Abstract:
A laser spark distribution and ignition system that reduces the high power optical requirements for use in a laser ignition and distribution system allowing for the use of optical fibers for delivering the low peak energy pumping pulses to a laser amplifier or laser oscillator. An optical distributor distributes and delivers optical pumping energy from an optical pumping source to multiple combustion chambers incorporating laser oscillators or laser amplifiers for inducing a laser spark within a combustion chamber. The optical distributor preferably includes a single rotating mirror or lens which deflects the optical pumping energy from the axis of rotation and into a plurality of distinct optical fibers each connected to a respective laser media or amplifier coupled to an associated combustion chamber. The laser spark generators preferably produce a high peak power laser spark, from a single low power pulse. The laser spark distribution and ignition system has application in natural gas fueled reciprocating engines, turbine combustors, explosives and laser induced breakdown spectroscopy diagnostic sensors.

Description:
The United States Government has rights in this invention pursuant to the employer-employee relationship between the Government and the Inventors. 
     FIELD OF THE INVENTION 
     A laser spark system providing for the delivery and distribution of optical pumping energy having a low peak power to plural spaced locations to be amplified into a high energy spark. 
     BACKGROUND OF THE INVENTION 
     Current emission regulations relating to NO x  require reciprocating engines to operate at very lean fuel/air mixtures. The excess air keeps the combusting gases cooler and limits thermal NO x  development. At the same time, the lean mixture requires much more energy to be delivered to the spark plug for successful ignition. The higher energy flowing through the spark plug electrodes increases erosion to the point that the spark plugs last only hundreds of hours. The spark plugs also cost in excess of $100 each because of the rare earth metals used in the electrodes to extend their life. The resulting maintenance costs are thus very high, especially for natural gas fueled energy generation engines which must run continuously for thousands of hours. 
     The concept of delivering peak energy with fiber optics has received much attention in this regard. However, when energy sufficient to generate a plasma pulse is directed through an optical fiber, the fiber and spot size must be large to prevent fiber destruction. The large fiber size dictates the size of the exit aperture, with a large exit aperture making it difficult to focus the light to a sufficiently small diameter to generate a plasma spark. It is possible to deliver enough energy for a spark when focused on a condensed material, but not for the gas phase. What is desired is to transmit the light through a small diameter, single mode fiber. However, when the energy is focused to a small enough diameter to match the smaller fiber size, it usually generates a spark prior to entering the fiber, or impurities in the fiber cause the fiber to fracture with the high power, in either case rendering the optical fiber useless. 
     Therefore, there is a need for a low cost and efficient laser spark system, for use in various applications such as reciprocating engines, turbine combustors, explosives, destruction or overloading of electronic imaging devices, and laser induced breakdown spectroscopy diagnostic sensors. 
     SUMMARY OF THE INVENTION 
     A laser spark system for providing a spark having an optical pumping source, an optical distributor, and a plurality of distinct spark generators. The optical pumping source has a peak optical power less than 1,000 Watts. The optical distributor is optically coupled to the optical pumping source. Each spark generator from the plurality of distinct spark generators is optically coupled to the optical distributor and capable of creating a high energy spark in a sequence directed by the optical distributor. 
     In one embodiment, the laser spark generators are each a laser amplifier having a laser media and a seed laser. The laser media is energized by optical pumping energy from the optical pumping source. A seed pulse from the seed laser is amplified by the energized laser media to produce a high energy spark. 
