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Dai D.,Center for Optical and Electromagnetic Research
Journal of Lightwave Technology

A short polarization beam splitter (PBS) is presented based on an asymmetrical evanescent coupling system, which consists of a narrow input waveguide, a narrow output waveguide, and a wide middle optical waveguide between them. The width of the waveguides is designed so that the phase-matching condition is satisfied for the TM fundamental (MT 0) mode in the narrow input/output waveguide and the first higher order TM (MT 1) mode in the wide middle waveguide. Meanwhile, there is a significant phase mismatch for the case with TE polarization. Therefore, for the launched TE polarized light, almost no coupling happens when it goes through the coupling region and finally the TE polarized light is output from the through port. For the launched (MT 0) mode in the narrow input waveguide, it is completely coupled to the (MT 1) mode in the wide middle waveguide by choosing the optimal length of the coupling region. Furthermore, the (MT 1) mode excited in the wide middle waveguide is then coupled to the (MT 0) mode in the narrow output waveguide through the evanescent coupling between them. A short (~25μm long) PBS is designed based on silicon-on-insulator nanowires, while the gap width is chosen as large as 300 nm to make the fabrication easy. Numerical simulations show that the present PBS has a good fabrication tolerance for the variation of the waveguide width (more than ±20nm) and a broadband (~50nm) for an extinction ratio of >15dB. © 1983-2012 IEEE. Source

Yu J.,Center for Optical and Electromagnetic Research | Yu J.,Lund University | Cai F.,Center for Optical and Electromagnetic Research | Cai F.,Lund University
Asia Communications and Photonics Conference, ACPC 2014

Being an excellent nonlinear nanomaterial, KNbO3 nanoneedles was used as XFROG nonlinear medium to measure the time/frequency-dependent intensity of a ~100 nm band dispersive wave, which was filtered from a super-continuum picoseconds pulse laser. © OSA 2014. Source

Cui Y.,Taiyuan University of Technology | Cui Y.,Center for Optical and Electromagnetic Research | Xu J.,Massachusetts Institute of Technology | Lin Y.,Taiyuan University of Technology | And 4 more authors.

In this paper, we employ an antireflective coating which comprises inverted π-shaped metallic grooves to manipulate the behaviour of a transverse-magnetic (TM)-polarised plane wave transmitted through a periodic nanoslit array. At normal incidence, such scheme cannot only retain the optical curtain effect in the output region but also generate the extraordinary transmission of light through the nanoslits with the total transmission efficiency as high as 90 %. Besides, we show that the spatially invariant field distribution in the output region as well as the field distribution of resonant modes around the inverted π-shaped grooves can be reproduced immaculately when the system is excited by an array of point sources beneath the inverted π-shaped grooves. Furthermore, we investigate the influence of centre groove and side-corners of the inverted π-shaped grooves on suppressing the reflection of light, respectively. Based on our work, it shows promising potential in applications of enhancing the extraction efficiency as well as controlling the beaming pattern of light emitting diodes. © 2013 Springer Science+Business Media New York. Source

Shen Y.,Center for Optical and Electromagnetic Research | Yan C.,Center for Optical and Electromagnetic Research
2010 OSA-IEEE-COS Advances in Optoelectronics and Micro/Nano-Optics, AOM 2010

In recent years, water pollution detection has been global issues, especially for metal and organic pollution. And the phenomenon of ultrasonic cavitation has been widely used in the decades. In this paper, a method of detector water pollution by using sonoluminescence is introduced and some results are showed and analyzed. Source

Wang J.,Center for Optical and Electromagnetic Research | Chen S.,Center for Optical and Electromagnetic Research | Dai D.,Center for Optical and Electromagnetic Research
Optics Letters

A monolithically integrated 64-channel hybrid demultiplexer on silicon is demonstrated experimentally to enable wavelength-division-multiplexing and mode-division-multiplexing simultaneously for realizing an ultra-large capacity optical-interconnect link. The present hybrid demultiplexer consists of a four-channel mode multiplexer realized with three cascaded asymmetrical directional-couplers and four identical arrayed-waveguide gratings (AWGs) with 16 channels. For the fabricated hybrid multiplexer, the excess loss and the crosstalk are about -7 and -10 dB, respectively. Better performances can be achieved by minimizing the imperfections (particularly in AWGs) in the fabrication processes. The present hybrid demultiplexer is scalable to have more channels by utilizing more wavelengths, modes, and polarizations. © 2014 Optical Society of America. Source

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