Claims
- 1. A method for producing a plurality of below 200 nm transmitting optical element preform optical fluoride crystals for formation into optical elements with below 200 nm transmission, comprising:
loading a fluoride raw material into a vertical stack having at least 6 crystal growth chambers; heating the vertical stack to a temperature sufficient to maintain the fluoride raw material in a molten condition; applying a crystal growth thermal gradient to the vertical stack to grow crystals from the molten fluoride raw material inside said crystal growth chambers; and cooling the plurality of grown crystals to provide below 200 nm transmitting optical element preform fluoride crystals.
- 2. The method of claim 1, wherein heating the vertical stack comprises positioning the vertical stack in a first zone of a furnace and heating the first zone of the furnace to the temperature sufficient to maintain the fluoride raw material in the molten condition.
- 3. The method of claim 2, wherein applying the crystal growth thermal gradient to the vertical stack to form crystals comprises translating the vertical stack from the first zone of the furnace to a second zone of the furnace that is maintained at a temperature lower than the temperature of the first zone of the furnace.
- 4. The method of claim 1, wherein translating the vertical stack comprises translating the vertical stack at a speed of 0.5 mm/hr to 5 mm/hr.
- 5. The method of claim 1, wherein cooling the crystals comprises slowly cooling the crystals to ambient temperature for 2 to 30 days.
- 6. The method of claim 1, wherein a diameter of the crystals ranges from 10 to 300 mm.
- 7. The method of claim 1, wherein a thickness of the crystals ranges from 40 to 400 mm.
- 8. The method of claim 1, wherein a refractive index of at least one of the crystals varies by less than 4 ppm across a flat surface of the crystal when measured using a 632-nm laser.
- 9. The method of claim 1, wherein an average birefringence of at least one of the crystals is less than 4 nm/cm when measuring using a 632-nm laser.
- 10. The method of claim 1, wherein an initial internal transmission of at least one of the crystals is greater than 99% at wavelengths greater than 155 nm and greater than 75% at wavelengths between 135 nm and 155 nm.
- 11. The method of claim 1, wherein applying the thermal gradient to the vertical stack to form crystals comprises decreasing the temperature of the vertical stack in a manner that allows a desired thermal gradient to be sustained within the crystal growth chambers.
- 12. The method of claim 1, wherein the crystal growth chambers in the vertical stack range from 6 to 10.
- 13. The method of claim 1, wherein the crystal growth chambers in the vertical stack range from 6 to 20.
- 14. A method for producing optical fluoride crystals, comprising:
loading a fluoride raw material into multiple vertical stacks of crystal growth chambers, wherein at least one vertical stack has at least 6 crystal growth chambers; heating the vertical stacks to a temperature sufficient to maintain the fluoride raw material in a molten condition; applying a thermal gradient to the vertical stacks to form crystals within the molten fluoride raw material; and cooling the crystals.
- 15. The method of claim 14, wherein heating the vertical stacks comprises positioning the vertical stacks in a first zone of a furnace and heating the first zone of the furnace to the temperature sufficient to maintain the fluoride raw material in the molten condition.
- 16. The method of claim 15, wherein applying the thermal gradient to the vertical stacks to form crystals comprises translating the vertical stacks from the first zone of the furnace to a second zone of the furnace that is maintained at a temperature lower than the temperature of the first zone of the furnace.
- 17. The method of claim 14, wherein translating the vertical stacks comprises translating the vertical stacks at a speed of 0.5 mm/hr to 5 mm/hr.
- 18. The method of claim 14, wherein cooling the crystals comprises slowly cooling the crystals to ambient temperature for 2 to 30 days.
- 19. The method of claim 14, wherein applying the thermal gradient to the vertical stacks to form crystals comprises decreasing the temperature of the vertical stacks in a manner that allows a desired thermal gradient to be sustained within the crystal growth chambers.
- 20. The method of claim 14, wherein the crystal growth chambers in the vertical stacks range from 6 to 10.
- 21. The method of claim 14, wherein the crystal growth chambers in the vertical stacks range from 6 to 20.
- 22. A device for growing optical fluoride crystals, comprising:
a furnace having a capacity to hold a vertical stack having at least 6 crystal growth chambers; and at least one heating element to maintain an appropriate treatment temperature inside the furnace.
- 23. The device of claim 22, wherein the crystal growth chambers in the vertical stack range from 6 to 20.
- 24. The device of claim 22, wherein the furnace comprises a first zone and a second zone.
- 25. The device of claim 24, further comprising a mechanism for translating the stack of crystal growth chambers from the first zone to the second zone.
- 26. The device of claim 24, further comprising a heating element positioned at a top end of the first zone.
- 27. The device of claim 24, further comprising a heating element positioned at a bottom end of the first zone.
- 28. The device of claim 24, wherein the at least one heating element is disposed in the first zone.
- 29. The device of claim 28, further comprising a heating element disposed in the second zone.
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority from U.S. Provisional Application No. 60/240,304, entitled “Device/Method for Producing Optical Fluoride CaF2 Crystals,” filed Oct. 13, 2000.
Provisional Applications (1)
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Number |
Date |
Country |
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60240304 |
Oct 2000 |
US |