work on coatings
play

Work on Coatings Wolfgang Riede, Paul Allenspacher Institute of - PowerPoint PPT Presentation

Work on Coatings Wolfgang Riede, Paul Allenspacher Institute of Technical Physics, DLR Stuttgart, Pfaffenwaldring 38 40, 70 569 Stuttgart, Germany E-Mail: Wolfgang.Riede@dlr.de ESA-NASA Working Meeting on Optoelectronics: Qualification of


  1. Work on Coatings Wolfgang Riede, Paul Allenspacher Institute of Technical Physics, DLR Stuttgart, Pfaffenwaldring 38 – 40, 70 569 Stuttgart, Germany E-Mail: Wolfgang.Riede@dlr.de ESA-NASA Working Meeting on Optoelectronics: Qualification of Technologies and Lessons Learned from Satellite LIDAR and Altimeter Missions; June 21, 2006

  2. Motivation : -> Qualification of optics for ADM-Aeolus mission (ALADIN instrument) -> Extensive test campaigns (IR, UV, VIS) to identify optics exposed to critical fluence levels Issues: Testing under application-oriented conditions (high vacuum, dry pump systems, laser parameters comparable to the ALADIN laser system) -> Development of a vacuum laser damage test bench Important aspects: Scaling of LIDT to Gshot levels from data based up to 10 4 shots/site ? Vacuum effect on coating performance ? Introduction Institute of Technical Physics 2

  3. Optical shutters HR HR f = 500 mm Wedge lambda/2 plate SHG / THG unit HR Pol. HeNe Pulse counter Aperture (stab.) 3 mm Pyroelectric 12 bit detector Nd:YAG Laser CCD Chopper 3 kHz y Sample 600 mm under vacuum x PC Low noise Flow box diode area Laser damage test bench: IR optical setup Institute of Technical Physics 3

  4. Optical shutters Aperture HR HR 2.2 mm f = 750 mm Wedge lambda/2 plate SHG / THG unit HR Pol. HeNe Pulse counter (stab.) Pyroelectric 12 bit detector Nd:YAG Laser CCD Pyroelectric Chopper detector 3 kHz y Sample 600 mm under vacuum x PC Low noise Flow box diode area Laser damage test bench: UV optical setup Institute of Technical Physics 4

  5. wavelength 1064 nm wavelength 355 nm repetition rate 100 Hz pulse energy 70 mJ (IR pump energy 300 mJ) pulse energy 400 mJ pulse duration (FWHM) 3 ns pulse duration (FWHM) 3.5 ns pulse to pulse energy stability < 3 % pointing stability (long term) < 20 µrad/h (IR pump energy 200 mJ) M 2 < 1.5 beam quality pulse energy stability long term (40 min) < 3 % (IR pump energy 200 mJ) linewidth < 250 MHz pulse to pulse spatial profile stability < 3 % repetition rate < 0.001 % spatial profile stability long term (40 min) < 2 % pulse to pulse energy stability < 1.3 % pulse to pulse pointing stability pulse to pulse spatial profile stability < 3.3 % < 25 µrad (horizontal / vertical direction) pulse to pulse temporal profile stability < 5 % pointing stability long term (40 min) < 25 µrad pulse to pulse pointing stability < 10 µrad (horizontal / vertical direction) Intensity [a.u.] Intensity [a.u.] 250 200 200 150 150 Far field beam profiles 100 100 (lhs: IR, rhs: UV) 50 50 0 -200 -150 -100 -50 0 50 100 150 200 0 0 500 1000 1500 2000 Position [µm] Position [µm] Laser damage test bench: specs and error budget of laser source Institute of Technical Physics 5

  6. Nd:YAG (1 w) Nd:YAG (3 w) HeNe diode lens beam stop sample pressure sensor 4,20 pressure signal 4,20 pressure signal 4,15 4,15 scatter probe signal scatter probe signal 4,10 4,10 laser pulses laser pulses 4,05 Signal [a.u.] 4,05 4,00 4,00 Signal [a.u.] 3,95 3,95 3,90 3,90 2 0.29 J/cm 2 pulses 0,5 2 0.37 J/cm 0,0 0,0 -5 0 5 10 -5 0 5 10 Pulses Pulses Background pressure: 18 10 -6 mbar Typical pressure rise: 4…8 10 -6 mbar Damage monitoring via scatter probing and transient pressure sensing Institute of Technical Physics 6

  7. • Test of scattering samples (light trap absorbers) • Vibration insensitive • Misalignment (drift) insensitive • Useful as backup signal • Fast (up to kHz bandwidth) • No interference with optical channels • Sensitive to front and back surface • No detection of bulk damage! Features of the transient pressure sensing Institute of Technical Physics 7

  8. Laser damage test bench: 1w / 3 w beamline / multi-functional vacuum chamber Institute of Technical Physics 8

  9. Data acquisition up to 800 Hz, multi channel Automation status semi- / fully automated Energy preselection binary / random; input & output parameter: pulse energy algorithm Damage detection 1. Lock-in based, collinear scatter probing modes 2. transient pressure sensing, cold cathode sensor Lifetime testing up to 50 Mio. Shots (flashlamp lifetime) Sample positioning completely inside vacuum Laser beam analysis 12 bit CCD, 4.4 µm pitch (Spiricon FireWire); online beam profiling; adaptation to sample position Laser wavelengths 1w & (2w; 3w) separate beam lines Mode of operation burst (intermittent) / non-burst operation 5 10 -6 mbar, oil-free pump system Typical vacuum quality Main features of damage test bench Institute of Technical Physics 9

