An Opto-Mechanical Microwave-Rate Oscillator

Transcription

1 An Opto-Mechanical Microwave-Rate Oscillator Tal Carmon and Kerry Vahala California Institute of Technology Diameter of a human hair

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3 Opto excited Vibration: Explanation Pump Res Wavelength Experimental setup for modal spectroscopy Experimental results: 1) Stokes and Anti-Stokes lines (device vibrations) ) Selective excitation of many spectral lines 3) Going above GHz to microwave rate vibration 4) Line split (perturbation induced) 5) Continuum Off resonance Cycle turns into a perpetual oscillation Start with casting this story into a set of equations

4 Dynamic Back-Action (V. Braginsky 1985) d x dt + Ω Q dx dt F m πn cm rad ( ) + Ω x = = A mech da dt = i cω0 1 ω0 B ( + iδω) A πnr Q Q c total A = B = P cav P in ω0 Δω = Δω0 + R x Mechanical Gain/Loss P cav 1 0) (0) 4β x (0) 16Qtot β = Pcav Pcav + Pcav β Qtot R + ( β + Qtot ) Rω0 ( 1 dx dt, β = Δω0 ω 0 γ = γ (1 P / P 0 threshold ), γ = Ω 0 / Qmech

5 Theory Time The oscillations will Damping increases increase its amplitude with intensity. and then become stationary Braginsky & Manukin Measurement of weak forces in Physics Experiments (1977) First observation of oscillations Experimental Observation of Dynamical Effect CLEO 005 CLEO 006 CLEO 007 Chaos: Non-periodic dynamic. Carmon, et. al. PRL 98, (007) Power 0Time [ns] 100 Carmon, PRL 94, 390 (005). Rokhsari Opt. Exp. 13, 593 (005). Kippenberg PRL 95, (005). Today: Spectroscopy at >GHz freq Continuum Line split. Stokes and Anti-Stokes lines Carmon, et. al. PRL 98, (007). Cooling, CLEO Thu 8AM Kleckner et. al. Nature 444, 75 (006) Gigan, et al., Nature 444, 67 (006) Arcizet et. al., Nature 444,71 (006) Schliesser et al, PRL 97, (006) Harris et. al Rev. of Sci. Ins (007) Corbitt et al. PRL 98, (007)

6 Resonance enhancement I = N x (source power) Area N = 100,000 P = 1mWatt Area = 1μm I = Watt / cm Multiple passes of the acoustical (electro-magnetic) wave enhance the mechanical (optical) amplitude. Swing

7 Experimental setup Frequency comparable with the (velocity of sound)/(cavity size) P input Input light (continuous in time) t????? Photodetector Oscilloscope P output Cavity was not designed to vibrate Effect came as an unexpected surprise T. Carmon, H. Rokhsari, L. Yang, T. J. Kippenberg, and K. J. Vahala, Phys. Rev. Lett. 94, 390 (005) t

8 Experimental results Side Optical Spectrum Analyzer I CW pump laser t Top 10 μm (1) Stokes and anti-stokes lines Output power Time[ μ s] Increasing input power Carmon, Rokhsari, Yang, Kippenberg, and Vahala, Phys. Rev. Lett. 94, 390 (005)

9 Period doubling and continuum Low power Periodic oscillations Medium power () Period doubling (Still periodic) Log power [au] 0-10 Output power spectra μm Frequency [GHz] High power -0 Turns into a (3) continuum Carmon et. al., Phys. Rev. Lett , (007)

10 Spectroscopy 4) Selectively exciting different modes By tuning the photon lifetime to be comparable with the acoustical period Modal spectroscopy: deduce from the spectral line of the scattered light on the mechanical vibrational mode. Carmon, and Vahala, Phys. Rev. Lett. 98, (007)

11 Spectroscopy: Perturbation fine split of spectral line 30 μ m 8.5μm Theory Calculated modes 11.3 MHz MHz Output power [au] Experiment (a) Frequency Results 0. MHz 111. MHz ) Line split (perturbation induced) 0.5 MHz fine split Carmon and Vahala, Phys. Rev. Lett. 98, (007)

12 Comparison between light-matter and light- structure interaction THz MHz Origin Frequency Line split High power Period doubling Raman Molecular vibration freq. THz (matter) Magnetic perturbation Spectral continuum Can we learn? Carmon et. al., Phys. Rev. Lett. 94, 390 (005) Carmon and Vahala., Phys. Rev. Lett. 98, (007) Carmon, Cross, and Vahala, Phys. Rev. Lett. 98, (007) Opto-excited vibration Cavity vibration freq MHz to GHz (structure) Eccentricity perturbation Spectral continuum

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14 Conclusions Mode spectroscopy, Experimental demonstration Selective excitation of different mechanical modes High order mechanical modes vibration at microwave rates (>GHz) Deducing on the mechanical vibrational mode from the optical spectral lines of the scattered light (Spectral Signature) Line split Doubling Continuum No external feedback or modulation Intrinsic cavity properties. Different geometries (tori and spheres) Behaviour is relevant to different types of resonators Sustained trend in Miniaturization (k~area/length, small=soft) Dissipation reduction (mechanical- and opticalresonance enhancement) Similar vibrations in other platforms at even higher frequencies are expected

15 Carmon Carmon et. et. al., al., Phys. Phys. Rev. Rev. Lett. Lett. 94, 94, (005) (005) Carmon Carmon and and Vahala., Vahala., Phys. Phys. Rev. Rev. Lett. Lett. 98, 98, (007) (007) Carmon, Carmon, Cross, Cross, and and Vahala, Vahala, Phys. Phys. Rev. Rev. Lett. Lett. 98, 98, (007) (007)