1. Photon absorption Local heating Thermal expansion INFN-LENS T2 Braginsky et al., Phys. Lett. A 264, 1 (1999) Cerdonio et al., Phys. Rev. D 63, 082003 (2001) STREGA kick-off meeting, Cascina 12 May 2004

2. Power modulation, P=P o + P m sin ω m t Phase-sensitive detection INFN-LENS T2 Fitting curve: l = L o K( / c ) ½ c = 2.8 ± 0.6 Hz (calculated: 1.8 2.7 Hz) absorption coefficient: ~ 5 10 -7 STREGA kick-off meeting, Cascina 12 May 2004 De Rosa et al., PRL 89, 237402 (2002)

3. INFN-LENS T2 Photothermal effect… First 18 months … for different interrogation area … for different transversal modes Then … for different substrates (silica, sapphire) … at low temperature (bar detector readout) Collaboration: Auriga-PD, LKB, INOA, … STREGA kick-off meeting, Cascina 12 May 2004

4. INFN-LENS T3 Folded Fabry-Pérot F. Marin et al., Phys. Lett. A 309, 15 (2003) P in =7 W D = 6 mm R = - 10 m d = 4 w Brownian noise Radiation Pressure noise a: radiation pressure effect (no correlations) b: radiation pressure effect (full) c: Brownian noise @ 1.3 kHz (no correlations) d: Brownian noise @ 1.3 kHz (full) e: Shot-noise limited displacement sensitivity STREGA kick-off meeting, Cascina 12 May 2004

5. INFN-LENS T3 Concave -Convex cavity (-R 2 ) = R 1 + r Stable if d > r If (d – r) << d << R 1, R 2 : Ex. : R = 10 m r = 10 mm d – r = 0.1 mm l = 1.064 mm w = 5.8 mm STREGA kick-off meeting, Cascina 12 May 2004

6. INFN-LENS T3 First 18 months Folded and Concave-Convex cavities: opto-mechanical feasibility Then Noise reduction characterization, possibly at low temperature Collaboration: Auriga-PD, LKB,INOA, … STREGA kick-off meeting, Cascina 12 May 2004