     In another embodiment, the laser spark generators are laser oscillators comprising a high reflectivity mirror, a Q-switch, a laser media, an output coupler, and a lens. The optical pumping source is optically connected to the laser media. The laser media is made of a material that emits a lasing energy when exposed to energy from the optical pumping source. The high reflectivity mirror is reflective to the lasing energy, and positioned adjacent to and optically connected to the Q-switch or the laser media along a pumping axis. The Q-switch is adjacent to and optically connected to the laser media along the pumping axis. The laser media or the Q-switch is adjacent to and optically connected to the output coupler along the pumping axis. The output coupler is adjacent to and optically connected to the lens along the pumping axis. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The appended claims set forth the novel features which characterize the invention. However, the invention itself, as well as further objects and advantages thereof, will best be understood by reference to the following detailed description of a preferred embodiment taken in conjunction with the accompanying drawings, where like reference characters identify like elements throughout the various figures, in which: 
         FIG. 1  generally depicts one embodiment of the laser spark system; 
         FIG. 2  shows one embodiment of the laser spark system incorporating the preferred laser oscillator; 
         FIG. 3  shows one embodiment of the laser spark system incorporating a seed laser and a laser amplifier; 
         FIGS. 4 ,  5 ,  6  and  6   a ,  7  show five embodiments of an optical distributor for use in the laser spark system; and 
         FIG. 8  shows an embodiment of the laser spark system incorporating a side pumped laser oscillator. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The laser spark system  10 , shown in  FIG. 1 , has an optical pumping source  12 , an optical distributor  14 , and a plurality of distinct laser spark generators  16   a - 16   d . The optical pumping source  12  is optically connected to the optical distributor  14  by a first optical fiber  18 . The optical distributor  14  is also optically connected to a laser spark generator from the plurality of distinct laser spark generators  16   a - 16   d  by an optical fiber from a plurality of distinct laser spark generators  20   a - 20   d , whereby the optical pumping energy can be directed to a single laser spark generator. Therefore, the plurality of distinct laser spark generators  16   a - 16   d  are optically pumped from the optical pumping source  12  via the first optical fiber  18 , the optical distributor  14 , and an optical fiber from the plurality of distinct laser spark generators  20   a - 20   d . The optical fibers (first optical fiber  18  and plurality of distinct laser spark generators  20   a - 20   d ) confine the optical pumping energy and limits the potential hazard to workmen in the area. For simplicity only four spark generators  16   a - 16   d  are shown in  FIG. 1 , but any number of spark generators may be used. 
     The optical pumping source  12  produces optical pumping energy having low peak power (less than 1,000 peak Watts, typically about 500-1,000 Watts depending on the laser media). The optical pumping energy generally needs to be large enough to charge the laser spark generator. The optical pumping energy may be a single pulse, as in the preferred embodiment, a continuous stream, or a series of pulses. In the preferred embodiment, the optical pumping source  12  is a laser diode providing optical pumping energy in the form of a single pulse having a low power (less than 1,000 peak Watts). 
     The optical distributor  14  sequentially provides the optical pumping energy from the first optical fiber  18  to each of the optical fibers from the plurality of distinct optical fibers  20   a - 20   d  in a precisely timed sequence. Each of the optical fibers from the plurality of distinct optical fibers  20   a - 20   d  is coupled to a distinct laser spark generator from the plurality of distinct laser spark generators  16   a - 16   d . In the preferred embodiment, each of the laser spark generators  16   a - 16   d  is adjacent to and optically connected to a combustion chamber of an internal combustion engine. 
     Each laser spark generator from the plurality of distinct laser spark generators  16   a - 16   d  deliver lasing energy focused into a high energy spark in a combustion chamber of an internal combustion engine. In the preferred embodiment, the laser spark generators  16   a - 16   d  are each at a combustion chamber to simplify alignment issues when focusing the laser beam into a high energy spark. The amount of power required to create a high energy spark is dependent upon the air and pressure of the air surrounding the desired spark. Each laser spark generator is preferably a laser oscillator or a laser amplifier, more preferably a laser oscillator. The laser oscillator requires only optical pumping energy from the optical pumping source  12  to create a high energy spark. The laser amplifier requires optical pumping energy from the optical pumping source  12 , and seed energy (generated by a seed laser) to create a high energy spark. 
       FIG. 2  shows additional details of the laser spark system  26  in accordance with the preferred embodiment. In the laser spark system  26 , an optical pumping source  28  provides optical pumping energy via a combination of coupling optics  30  and a first optical fiber  32  to an optical distributor  34 . The optical distributor  34  is coupled via a second optical fiber  36  to a laser spark generator. The laser spark generator is more specifically a laser oscillator  38 . The optical pumping energy is coincident with the absorption line of a laser media  38   c  of the laser oscillator  38 . The laser oscillator  38 , creates a spark that is directed to an adjacent and optically connected combustion chamber  41 . Although only a single combination of the second optical fiber  36  and the laser oscillator  38  is shown in the figure for simplicity, any number of the combination of the second optical fiber  36  and the laser oscillator  38  may be used to create sparks in a single combustion chamber, multiple combustion chambers, multiple distinct combustion chambers, or combinations thereof. 
