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Scattering|3 Article(s)
Impact of nanoparticle-induced scattering of an azimuthally propagating mode on the resonance of whispering gallery microcavities
Junda Zhu, Ying Zhong, and Haitao Liu
Optical whispering gallery microcavities with high-quality factors have shown great potential toward achieveing ultrahigh-sensitivity sensing up to a single molecule or nanoparticle, which raises a huge demand on a deep theoretical insight into the crucial phenomena such as the mode shift, mode splitting, and mode broadening in sensing experiments. Here we propose an intuitive model to analyze these phenomena from the viewpoint of the nanoparticle-induced multiple scattering of the azimuthally propagating mode (APM). The model unveils explicit relations between these phenomena and the phase change and energy loss of the APM when scattered at the nanoparticle; the model also explains the observed polarization-dependent preservation of one resonance and the particle-dependent redshift or blueshift. The model indicates that the particle-induced coupling between the pair of unperturbed degenerate whispering gallery modes (WGMs) and the coupling between the WGMs and the free-space radiation modes, which are widely adopted in current theoretical formalisms, are realized via the reflection and scattering-induced free-space radiation of the APM, respectively, and additionally exhibits the contribution of cross coupling between the unperturbed WGMs and other different WGMs to forming the splitting resonant modes, especially for large particles. Optical whispering gallery microcavities with high-quality factors have shown great potential toward achieveing ultrahigh-sensitivity sensing up to a single molecule or nanoparticle, which raises a huge demand on a deep theoretical insight into the crucial phenomena such as the mode shift, mode splitting, and mode broadening in sensing experiments. Here we propose an intuitive model to analyze these phenomena from the viewpoint of the nanoparticle-induced multiple scattering of the azimuthally propagating mode (APM). The model unveils explicit relations between these phenomena and the phase change and energy loss of the APM when scattered at the nanoparticle; the model also explains the observed polarization-dependent preservation of one resonance and the particle-dependent redshift or blueshift. The model indicates that the particle-induced coupling between the pair of unperturbed degenerate whispering gallery modes (WGMs) and the coupling between the WGMs and the free-space radiation modes, which are widely adopted in current theoretical formalisms, are realized via the reflection and scattering-induced free-space radiation of the APM, respectively, and additionally exhibits the contribution of cross coupling between the unperturbed WGMs and other different WGMs to forming the splitting resonant modes, especially for large particles.
Photonics Research
- Publication Date: Jul. 01, 2017
- Vol. 5, Issue 5, 05000396 (2017)
Raman tensor of AlN bulk single crystal
Wei Zheng, Ruisheng Zheng, Feng Huang, Honglei Wu, and Fadi Li
The angle dependence of optical phonon modes of an AlN bulk single crystal from the m-plane (1100) and c-plane (0001) surfaces, respectively, is investigated by polarized Raman spectroscopy in a backscattering configuration at room temperature. Corresponding Raman selection rules are derived according to measured scattering geometries to illustrate the angle dependence. The angle-dependent intensities of phonon modes are discussed and compared to theoretical scattering intensities, yielding the Raman tensor elements of A1(TO), E22 , E1(TO), and A1(LO) phonon modes and the relative phase difference between the two complex elements of A1_TO_. Furthermore, the Raman tensor of wurtzite AlN is compared with that of wurtzite ZnO reported in previous work, revealing the intrinsic differences of lattice vibration dynamics between AlN and ZnO. The angle dependence of optical phonon modes of an AlN bulk single crystal from the m-plane (1100) and c-plane (0001) surfaces, respectively, is investigated by polarized Raman spectroscopy in a backscattering configuration at room temperature. Corresponding Raman selection rules are derived according to measured scattering geometries to illustrate the angle dependence. The angle-dependent intensities of phonon modes are discussed and compared to theoretical scattering intensities, yielding the Raman tensor elements of A1(TO), E22 , E1(TO), and A1(LO) phonon modes and the relative phase difference between the two complex elements of A1_TO_. Furthermore, the Raman tensor of wurtzite AlN is compared with that of wurtzite ZnO reported in previous work, revealing the intrinsic differences of lattice vibration dynamics between AlN and ZnO.
Photonics Research
- Publication Date: Mar. 17, 2015
- Vol. 3, Issue 2, 02000038 (2015)
Polarization behavior of elastic scattering from a silicon microsphere coupled to an optical fiber
Mohammed Sharif Murib, Emre Yuce, Oguzhan Gurlu, and and Ali Serpenguzel
The polarization behavior of elastic scattering at 1473 nm is analyzed from a silicon microsphere on an optical fiber half-coupler. The 0.27 nm angular mode spacing of the resonances correlates well with the optical size of the silicon sphere. The spectral linewidths of the resonances are on the order of 10-3 nm, which corresponds to quality factors on the order of 106. The transverse magnetically polarized elastic scattering signal has higher resonance to modulation depth and background ratio than the transverse electrically polarized elastic scattering signal and is suitable for high-resolution optical filtering applications such as optical monitoring and sensing. The polarization behavior of elastic scattering at 1473 nm is analyzed from a silicon microsphere on an optical fiber half-coupler. The 0.27 nm angular mode spacing of the resonances correlates well with the optical size of the silicon sphere. The spectral linewidths of the resonances are on the order of 10-3 nm, which corresponds to quality factors on the order of 106. The transverse magnetically polarized elastic scattering signal has higher resonance to modulation depth and background ratio than the transverse electrically polarized elastic scattering signal and is suitable for high-resolution optical filtering applications such as optical monitoring and sensing.
Photonics Research
- Publication Date: Jan. 01, 2014
- Vol. 2, Issue 2, 02000045 (2014)
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