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Lasers for Advanced Interferometers

Lasers for Advanced Interferometers. Benno Willke. ILIAS WG3 Hannover, October 2004. Requirements - Topology. Sagnac: broadband source to reduce scattered light noise power control recycled Michelson: coherence control power control spatial control squeezed light IFOs

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Lasers for Advanced Interferometers

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  1. Lasers for Advanced Interferometers Benno Willke ILIAS WG3 Hannover, October 2004

  2. Requirements - Topology • Sagnac: • broadband source to reduce scattered light noise • power control • recycled Michelson: • coherence control • power control • spatial control • squeezed light IFOs • different wavelength Prestabilized Laser System (PSL)

  3. Requirement – High Power trade off:

  4. Requirement – Noise Frequency Noise Intensity Noise

  5. Requirement – Noise / Design Spatial Fluctuations Design Requirements • stability / reliability • soft failure mode • easy to maintain / rare maintenance interval • good efficiency • good stationarity / low glitch rate • high bandwidth / large range actuators

  6. Laser Design • common concept: • laser diode pumped solid state lasers • transfer frequency stability of low power master laser to high power stage • Maser Laser Power Amplifier (MOPA) • injection locked oscillator • different power stage concepts: • rods • zig-zag slabs • fibers • thin disc lasers / active mirror laser

  7. Nd:YAG Master-Laser NPRO (non-planar ring oscillator) • output power: 800mW • frequency noise: [ 10kHz/f ] Hz/sqrt(Hz) • power noise: 10-6 /sqrt(Hz)

  8. High Power Stage • main problem: thermal design • stress fracture • thermal lensing – spatial profile • birefringence with tangential and radial principle axis • solutions • reduce deposited heat – Yb:YAG, high efficiency • propagate beam perpendicular to temperature gradient – zig-zag, thin disc lasers • increase interaction length – fiber lasers • compensate birefringence

  9. Face-pumping - Edge-pumping Pumping zig-zag plane Face- pumping zig-zag slab Cooling Edge- pumping zig-zag plane Pumping Cooling Stanford High Power Laser Lab Adelaide University

  10. End pumped slab geometry 808nm Pump undoped end signal OUT 3.33cm 1.51cm 1.51cm 0.6% Nd:YAG signal IN undoped end 808nm Pump 1.1mm X 0.9mm Stanford High Power Laser Lab

  11. Mode-matching optics 10W LIGO MOPA System 20 W Amplifier ISOLATOR Lightwave Electronics Mode-matching optics 2-pass End Pumped Slab #2 Pump Power = 430 W Expected TEM00 Output Power = 160W Stanford High Power Concept Pump Power = 130 Output TEM00Power = 50 W 2-pass End Pumped Slab #1 TO PRE MODE CLEANER

  12. End Pumped Rods Nd:YAG - GEO600 Laser (14W) Nd:YVO4 - Virgo Laser (20W) Laser Zentrum Hannover

  13. output QR f f BP from Master QR f f HR@1064 f 2f f HT@808 LZH High Power Concept

  14. Fiber Lasers courtesy H. Zellmer

  15. Fiber Laser Result of Jena Group Backscattered signal Dichr. mirror 9.4 m Yb-doped LMA-fiber NPRO Fiber coupled laser diode Isolator To experiment Input-output diagram Yb-doped LMA-Fiber Core:  = 28.5 µm, NA = 0.06 MFD 23 µm Doping. 700 ppm (mol) Yb2O3 Pumpc.:  = 400 µm, NA = 0.38, D-Form Seed: 800 mW Diffraction limited (M2 = 1.1) Polarization 82% (10:1)

  16. Power / Beamprofile: 165W in gausian TEM00 mode less than 5W in non- TEM00 modes Drift: 1% power drift over 24hr. 2% pointing drift Control: tidal frequency acuator +/- 50 MHz, time constant < 30min power actuator 10kHz BW, +/-1% range frequency actuatot BW:<20o lag at 100kHz, range: DC-1Hz: 1MHz, 1Hz-100kHz: 10kHz Advanced LIGO Laser – Requirements

  17. key elements: undoped bonded end-caps birefringence compensation pumplight homogenization NPRO output QR f f EOM FI BP FI modemaching YAG / Nd:YAG 3x2x6 optics QR f f BP YAG / Nd:YAG / YAG HR@1064 f 2f f 3x 7x40x7 HT@808 20 W Master High Power Slave Injection Locked Oscillators - Hannover

  18. Prestabilized Laser PSL • frequency stability: • stabilize master laser to rigid or suspended-mirror cavity • power stability: • feed-back to pump source of high power stage • passive filtering at rf • spatial profile • passiver modecleaning • active mode compesation

  19. frequency noise requirement

  20. intensity noise requirement

  21. high power ring laser 200W GEO typring laser15W spatial filterresonator (PMC) NPRO1W frequencyreferenceresonator AOM Adv LIGO - PSL optical layout

  22. PSL – stabilization scheme intensity stabilizationouter loop injection locking intensity stabilizationinner loop PMC loop frequency stabilizationinner loop frequency stabilizationouter loop

  23. Power Noise Reduction

  24. Relock Time relock time < 500 ms faster relock possible depending on piezo ramp

  25. Birefringence Compensation

  26. output QR f f BP from Master QR f f HR@1064 f 2f f HT@808 End-Pumped Rods

  27. high power stage status Feb 2004 linear polarized with birefringencecompensation

  28. Summary • different high power stages: • end-pumped slabs • end-pumped rods • fiber amplifier • different topologies: • MOPA • injection locking • Advanced LIGO pre-stabilized laser system • status of laser development • possible stabilization schemes

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