Resonators|10 Article(s)
High-Q ring resonators directly written in As2S3 chalcogenide glass films
Shahar Levy, Matvei Klebanov, and Avi Zadok
Planar ring resonator waveguides are fabricated in thin films of As2S3 chalcogenide glass, deposited on silica-on-silicon substrates. Waveguide cores are directly written by scanning the focused illumination of a femtosecond Ti:sapphire laser at a central wavelength of 810 nm, through a two-photon photo-darkening process. A large photo-induced index change of 0.3–0.4 refractive index units is obtained. The radius of the ring resonator is 1.9 mm, corresponding to a transmission free spectral range of 9.1 GHz. A high loaded (intrinsic) Q value of 110,000 (180,000) is achieved. The thermal dependence of the resonator transfer function is characterized. The results provide the first report, to the best of our knowledge, of directly written high-Q ring resonators in chalcogenide glass films, and demonstrate the potential of this simple technique towards the fabrication of planar lightguide circuits in these materials.
Photonics Research
  • Publication Date: Apr. 06, 2015
  • Vol. 3, Issue 3, 03000063 (2015)
Experimental observation of Fano-like resonance in a whispering-gallery-mode microresonator in aqueous environment
Yan-Lei Shang, Ming-Yong Ye, and Xiu-Min Lin
Photonics Research
  • Publication Date: Mar. 01, 2017
  • Vol. 5, Issue 2, 02000119 (2017)
Bandpass transmission spectra of a whispering-gallery microcavity coupled to an ultrathin fiber
Fuchuan Lei, Rafino M. J. Murphy, Jonathan M. Ward, Yong Yang, and Síle Nic Chormaic
Tapered fibers with diameters ranging from 1 to 4 μm are widely used to excite the whispering-gallery (WG) modes of microcavities. Typically, the transmission spectrum of a WG cavity coupled to a waveguide around a resonance assumes a Lorentzian dip morphology due to resonant absorption of the light within the cavity. In this paper, we demonstrate that the transmission spectra of a WG cavity coupled with an ultrathin fiber (500–700 nm) may exhibit both Lorentzian dips and peaks, depending on the gap between the fiber and the microcavity. By considering the large scattering loss of off-resonant light from the fiber within the coupling region, this phenomenon can be attributed to partially resonant light bypassing the lossy scattering region via WG modes, allowing it to be coupled both to and from the cavity, then manifesting as Lorentzian peaks within the transmission spectra. This implies the system could be implemented within a bandpass filter framework.
Photonics Research
  • Publication Date: Jul. 18, 2017
  • Vol. 5, Issue 4, 04000362 (2017)
Chimera states in plasmonic nanoresonators
Eesa Rahimi, and Kürşat Şendur
The chimera state is the concurrent combination of synchronous and incoherent oscillations in a set of identical oscillators. In this study, we demonstrate the states for optical nanoresonators where the oscillators are designed based on a plasmonic dimer cavity. This resonator interchanges radiative energy with an active medium located at its hotspot, and therefore forms an amplitude-mediated oscillating system. Finite-difference time-domain (FDTD)-based numerical analysis of a circular array of the coupled oscillators reveals that regardless of identical nature, oscillator phase is not concordant over time for all members. The effect of coupling strength on the phase escape/synchronization of the oscillators is investigated for the plasmonic nanoresonator system. It is shown that for identical oscillators, which are placed symmetrically over the perimeter of a disc, the array can be divided to several subgroups of concurrent coherent and incoherent members. While the oscillator of each subgroup seems to be locked together, one member can escape from synchronization for a while and return to coherency, or it can sync with the other groups. The effect of coupling strength and number of oscillators on the phase-escape pace is studied for this system, and strong coupling is shown to force the array members to fully synchronize while weaker coupling causes chimera states in the array.
Photonics Research
  • Publication Date: Apr. 23, 2018
  • Vol. 6, Issue 5, 05000427 (2018)
Theoretical aspects and sensing demonstrations of cone-shaped inwall capillary-based microsphere resonators
Xiaobei Zhang, Yong Yang, Huawen Bai, Jiawei Wang, Ming Yan, Hai Xiao, and Tingyun Wang
In this paper, a detailed theoretical study on the characteristics of cone-shaped inwall capillary-based microsphere resonators is described and demonstrated for sensing applications. The maximum, minimum, slope, contrast, and width of the Fano resonance are analyzed. As the transmission coefficient of the capillary resonator increases, the absolute value of the slope of Fano resonances increases to reach its maximum, which is useful for sensors with an ultra-high sensitivity. There occurs another phenomenon of electromagnetically induced transparency when the reflectivity at the capillary–environment interface is close to 100%. We also experimentally demonstrated its capability for temperature and refractive index sensing, with a sensitivity of 10.9 pm/°C and 431 dB/RIU based on the Fano resonance and the Lorentzian line shape, respectively.
