Max Planck Institute Gravitational Physics · Albert Einstein Institute 7th International LISA...
Transcript of Max Planck Institute Gravitational Physics · Albert Einstein Institute 7th International LISA...
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Albert Einstein Institute
www.lisa.aei-hannover.de
LISA Technology II – June 18, 2008 / 15:30 h7th International LISA Symposium – Barcelona, Spain / June 16-20, 2008
HannoverMax Planck InstituteforGravitational Physics
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LISA Technology II – June 18, 2008 / 17:15 h7th International LISA Symposium – Barcelona, Spain / June 16-20, 2008
Measurement of the nonreciprocal phase noise of a singlemode polarization maintaining optical fiber
R. Fleddermann, F. Steier, M. Tröbs, G. Heinzel and K. Danzmann
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LISA Group AEI Hannover, Germany Roland Fleddermann, June 18, 2008http://www.lisa.aei-hannover.de/ 7th International LISA Symposium – LISA Technology II
Measurement of the nonreciprocal phase noise of a single mode polarization maintaining optical fiber
Fiber reciprocity
• Desirable to exchange light between two optical benches
• Benches move fiber• Fiber introduces reciprocal
phase noise, but can be subtracted
• Nonreciprocal phase noise can not be subtracted
• Possible sources• Travel time effects • Light in wrong fiber axis• Reflections at fiber ends• … ?
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LISA Group AEI Hannover, Germany Roland Fleddermann, June 18, 2008http://www.lisa.aei-hannover.de/ 7th International LISA Symposium – LISA Technology II
Measurement of the nonreciprocal phase noise of a single mode polarization maintaining optical fiber
Tests of the reciprocity
• Two possibilities:• Sagnac• LISA-like
• First experiments using sagnac setup• Phasenoise above LISA requirements• Reduction not possible
LISA-like setup
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LISA Group AEI Hannover, Germany Roland Fleddermann, June 18, 2008http://www.lisa.aei-hannover.de/ 7th International LISA Symposium – LISA Technology II
Measurement of the nonreciprocal phase noise of a single mode polarization maintaining optical fiber
Initial Sagnac results
• Noise Level of about
observed• External influences investigated:
• Fiber temperature• Electronic noise• Polarization inside fiber• Reciprocity• Coherence length• Backscatter• Temperature of EOM
Hzrad/ 3103 −⋅
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LISA Group AEI Hannover, Germany Roland Fleddermann, June 18, 2008http://www.lisa.aei-hannover.de/ 7th International LISA Symposium – LISA Technology II
Measurement of the nonreciprocal phase noise of a single mode polarization maintaining optical fiber
LISA-like setup
• Sagnac does not show required performance• Switch to setup closer to actual LISA application
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LISA Group AEI Hannover, Germany Roland Fleddermann, June 18, 2008http://www.lisa.aei-hannover.de/ 7th International LISA Symposium – LISA Technology II
Measurement of the nonreciprocal phase noise of a single mode polarization maintaining optical fiber
LISA like setup
• Improvements:• LISA Pathfinder laser system• Vacuum• Matched path lengths• New photodiode amplifiers
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LISA Group AEI Hannover, Germany Roland Fleddermann, June 18, 2008http://www.lisa.aei-hannover.de/ 7th International LISA Symposium – LISA Technology II
Measurement of the nonreciprocal phase noise of a single mode polarization maintaining optical fiber
Comparison of spectra
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LISA Group AEI Hannover, Germany Roland Fleddermann, June 18, 2008http://www.lisa.aei-hannover.de/ 7th International LISA Symposium – LISA Technology II
Measurement of the nonreciprocal phase noise of a single mode polarization maintaining optical fiber
Pathlength noise
• Setup sensitve to changes in pathlength
• Simple IFO for comparison• Heterodyne Mach-Zehnder• 10 cm Armlength
• Measure pathlength noise• Add.: Measurement w/o fiber
Zerodur Mach-Zehnder
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LISA Group AEI Hannover, Germany Roland Fleddermann, June 18, 2008http://www.lisa.aei-hannover.de/ 7th International LISA Symposium – LISA Technology II
Measurement of the nonreciprocal phase noise of a single mode polarization maintaining optical fiber
Pathlength noise
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LISA Group AEI Hannover, Germany Roland Fleddermann, June 18, 2008http://www.lisa.aei-hannover.de/ 7th International LISA Symposium – LISA Technology II
