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This invention relates to lasers and particularly relates to a laser having
addressed compensated optical paths wherein a series of temporally spaced
pulses can arrive simultaneously at a target to generate high energy.
SUMMARY OF THE PRIOR ART
High energy lasers have heretofore relied upon discrete time-compensated
optical paths for energy storage of lased light in transit. However, such
lasers have required discrete multiangular optical paths through a laser
amplifier. These discrete, multiangular paths have included separate
inputs as well as separate outputs with the only path intersection
occurring within the laser amplifier. The sheer geometry of mirrors and
paths having differing angularities intersecting through a single laser
amplifier has caused amplifiers with relatively low energy compression
ratios.
In attempts to compress light paths of differing angularities passing
through these same laser amplifiers, schemes of light frequency
transducing have been necessary to provide the desired compression.
However, such light transducing loses efficiency; relatively large amounts
of energy in for corresponding energy out are required.
Krypton fluoride, the preferred lasing media herein, has heretofore been
proposed as media for compressed pulse lasing. However, its efficiencies
never have been fully realized because of the difficulties enumerated
above.
SUMMARY OF THE INVENTIONS
A long pulse laser amplifier is sequentially lased over a 0.5 microsecond
period by an additive group of temporally spaced discrete lasing colors
(frequencies) each of slightly different color (approximately 1/10 of an
Angstrom separation with less than a 1/1000 angstrom band width). An
oscillator array generates the actuating pulses which are channelled to
common optical path, amplified by a factor of 10.sup.4 and split up and
shaped before injection into approximately 10 final amplifiers. Each final
amplifier is preceded by a chromatic deflector, preferably a diffraction
grating, so that each short pulse (in the order of about 10.sup.-8
seconds) is sent through the amplifier at slightly different directions.
These differently directed pulses are amplified and individually address a
mirror array placed at some distance away. Due to the narrow band width of
each pulse, each address point is unique; there is no overlapping. As a
result, the distance from each point on the mirror array may be to
optically compensated for the difference in propagation time for each
short pulse. By the expedient of sending the earlier pulses through longer
paths and the later pulses through shorter paths, a mirror array can
reflect to a spot of extreme small dimension with simultaneity of all
pulses in time of arrival. By sequentially timing the pulses through each
amplifier, large amounts of energy can be delivered to a spot of small
dimension with a much shorter pulse length than that of the laser
amplifier. Optionally, by phasing locking the discrete amplifier outputs
together, large apparent apertures can be generated for either small
target size or long path lengths. Phase locking can occur within given
colors or all colors.
OTHER OBJECTS AND ADVANTAGES
An object of this invention is to adapt a rare gas halide laser to a high
energy lasing mode. Rare gas halide lasers--especially krypton
fluoride--can have inverted populations generated by electron bombardment
techniques. During any time period greater than 10.sup.-9 seconds, the
krypton fluoride will invert its population and become capable of lasing.
By providing a series of pulses, all at greater intervals than 10.sup.-9
seconds, discrete color bands (in the order of 10.sup.-3 angstroms) will
liberate energy contained within the gain profile of the inverted krypton
fluoride population and lase in the 2484 angstrom range. I find that
krypton fluoride is preferred as a lasing material becuase its transition
line is homogeneous. Moreover, by maintaining a relatively narrow band
width over the discrete color bands, it is possible to constructively
interfere light at a target so that extreme high energy can be focused to
a small unit area.
An object of this invention is to disclose a laser excited by temporally
spaced, discrete color bands distributed over a narrow frequency
differential (in the order of 5 angstroms). This laser utilizes the
discrete colors by chromatic deflection (preferably a diffraction grating)
to address a mirror array having compensated optical paths to provide for
simultaneity of pulse arrival.
A surprising result is that by chromatically assigning angularity at the
final laser amplifier, optical train geometric problems through the final
lasing media are virtually eliminated. Moreover, each optical path can
have its optical elements--especially mirrors--designed well within
allowable energy fluence levels.