     The optical pumping source  28  with coupling optics  30  preferably delivers optical pumping energy to the optical distributor  34  as a point source of one millimeter or less and divergence of 45 degrees or less, typical of an optical fiber. The optical pumping source  28  is preferably in the form of an array of diode lasers in a linear or square matrix. The array is a set of laser point sources. A set of optical components in the form of coupling optics  30  collect the light from the array of diode lasers and collectively focus the light into the first optical fiber  32 . These diode lasers preferably collectively produce up to several thousand Watts of optical pumping energy. The energy is in a narrow wavelength range tuned to the absorption band of a laser media  38   c , e.g., 808 nm for the preferred Nd:YAG (neodymium-doped yttrium aluminium garnet) laser media  38   c . This energy, when optically switched, is easily transmitted through the first optical fiber  32 , the optical distributor  34 , and the second optical fiber  36  because it is less than 1,000 peak Watts and cannot form a high energy spark. Preferably, the peak power and the average power of the optical pumping energy is about 500-1,000 Watts depending upon the laser media  38   c . However, a pulse of this optical pumping energy of less than 1 milliseconds is sufficient to energize the laser media  38   c.    
     The optical pumping source  28  may consist of one or more laser diode bars with a row of emitting elements typically 100 microns long situated on 200 micron centers. The geometry of the individual emitting elements causes the light to be highly divergent in one direction. Therefore, coupling optics  30  may be required to focus the divergent beams into a beam capable of being handled and directed into the first optical fiber  32 . 
     The optical distributor  34  collects the optical pumping energy coming from the first optical fiber  32 , and relays it to the second optical fiber  36  in sequence to optically pump an individual laser oscillator  38  to ignite fuel/air mixtures in the combustion chamber  41  of an engine with microsecond accuracy. The optical distributor  34  has a timing precision of less than 10 microseconds and maintains the optical pumping energy focused on the second optical fiber  36  for a dwell time less than a millisecond. The optical distributor  34  may take the form of a rotating element which may be either a lens, a prism, or a mirror for deflecting light at a select angle from its axis of rotation. The rotation may be continuous or stepwise. When the optical distributor  34  rotates continuously, the angle of deflection will be small such that the radial velocity of the focused energy permits a less than 1 millisecond dwell time on the second optical fiber  36  delivering optical pumping energy to the laser oscillator  38 . When the rotation is stepwise, the optical distributor  34  may be either a mirror or a lens, but there is no restriction on the angle of deflection, since dwell time is determined by the stepping mechanism. A shallow angle deflection is desired since it requires much less precision in the controlling motor, making for a more economical apparatus. 
     One embodiment of an optical distributor  68 , shown in  FIG. 4 , comprises of a rotating mirror  72  reflecting the light at a shallow oblique angle (&lt;10 degrees) relative to the mirror&#39;s axis of rotation A-A′. The incident light is focused by means of a lens  70  onto the ends of a plurality of distinct optical fibers arranged in a circular array. For simplicity, only two optical fibers  74   a  and  74   b  in the plane of the drawing sheet are shown. In addition,  FIG. 4  shows, in simplified block diagram form, a rotary drive  76  coupled to the rotating mirror  72 . 
     Another embodiment of an optical distributor  80 , shown in  FIG. 5 , comprises of a mirror  84  oriented at a greater angle relative to the mirror&#39;s axis of rotation A-A′ to reflect the light at a steeply obtuse angle (&gt;170 and &lt;180 degrees), with the angles of incidence and reflectance &lt;10 degrees. A rotary drive is also coupled to the reflector  84  although not shown for simplicity. A lens  82  focuses the incident optical pumping energy on the ends of a plurality of distinct optical fibers arranged in a circular array, where only two optical fibers  86   a  and  86   b  are shown for simplicity. 
     Another embodiment of an optical distributor  90 , shown in  FIG. 6 , is in the form of a rotating lens  92  which has its optical axis offset from its axis of rotation such that the focal point traces a circle about a rotation axis A-A′, with a plurality of distinct optical fibers  94   a ,  94   b , etc. disposed in the circle. 
