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Parametric Effects in a Macroscopic Optical Cavity

AIGO. Parametric Effects in a Macroscopic Optical Cavity. Sascha Schediwy schediwy@physics.uwa.edu.au. AIGO Workshop Thursday 6 th October. Optical Spring. Circulating Power. Frequency. Q reduction Q increase. Q Increase - Parametric Gain. Niobium Resonator. Cavity Properties Niobium

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Parametric Effects in a Macroscopic Optical Cavity

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  1. AIGO Parametric Effects in aMacroscopic Optical Cavity Sascha Schediwyschediwy@physics.uwa.edu.au AIGO WorkshopThursday 6th October

  2. Optical Spring CirculatingPower Frequency Q reductionQ increase

  3. Q Increase - Parametric Gain

  4. Niobium Resonator • Cavity Properties • Niobium • Qm = 1.562 (8)*105 • fmech = 780 Hz • meff = 32.3 g • l = 0.10m • Proxy Mirrors • R = 0.98 • F = 155 • roc = 10.0 m • Super Mirrors • R ~ 0.99968 (rated: 0.9994+) • F ~ 9800 (rated: 5200+) • roc = 1.0 m

  5. Yacca Gum Properties • viscous at 80°C+ • reversible bonds • dissolves in alcohol • relatively low loss • Q ~ 100 60°C 70°C 80°C 90°C

  6. Yacca Gum Bonding

  7. temp mirror 2 key: 3525 object position (mm) beam power (%) optical loss (%) temp mirror 1 Experimental Design

  8. Optical Error Signal Ringdown Ringdown Linear Fit time (s) time (s) (experimental results)

  9. Quality Factor Q = 0.700 ± 0.002 x105

  10. Proxy Mirror Q Modification F[rad] (N) Quality Factor (-) Mechanical Q k[opt] (N/m) Modified Q

  11. Super Mirror Q Modification F[rad] (N) Quality Factor (-) Mechanical Q (Hz) Damage Threshold Limited k[opt] (N/m) (Hz) (Hz) Laser Maximum

  12. Parametric Instability Tranquilisation • Model proposed by:Braginsky & Vyatchanin (Phys. Lett. A 293 (2002) 228-234)

  13. Any Question?

  14. Q Modification / Optical Spring Const.

  15. Circulating Power • Cavity Properties • Rayleigh Range / Beam Waist • R1 = R2 = 1.0 m • L = 0.1 m • Spot Size at Mirror ( z = 0.05 m )

  16. Circulating Power • Newport Supermirrors • Damage Threshold: • Maximum Circulating Power: • Maximum Input Power • R1 = R2 > 99.94% • T1 > 0.06%

  17. Radiation Pressure Force • Radiation pressure force for FP Cavity ≈ unity • let:

  18. Optical Spring Constant • substitute ABC back in x space in f space

  19. Cavity Alignment

  20. “Low Q” / “High Q” • Low Q – when the bandwidth is larger than ωm • High Q – when the bandwidth is smaller than ωm FWHM –ωm ωm FWHM –ωm ωm

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