A further advantage of the disclosed invention is that energy compression
on an array of such amplifiers can be generated up to a factor of 100. The
system is capable of generating essentially large powers at extreme
distances (in the order of a kilometer) to small spot sizes.
A further advantage is that the narrow band width separation between the
most widely separated colors is such that constructive interference of
light at a target is possible. High power outputs with low effective
aperture targets are possible.
A further advantage is that an array of the laser amplifiers has a high
conversion efficiency with power loss only in the range of 5-10%. By way
of example, a 10.sup.6 joule power output with 3 pulses per second with
each pulse length being in the range of 10.sup.-8 seconds with a power
range of 2.times.10.sup.14 watts is possible.
A further object of this invention is to disclose an oscillator array for a
high energy laser. According to this aspect of the invention, a singular
array of lasers having 0.8 angstrom band separations and timed outputs in
the order of 80 nano seconds are addressed at chosen angular intervals to
a chromatic deflection media (preferably a diffraction grating). Each of
these elements (preferably eight) is angularly addressed with respect to
the chromatic deflection media to provide a commonality of optical path
output. By providing a group of such arrays channeling this pulse to a
common path with pulse outputs timed to the order of ten nanosecond
intervals, a laser amplifier exciting pulse may be generated. Amplifying
with suitably placed laser amplifiers and shaping with telescopes, an
oscillator with a common output optical path is provided having temporally
spaced discrete color pulses.
An advantage of the oscillator of this invention is that by using a common
optical path, path lengths can be maintained substantially identical in
the oscillator section to provide the necessary constructively interfering
output.
Additionally, a single optical path provides for ease of construction and
similar ease of maintenance.
A further object of this invention is to disclose a high energy laser
amplifier which can be particularly adapted to a high energy lasing
system. Specifically, an electron bombarded krypton fluoride lasing and
lasing media is maintained in an inverted state and sequentially lased by
discrete pulses of light having pulse lengths in the range of 10
nanosecond intervals. A series of chromatically separate, discrete
excitation light bands are impinged upon the lasing media; amplification
in rapid sequence occurs. By passing either the light in or the light out
through a chromatic deflection media (such as a prism or preferably
diffraction grating) lased light passes through the system with discrete
angular addresses from the amplifier.
An advantage of the amplifier is that the discrete angular addresses can
all pass to separate optically compensated paths for simultaneity of
arrival at a target. Energies can in effect be added and pulse compressed
by a factor of 100. Moving parts are not required.
An advantage of this laser amplifier is that one high energy pulse can be
lased from as many as 100 (and more typically 50) separate pulses. Each of
these separate pulses are well within the energy fluence levels of
conventional windows, deflection mediums and mirrors. High energy lasing
can occur without being destructive of the optical train.
Another advantage is that since the laser amplifier is operated
substantially continuously the gain is suppressed relative to a system
that stores energy. This leads to ability to build larger volumes of
lasing media with larger output.
Yet another object of this invention is to disclose a propagation array for
a high energy output laser. Accordingly, a laser emitting temporally
spaced discrete color bands addresses with differing angularities arrays
of mirrors spaced at differing distances. The first pulse of a series from
the laser is directed at a first angle along a long optical path to a
first mirror; the second and later pulses are directed at second and
different discrete angles along a shorter optical path to second and later
mirrors. By focusing all mirrors to a common target and compensating the
path length with each temporally spaced narrow and discrete color band,
simultaneity of arrival of a constructively interfering light wave front
at a target can occur.
An advantage of this propagation array is that designs can occur well
within the limits of allowable optical train diffraction limits. Damage to
the optical train can be avoided due to the low level of energy fluence
for each optical path. Specifically, energy levels in the order one joule
per centimeter squared or 10.sup.4 joules per meter squared can be used.
