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Strong Optomechanical Interaction in Hybrid Plasmonic-Photonic Crystal Nanocavities with Surface Acoustic Waves.

Lin TR, Lin CH, Hsu JC - Sci Rep (2015)

Bottom Line: The crystal nanocavity used in this study consisted of a defective photonic crystal beam coupled to a metal surface with a nanoscale air gap in between and provided hybridization of a highly confined plasmonic-photonic mode with a high quality factor and deep subwavelength mode volume.Efficient photon-phonon interaction occurs in the air gap through the SAW perturbation of the metal surface, strongly coupling the optical and acoustic frequencies.As a result, a large modulation bandwidth and optical resonance wavelength shift for the crystal nanocavity are demonstrated at telecommunication wavelengths.

View Article: PubMed Central - PubMed

Affiliation: National Taiwan Ocean University, Department of Mechanical and Mechatronic Engineering, Keelung, 20224, Taiwan.

ABSTRACT
We propose dynamic modulation of a hybrid plasmonic-photonic crystal nanocavity using monochromatic coherent acoustic phonons formed by ultrahigh-frequency surface acoustic waves (SAWs) to achieve strong optomechanical interaction. The crystal nanocavity used in this study consisted of a defective photonic crystal beam coupled to a metal surface with a nanoscale air gap in between and provided hybridization of a highly confined plasmonic-photonic mode with a high quality factor and deep subwavelength mode volume. Efficient photon-phonon interaction occurs in the air gap through the SAW perturbation of the metal surface, strongly coupling the optical and acoustic frequencies. As a result, a large modulation bandwidth and optical resonance wavelength shift for the crystal nanocavity are demonstrated at telecommunication wavelengths. The proposed SAW-based modulation within the hybrid plasmonic-photonic crystal nanocavities beyond the diffraction limit provides opportunities for various applications in enhanced sound-light interaction and fast coherent acoustic control of optomechanical devices.

No MeSH data available.


/E/2 field distribution of the SPP cavity mode with d = 20 nm perturbed by the 3-GHz traveling SAWs at the chosen phase shown in Fig. 5a. The perturbed /E/2 field has a redistributed asymmetric concentration pattern.The resulting shift is Δλr = 1.07 nm with a resonance wavelength λr = 1549.78 nm.
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f6: /E/2 field distribution of the SPP cavity mode with d = 20 nm perturbed by the 3-GHz traveling SAWs at the chosen phase shown in Fig. 5a. The perturbed /E/2 field has a redistributed asymmetric concentration pattern.The resulting shift is Δλr = 1.07 nm with a resonance wavelength λr = 1549.78 nm.

Mentions: To relate the resonance wavelength shift Δλr of the SPP cavity mode perturbed by the SAW field to the resonant mode characteristics, their trends as a function of the air-gap width d were compared. The SAW field lay in an arbitrarily chosen phase relative to the unperturbed SPP cavity mode, as shown in Fig. 5a,b. Figure 5c shows the resonance wavelength λr of the SPP cavity mode with different air gap width d and the corresponding shift Δλr which was perturbed by the 3-GHz SAWs with a restricted amplitude of Uy = 4 nm. When the air gap d was increased, the resonance wavelength decreased because the coupling of the silicon photonic mode and surface plasmonic mode was reduced with a decreased effective index4754, and the wavelength shift was smaller because the interface effect at larger d values becomes weaker for photon-phonon interaction. The dependences of the Q factor, mode volume Vm, inverse of mode volume 1/Vm, and Q/Vm ratio on gap width d for the SPP cavity mode are shown in Fig. 5d,e. Figure 5e exhibits a positive correlation between the 1/Vm and Q/Vm ratio and wavelength shift Δλr from Fig. 5c, while the influence of the strength of the interface effect was dominated by the low optical mode volume because small Vm is susceptible to the deformation. The SAW field also broke the symmetry of the cavity geometry, resulting in an asymmetric SPP cavity mode shape. Figure 6 illustrate the /E/2 field distribution of the SPP cavity mode with d = 20 nm perturbed by the SAW field. The perturbed /E/2 field has a redistributed concentration pattern, corresponding to a wavelength shift Δλr of 1.07 nm (λr = 1549.78 nm).


