1. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. Micromechanical oscillators in the Casimir regime: A tool to investigate the existence of hypothetical forces Ricardo S. Decca Department of Physics, IUPUI

2. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. Daniel LópezArgonne National Labs Ephraim FischbaschPurdue University Dennis E. Krausse Wabash College and Purdue University Valdimir M. MostepanenkoNoncommercial Partnership “Scientific Instruments”, Russia Galina L. KlimchitskayaNorth-West Technical University, Russia Ho Bun ChanUniversity of Florida Jing DingIUPUI Hua XingIUPUI NSF, DOE, LANL Collaborators Funding

3. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. Jonathan L. Feng, Science 301, 795 (’03) The strength of gravity for various numbers of large extra dimensions n, compared to the strength of electromagnetism (dotted) Without extra dimensions, gravity is weak relative to the electromagnetic force for all separation distances. With extra dimensions, the gravitational force rises steeply for small separations and may become comparable to electromagnetism at short distances. What is the background?

4. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. Dominant electronic force at small (~ 1 nm) separations Non-retarded: van der Waals Retarded: Casimir Attractive force! 2a2a No mode restriction on the outside

5. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. Importance of the Casimir effect Consequences in nanotechnology (MEMS and NEMS) “Long-range” interaction between moving parts Possibility of controlling the interaction by engineering materials Consequences in quantum field theory Thermal dependence Consequences in gravitation and cosmology Background to measure deviations from Newtonian potential at small separations Source of “missing mass”

6. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. Yukawa-like potential Arises from very different pictures: Compact extra-dimensions Exchange of single light (but massive,  =1/ ) boson Moduli; Graviphotons; Dilatons; Hyperphotons; Axions PRL 98, 021101 (2007) ff1ff1 ff2ff2 12 

7. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. Yukawa-like potential Arises from very different pictures: Compact extra-dimensions Exchange of light (but massive,  =1/ ) boson -Moduli -Graviphotons -Dilatons -Hyperphotons -Axions How do we establish limits? Measure background and subtract it Get rid of the background altogether

8. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. Experimental setup

9. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. Dynamic measurements

10. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. Separation measurement z g = (2389.6 ± 0.1) nm, interferometer z i = ~(10000.0 ± 0.2) absolute interferometer z o = (6960.1 ± 0.5) nm, electrostatic calibration b = (210 ± 3)  m, optical microscope  = ~(1.000 ± 0.001)  rad zgzg z meas is determined using a known interaction z i,  are measured for each position

11. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. Separation measurement Electrostatic force calibration Determine: R V Au  o  Originally using the whole expression, lately using the 8 term fit found on Mohideen’s papers

12. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. Pressure determination

13. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. Comparison with theory v i : Fraction of the sample at separation zi AFM image of the Au plane

14. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. Comparison with theory

15. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. “Casimir-less” experiments AuGe Au Si MTO Al 2 O 3

16. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. Signal optimization: Work at  o !!! Heterodyne Oscillate plate at f 1, sphere at f 2 such that f 1 + f 2 = f o “Casimir-less” experiments

17. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. 1 sec 1000 sec100 sec 10 sec z = 500 nm

18. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. Signal optimization: Work at  o !!! Oscillate plate at f 1, sphere at f 2 such that f 1 + f 2 = f o F 95% confidence level Net force! “Casimir-less” experiments

19. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. Sanity check: more samples! “Casimir-less” experiments

20. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. F

21. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. Au Background Au Ge Si MTO Al 2 O 3 Au Motion not parallel to the axis (too small) Step (0.1 nm needed) Difference in electrostatic force (0.1 mV needed) Difference in Au coating (unlikely) Au coating not thick enough (unlikely)

22. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. -Reduce background What next? -Improve signal

23. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009.

24. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. Two orders of magnitude improvement About five orders of magnitude improvement

25. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. Conclusions Most sensitive measurements of the Casimir Force and Casimir Pressure Unprecedented agreement with theory First realization of a “Casimir-less” experiment Improvement of about three orders of magnitude in Yukawa-like hypothetical forces

26. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. Separation measurement Electrostatic force calibration V o must be constant as a function of separation… … and time

27. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. -Dark grey, Drude model approach -Light grey, Leontovich impedance approach PRD 75, 077101 Comparison with theory

28. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. -Problems in lack of parallelism (curvature of wavefronts) are compensated when subtracting the two phases -Gouy phase effect is ~, and gives an error much smaller than the random one (Yang et al., Opt. Lett. 27, 77 (2005) Interferometer Distance measurement LC =(1240 +/-  ) nm (low coherence), CW 1550 nm (high coherence) in x Mirror (v ~ 10  m/s)  x = z i Readout

29. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. LC =(1240 +/-  ) nm (low coherence), CW 1550 nm (high coherence) in x Mirror (v ~ 10  m/s)  x = z i Readout -Phases obtained doing a Hilbert transform of the amplitude -Changes in  about 2 nm) give different curves. Intersections provide  x -Quite insensitive to jitter. Only 2  x’/( CW ) 2 Instead of 2  x’/ CW (Yang et al., Opt. Lett. 27, 77 (2005) Interferometer Distance measurement

30. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. t w w, t = 2  m Experimental setup

31. Tests of Gravity and Gravitational PhysicsCase Western Reserve University, May 19 th, 2009. Experimental setup