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Laser Development for Gravitational-Wave Interferometry in Space

Laser Development for Gravitational-Wave Interferometry in Space. Kenji Numata 1,2 , Jordan Camp 2 1 Department of Astronomy, University of Maryland, College Park, Maryland, 20742, USA 2 NASA Goddard Space Flight Center, Greenbelt, Maryland, 20771, USA. Outline. 1. Introduction

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Laser Development for Gravitational-Wave Interferometry in Space

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  1. Laser Development for Gravitational-Wave Interferometry in Space Kenji Numata1,2, Jordan Camp2 1Department of Astronomy, University of Maryland, College Park, Maryland, 20742, USA 2NASA Goddard Space Flight Center, Greenbelt, Maryland, 20771, USA

  2. Outline • 1. Introduction • GSFC’s space laser history and recent trends • 2. Master oscillator • Planar waveguide external cavity diode laser (PW-ECL) • 3. Pre-amplifier • Low-risk component • 4. Power amplifier • Noise and qualification tests • 5. Summary

  3. 1. Introduction • NASA/GSFC space laser history • Nd:YAG laser altimeters • Recent activities and trends • Advanced laser altimeter (ICESat2, LIST, etc.) • Yb fiber + Waveguide amp. • Gas sensing lidar (ASCENDS, etc.) • Er fiber + Waveguide amp., stabilized seed laser • Parametric amplification • Laser communication (LCRD, etc.) • Er fiber amp., telecom fiber components • Interferometry (NGO/SGO, OpTIIX, etc.) • Fiber & waveguide technologies wherever possible LRO/LOLA - moon (2008-2012) Nd:YAG laser, 1+ Billion shots to date MESSENGER/MLA - Mercury (2004-2012) Nd:YAG laser, >0.5B shots to date MGS/MOLA - Mars (1996 -2000) Nd:YAG laser, 670 million shots ICESat/GLAS– Earth (2003-2010) Nd:YAG laser, 1.98 billion shots

  4. Space laser for interferometry • Master oscillator/fiber amplifier (MOFA) configuration • Both 1.0 µm and 1.5 µm • Fiber/waveguide advantages • High robustness, high efficiency, small mass & size, easy cooling • Reliability data available (Telcordia) for many components • Reliable pump source at 97x ~ 980 nm for amplifier • New technologies become available * Modulator, isolator, redundant LDs are not shown. MO+Preamplifier package OpTIIX, GRACE-FO (1.54µm) NGO/SGO (1.06µm)

  5. 2. Master Oscillator • Looking into various possibilities • Non-planar ring oscillator (NPRO) • Best high-freq. noise performance. Legacy device. • Fiber laser • Ring design (GSFC), DBR design (NP photonics) • Large relaxation oscillation • Planar-waveguide external cavity laser (PW-ECL) • Semiconductor laser • Simplest, smallest, and most cost-effective • Best noise performance at low frequency DBR FL under thermal cycle test K. Numata, 10.7452/lapl.201210034 Ring FL and its frequency noise performance NPRO and PW-ECL package comparison

  6. PW-ECL features & status • Features • Semiconductor gain chip + Planar lightwave circuit (PLC) • Design details open to NASA • C-band (~1550nm), ~10mW output • Conversion to 1064nm underway • Gain chip material change • Awarded SBIR contract to RIO for $750K (3/2012 ~ 9/2013) • NGO/SGO and other lidar applications • Passed all space qualification tests • No performance degradation by • Gamma, low/high energy proton, vacuum thermal cycling, pyro shock PLC Example result of high energy proton irradiation Example result vacuum thermal cycling

  7. PW-ECL noise performance • Relative intensity noise (RIN) • Smallest level among any lasers • No relaxation oscillation peak around MHz range • Shot noise limited above ~100kHz • Frequency noise • Phase lockable by injection current (100kHz UGF) • Frequency lockable to high finesse cavity and/or hyperfine molecular line • NGO requirement level demonstrated by 13C2H2 molecule at 1542nm • Cavity stabilization facility under construction at UT Brownsville (V. Quetschke) • GSFC funded 1/f noise reduction activity Freerun RIN of various lasers C. Clivati 10.1109/TUFFC.2011.2121 PW-ECL cavity locking PW-ECL molecular line locking Freerun freq. noise of various lasers

  8. 3.Pre-amplifier • Design • Single-clad Er- or Yb-doped fiber • Core pump by PM 97x-nm diode • Redundancy addition by polarization combiner • Noise performance • No significant noise addition • Controllable after amplifier (demonstrated) • Low risk component • Gamma radiation tests done on 1µm components • Simulation tools, many different vendors available Frequency noise before/after pre-amplifier RIN before/after pre-amplifier

  9. Metrology interferometer for OpTIIX • PW-ECL + preamp to be flown with OpTIIX • Optical Testbed and Integration on ISS eXperiment • Technology demonstrator of ATLAST (~16m space telescope) • Spaceflight of PW-ECL + acetylene cell • Planned launch: ~2015 • Metrology system: heterodyne interferometer (S. Rao) • <1nm measurement error over hours • Requirement achieved by simplified saturation setup • No external modulator, single pass Laser truss system concept Simplified C2H2 locking setup with PW-ECL

  10. 4.Power Amplifier • Design • All fiber coupled (tapered fiber bundle) • Large mode area, double-clad Yb fiber • Forward pump to avoid risk and noise sources • Catastrophic failure can occur with improper implementations • Noise performance • No additional frequency noise • NGO requirement level • Differential phase noise (@2GHz) • Stabilized low frequency RIN Differential phase noise RIN and its stabilization (low/high frequency ends)

  11. Qualification tests on power amp. • Packaging optimization for TFB • Screening by thermal imager • Proper packaging reduces temperature gradient • Gamma irradiation on gain fiber • 200 Rads(Si)/min to a total dose of 60 kRads(Si) • Certain brand shows unrecoverable damage • Probably due to dopants in the core • Sensitive but no showstopper • Vacuum thermal cycling • Marginal power/PER degradation at ~1.5W level Gamma on two different Yb fibers Vacuum thermal cycling test

  12. Summary • NASA/GSFC has been involved in space-borne laser since 90’s • Actively seeking innovative solutions to meet future science missions’ goals • Fiber/waveguide technologies to space • In-house capability to build & test space lasers • Common requirements for all laser instruments • Lifetime, reliability, and efficiency • GSFC invested ~$1.2 M over 3 years on LISA laser development • Amplifier development and noise measurements • PW-ECL noise and reliability studies • Expected to finish qualification of LISA laser by the end of FY13 • System test with 1064nm PW-ECL + pre-amp. + power amp. to be done • 1542nm PW-ECL + Er pre-amplifier to be flown to ISS • No showstopper found

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