1. Optomechanics Experiments
Radiation Pressure Rules
MIT Quantum Measurement Group

2. Quantum optomechanics
Techniques for improving gravitational wave detector sensitivity
Tools for quantum information science
Opportunities to study quantum effects in macroscopic systems
Observation of quantum radiation pressure
Generation of squeezed states of light
Entanglement of mirror and light quantum states
Quantum states of mirrors

3. Optomechanical coupling
The radiation pressure force couples the optical field to mirror motion
Alters the dynamics of the mirror
Spring-like forces  optical trapping
Viscous forces  optical damping
Tune the frequency response of the GW detector
Manipulate the quantum noise
Quantum radiation pressure noise and the standard quantum limit
Produce quantum states of the mirrors and light
Classical
Tuning frequency response is used to manipulating the signal. Improved sensitivity at optical spring resonant frequency.
Squeezing manipulates the noise
Quantum

4. Optomechanical coupling: Radiation pressure forces
Detune optical field from cavity resonance
Change in mirror position changes intracavity power  radiation pressure exerts force on mirror
Time delay in cavity results in cavity response doing work on mechanics

5. Gram-scale mirrors

6. Experimental cavity setup
10%
90%
5 W
Optical fibers
1 gram mirror
Coil/magnet pairs
for actuation (x5)‏

7. Trapping and cooling Stable optical trap with bichromatic light
Dynamic backaction cooling
Stiff!
Stable!
T. Corbitt et al., Phys. Rev. Lett 98, (2007)

8. The experiment grows
Squeezed
Vacuum fluctuations
T. Corbitt et al., Phys. Rev. A 73, (2006)
Two identical cavities with 1 gram mirrors at the ends
Common-mode rejection cancels out laser noise

9. The experiment grows

10. Optically trapped and cooled mirror
Optical fibers
Teff = 0.8 mK N = 35000
Mechanical Q = 20000
Cooling factor larger than mechanical Q because Gamma = Omega_eff/Q. The OS increases Omega but doesn’t affect Gamma (OS is non-mechanical), so Q must increase to keep Gamma constant.
1 gram mirror
C. Wipf, T. Bodiya, et al. (March 2010)

11. That elusive quantum regime
Thermal noise
Radiation pressure
noise goal (5 W input)
C. Wipf, T. Bodiya, et al. (Feb. 2011)

12. Ponderomotive Squeezing
7 dB or 2.25x
Squeezing
T. Corbitt, Y. Chen, F. Khalili, D.Ottaway, S.Vyatchanin, S. Whitcomb, and N. Mavalvala, Phys. Rev A 73, (2006)

13. Cryogenic microgram-scale mirrors Thomas Corbitt @ MIT (but soon LSU)

14. Micromirror oscillators
AlGaAs layers forming a Bragg mirror
~ 1 to 5 mm long, ~10 μm supports, 50 to 100 μm mirror pads
Fundamental frequency ~ 200 Hz
Q factor ~ 2x105 at 5 K
Mass ~ 250 nanograms
Reflectivity ~ %
Very fragile
Power handling: breaks at >100 mW of incident power
Fabricated by Garrett Cole at Univ. of Vienna

15. Experimental layout

16. Noise budget

17. What can we learn?
Verify models of radiation pressure noise, squeezed radiation pressure noise, sub-SQL topologies
Verify models of thermal noise (ability to measure thermal noise as function of both frequency and temperature across broad bandwidth in monolithic structure)
Characterize materials and understand dissipation mechanisms
Gain experience in low vibration cryogenics

18. Amazing cast of characters
MIT
Thomas Corbitt
Christopher Wipf
Timothy Bodiya
Sheila Dwyer
Lisa Barsotti
Nicolas Smith-Lefevbre
Eric Oelker
Rich Mittleman
MIT LIGO Laboratory
Collaborators
Yanbei Chen & group
David McClelland & group
Roman Schnabel & group
Stan Whitcomb
Daniel Sigg
Caltech 40m Lab team
Caltech LIGO Lab
Garrett Cole of Aspelmeyer group (Vienna)
LIGO Scientific Collaboration