Having final mirror arrays in the order of 100 square meters enables peak
power delivery in the order of 10.sup.6 joules over a 10.sup.-8 second
time frame with focus in the order of 25 microns.
According to one aspect of this invention, a plurality of, say, ten laser
amplifiers addresses in sequence 48 mirror strips located along and within
a vacuous conduit in the order of one kilometer in length. The mirrors in
turn are focused to a common target and spatially varied from each
amplifier in the order of 1.5 meters. The spatial variation in a
retro-reflected optical paths such that simultaneity of pulse arrival at a
target occurs.
Yet another aspect of this invention is to disclose for each discrete
amplifier a corresponding and discrete mirror array. The light path from
each amplifier to each mirror array can be at least in part a series of
smaller vacuous conduits. Light reflected from the mirror arrays impinges
upon focusing optics (typical a convengent mirror array) and thence to a
target. By time compensating the optical paths, a Z-shaped lasing path is
configured with simultaneous wave front arrival at a target.
The array is conveniently configured for opposition to another and similar
lasing path. Pressures between constructively interfering and colliding
wave front in the vicinity of stellar magnitudes are possible. Fusion
pressures may possibly result.
Other objects, features and advantages of this invention will become more
apparent after referring to the following specification and attached
drawings in which:
FIG. 1 is a schematic diagram of the laser of this invention illustrating
sequentially an oscillator, a typical primary amplifier and the optically
compensated propagating path with simultaneous light pulse arrival at a
target;
FIG. 2 is a typical gain profile of the rare halide gas krypton fluoride;
FIG. 3A is a typical oscillator laser array illustrating one laser with
mirror, etalons and Pockels cells outputting to a diffraction grating to
produce a multicolor temporally spaced array of pulses along a common
output path;
FIG. 3B is a pulse diagram illustrating the relative pulse width and, pulse
spacing of sequential pulses from the oscillator of this invention;
FIG. 4A is a schematic illustrating additives beam splitters for combining
in a single output path a plurality--preferably 48--discrete color pulses
from eight (8) laser arrays similar to those shown in FIG. 3A;
FIG. 4B is a timing and band width diagram for the oscillator;
FIG. 4C is a graphic array similar to FIG. 3B illustrating the final output
of the oscillator array of this invention;
FIG. 4D is a perspective schematic of a timing system for sequencing the
Pockels cells to generate outputs according to the limitations of FIG. 4C;
FIG. 5 is a schematic of the output of the oscillator passing through beam
shaping telescopes and amplifiers illustrating with the particularity the
passing of one beam of a split beam output array to a final amplifier;
FIG. 6A is a perspective view of one of the large lasing amplifiers of this
invention;
FIG. 6B is a perspective and partially schematic view of a cold cathode
electron emitter for inverting the population of krypton fluoride;
FIG. 6C is a detail of the emitter membrane;
FIG. 6D is a schematic showing one of the pulse forming networks for
exciting the laser media; and
FIG. 6E illustrates one of the command trigger mechanisms for actuating the
pulse forming networks;
FIGS. 7A-7C are a series illustrating a series of amplifier arrays
impinging upon an optically compensating mirror system for direction to a
target;
FIGS. 8A-8C show an alternate optically compensated system of shorter
length with addressing of the target in opposition to a similar opposed
laser being partly shown.
Referring to FIG. 1, this invention is schematically illustrated. An
oscillator A generates temporally spaced discrete lasing colors
(frequencies). Each of these lasing colors is of a slightly different
color (approximately 1/10 of an angstrom separating between discrete
colors) and each color is essentially monochromatic having a discrete band
width of less than 1/1,000 of an angstrom. All this will be more fully
explained with reference to FIGS. 3A, 3B, 4A, 4B and 4C. Total frequency
separation from the first emitted color to the last emmitted color is less
than 5 angstroms.
The discrete pulses from the amplifier are timed or temporally spaced.
