1. An Introduction to Omega and Omega EP Frequency 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

15. 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