Development of Crystal Furnace to Produce Large Single Crystal Nd:YAG Slabs for High Power Industrial Laser Systems

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9413860 Chai Current U.S. sheet metal (especially auto) industries have the need of high power and high repetition rate lasers which are deliverable via optical fibers and linked to robotic arms for high speed and high precision drilling, cutting and welding processes. While both the power supply and optical delivery system are available now, the heart of the laser system, the lasing medium, is still missing. The lasing medium is a large single crystal Nd:YAG slab which produces the laser power under either coherent (laser diode) or incoherent (flash lamp) pumping. Current state-of-the-art growth process is limited to a maximum of 25x200x10mm3 slab due to intrinsic core defects in melt pulled single crystals. Lasers based on slab configuration can generate more power with simpler design and better efficiency. It fits well with current diode array pumping design. We propose construct a novel crystal growth system to grow such Nd:YAG slabs. The system is designed and will be constructed and operated by the students and research staffs. It will provide training experience of enormous scale. It is based on high temperature profile control operating at principle with three RF induction heated zones and precise temperature profile control operating at temperature in excess of 2000{SYMBOL 176 \f "Symbol"}C. The system is fully automatic using adaptive PID feed-back control with a computer to monitor the entire growth cycle from heating up to growth and to cool down in all zones simultaneously. The system in its proto-form already has the capability of producing up to 125x300x10mm3 single crystal slabs. The Nd:YAG crystals produced in this new system will not contain core nor angular growth striations which are common in conventional crystal boules. The crystals produced by this process is capable to deliver multi-kilo watt power with multi-kilo hertz repetition rate and joules energy per pulse in near defraction limited beam quality so that it is deliverable via optical fibers. Our pr ocess represents a giant step forward in the Nd:YAG crystal growth technology. The proposed system will be the only one in the U.S. At present, both Japan and China have pursued the same aim with good progress. The benefit of this technology is to produce the needed Nd:YAG crystal slabs which will create a totally new generation laser manufacturing systems for a variety of industrial applications. Our growth system, once perfects its operation, can be further scaled up to produce even larger size slabs for large aperture laser beam delivery systems. It will open a total new era for both research and manufacture. Another example of potential use of this high power Nd:YAG slab laser is to build a table top soft x-ray generating system for sub-micron lithography applications. This will provide a low cost system for small to medium companies (who can not afford synchrotron radiation facilities) to be able to manufacture their own chips at any locations of their choice to compete in the market. ***