Specifically, they are timed so that a complete sequence of colors is
emitted within half of a microsecond. Each color is separated by a
temporal interval in the order of 10 nanoseconds.
This array of temporally spaced discrete lasing colors is generated by a
plurality of laser arrays, each array having six monochromatic lasers
finely tuned. Each laser array emits color bands separated by 0.8 angstrom
intervals at differing angularities to a chromatic deflecting element,
such as a diffraction grating. The angularity of beam address and the
chromatic deflecting element are all aligned so that a common optical path
occurs from the output of oscillator A, through a preamplification and
shaping section B at least to a primary amplifier C. Thus the primary
amplifier is subjected to a sequence of stable single monochromatic bands
of light at discrete timed intervals.
The preamplification and shaping section B is located along the common
optical path (see FIG. 5). This section includes further laser
amplification and terminates with beams splitter outputs along phase
compensated optical paths to an array of final amplifiers such as that
illustrated in FIGS. 6A, 6B, 6C, 6D and 6E.
In the amplifier section, overall energy efficiency of the device is
realized, energy input in the oscillator, preamplification and shaping
section being negligible. A krypton fluoride rare halide gas lasing media
(preferably used throughout the invention in all lasers) is sequentially
lased in discrete colors (i.e. frequencies) with tenth angstrom
separation, 1/1,000 angstrom band width, and timed intervals in the order
of 10 nanoseconds. The light through the amplifier, (preferably at the
amplifier input) is channeled through a chromatic deflection element D
such as a diffraction grating. This chromatic deflecting element imparts
to the discrete bands of lased light specific angular addresses which then
can be focused to a mirror array E.
Mirror array E includes two specific characteristics. First, each mirror of
the mirror array is at an angular address relative to the primary
amplifier C and the chromatic deflecting element D. These angular
addresses are such that discrete band widths in the order of 1/1,000
angstrom address corresponding discrete mirrors.
Secondly, the mirrors are spaced at differing optical path lengths between
a target T and mirror array E. The path lengths are chosen so that the
first pulse emitted by an amplifier C has a long path and the second and
later pulses have a short path. Path lengths are chosen so that target T
has simultaneity of pulse arrival as well as constructive phase
interference to generate a short (10.sup.-8 second pulse) intense power
(2.times.10.sup.12 watts) over an area in the order of 25 microns.
In reading the enclosed disclosure it will be understood that the optical
train disclosed herein is designed for little scatter of the optical flux.
Such scattering would destroy the spatio-temporal and discrete color array
herein created. All lasing media is preferred to be krypton fluoride, a
rare halide gas. This media is excited by electron bombardment. Methods of
excitation are only described with respect to the large laser amplifiers
illustrated in FIG. 6A through FIG. 6E, as ordinary excitation of this gas
is within ordinary skill in the art.
Mirror, window, and chromatic deflecting elements sizing is performed
primarily on the basis of allowable loading on the mirrors. Consequently
the disclosed design is limited to a flux of 1 joule per centimeter square
or 10.sup.4 joules per meter squared. This represents a very conservative
loading of presently known optical elements by energy fluence.
As will hereinafter be set forth, so that the optical element loadings
through the final amplifier chain may be at the level of several joules
per centimeter squared, the present design has as the target mirror array
a set of vertical mirror strips staggered over approximate 250 foot
intervals. This is a difference in the optical path of 50 feet if the
light is reflected near the incidence angle which corresponds to a 500
nanosecond electrical pulse. The area in the mirror arrays herein
presented is about 10 meters squared and is shaped in a 10 meter by 10
meter square, whether utilizing the single mirror array of FIGS. 7A-7C or
the discrete mirror array of FIGS. 8A, 8C.
All windows to the lasing elements are of high purity fused silica such as
MgF.sub.2, or CaF.sub.2. The thickness to shortest unsupported length
ratio is in the order of 0.03 to 0.1. Total window areas are in the order
of 50 to 500 meters squared for the whole system. Overall figuring is in
the order of 0.5 to 1 wavelength per window, if phase locking
considerations are to be ignored. The windows are reinforced to withstand
differential pressures of one atmosphere and are antireflection coated.