     The preferred embodiment of an optical distributor  150 , shown in  FIG. 6   a , is a rotating wedge prism  152  between two fixed lenses  154  and  156  where the prism  152  changes the direction of propagation of the light such that the focal point traces a circle about a rotation axis with a plurality of distinct optical fibers  158  and  160  disposed on the circle. The wedge prism  152  has a flat face and an angled face. The angled face of the wedge prism  152  is angled up to 45 degrees off-parallel from the flat face. The flat face and angled face may have an anti-reflection coating for pumping energy, as in the preferred embodiment. The rotating wedge prism  152  can be rotated in a continuous or stepwise fashion. In either mode of rotation, an indexing mechanism can be used to easily determine the location of the prism  152  at all times. The use of an indexing mechanism allow the prism  152  to be synchronized with the operation of a crank shaft of an internal combustion engine. The indexing mechanism is preferably a high resolution optical encoder. The radial spacing and radial dimension of the plurality of distinct optical fibers  158  and  160  will be adjusted with respect to the angle of the angled face and the number of combustion chambers. 
     Referring to  FIG. 2 , the optical fibers (first optical fiber  32  and second optical fibers  36 ) are of suitable optical quality to transmit the optical pumping energy with low loss. The core diameter is small enough to render a point source of light suitable for focusing optics. The optical fibers are also preferably flexible enough for the optical fibers to be rugged enough to survive in over 10,000 hours of engine operation. Optical fibers with a core diameter less than 1 millimeter is considered suitable, as the diameter is small enough to be flexible and large enough for the optical fibers to simplify the dwell issue in the optical distributor. 
     The laser oscillator  38 , a spark generator, comprises a high reflectivity mirror  38   a , a Q-switch  38   b , a laser media  38   c , an output coupler  38   d , and a lens  38   e . The high reflectivity mirror  38   a  is positioned adjacent to and optically connected to the Q-switch  38   b  along a pumping axis. The Q-switch  38   b  is adjacent to and optically connected to the laser media  38   c  along the pumping axis. The laser media  38   c  is adjacent to and optically connected to the output coupler  38   d  along the pumping axis. The output coupler  38   d  is adjacent to and optically connected to the lens  38   e  along the pumping axis. 
     The optical pumping energy emitted from the second optical fiber  36  passes through the high reflectivity mirror  38   a , passes through the Q-switch  38 , and excites the laser media  38   c . The stored excited states of the laser media  38   c  spontaneously decay producing lasing energy in random directions. The lasing energy emitted towards the output coupler  38   d  will be partially reflected back to the laser media  38   c . Preferably, the output coupler  38   d  will reflect less than 50% of the lasing energy towards the laser media  38   c . Lasing energy emitted from the laser media  38   c  towards the Q-switch  38   b  is partially absorbed by the Q-switch  38   b . Lasing energy that is not absorbed by the Q-switch  38   b  is reflected back towards the Q-switch  38   b  by the high reflectivity mirror  38   a.    
     The lasing energy will reflect back and forth between the high reflectivity mirror  38   a , and the output coupler  38   d . The lasing energy will traverse the laser media  38   c  and interact with excited Nd atoms within the laser media  38   c , inducing stimulated emission where the original photons from the lasing energy cause the decay of an excited state. The stimulated event produces light of the same wavelength (about 1064 nm for a Nd:YAG laser media  38   c ), phase, and in the same direction as the stimulating photon. At the same time the Q-switch  38   b  allows a certain percentage of the incident photons to pass through unimpeded. The balance of the certain percentage of photons are absorbed within the Q-switch  38   b  inducing excited states. When the material of the Q-switch  38   b  is in an excited state it is virtually transparent to the lasing energy. Therefore as more of the lasing energy is absorbed effectively make the Q-switch  38   b  more and more transparent for a short time. This allows more lasing energy to pass through and return producing more stimulated lasing energy within the laser media  38   c.    
     This process of bleaching the Q-switch  38   b  allows a large number of excited states to build up within the laser media  38   c  until the Q-switch  38   b  reaches a threshold transparency. The Q-switch  38   b  begins to bleach exponentially and the number of photons within the laser cavity also grows exponentially. At this point, the Q-switch  38   c  is virtually clear of losses and the large scale lasing depletes the excited states in the laser media  38   c  within a few round trips. The output lasing energy produced is high energy and has very short pulse width. This output lasing energy is directed through the lens  38   e  and into a combustion chamber  41 . The lens  38   e  focuses the lasing energy into a high energy spark of a sufficiently small spot size so as to create a spark, about the power density or photon flux density of about 1×10 11  W/cm 2 . This level of power density inside the combustion chamber  41  under compression is more than enough to initiate a laser spark and ignition of the fuel and ambient air mixture under over 1 Atm. Different pressures, and air will require a different power density. For instance, if air having an AQI (Air Quality Index) of 49 is used about 1×10 13  W/cm 2  of power density or photon flux density will be required. 
