The proposed optomechanical zipper cavity and its physical model. (A) Schematic of a Fabry-Perot cavity that consists of two pendulums as the reflecting mirror that act as mechanical modes b1 and b2 with oscillation frequency, Ω1 and Ω2, and are coupled to the thermal bath at the rate of γ1 and γ2, respectively. The optical mode of the Fabry-Perot cavity loses energy via the intrinsic loss channel at rate ki and detectable extrinsic coupling channel at rate kex. (B) Scanning electron microscope (SEM) image of silicon optomechanical zipper cavity. Magnified SEM image of (C) periodic structure in P-I region and (D) periodic structure in P-II region. (E) Displacement field |u| of the breathing mode simulated with the finite element method (FEM) in one arm of the optomechanical zipper cavity. FEM simulation of (F) electric field |E| of first-order optical mode in a single nanobeam cavity and (G) electric field Ey component of first-order odd optical mode in zipper cavity. (E and F) Black arrows represent the field directions of the mechanical displacement field and the electric field on the top surface of the silicon structure. uy and Ey are the main components of the mechanical displacement field and electrical field, respectively. The optomechanical coupling mainly originates from the overlap between the strain component Syy = ∂uy/∂y and the electric field component Ey in this structure. Credit: Science Advances (2023). DOI: 10.1126/sciadv.abp8892

Characterization of the fabricated optomechanical zipper cavity. (A) Experimental setup schematic. VOA, variable optical attenuator; PC, polarization controller; EOM, electro-optic modulator; VNA, vector network analyzer; FBS, fiber beam splitter; PM, power meter; OS, optical switch; PD, photodetector; ESA, electric spectrum analyzer. (B) Low–input power optical transmission spectrum. The first (1534.9 nm) and second (1543 nm) resonant dips correspond to odd and even optical modes, respectively. (C) Amplitude response of S21. k values at high optical power and detuning Δ are deduced from this response. (D) PSD of mechanical spectrum after subtracting the background noise, obtained under the same condition in (C). Green dashed line represents intrinsic resonant frequency of both mechanical oscillators. (B to D) Black solid lines represent fitting results. Credit: Science Advances (2023). DOI: 10.1126/sciadv.abp8892

The evolution of mechanical modes. (A and B) PSD of mechanical spectra after subtracting the background noise when optical detuning is scanned with fixed laser power Pin = 11 dBm and Pin = 13 dBm, respectively. Black solid lines represent fit to experimental data. (C and D) Mechanical resonant frequencies ω±/2π versus the optical detuning Δ, deduced from the spectra in (A) and (B), respectively. (E and F) Mechanical dissipation rate γ±/2π versus the optical detuning Δ, deduced from the spectra in (A) and (B), respectively; (C to F) square markers correspond to fitting results of experimental spectra, and blue and red lines are theoretical results using the linear approximation. Credit: Science Advances (2023). DOI: 10.1126/sciadv.abp8892

Characterization of the experimental results near the mechanical EP. (A) Resonant frequencies ω±/2π and (B) dissipation rate γ±/2π of mechanical modes versus detuning Δ and intracavity photon number ncav. (C) Amplitude of eigenvalue splitting S versus the dissipative and coherent coupling strength. In (A) to (C), topology surfaces are calculated from the theoretical model using parameters deduced from experimental results. Blue and red points are experimental results. (D) Distribution of the experimental data (circle markers) in parameter space. (E) Amplitude of eigenvalue splitting S versus amplitude of perturbation ε. Inset shows alternative logarithmic scale presentation where the 1/2 order response corresponds to the line with slope = 1/2. (A to D) Green point corresponds to an EP. Credit: Science Advances (2023). DOI: 10.1126/sciadv.abp8892