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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) Schematic of optimization for the crystal nanocavity by shifting the two neighbor circular holes of the defect region outward from their lattice point by a distance s. (b) The electric field intensity /E/2 distributions with s = 0 and 0.125a, where the mode mismatch with s = 0.125a is reduced to achieve a higher Q factor. (c) Variations of Q and Vm as a function of the shift distance s. (d) Variations of λr and Δλr with the increasing of s under the perturbation of 4-GHz TSAW field of amplitude Uy = 4 nm at θT = 0, where the maximum Δλr occurs at s = 0.1a.
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f9: (a) Schematic of optimization for the crystal nanocavity by shifting the two neighbor circular holes of the defect region outward from their lattice point by a distance s. (b) The electric field intensity /E/2 distributions with s = 0 and 0.125a, where the mode mismatch with s = 0.125a is reduced to achieve a higher Q factor. (c) Variations of Q and Vm as a function of the shift distance s. (d) Variations of λr and Δλr with the increasing of s under the perturbation of 4-GHz TSAW field of amplitude Uy = 4 nm at θT = 0, where the maximum Δλr occurs at s = 0.1a.

Mentions: To achieve a stronger optomechanical effect with a more sophisticated optical nanocavity, we optimized the crystal nanocavity by shifting the two neighbor circular air holes of the defect region outward from their lattice point by a distance s, as shown in Fig. 9a. Compared with the case of s = 0, Fig. 9b shows that the electric field intensity /E/2 with s = 0.125a has reduced mode mismatch with a larger cavity length so that the Q factor is increased. Figures 9c shows the variations in the quality factor Q and mode volume Vm as functions of the shift distance s. Increasing the distance s from 0 to 0.125a increased the resonance wavelength and Q factor, while the mode volume Vm was not significantly influenced. The highest Q/Vm ratio occurred at s = 0.125a. The variations of λr and Δλr with increasing s under the perturbation of the 4-GHz SAW field of amplitude Uy = 4 nm with θT = 0 are shown in Fig. 9d. The refined effective cavity length further improves the SPP confinement to increase the wavelength shift Δλr by the SAW field. With s = 0.1a, the wavelength shift Δλr achieved 9.16 nm. Q and Vm can be further increased and reduced, respectively, to boost the optomechanical interaction or photon-phonon interaction by optimizing the overall geometry of the SAW-based tuning nanocavity structure, when optical losses and air gap width are optimized. The ultrahigh-frequency SAW field can also be tailored to provide a resonant phonon intensity distribution that closely resembles or correlates to the spatial mode profile of the hybrid optical field using phononic bandgap structures to enhance the multiphonon absorption and emission by a photon and to increase the photon-phonon interaction time555657.


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

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

(a) Schematic of optimization for the crystal nanocavity by shifting the two neighbor circular holes of the defect region outward from their lattice point by a distance s. (b) The electric field intensity /E/2 distributions with s = 0 and 0.125a, where the mode mismatch with s = 0.125a is reduced to achieve a higher Q factor. (c) Variations of Q and Vm as a function of the shift distance s. (d) Variations of λr and Δλr with the increasing of s under the perturbation of 4-GHz TSAW field of amplitude Uy = 4 nm at θT = 0, where the maximum Δλr occurs at s = 0.1a.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f9: (a) Schematic of optimization for the crystal nanocavity by shifting the two neighbor circular holes of the defect region outward from their lattice point by a distance s. (b) The electric field intensity /E/2 distributions with s = 0 and 0.125a, where the mode mismatch with s = 0.125a is reduced to achieve a higher Q factor. (c) Variations of Q and Vm as a function of the shift distance s. (d) Variations of λr and Δλr with the increasing of s under the perturbation of 4-GHz TSAW field of amplitude Uy = 4 nm at θT = 0, where the maximum Δλr occurs at s = 0.1a.
Mentions: To achieve a stronger optomechanical effect with a more sophisticated optical nanocavity, we optimized the crystal nanocavity by shifting the two neighbor circular air holes of the defect region outward from their lattice point by a distance s, as shown in Fig. 9a. Compared with the case of s = 0, Fig. 9b shows that the electric field intensity /E/2 with s = 0.125a has reduced mode mismatch with a larger cavity length so that the Q factor is increased. Figures 9c shows the variations in the quality factor Q and mode volume Vm as functions of the shift distance s. Increasing the distance s from 0 to 0.125a increased the resonance wavelength and Q factor, while the mode volume Vm was not significantly influenced. The highest Q/Vm ratio occurred at s = 0.125a. The variations of λr and Δλr with increasing s under the perturbation of the 4-GHz SAW field of amplitude Uy = 4 nm with θT = 0 are shown in Fig. 9d. The refined effective cavity length further improves the SPP confinement to increase the wavelength shift Δλr by the SAW field. With s = 0.1a, the wavelength shift Δλr achieved 9.16 nm. Q and Vm can be further increased and reduced, respectively, to boost the optomechanical interaction or photon-phonon interaction by optimizing the overall geometry of the SAW-based tuning nanocavity structure, when optical losses and air gap width are optimized. The ultrahigh-frequency SAW field can also be tailored to provide a resonant phonon intensity distribution that closely resembles or correlates to the spatial mode profile of the hybrid optical field using phononic bandgap structures to enhance the multiphonon absorption and emission by a photon and to increase the photon-phonon interaction time555657.

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.