The illustrated mirrors in mirror arrays are either aluminized or
preferably dielectrically coated. There are two types of mirrors. Mirrors
up to the primary amplifier must withstand energy fluences of 1 to 10
joules per centimeter square for approximately half microsecond intervals
at 3 per second loadings. Mirrors including the primary amplifier C and to
target T are typically placed in a vacuum, inert gas or clean air
atmosphere and have 1 to 5 joules per centimeter squared at 10.sup.-8
second intervals. Three regions for the optical path exist. First and up
to the final amplifier, clean air or inert gas may be ued. Second, up to
the point of substantial vergence to the target, inert gas or vacuum may
be used. Thirdly, and thereafter, vacuum is required to the target.
Having set forth the general construction parameters of the optical train,
attention can now be devoted to FIG. 2.
FIG. 2 illustrates a gain profile of krypton fluoride when lased in the
region of 2484 angstroms. Specifically, a curve of intensity versus
frequency for unresonated krypton fluoride is illustrated. For the
purposes of my invention, the following characteristics of krypton
fluoride are important and can be used in choosing alternate lasing
mediums.
First, it will be noted that the gain profile is substantially homogeneous;
it is distributed in a Gaussian type curve around a resonant frequency of
2,484 angstroms.
Secondly, and in a laser amplifier, lasing anywhere within the five
angstrom range illustrated will liberate at the precise frequency of
lasing the energy contained within the relevant inverted population of the
krypton fluoride gas.
Thirdly, and assuming that a lasing media is excited by conventional
electron bombardment, populations previously lased will re-invert for
temporally spaced sequential lasings within a timed interval of
approximately 10.sup.-9 seconds. For the purposes of my invention, this
rapid characteristic re-inversion period of krypton fluoride enables
sequential lasing at intervals of 10.sup.-8 seconds. These sequential
lasings are necessary to utilize the optically compensated paths of this
invention for simultaneous pulse arrival.
Moreover, it will be noted that all of the lased signals hereinafter
utilized are each in the order of less than 10.sup.-3 angstroms band width
and chromatically separated on the order of a tenth of an angstrom. Since
it is characteristic of the krypton fluoride that it preserves relatively
precisely the temporal and chromatic separations used to produce
excitation, it is a uniquely suitable gas for the large capacity lasing
disclosed in this invention.
Finally, it will be understood that constructive interference of
simultaneously arriving wave lengths at the target is possible. This may
be desirable both for producing a small aperture size as well as providing
a high power level. By utilizing krypton fluoride over a range of less
than 5 angstroms, in-phase constructive interference of light can be
generated at a target T in the disclosed laser. The system will work
without phase locking--but performance can be improved by using phase
locking.
Referring to FIGS. 3A and 4A simultaneously, a laser array 20 is
illustrated. Referring specifically to FIG. 3A, a conventionally excited
krypton fluoride laser 10 is lased between paired mirror 11 and Pockels
cells 12. Within the lasing paths there are placed conventional laser
etalons 16 for restricting the lased frequency to band widths in the order
of less than 1/1,000 of an angstrom. As will hereinafter be illustrated
with respect to FIG. 4B, each laser 14 of each laser array 20 is precisely
tuned by the inserted etalons to lase in the at less than a 1,000 angstrom
band width at intervals in the order of 8/10 of an angstrom. Each laser 14
addresses a chromatic deflecting element D, here diffraction grating 17.
Diffraction grating 17 utilizes the chromatic characteristic of each laser
to address all outputs to common path out 19.
Pockels cells 12 are timed to sequentially trigger each laser over
10.sup.-8 second intervals; these intervals are precisely timed as
illustrated in FIG. 4B and will hereinafter be more carefully set forth.
