Le 26/08/2016 par jayjoe1010 :
The holding of photons in low-refraction-index materials is thought to be difficult in conventional photonic structures that employ total internal depiction. Specifically, the whispering gallery mode (WGM) microcavity, which is an important optical component, has to rely on a refraction index with high contrast to the surrounding environment to manifest excellent light confinement. A team led by Mentor Yun-Feng Xiao at Peking University collaborated with researchers from the Harbin Institute of Technology, and demonstrated that an optical microcavity structure consisting of a low-refraction-index silica microtoroid that was directly bonded on a high-refraction-index silicon substrate supports high-Q fundamental WGMs. This work has been [url=http://www.antyco.com]LBO crystal[/url] published in a recent issue of Optica. Among on-chip resonators, high-refraction-index microcavities usually have quality [url=http://www.antyco.com]Color Filter Glass[/url] factors no more than a million, which becomes an barrier to applications in the fields of on-chip nonlinearity and quantum manipulation, etc. When compared, low-refraction-index materials have advantages in many aspects, especially in the fabrication of high-Q devices. In the publication, the authors demonstrated experimentally excellent light confinement in low-refraction-index material. The photonic microstructure is made up of donut-shaped silica microcavity with a circular cross section bonded on a silicon substrate. The refraction indices of silicon and silica are 3. forty-eight, 1. forty four, respectively. "The circular cross section of the microresonator remarkably reduces the electric field distribution area in the vertical direction compared with traditional square cross-section, providing a better light confinement in the silica, " said Li Wang, one of the first co-authors of this work. In the transmission spectra, high-Q fundamental methods are observed while most higher-order methods are suppressed due to much more resilient [url=http://www.antyco.com]Sapphire Window[/url] energy leakage into the substrate, which produces a very clean mode selection range. The [url=http://www.antyco.com]Silicon Window[/url] resonant structure supports high-Q fundamental WGMs in both visible and communication bands. In the communication wavelength band, the quality factors increase exponentially as the minor diameter of the microcavity increases. With a larger minor diameter, the highest quality factor can be even up to 10 million. In the visible wavelength band, the quality factors always maintain large values more than 10 million.