STREGA WP1M1 mirror substrates LIGOStrega wp11镜基板 LIGO.pptVIP

Temperature dependence of the mechanical dissipation in single layer tantalum pentoxide coatings on thin single-crystal silicon substrates. Scientific motivation Silicon is of interest as a mirror substrate material for future detectors – its mechanical loss is predicted to decrease at low temperatures Mechanical dissipation from dielectric mirror coatings is predicted to be a significant source of thermal noise for advanced detectors. (Coatings must also be of low optical loss.) Experiments suggest Ta2O5 is the dominant source of dissipation in current ion-beam-sputtered SiO2/Ta2O5 coatings Doping the Ta2O5 with TiO2 can reduce the mechanical dissipation Mechanism responsible for the observed mechanical loss in Ta2O5 as yet not clearly identified Experimental setup Silicon cantilever with coating The silicon samples have been fabricated by wet etching from silicon wafers at Stanford (Stefan Zappe) The coatings were deposited by LMA. Experimental procedure Resonant modes of samples excited using an electrostatic drive Sample displacement monitored using shadow sensor Measure rate of decay of the mode amplitudes, from which mechanical dissipation, f(w0), can be determined. Coated silicon cantilever Results – third bending mode at ~1.9kHz Coated silicon cantilever Results – fifth bending mode at ~3.8kHz Coated silicon cantilever – energy distribution Interpretation: calculating the energy stored in the coating layer Coated silicon cantilever – energy distribution Interpretation: calculating the energy stored in the coating layer ctd Coated silicon cantilever – energy distribution Interpretation: calculating the energy stored in the coating layer ctd Coating loss - results Results – third bending mode – coating loss Coating loss - results Results – fifth bending mode – coating loss Investigation to study energy coupling to the clamping structure. Both sets of results show similar features, with the loss of the tantala coating typically decreasing with temperature fro