Krypton fluoride lasers suitable for use in the oscillators 10 are
described in Applications of Rare Gas Halides and HF Laser Workshop of
Sep. 19, 1978 published by Wally Schafer and Associates at pages MA 1-39.
Etalons 16 suitable for use in the invention are known and referenced in
Applications of Rare Gas Halides and HF Laser Workshop of Sep. 19, 1978
published by Walley Schafer and Associates at pages MU 32-34.
Pockels cells 12 suitable for use with this invention are described in
Optical Laser in Electronics by Earl L. Steele published by John Wiley and
Sons, Inc. New York in 1968 at pages 51-72. See FIGS. 2-15 and substitute
a Pockel Cell in conjunction with the illustrated Glan-Thompson prisms.
Circuitry necessary for actuating the time intervals of the Pockels cells
as set forth in the oscillator diagram of FIG. 4B are set forth in FIG. 4D
and described hereafter.
The function of each laser in conjunction with the Pockels cells in known
in the prior art and can be easily described. Specifically, one
Glan-Thompson prism 12a is aligned to pass light of a first polarity and
the second and remaining Glan-Thompson prism 12a is aligned to pass eight
of a second and differing polarity. The Pockels cell 12 between the
respective prisms is an energized polarity transducer. In the energized
state, it transduces the light from the polarity of the first
Glan-Thompson prism 12a to the polarity of the second Glan-Thompson prism
12a. Passage of light at the etalon selected discrete lasing frequency
occurs.
Referring to FIG. 3A, it will be shown that only one laser 14 is
illustrated. Each oscillator array includes six such lasers all eminating
discrete colors (frequencies) at 8/10 of an angstrom separation. By
addressing discrete lasers with 8/10 of an angstrom separation, a
convenient and relatively wide angular spacing of each of the lasers
relative to diffraction grating 17 can be provided. Convenient diffraction
grating address is included to allow all of the tuned krypton fluoride
lasers to have a common output optical path 19. An optical and/or order
stop 18 in common output optical path 19 functions to assure monochromatic
output of each laser in combination with diffraction grating 17.
It will be understood that each of the exciting lasers may be equipped with
wave shaping lenses, additional chromatic stops and other common optics to
provide the common path herein illustrated.
Referring to FIG. 3B an intensity versus angstrom separation plot is
illustrated for a typical laser array such as the array shown in FIG. 3A.
As can be seen, discrete pulses of band widths less than 1/1,000 of an
angstrom are emitted at 8/10 of an angstrom interval. On a timing basis
and referring to FIG. 4B discrete and sequential triggering of each of the
lasers in its turn occurs in the order of 8.times.10.sup.-8 seconds.
Referring to FIG. 4A, a group of arrays 20A through 20H are illustrated. By
way of example, array 20A only illustrates one laser including the
diffraction grating 17. From each such grating 17 on array 20A and all
remaining arrays 20B through 20H, it will be understood that all arrays
have common output paths. Commonality of output is provided by beam
splitters generally denominated 22. As is well known to those skilled in
the art, the beam splitters pass light slightly less than 50% of that
originally fluent on the beam splitters 22. The output intensity of the
arrays through the beam spitters 22 is adjusted so that the input to the
preamplifier 24 from each discrete emitted pulse is of a substantially
equal amplitude.
Understanding the array, attention can now be devoted to FIG. 4B. In FIG.
4B, each of the arrays 20A through 20H is illustrated on the left-hand
side of the diagram. The laser oscillators are each separated around a
2484 angstrom band plus or minus 3 angstroms.
Turning the attention to the array 20A, it will be seen that pulses of less
than a 1/1000 of an angstrom are emitted each separated by 8/10 of an
angstrom of band spread. Typically, the pulses are emitted at timed
intervals in the order of 8.times.10.sup.-8 seconds.
