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An Introduction to Omega and Omega EP Frequency Conversion Crystals

An Introduction to Omega and Omega EP Frequency Conversion Crystals. FCCs: A Little History. Why do we convert to UV? Retro reflections and Laser/Plasma interactions Why not convert EP short pulses? Damage threshold High efficiency conversion technology developed right here at LLE

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An Introduction to Omega and Omega EP Frequency Conversion Crystals

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  1. An Introduction to Omega and Omega EPFrequency Conversion Crystals

  2. FCCs: A Little History • Why do we convert to UV? • Retro reflections and Laser/Plasma interactions • Why not convert EP short pulses? • Damage threshold • High efficiency conversion technology developed right here at LLE • Steve Craxton • Wolf Seka

  3. What is a FCC? • KDP = Potassium Dihydrogen Phosphate • Dichroic Crystal • A Nonlinear Optical Material • Water Soluble!!! • Very Expensive!!!

  4. Omega FCCs • Located in the laser bay just before the shield wall • Isolated enclosure to control temperature and humidity • FCC doors close automatically in case of a power outage

  5. Omega FCC • Four Optical Components in FCC Gimbal • UV Absorber Window • Doubler • First Tripler • Second Tripler • Two Additional Optical Compontents • Input Polarizer • IR Absorbing Glass

  6. Omega FCC

  7. Omega FCCs • Doubler doubles the frequency of a portion of the incoming 1054nm beam • First Tripler combines the resulting green photons with residual IR photons to produce UV photons • Second Tripler provides for efficiently converting beams with SSD bandwidth on

  8. Omega FCC

  9. Omega FCCs • Optical Coatings: • First layer is a moisture barrier • Second layer is Sol-Gel • Coatings are optimized for three wavelengths depending on the surface

  10. Omega FCCs • Frequency Conversion Depends On: • Input Polarization Angle • Crystal Axis Orientation • Temperature (Maintained to within 0.1˚C) • Input Beam Intensity • Conversion Efficiency Up to 80%

  11. Omega EP FCCs • Located on the South side of the TAS structure between the PMA and the UV end mirror • Temperature is controlled more closely in the EP bay, eliminating the need for thermal enclosures

  12. Omega EP FCCs • Only two crystals are used (No SSD on EP) • Doubler converts approximately 67% of the IR light to its second harmonic • Tripler mixes this with residual IR light to form the third harmonic

  13. Omega EP FCCs

  14. Omega EP FCCs

  15. Omega EP FCCs • What else is different? • Different method used for producing third harmonic photons • Advantage: No input polarizer needed • Disadvantage: Tighter alignment requirement • No opposing beam ports • Eliminates the need for UV Absorption window

  16. Omega and Omega EP FCCs • Crystals are marked by the manufacturer and rough aligned during assembly by OMAN • Initial tuning is done offline on the FCC tuning testbed • Once installed on Omega/EP, a series of shots are taken to optimize tuning and harden coatings • Performance is monitored by HEDs • Online tuning shots are performed as necessary

  17. Omega Doubler Tuning Scan

  18. FCC Tuning Testbed

  19. KDP Crystal Growth for NIF

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