Optical Transducer

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Optical Transducer Powered By Docstoc
					              an optomechanical transducer
           for the AURIGA “bar” gw detector


cryogenic optics towards the quantum limit:
high finesse cavities, fibers, piezo actuators, etc @ 4.2 K



concept and optics: Livia Conti, Maurizio DeRosa, Francesco Marin
cryogenics: Michele Bonaldi, Giovanni A. Prodi, Luca Taffarello, Jean-Pierre Zendri
                              Optical Transducer
                                                  The Concept
                                                                          Variations of the transducer
                                                        transducer
                                                                          cavity length are measured
                                                        cavity            by the stabilized laser
                                  optical fiber
                        beam-splitter

Nd:YAG      Phase         Power
laser       mod.          stab.

Frequency                                                               bar
locking


         FM sidebands                        FM sidebands              Transducer cavity:
         technique                           technique
                                                                       a Fabry-Perot cavity between
                                                         Data
                                                         acquisition
                                                                       the bar and the resonant plate
            reference
            cavity
                                             Low frequency             Reference cavity:
                                             locking
            temperature                                                a stable Fabry-Perot cavity
            control
                                                                       acting as length reference
             pzt actuator

                                                                       Laser source frequency
                                                                       locked to the reference cavity
          Optical Transducer
         Status: Room temperature test
Experimental set-up

                            Achieved gw sensitivity




                      L.Conti et al,. Jour. Appl. Phys. 93 (2003) 3589
             Optical Transducer
                    Status: Cryogenics
 Q measurements in the
Transducer Test Facility


                                  New Cryostat for the bar
                               resonator under construction
        will operate at 4.2 K ~ 1 year
             • a prototype gw detector in coincidence with AURIGA
             • study at low T the coating thermal noise and the substrate
                thermoelastic noises (“thermodynamic” and “photothermal”)
                at the displacement level ~ 10-20 m/Hz1/2




        1E-18
)
1/2




        1E-19
(1/Hz




                             Optical transducer 4.2 K
1/2
Shh




        1E-20


                Auriga now

        1E-21
            800        850        900         950       1000
                             Frequency (Hz)

				
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