Measurement of the nonreciprocal phase noise of a single mode polarization maintaining optical fiber
Measurements without fiber
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LISA Group AEI Hannover, Germany Roland Fleddermann, June 18, 2008http://www.lisa.aei-hannover.de/ 7th International LISA Symposium – LISA Technology II
Measurement of the nonreciprocal phase noise of a single mode polarization maintaining optical fiber
Zerodur Interferometer
• Aluminum limits pathlength noiseZerodur
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LISA Group AEI Hannover, Germany Roland Fleddermann, June 18, 2008http://www.lisa.aei-hannover.de/ 7th International LISA Symposium – LISA Technology II
Measurement of the nonreciprocal phase noise of a single mode polarization maintaining optical fiber
First results with Zerodur Interferometer
Still way above requirements, even worse than Sagnac results
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LISA Group AEI Hannover, Germany Roland Fleddermann, June 18, 2008http://www.lisa.aei-hannover.de/ 7th International LISA Symposium – LISA Technology II
Measurement of the nonreciprocal phase noise of a single mode polarization maintaining optical fiber
Improvements
• Straylight correction• Pi measurements high noise level• Straylight must enter measurement
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LISA Group AEI Hannover, Germany Roland Fleddermann, June 18, 2008http://www.lisa.aei-hannover.de/ 7th International LISA Symposium – LISA Technology II
Measurement of the nonreciprocal phase noise of a single mode polarization maintaining optical fiber
Effect of straylight correction
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LISA Group AEI Hannover, Germany Roland Fleddermann, June 18, 2008http://www.lisa.aei-hannover.de/ 7th International LISA Symposium – LISA Technology II
Measurement of the nonreciprocal phase noise of a single mode polarization maintaining optical fiber
Polarization control
• Polarization must match fiber axis• Different indices of refraction act like waveplate• Output polarization state will generally be elliptic and time dependant
• Introduce polarizers into zerodur setup• Alignment is difficult• Polarimeter needed
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LISA Group AEI Hannover, Germany Roland Fleddermann, June 18, 2008http://www.lisa.aei-hannover.de/ 7th International LISA Symposium – LISA Technology II
Measurement of the nonreciprocal phase noise of a single mode polarization maintaining optical fiber
Null measurement
• Measurement without fiber• Foreseen in design of Zerodur IFO• Shows noise of setup
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LISA Group AEI Hannover, Germany Roland Fleddermann, June 18, 2008http://www.lisa.aei-hannover.de/ 7th International LISA Symposium – LISA Technology II
Measurement of the nonreciprocal phase noise of a single mode polarization maintaining optical fiber
Summary
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LISA Group AEI Hannover, Germany Roland Fleddermann, June 18, 2008http://www.lisa.aei-hannover.de/ 7th International LISA Symposium – LISA Technology II
Measurement of the nonreciprocal phase noise of a single mode polarization maintaining optical fiber
Summary
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LISA Group AEI Hannover, Germany Roland Fleddermann, June 18, 2008http://www.lisa.aei-hannover.de/ 7th International LISA Symposium – LISA Technology II
Measurement of the nonreciprocal phase noise of a single mode polarization maintaining optical fiber
Summary
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LISA Group AEI Hannover, Germany Roland Fleddermann, June 18, 2008http://www.lisa.aei-hannover.de/ 7th International LISA Symposium – LISA Technology II
Measurement of the nonreciprocal phase noise of a single mode polarization maintaining optical fiber
Conclusions/Outlook
• Requirements not (yet) fulfilled• Made good progress• Nonreciprocity observed still limited by setup• Backreflection identified as noise source
• Possible ways of improvement• Less backreflection (couplers, lenses, fibers, alignment)• Better polarization alignment/control
• Next steps• Investigate backreflection• Try other fiber couplers (LPF Fiber injector prototypes?)• Improve polarization alignment (Polarimeter)• Other fibers• Fiber temperature/length stabilization
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LISA Group AEI Hannover, Germany Roland Fleddermann, June 18, 2008http://www.lisa.aei-hannover.de/ 7th International LISA Symposium – LISA Technology II
Measurement of the nonreciprocal phase noise of a single mode polarization maintaining optical fiber
End
ThankThank youyou forfor youryour attentionattention