It will be observed that the output of array 20A is staggered with respect
to the output of array 20B. Specifically, each pulse of array 20B is
staggered so that it is emitted at a time on the order of 10.sup.-8
seconds later than the corresponding pulse of array 20A. This same
staggering is provided for arrays 20C through 20H.
Noting that there are eight arrays each with six discrete color outputs, it
can be seen than a 0.5 microsecond output of the oscillator consists of
48 discrete colors, each separated by distance intervals in the order of
10.sup.-8 seconds. A total difference in color between the first emitted
color of array 20A in the last emitted color of array 20H is in the order
of 4.8 angstroms.
Those skilled in the art will respect that there are two limits to the
timing output of each of the lasers of the oscillator. A first will be the
switching action of the Pockels cell 12. The remaining limitation will be
the pulse length of the active medium of laser 10 (or the approximate time
an optical pulse exists for a high gain medium). The oscillator band width
should be such that the switch time of the Pockels cell dominates the band
width of the exit beam.
Moreover, and if phase locking is desired the path lengths from each laser
of the oscillator A through and to the target T will be kept almost
exactly the same. Where path length differs substantially, it becomes
increasingly harder to match the phase at the target T to produce the
desired constructive interference and apparent aperture effects necessary
for high energy impact over a small target area.
Referring to FIG. 4D, timing of the individual Pockels cells in their
firing to produce lasing according to the timing diagrams of FIG. 4B, 4C
can be schematically understood. Specifically, a YAG laser lases through a
sequence of switches 50A, 50B, 50C, etc. Each of these switches includes
paired electrodes 51 and 52 contained in a high pressure nitrogen envelope
(not shown).
Working of such switches is known. Specifically, YAG laser 50 is energized
and passes light. When YAG laser is energized, conducting between the top
portion 53 at an energized potential and bottom portion 54 at ground
occurs.
Typically, the optical path 56 between all of the switches 50a, 50b, 50c
can be folded. This folding is to make the path of light of laser 50
time-compensated so that switch 50a is closed in the desired firing
sequence of laser array 20a, switch 50b is fired in the sequence of array
20b, etc.
Each of the switches 50a, 50b, etc. includes six discrete outputs. The
function of only one of these outputs is illustrated.
As can be seen, single conductor 58 connects the energized portion 53 to a
coaxial cable 59. Single conductor 58 becomes the inner and energized
portion of the coaxial cable. The outer sheath of the coaxial cable 59 is
connected to ground through bottom portion 54.
Output 57 is a discrete and chosen length. Specifically, it is sized so
that the output pulse from switch 50A at each of the discrete outlets will
be on the order of 10 nanoseconds.
Cable 57 outputs to a peaking circuit or gap 60. Peaking circuit or gap 60
assigns to the generated 10 nanosecond pulse a square wave shape. This
abrupt square wave shape is utilized for abruptly turning on and off the
respective Pockels cells 12.
It will be seen that with respect to FIG. 4D, all outputs of 50a will fire
at the same time. Differential time of firing can be generated by having
cables of differing lengths from the respective peaking circuits or gaps
60. Specifically, by sizing the length of cables in nanoseconds from each
of the peaking circuits to the respective Pockels cells, differing timings
for differing outputs can be generated.
It will be realized that the optical switches here shown can thus easily
generate the timing more particularly set forth in the diagram of FIG. 4B.
In actual practice, it may be desirable to have each of the respective
switches 50a, 50b, etc. to have outputs to more than one array or less
than one array of lasers, so long as the overall timing of the discrete
colors remains in accordance with the diagram of FIG. 4B. Likewise it will
be appreciated that other methods of generating timed pulses may be used.
Referring to FIG. 5, a common output from the oscillator is passed to a
shaping telescope 30 and thence to a krypton fluoride laser amplifier 31.
Telescope 30 shapes the temporally spaced discrete color sequence from the
oscillator to the configuration of amplifier 31. Amplifier 31 is a
conventional krypton fluoride laser sized an | | |
