capacitor is enclosed within a cool-
tors 31 through 36 connected to a common bank 37.
 an, tank 3g circumferentially disposed around the
Each one of the capacitors 31 through 36 is electrically ,aser rod , j are the six nash tubes 2, tnrough 26. The
connected to one of the xenon discharge lamps 21 20
 entjre ,aser assembly js a,SQ enclosed within a cooling
through 26; i.e. capacitor 31 is electrically connected
 chamber 28. Recirculating pump 39 connects the cool-
to xenon discharge lamp 21, etc. The capacitors 31
 ant tank 38 to the laser chamber 28. The coherent light
through 36 are preferably 15 mfd at 20 kv with a self
 emjtted from the ,aser transmitter is collected at a dis-
inductance of 0.06 microhenries. The energy content
 {ant point by an e collector in the form of a para-
of each capacitor 31 through 36 is approximately 3000 25 ^ ^^
 1?J ^.^ ^ .^ ^ ^ & ^ ^.^ Qf hjgh
J°ules- . . ,„ . c current solar cells 172. These solar cells 172 areThe capacitor bank 37 is powered by means of a
 moumed at ^ foca, ,an£ Qf and ted from the
power supply circuit including a high voltage power
 reflector b means of
H
tubes 173 ^^ which a,so
transformer 41 connected to a full bridge rectifier 42
 sefve ^ coo,ant channe,s These channe,s ,?3 and 1?4
which in turn is connected to a charging reactor 43. J1J . , . . ,_, _,
_.
 r „, ., .„ ., . , • carry a coolant from a pump and tank 175. The coolantThe full bridge rectifier 42 converts the alternating cur- . J ..... . , ,,,, ., ,
,. " ,., , . .,7. .. is transmitted to channel 173 through a mirror support
rent to direct current and the charging reactor 43 limits , _, .. , . . . . , . . . , . */
. . . t i n c . u '•'6 which i s also a channel a n d i s carried back fromthe charging current to a safe value. Power from the ., . , . ,_. , , . ,__
. •
 A-i • . • , , •. this channel 174 through mirror support 177.charging reactor 43 is transmitted to the capacitor - . " rK , , .
, . „.. . ... -. v. c« rv A 35 In FIG. 3 is shown another embodiment of the instantbank 37 through a commutator-type switch 51. Diodes •" . . . . , .
.... , ._ . . e n • u i . . u invention wherein repetitive flashing is obtained by44 through 49 prevent current from flowing back to the „ ... . , r , ,.
power supply. The switch includes a rotating member mea"s °/ an "pjodmg wire. In this embodiment a
52 having a cutaway portion 53 and adapted thereby to '^th °f Wlre »" ™ou"*d ,°" a w're reel 121 1S fed
contact and transmit current to all but one of the ca- through a Palr °f [ol er^ J ", 123 and moved in a direc-
pacitors. Rotating member 52 is mounted on an electri- 40 tlon of a fin"8 block 124 whlch ls sPaced aPart from
cally conductive shaft 54. the rollers 122' 123" When the wlre "' comes into
The induction coil triggering circuit includes a step contact wlth the finn8 block 124 a Clrcult consisting of
down transformer 61, an interrupter 62, a capacitor 63, a bank of raP'd cycling high v°ltage capacitors 131
an induction coil 64 and a plug 60 adapted to be con- connected to the firing block 124 and the rollers 122,
nected to a source of voltage. Power from the induction 45 '23 ls completed and the bank of high voltage capaci-
coil triggering circuit is selectively transmitted through tors 131 are discharged causing the wire 111 to ex-
an electrical conductor 65 from a switch 71 to a plural- Plode- whlle the free end of the wire nl IS moving to-
ity of six trigger coils 81 through 86 which are con- ward the flring block 124'the bank of high voltage ca-
nceled respectively to the six discharge lamps 21 pacitors 131 is being charged through a high frequency
through 26. power supply 141. The feed system includes a drive
The switch 71 which may be in the form of an auto- motor lsl mechanically connected to the rollers. A
mobile distributortype switch which is electrically con- blocking diode 142 is connected between the high fre-
ductive and the power supply (or commutator) switch quency power supply 141 and the bank of high voltage
51 are mechanically coupled by means of a drive shaft capacitors 131. The wire 111 and laser rod 161 are en-
91 which is turned by means of a variable speed motor closed in a vacuum chamber 162.
92 which may be regulated by a variable speed control Obviously, many modifications and variations of the \
means 95 such as silicon controlled rectifiers or thyra- present invention are possible in light of the above ";
irons. Couplings 93 and 94 electrically separate the teachings. It is therefore to be understood that, within /
commutator switch 51 .and the distributor switch 71. the scope of the appended claims, the invention may be
Switch 71 includes a disc 72 mounted on an electrically practiced other than as specifically described,
conductive shaft 73. We claim:
By means of this coupling arrangement at any one in- 1. A high power transmission system comprising
terval of time, one of the xenon discharge lamps 21 a laser for transmitting a beam of coherent light, said
through 26 will be firing.
 65 laser including
For example, with the switches in the position shown a rod of a laser material,
in the embodiment in FIG. 1 capacitors 31, 32, 33, 35, a plurality of gaseous discharge lamps for pumping
and 36 are being charged. At the same time the indue- said rod,
3,894,289
a capacitor electrically connected to each of said
• dfscharge lamps,
triggering circuit means for providing a high volt-
age,
first switching means for selectively connecting the
triggering means to one of said discharge lamps,
power supply means, and
second switching means for electrically connecting
the power supply means to all but one of said ca-
pacitors, said first switching means being me-
chanically coupled to said second switching
means whereby said capacitor not connected to
10
said power supply means is electrically con-
nected to said discharge lamp which is electri-
cally connected to said triggering circuit means,
a parabolic reflector spaced apart from said laser for
collecting the beam of coherent light emitted from
the transmitter,
a photovoltaic device for converting said beam of
collected coherent light into electrical energy, and
means for cooling the laser, parabolic reflector, and
the photovoltaic device.
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High power laser apparatus and system

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