Photonics Research
  • Publication Date: Aug. 27, 2017
  • Vol. 5, Issue 5, 05000516 (2017)
Surface-enhanced Raman scattering on dielectric microspheres with whispering gallery mode resonance
Steven H. Huang, Xuefeng Jiang, Bo Peng, Corey Janisch, Alexander Cocking, Şahin Kaya Özdemir, Zhiwen Liu, and Lan Yang
Conventionally, metallic nanostructures are used for surface-enhanced Raman spectroscopy (SERS), but recently there has been increasing interest in the enhancement of Raman scattering from dielectric substrates due to their improved stability and biocompatibility compared with metallic substrates. Here, we report the observation of enhanced Raman scattering from rhodamine 6G molecules coated on silica microspheres. We excite the whispering gallery modes (WGMs) supported in the microspheres with a tapered fiber coupler for efficient WGM excitation, and the Raman enhancement can be attributed to the WGM mechanism. Strong resonance enhancement in pump laser intensity and modified Raman emission from the Purcell effect in the microsphere resonator are observed from the experiment and compared with theoretical results. A total Raman enhancement factor of 1.4×104 is observed, with contribution mostly from the enhancement in pump laser intensity. Our results show that, with an efficient pumping scheme, dielectric microspheres are a viable alternative to metallic SERS substrates.
Photonics Research
  • Publication Date: Apr. 04, 2018
  • Vol. 6, Issue 5, 05000346 (2018)
Experimental demonstration of dissipative sensing in a self-interference microring resonator
Shuai Wan, Rui Niu, Hong-Liang Ren, Chang-Ling Zou, Guang-Can Guo, and Chun-Hua Dong
The dissipative sensing based on a self-interference microring resonator composed of a microring resonator and a U-shaped feedback waveguide is demonstrated experimentally. Instead of a frequency shift induced by the phase shift of the waveguide or the microcavity, the dissipative sensing converts the phase shift to the effective external coupling rate, which leads to the change of linewidth of the optical resonance and the extinction ratio in the transmission spectrum. In our experiment, the power dissipated from a microheater on the feedback waveguide is detected by the dissipative sensing mechanism, and the sensitivity of our device can achieve 0.22 dB/mW. This dissipative sensing mechanism provides another promising candidate for microcavity sensing applications.
Photonics Research
  • Publication Date: Jun. 11, 2018
  • Vol. 6, Issue 7, 07000681 (2018)
Electric field tunable strong transverse light current from nanoparticles embedded in liquid crystal
Jinhua Li, and Xiangdong Zhang
Photonics Research
  • Publication Date: May. 24, 2018
  • Vol. 6, Issue 6, 06000630 (2018)
Loss-induced control of light propagation direction in passive linear coupled optical cavities
Carlo Edoardo Campanella, Martino De Carlo, Antonello Cuccovillo, and Vittorio M. N. Passaro
Redirecting the flow of light on the basis of the absorption/gain properties of optical systems is of great interest in many research fields, ranging from optical routing to optical cloaking. In this paper we investigate the control of the direction of the light propagation through loss-induced absorption in passive linear coupled optical systems. The considered optical system consists of a mode-splitting resonant cavity formed by coupling a Fabry–Perot (FP) cavity with a ring resonator. The coalescence of the asymmetric resonances, generated through mode-splitting dynamics, is the spectral result of the parity time symmetry breaking at FP resonance wavelengths. For specific values of the FP overall loss, a predominant backward propagation in the FP ring resonator occurs. In fiber optics technology, this device shows an ability to invert the sense of propagation of the light, quantified through the contrast ratio, in the order of 20 dB. This value can be obtained by externally varying the FP loss coefficient for a fixed set of the other physical parameters of the FP ring resonator. Our results can open a new way toward novel high-performance optical modulation and routing schemes.
Photonics Research
  • Publication Date: Apr. 27, 2018
  • Vol. 6, Issue 6, 06000525 (2018)