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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.


(a) TSAW and (b) SSAW schemes with fSAW = 4 GHz at different phases, where the TSAWs propagate their energy forward, and the SSAWs remain in constant positions with no net propagation of acoustic energy. (c) Evolution of the resonance wavelength λr by changing the 4-GHz TSAW phase θT. The inset shows the status θT = 0. (d) Evolution of the resonance wavelength λr perturbed by 4-GHz SSAW fields with different nodal points (corresponding to the instant of time at θT = π/2 and θT = 3π/5 and 2π/5 that determine the upper and lower bounds of the changes of λr) as a function of SSAW phase θS.
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f8: (a) TSAW and (b) SSAW schemes with fSAW = 4 GHz at different phases, where the TSAWs propagate their energy forward, and the SSAWs remain in constant positions with no net propagation of acoustic energy. (c) Evolution of the resonance wavelength λr by changing the 4-GHz TSAW phase θT. The inset shows the status θT = 0. (d) Evolution of the resonance wavelength λr perturbed by 4-GHz SSAW fields with different nodal points (corresponding to the instant of time at θT = π/2 and θT = 3π/5 and 2π/5 that determine the upper and lower bounds of the changes of λr) as a function of SSAW phase θS.

Mentions: The strength of the optomechanical interaction also highly correlated to the wavelength of the SAW field. We examined the nanocavity modulation at several SAW frequencies (2, 3, 4, and 5 GHz) corresponding to different SAW wavelengths (λSAW = 1.78a, 1.15a, 0.91a, and 0.67a, respectively). Table 1 lists the unperturbed resonance wavelength λr and Δλr and Δλc of the SPP cavity mode under the perturbation of the SAW fields with different frequencies and phases based on the TSAW scheme. The SAW field of 4-GHz frequency exhibited the strongest modulation for the optical resonance wavelength shift and total bandwidth, which correspond to Δλr = 8.58 nm and Δλc = 13.95 nm, respectively. The wavelength of the 4-GHz SAW field closely matches the spacing of the two closest nodal points of the /E/2 field profile of the SPP cavity mode, demonstrating the condition (wavelength matching) which maximizes the interface effect for the photon-phonon interaction. The modulation using the SSAW scheme can be derived from the results of TSAW scheme. Figure 8a,b compare the traveling and standing SAW schemes, respectively. The TSAWs propagate their acoustic energy forward, whereas SSAWs remained in a constant position with no net propagation of acoustic energy. Figure 8c illustrates the resonance wavelength variations of the SPP cavity mode perturbed by the 4-GHz SSAW field with different phases (Fig. 8a) related to that perturbed by a TSAW field of the same frequency and maximum amplitude. The inset of Fig. 8c shows the spatial relation between the TSAW and SPP cavity mode. Figure 8d corresponds to the SSAW fields with nodal points located at the middle of the cavity and 0.3λSAW from it, respectively. Then these two SSAW fields can be regarded as identical to the TSAW fields at the instant of time at which the phase are θT = π/2 and θT = 3π/5 and 2π/5, respectively. As a result, the upper and lower bounds for the range of λr variation caused by a SSAW field can be determined using Fig. 8c with the corresponding values of θT.


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

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

(a) TSAW and (b) SSAW schemes with fSAW = 4 GHz at different phases, where the TSAWs propagate their energy forward, and the SSAWs remain in constant positions with no net propagation of acoustic energy. (c) Evolution of the resonance wavelength λr by changing the 4-GHz TSAW phase θT. The inset shows the status θT = 0. (d) Evolution of the resonance wavelength λr perturbed by 4-GHz SSAW fields with different nodal points (corresponding to the instant of time at θT = π/2 and θT = 3π/5 and 2π/5 that determine the upper and lower bounds of the changes of λr) as a function of SSAW phase θS.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f8: (a) TSAW and (b) SSAW schemes with fSAW = 4 GHz at different phases, where the TSAWs propagate their energy forward, and the SSAWs remain in constant positions with no net propagation of acoustic energy. (c) Evolution of the resonance wavelength λr by changing the 4-GHz TSAW phase θT. The inset shows the status θT = 0. (d) Evolution of the resonance wavelength λr perturbed by 4-GHz SSAW fields with different nodal points (corresponding to the instant of time at θT = π/2 and θT = 3π/5 and 2π/5 that determine the upper and lower bounds of the changes of λr) as a function of SSAW phase θS.
Mentions: The strength of the optomechanical interaction also highly correlated to the wavelength of the SAW field. We examined the nanocavity modulation at several SAW frequencies (2, 3, 4, and 5 GHz) corresponding to different SAW wavelengths (λSAW = 1.78a, 1.15a, 0.91a, and 0.67a, respectively). Table 1 lists the unperturbed resonance wavelength λr and Δλr and Δλc of the SPP cavity mode under the perturbation of the SAW fields with different frequencies and phases based on the TSAW scheme. The SAW field of 4-GHz frequency exhibited the strongest modulation for the optical resonance wavelength shift and total bandwidth, which correspond to Δλr = 8.58 nm and Δλc = 13.95 nm, respectively. The wavelength of the 4-GHz SAW field closely matches the spacing of the two closest nodal points of the /E/2 field profile of the SPP cavity mode, demonstrating the condition (wavelength matching) which maximizes the interface effect for the photon-phonon interaction. The modulation using the SSAW scheme can be derived from the results of TSAW scheme. Figure 8a,b compare the traveling and standing SAW schemes, respectively. The TSAWs propagate their acoustic energy forward, whereas SSAWs remained in a constant position with no net propagation of acoustic energy. Figure 8c illustrates the resonance wavelength variations of the SPP cavity mode perturbed by the 4-GHz SSAW field with different phases (Fig. 8a) related to that perturbed by a TSAW field of the same frequency and maximum amplitude. The inset of Fig. 8c shows the spatial relation between the TSAW and SPP cavity mode. Figure 8d corresponds to the SSAW fields with nodal points located at the middle of the cavity and 0.3λSAW from it, respectively. Then these two SSAW fields can be regarded as identical to the TSAW fields at the instant of time at which the phase are θT = π/2 and θT = 3π/5 and 2π/5, respectively. As a result, the upper and lower bounds for the range of λr variation caused by a SSAW field can be determined using Fig. 8c with the corresponding values of θT.

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.