  10. 9,0 -N/c 1 + F 2 N -c 2 8,5 F = F 1 e 8,0 2 ] sample: ES_LC_AR_096 Chi^2 = 0.00498 Fluence F [J/cm 7,5 -6 mbar R^2 = 0.98613 pressure: 5 10 7,0 c 1 10.13052 ±1.50773 6,5 c 2 0.01201±0.00305 F 1 3.81689±0.5483 6,0 F 2 5.09429±0.10386 5,5 5,0 4,5 4,0 1 10 100 1000 10000 100000 Number of pulses N Empirical fitting curve: F = F 1 *exp[-N/c1] + F 2 *N -c2 exponentially decaying part F 1 *exp[-N/c1]; slowly decaying part F 2 *N -c2 -> valid for all types of samples tested -> valid for 1064 nm / 355 nm wavelength -> independent of atmospheric conditions Characteristic damage curve: laser fatigue effect Institute of Technical Physics 10

  11. 9,0 9,0 -N/c 1 + F 2 N -c 2 F = F 1 e 8,5 -N/c 1 + F 2 N -c 2 8,5 F = F 1 e 8,0 8,0 sample: ES_LC_AR_096 Chi^2 = 0.00105 2 ] 2 ] sample: ES_LC_AR_096 Fluence F [J/cm pressure: 1000 mbar N 2 R^2 = 0.99776 Fluence F [J/cm Chi^2 = 0.00498 7,5 7,5 -6 mbar R^2 = 0.98613 pressure: 5 10 c 1 5.79939 ±0.32053 7,0 7,0 c 2 0.00051 ±0.00108 c 1 10.13052 ±1.50773 6,5 F 1 3.18984 ±0.13933 6,5 c 2 0.01201±0.00305 F 2 5.62741 ±0.04031 F 1 3.81689±0.5483 6,0 6,0 F 2 5.09429±0.10386 5,5 5,5 5,0 5,0 4,5 4,5 4,0 4,0 1 10 100 1000 10000 100000 1 10 100 1000 10000 100000 Number of pulses N Number of pulses N 1 bar N 2 Vacuum Degradation under vacuum Institute of Technical Physics 11

  12. -N/c 1 + F 2 N -c 2 9,0 F = F 1 e 9,0 -N/c 1 + F 2 N -c 2 F = F 1 e 8,5 8,5 Sample: ES_LC_AR_098 8,0 Chi^2 = 0.00425 8,0 2 ] Sample: ES_LC_AR_099 Fluence F [J/cm ] pressure: 4 bar (He) R^2 = 0.97465 Chi^2 = 0.01148 2 Fluence F [J/cm 7,5 -1 mbar - 5 10 -5 mbar R^2 = 0.945 7,5 pressure: 5x10 c 1 10.65326 ±3.21496 7,0 7,0 c 1 12.90994 ±5.09142 c 2 0.00984±0.00263 c 2 0.00759±0.00434 F 1 1.82971±0.53515 6,5 6,5 F 1 1.21662±0.27352 F 2 5.76169±0.10323 6,0 F 2 5.72651±0.16983 6,0 5,5 5,5 5,0 5,0 4,5 4,5 4,0 4,0 1 10 100 1000 10000 100000 1 10 100 1000 10000 100000 Number of pulses N Number of pulses N vacuum 4 bar He Effect of gas thermal conductivity Institute of Technical Physics 12

  13. 9,0 9,0 -N/c 1 + F 2 N -c 2 -N/c 1 + F 2 N -c 2 F = F 1 e F = F 1 e 8,5 8,5 8,0 8,0 2 ] Fluence F [J/cm ] Sample: ES_LC_AR_099 Sample: ES_LC_AR_099 Chi^2 = 0.01148 2 Chi^2 = 0.00273 Fluence F [J/cm 7,5 7,5 -1 mbar - 5 10 -5 mbar R^2 = 0.945 -6 mbar R^2 = 0.98766 pressure: 5x10 pressure: 5 10 7,0 7,0 c 1 12.90994 ±5.09142 c1 33.22866 ±8.58043 c2 0.01121±0.00396 c 2 0.00759±0.00434 6,5 6,5 F1 0.75737±0.1074 F 1 1.21662±0.27352 F2 5.14173±0.13947 6,0 6,0 F 2 5.72651±0.16983 5,5 5,5 5,0 5,0 4,5 4,5 4,0 4,0 1 10 100 1000 10000 100000 1 10 100 1000 10000 100000 Number of pulses N Number of pulses N Immediate testing 42 h under vacuum Effect of vacuum residence time Institute of Technical Physics 13

  14. testing of 14 different types of optics, 38 samples overall * Stated are „best LIDT values“ for tested types of optics LIDT-tested ALADIN laser optic components (wavelength 1064 nm) Institute of Technical Physics 14

  15. testing of 8 different types of optics, 22 samples overall * Stated are „best LIDT values“ for tested types of optics LIDT-tested ALADIN laser optic components (wavelength 355 nm) Institute of Technical Physics 15

  16. Test bench for LIDT vacuum testing at 355 nm / 532 nm / 1064 nm Transient pressure sensing technique: suitable in a vacuum environment for online detection of laser damage Air – vacuum effect: small negative fluence offset found under vacuum indication residence time effects thermal isolation under vacuum (no thermal conductivity -> no ambient gas) must be excluded as cause of vacuum degradation. Laser fatigue effect : step-like degradation within several pulses leveling off along a slowly decreasing ramp (> 100 shots applied per site) Summary Institute of Technical Physics 16

  17. Last not least: The support by the European Space Agency , Galileo Avionica and Astrium-F is gratefully acknowledged! Thank you for your attention! Institute of Technical Physics 17

Recommend


More recommend