     The high reflectivity mirror  38   a  allows pumping energy emitted from the second optical fiber  36 , to pass through, while reflecting the lasing energy. Preferably, the high reflectivity mirror  38   a  is fused silica, or sapphire having a reflective coating that is reflective to the lasing energy, and an anti-reflective coating that is transparent to the pumping energy. More preferably, the high reflectivity mirror  38   a  is fused silica having a reflective coating that is reflective to the lasing energy, and an anti-reflective coating that is transparent to the pumping energy. 
     The Q-switch  38   b  is preferably Cr:YAG (chromium-doped yttrium aluminium garnet), having enough Cr such that the small signal transmission of the lasing energy is in the range of 30-70%. 
     The laser media  38   c  can be a plurality of materials as discussed in Koechner, W., Bass, M., “Solid-State Lasers: A Graduate Text” Springer, N.Y., 2003 hereby fully incorporated by reference. The laser media  38   c  is generally a host material that is doped. The host materials can be materials such as Glasses, Oxides, Garnets, Vanadates, Fluorides. The Glasses are typically doped with Nd, Er, or Yb. The Oxides such as sapphire is typically doped with Ti. The Garnets are Yttrium Aluminum Garnet Y 3 Al 5 O 12  (YAG), Gadolinium Gallium Garnet Gd 3 Ga 5 O 12  (GGG), and Gadolinium Scandium Aluminum Garnet Gd 3 Sc 2 Al 3 O 12  (GSGG) and are typically doped with rare earths such as Nd, Tm, Er, Ho, Yb. The Vanadates or Yttrium Orthovanadate (YVO 4 ) is typically doped with Nd. The Fluorides or Yttrium Fluoride (YLiF 4 ) and is typically doped with Nd. The laser media  38   c  is preferably Nd:YAG (neodymium-doped yttrium aluminium garnet), Nd:Glass (neodymium-doped glass), Nd:YLF(neodymium-doped yttrium lithium fluoride), Nd:YVO 4  (Yttrium Vanadate), Er:Glass (Erbium doped glass), Yb:YAG (ytterbium-doped yttrium aluminium garnet), Alexandrite, Ti:Sapphire (Titanium-sapphire). In the preferred embodiment the laser media  38   c  is Nd:YAG having about 0.5% atomic weight of Nd, which will emit lasing energy at about 1064 nm. The dopant level of the laser media  38   c  is intentionally low to improve the performance of the laser oscillator  38 . Lowering the dopant concentration effects the overall output by modifying the beam overlap, the absorption depth of the optical pumping energy, reducing thermal lensing losses, and reducing losses due to ASE (Amplified Spontaneous Emission). This leads to a much more uniform pumped gain profile as well as more uniformly distributed thermal stresses which lessens the effects of thermal lensing. The reduction of dopant concentration lowers the gain of the material slightly but offers larger energy storage capacity in return. 
     The output coupler  38   d  partially reflects the lasing energy, preferably less than 50% of the lasing energy is reflected. In the current, preferred embodiment, the output coupler  38   d  reflects about 20-50% of the lasing energy. 
     The lens  38   e  focuses the lasing energy into the high energy spark. In the preferred embodiment, the lens is a convex lens having a focal point of about one centimeter inside the combustion chamber  41 . 
     In the preferred embodiment, a window  39  is placed between the lens  38   e  and the combustion chamber  41 . The window seals the laser oscillator  38  and is scaled to resist the temperature and pressure from the combustion chamber  41 . Fused silica and sapphire are a suitable materials for the window, preferably fused silica due to its lower cost. 
     The optical pumping source  28 , coupling optics  30 , first optical fiber  32 , and second optical fiber  36  may have anti-reflection coatings to commensurate with the optical distributor  34 . The anti-reflection coatings reduce the optical losses through lasing energy) coating on the lens  38   e . The window  39  and the lens  38   e  may also be combined by making a suitable window material convex so as to focus the lasing energy into a high energy spark. Likewise, the lens  38   e , output coupler  38   d , and window  39  may all be combined into a partially reflective focusing window by making a suitable window material convex so as to focus the lasing energy into a high energy spark, and adding a partially reflective coating on the window. 
