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Adaptive Optics for Wavefront Correction of High Average Power Lasers

Adaptive Optics for Wavefront Correction of High Average Power Lasers. Justin Mansell, Supriyo Sinha, Todd Rutherford, Eric Gustafson, Martin Fejer and Robert L. Byer. LIGO-G010113-00-Z. Outline. Motivation – Laser Aberration Removal Effects of Zernike Aberrations on Laser Beam Quality

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Adaptive Optics for Wavefront Correction of High Average Power Lasers

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  1. Adaptive Optics for Wavefront Correction of High Average Power Lasers Justin Mansell, Supriyo Sinha, Todd Rutherford, Eric Gustafson, Martin Fejer and Robert L. Byer LIGO-G010113-00-Z

  2. Outline • Motivation – Laser Aberration Removal • Effects of Zernike Aberrations on Laser Beam Quality • Measured Laser Aberrations • New Micromachined Deformable Mirror • Laser Aberration Compensation Experiment • Conclusions and Future Work Justin Mansell – jmansell@intellite.com

  3. Rejected Light FI & EOM Laser Aberrations Mode Cleaner Amplifier Motivation • Aberrations remove light from the interferometer • “Quasi-Static” - diode failures and power fluctuations change the aberration shape and amplitude. LIGO Front End Justin Mansell – jmansell@intellite.com

  4. Effects of Zernike Aberrations • Zernikes - a set of orthogonal polynomials defined about a unit circle used to describe wavefront aberrations in optical metrology • Effect of Zernikes can be understood by performing the overlap integral (a.k.a., inner product) of the perfect and aberrated electric field distributions. • Mansell et al. “Evaluating the Effect of Transmissive Optic Thermal Lensing on Laser Beam Quality With a Shack -Hartmann Wave-Front Sensor” Applied Optics 40, p.366. Justin Mansell – jmansell@intellite.com

  5. Zernike Polynomials Triangular Astigmatism 10 X-Axis Tilt 30 40 11 X-Axis Coma Y-Axis Tilt 31 41 Spherical Aberration 20 Y-Axis Coma Vertical Astigmatism 32 42 21 Triangular Astigmatism Focus 33 43 22 45 Astigmatism 44 Justin Mansell – jmansell@intellite.com

  6. Effect of 1st and 2nd Order Zernikes on TEM00 Mode Content Justin Mansell – jmansell@intellite.com

  7. Effect of 3rd and 4th Order Zernikes on TEM00 Mode Content Justin Mansell – jmansell@intellite.com

  8. Transmissive Optic Thermal Lensing Justin Mansell – jmansell@intellite.com

  9. Slab Laser Amplifier Aberrations PV=813nm Tilt-Removed Aberrations for 175W Pump Justin Mansell – jmansell@intellite.com

  10. 3D View of Mirror Architecture Justin Mansell – jmansell@intellite.com

  11. Gold Silicon Nitride Bond Material Silicon 2.3mm 0.4mm Cross-Section of Mirror Architecture Justin Mansell – jmansell@intellite.com

  12. Stanford DM Photograph Justin Mansell – jmansell@intellite.com

  13. Stanford’s Silicon DM Characteristics • 19 actuators with 2.3mm spacing in a 1.6cm aperture • Low Static Aberrations (~/2 PV in astigmatism) • Good Power Handling (42nm rms surface distortion from 4.5W of cw 1064nm laser light) • Versatile (10m throw in center actuator) • Low Power (200V to actuate, but almost no current) • Fast (>500Hz mechanical resonance frequency) • Low-cost fabrication • Robust (Electrostatic snap-down does not damage the mirror and is fully recoverable) Justin Mansell – jmansell@intellite.com

  14. Stanford DM in Zernike Terms X-Axis Tilt Triangular Astigmatism Y-Axis Tilt X-Axis Coma Vertical Astigmatism Y-Axis Coma Spherical Aberration Focus Triangular Astigmatism 45 Astigmatism Justin Mansell – jmansell@intellite.com

  15. “Optical Communications” via Spatial Phase STANFOrD INTELLITE Justin Mansell – jmansell@intellite.com

  16. Image 1 Image 2 HWP QWP 150mm 75mm PBS Laser DM PBS 25mm 50mm 400mm 100mm 1000mm Hartmann WavefrontSensor Cooling Image 3 Cooling 50mm Far-Field CCD Image 4 Power Meter M1 M2 MOPA Experimental Setup Justin Mansell – jmansell@intellite.com

  17. Experimental Results Distorted Wavefront • Started 92% in TEM00 mode. • AO increased to 95%. • Pumping reduced to 31% • AO increased to 89% Initial Corrected Wavefront Corrected Wavefront Justin Mansell – jmansell@intellite.com

  18. MOPA AO Far-Fields No Pump No Voltage No Pump Optimized 175W Pump No Voltage 175W Pump Optimized Justin Mansell – jmansell@intellite.com

  19. Conclusions • Introduced new type of silicon deformable mirror designed for high power laser operation. • Demonstrated active compensation of slab amplifier distortions. • Increased TEM00 mode power coupling from 31% to 89%. • Thanks to the NSF for funding this work. Justin Mansell – jmansell@intellite.com

  20. Future Work • Low Absorption Coatings • Three-Level Architecture • Piston Bias Condition • Larger Area & Higher Resonance Frequency • Lower Crosstalk • Low Cost System Integration • Cheap Wavefront Sensor • Cheap Control Computer Justin Mansell – jmansell@intellite.com

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