Strong Optomechanical Interaction in Hybrid Plasmonic-Photonic Crystal Nanocavities with Surface Acoustic Waves.

Lin TR, Lin CH, Hsu JC - Sci Rep (2015)

/E/2 field distribution of the SPP cavity mode with d = 20 nm perturbed by the 3-GHz traveling SAWs at the chosen phase shown in Fig. 5a. The perturbed /E/2 field has a redistributed asymmetric concentration pattern.The resulting shift is Δλr = 1.07 nm with a resonance wavelength λr = 1549.78 nm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4561905&req=5

f6: /E/2 field distribution of the SPP cavity mode with d = 20 nm perturbed by the 3-GHz traveling SAWs at the chosen phase shown in Fig. 5a. The perturbed /E/2 field has a redistributed asymmetric concentration pattern.The resulting shift is Δλr = 1.07 nm with a resonance wavelength λr = 1549.78 nm.
Mentions: To relate the resonance wavelength shift Δλr of the SPP cavity mode perturbed by the SAW field to the resonant mode characteristics, their trends as a function of the air-gap width d were compared. The SAW field lay in an arbitrarily chosen phase relative to the unperturbed SPP cavity mode, as shown in Fig. 5a,b. Figure 5c shows the resonance wavelength λr of the SPP cavity mode with different air gap width d and the corresponding shift Δλr which was perturbed by the 3-GHz SAWs with a restricted amplitude of Uy = 4 nm. When the air gap d was increased, the resonance wavelength decreased because the coupling of the silicon photonic mode and surface plasmonic mode was reduced with a decreased effective index4754, and the wavelength shift was smaller because the interface effect at larger d values becomes weaker for photon-phonon interaction. The dependences of the Q factor, mode volume Vm, inverse of mode volume 1/Vm, and Q/Vm ratio on gap width d for the SPP cavity mode are shown in Fig. 5d,e. Figure 5e exhibits a positive correlation between the 1/Vm and Q/Vm ratio and wavelength shift Δλr from Fig. 5c, while the influence of the strength of the interface effect was dominated by the low optical mode volume because small Vm is susceptible to the deformation. The SAW field also broke the symmetry of the cavity geometry, resulting in an asymmetric SPP cavity mode shape. Figure 6 illustrate the /E/2 field distribution of the SPP cavity mode with d = 20 nm perturbed by the SAW field. The perturbed /E/2 field has a redistributed concentration pattern, corresponding to a wavelength shift Δλr of 1.07 nm (λr = 1549.78 nm).

Bottom Line: The crystal nanocavity used in this study consisted of a defective photonic crystal beam coupled to a metal surface with a nanoscale air gap in between and provided hybridization of a highly confined plasmonic-photonic mode with a high quality factor and deep subwavelength mode volume.Efficient photon-phonon interaction occurs in the air gap through the SAW perturbation of the metal surface, strongly coupling the optical and acoustic frequencies.As a result, a large modulation bandwidth and optical resonance wavelength shift for the crystal nanocavity are demonstrated at telecommunication wavelengths.

View Article: PubMed Central - PubMed

Affiliation: National Taiwan Ocean University, Department of Mechanical and Mechatronic Engineering, Keelung, 20224, Taiwan.

ABSTRACT
We propose dynamic modulation of a hybrid plasmonic-photonic crystal nanocavity using monochromatic coherent acoustic phonons formed by ultrahigh-frequency surface acoustic waves (SAWs) to achieve strong optomechanical interaction. The crystal nanocavity used in this study consisted of a defective photonic crystal beam coupled to a metal surface with a nanoscale air gap in between and provided hybridization of a highly confined plasmonic-photonic mode with a high quality factor and deep subwavelength mode volume. Efficient photon-phonon interaction occurs in the air gap through the SAW perturbation of the metal surface, strongly coupling the optical and acoustic frequencies. As a result, a large modulation bandwidth and optical resonance wavelength shift for the crystal nanocavity are demonstrated at telecommunication wavelengths. The proposed SAW-based modulation within the hybrid plasmonic-photonic crystal nanocavities beyond the diffraction limit provides opportunities for various applications in enhanced sound-light interaction and fast coherent acoustic control of optomechanical devices.

No MeSH data available.