     In an alternative embodiment, the positions of the laser media  38   c  and the Q-switch  38   b  are switched. The high reflectivity mirror  38   a  is positioned adjacent to and optically connected to the laser media  38   c  along a pumping axis. The laser media  38   c  is adjacent to and optically connected to the Q-switch  38   b  along the pumping axis. The Q-switch  38   b  is adjacent to and optically connected to the output coupler  38   d  along the pumping axis. The output coupler  38   d  is adjacent to and optically connected to the lens  38   e  along the pumping axis. 
     The optical pumping source  28  may be positioned at the laser oscillator  38  to eliminate the first optical fiber  32 , the optical distributor  34 , and the second optical fiber  36 . However, placing the optical pumping source  28  at the laser oscillator  38  may not be desirable since the optical pumping source  28  is the most expensive component and replicating it through the optical distributor  34  to several laser oscillators is more cost effective. It is also easier to cool the optical pumping source  28  when it is not directly connected to the heat generating combustion chamber  41 . 
     One embodiment of a side pumped laser oscillator  126 , shown in  FIG. 8 , comprises a laser media  128 , one or more optical pumping sources  130 , an output coupler  132 , a Q-switch  134 , a high reflectivity mirror  136 , and a lens  138 . The high reflectivity mirror  136 , Q-switch  134 , laser media  128 , output coupler  132 , and lens  138  are the same as the respective component as described in the laser oscillator  38  shown in  FIG. 2 . The operation of the side pumped laser oscillator  126  is the same as with the laser oscillator  38  shown in  FIG. 2 , except the laser media  128  is pumped directly by the optical pumping sources  130 . The optical pumping sources  130  are each the same as the optical pumping source  28  shown in  FIG. 2 , preferably diode lasers that emit an optical pumping energy at about 808 nm producing less than 1,000 peak Watts of power combined. Preferably, the optical pumping sources  130  are positioned along the length of the laser media  128 . 
     In order to prevent multiple output pulses of the side pumped laser oscillator  126 , either the output coupler  132  or the high reflectivity mirror  136  must be convex, creating a focal region, preferably within the Q-switch  134 . In one embodiment, the output coupler  132  is convex and the high reflectivity mirror  136  is flat. In an alternative embodiment the output coupler  132  is flat and the high reflectivity mirror  136  is convex. 
     In another embodiment, shown in  FIG. 3 , the spark generator is a laser amplifier  58  comprising of a laser media  63 , a lens  58   a , a seed laser  60  and a third optical fiber  62 . In this embodiment, the second optical fiber  36  pumps the laser media  63  to an excited state without feedback mirrors. The third optical fiber  62  delivers a seed energy at the lasing energy wavelength to the laser media  63  to be amplified by the excited laser media  63 . The seed energy is preferably less than about 1 mega-joule having a duration of about 5-10 ns, or about 200 KW. The resultant lasing energy focused by the focusing lens  58   a  into a high energy spark. Preferably the high energy spark is focused through a pressure barrier window  59  into a combustion chamber  41  to form a spark approximately 1 centimeter inside the combustion chamber  41 . 
     The seed laser  60  provides a seed energy at the lasing energy wavelength via the third optical fiber  62  to the laser amplifier  58 . The seed laser  60  is preferably a high beam quality, Q-switched Nd:YAG (neodymium-doped yttrium aluminum garnet) laser. The third optical fiber  62  is a small diameter optical fiber capable of delivering the seed pulse to the laser media  63 . The optical pumping source  28 , first optical fiber  32 , optical distributor  34 , second optical fiber  36 , and combustion chamber  41  are the same as with the laser spark system  26  shown in  FIG. 2 . The laser media  63 , lens  58   a , and window  59 , are also the same as the respective laser media  38   c , lens  38   e , and window  39  as with the laser spark system  26  shown in  FIG. 2 . Anti-reflective coatings may be applied to the various components of the laser spark system for pumping energy, anti-reflective coatings may also be add for the seed energy. Anti-reflective coatings for pumping energy and seed energy will reduce optical losses and improve system efficiency. 
     Although not shown in  FIG. 3 , a lens may be placed at the output of the third optical fiber  62  to collimate the seed energy from the seed laser  60  and direct it to the laser media  63 . 
