Photonics Research, Volume. 8, Issue 6, 844(2020)
Optomechanical cooling and self-stabilization of a waveguide coupled to a whispering-gallery-mode resonator
Fig. 1. Nanospike coupled to a WGM bottle resonator. (a) Sketch of the experimental setup. NS, nanospike; BR, bottle resonator; QPD, quadrant photodiode; PD, photodiode. (b) Optical micrograph of the nanospike coupled to a WGM resonator from the side. (c) Micrograph of a bottle resonator when the laser light is locked into resonance, light being launched from the right. The weak signal radiated by the bottle resonator on resonance could be used to image the near-field of the optical mode using a microscope objective and a sensitive NIR camera. (d) Zoom-in of one of the measured optical mode profiles compared with the result of finite element simulations.
Fig. 2. Optomechanical cooling of nanospike motion. (a) Measured mechanical power spectrum in the vicinity of the fundamental (flexural) nanospike mode for five different pump powers. Inset: measured power spectrum for vibrations parallel to the surface (see text) for 0 and 250 μW pump power. The solid lines are Lorentzian fits. (b) Mechanical linewidth (left axis) and inferred effective temperature
Fig. 3. (a) Temporal motion of the nanospike for different launching pump powers (sampling rate 20 kHz). (b) Histogram plots of the nanospike displacements. (c) Mean-squared displacements of the nanospike as a function of pump power. (d) and (e) 50 consecutive measurements of a cavity resonance observed with the second probe laser (1550 nm) when
Fig. 4. (a) Measured frequency shift of the fundamental flexural mode of the nanospike coupled to a WGM resonator with a diameter of 350 μm, plotted against laser detuning for a launched power of 70 μW (blue dots). The solid line is a fit to the model for generalized optomechanical coupling. Inset: nanospike deflection as a function of time when the pump power was raised just above the threshold for self-oscillation for a laser detuning of 1.6 MHz. (b) Measured mechanical frequency as a function of laser detuning for mechanical oscillation of the nanospike parallel (
Fig. 5. (a) Measured frequency shift (left axis) and linewidth (right axis) for the excited WGM plotted against nanospike position. The solid lines are fits to the data using exponential functions. (b) Coupling parameters
Fig. 6. (a) Dissipative coupling parameter
Fig. 7. Measured resonant frequency shift over time for bottle-resonators with diameters (a) 350 μm and (b) 40 μm. Fitting the data to exponential functions (solid lines) yields thermal time constants (a)
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Riccardo Pennetta, Shangran Xie, Richard Zeltner, Jonas Hammer, Philip St. J. Russell. Optomechanical cooling and self-stabilization of a waveguide coupled to a whispering-gallery-mode resonator[J]. Photonics Research, 2020, 8(6): 844
Category: Physical Optics
Received: Oct. 10, 2019
Accepted: Mar. 27, 2020
Published Online: May. 7, 2020
The Author Email: Riccardo Pennetta (riccardo.pennetta@mpl.mpg.de)