     Alternatively, the seed laser  60  may be directly attached to the laser amplifier  58  for direct distribution of seed energy, distributed through the optical distributor  34 , distributed through a separate seed energy optical distributor, or distributed co-linearly through the second optical fiber  36 . The seed energy can be delivered to each laser amplifier  58  for every single ignition event, whereby its energy is divided equally and is synchronized with the timing signals available from a crank shaft and/or cam shaft encoder of an internal combustion engine. 
     The seed energy may be distributed through the optical distributor  34 , whereby only a single seed laser  60  is required for any number of laser amplifiers. In this embodiment, the seed energy is distributed with the optical pumping energy when properly timed and aligned for differences in refraction due to wavelength differences between the optical pumping energy and seed energy. The seed energy may also be distributed through a separate seed energy optical distributor separate and distinct from the optical distributor  34 . 
     One embodiment of an optical distributor  100  distributing seed energy is shown in  FIG. 7 . A rotating mirror  102  has an angle of reflection of about 90°. A first optical fiber  104  directs optical pumping energy through collimating optics  114 , followed by a partial mirror  112  and onto the rotating mirror  102 . A third optical fiber  110  directs seed energy towards the partial mirror  112 , which reflects the seed energy towards the rotating mirror  112 . The rotating mirror  102  is coupled to and rotated by a drive motor  120  in a stepwise or continuous manner. The optical pumping energy and the seed energy is directed by the rotating mirror  102  to an optical fiber coupling lens from a plurality of distinct optical fiber coupling lenses  116  and into an optical fiber from a plurality of distinct second optical fibers  106 . For simplicity, only two fibers from the plurality of distinct second optical fibers  106  are shown in  FIG. 7 , however additional optical fibers arranged in a generally circular array are also disposed in the plane of the plurality of distinct second optical fibers  106  shown in  FIG. 7 . 
     Referring to  FIG. 3 , seed energy may also be inserted into the second optical fiber  36  collinearly with the optical pumping energy using a beam splitter or polarizing device upstream from the laser optics. This co-linear delivery arrangement allows for a stronger seed energy pulse for each ignition event. 
     The laser amplifier  58  can also be fitted with a single seed laser optical fiber equally divided from one seed laser to all combustion chambers. The pump fiber can then be arranged for side or end pumping or in a multitude of fibers in a circular fashion around the seed fiber. The seed fiber in this case may use a GRIN(graded-index) lens, but any other collimating lens may be used as well. The lens collimates the seed beam for the end seeding application. The distribution system described herein is a means to deliver the pump energy to a specified amplifier at a specified time. 
     The optical pumping source  28 , the seed laser  60 , or both the optical pumping source  28  and the seed laser  60  may be positioned at the laser amplifier  58  to eliminate the first optical fiber  32 , optical distributor  34 , second optical fiber  36 , third optical fiber  62 , or combinations thereof. However, placing the optical pumping source  28  at the laser amplifier  58  may not be desirable since the optical pumping source  28  is the most expensive component and replicating it through the optical distributor  34  to several laser amplifiers is more cost effective. It is also easier to cool the optical pumping source  28 , and the seed laser  60  when they are not directly connected to the heat generating combustion chamber  41 . 
     Although the preferred use of the laser spark system is for initiating combustion in a combustion chamber, other uses may be possible. For example any of the above embodiments can be used to ignite an explosive, by a single or successive laser sparks. Likewise, any of the above embodiments can be used for the destruction or overloading of electronic imaging devices, by a single or successive laser sparks. In the case of the destruction or overloading of a typical CCD camera, a spark capable of initiating combustion is used to create a high intensity light that, when exposed, will overload or destroy a CCD typically found in digital imaging equipment (e.g. digital cameras). 
     While particular embodiments of the laser spark system have been shown and described, it will be obvious to those skilled in the relevant arts that changes and modifications may be made without departing from the invention in its broader aspects. Therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention. The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation. The actual scope of the invention is intended to be defined in the following claims when viewed in their proper perspective. 
     It is to be understood that the above-described arrangements are only illustrative of the application of the principles of the present invention. Numerous modifications and alternative arrangements may be devised by those skilled in the art without departing from the spirit and scope of the present invention and the appended claims are intended to cover such modifications and arrangements. 
     All publications and patent documents cited in this application are incorporated by reference in their entirety for all purposes to the same extent as if each individual publication or patent document were so individually denoted.