4,069 research outputs found
Mapping the optical properties of slab-type two-dimensional photonic crystal waveguides
We report on systematic experimental mapping of the transmission properties
of two-dimensional silicon-on-insulator photonic crystal waveguides for a broad
range of hole radii, slab thicknesses and waveguide lengths for both TE and TM
polarizations. Detailed analysis of numerous spectral features allows a direct
comparison of experimental data with 3D plane wave and finite-difference
time-domain calculations. We find, counter-intuitively, that the bandwidth for
low-loss propagation completely vanishes for structural parameters where the
photonic band gap is maximized. Our results demonstrate that, in order to
maximize the bandwidth of low-loss waveguiding, the hole radius must be
significantly reduced. While the photonic band gap considerably narrows, the
bandwidth of low-loss propagation in PhC waveguides is increased up to 125nm
with losses as low as 82dB/cm.Comment: 10 pages, 8 figure
Melody based tune retrieval over the World Wide Web
In this paper we describe the steps taken to develop a Web-based version of an existing stand-alone, single-user digital library application for melodical searching of a collection of music. For the three key components: input, searching, and output, we assess the suitability of various Web-based strategies that deal with the now distributed software architecture and explain the decisions we made. The resulting melody indexing service, known as MELDEX, has been in operation for one year, and the feed-back we have received has been favorable
Transmission of Slow Light through Photonic Crystal Waveguide Bends
The spectral dependence of a bending loss of cascaded 60-degree bends in
photonic crystal (PhC) waveguides is explored in a slab-type
silicon-on-insulator system. Ultra-low bending loss of (0.05+/-0.03)dB/bend is
measured at wavelengths corresponding to the nearly dispersionless transmission
regime. In contrast, the PhC bend is found to become completely opaque for
wavelengths range corresponding to the slow light regime. A general strategy is
presented and experimentally verified to optimize the bend design for improved
slow light transmission.Comment: 4 pages, 3 figures; submitted to Optics Letter
Mode mixing in asymmetric double trench photonic crystal waveguides
e investigate both experimentally and theoretically the waveguiding
properties of a novel double trench waveguide where a conventional single-mode
strip waveguide is embedded in a two dimensional photonic crystal (PhC) slab
formed in silicon on insulator (SOI) wafers. We demonstrate that the bandwidth
for relatively low-loss (50dB/cm) waveguiding is significantly expanded to
250nm covering almost all the photonic band gap owing to nearly linear
dispersion of the TE-like waveguiding mode. The flat transmission spectrum
however is interrupted by numerous narrow stop bands. We found that these stop
bands can be attributed to anti-crossing between TE-like (positive parity) and
TM-like (negative parity) modes. This effect is a direct result of the strong
asymmetry of the waveguides that have an upper cladding of air and lower
cladding of oxide. To our knowledge this is the first demonstration of the
effects of cladding asymmetry on the transmission characteristics of the PhC
slab waveguides.Comment: 7 pages, 6 figure
Managing complexity in a distributed digital library
As the capabilities of distributed digital libraries increase, managing organizational and software complexity becomes a key issue. How can collections and indexes be updated without impacting queries currently in progress? How can the system handle several user-interface clients for the same collections? Computer science professors and lectors from the University of Waikato have developed a software structure that successfully manages this complexity in the New Zealand Digital Library. This digital library has been a success in managing organizational and software complexity. The researchers' primary goal has been to minimize the effort required to keep the system operational and yet continue to expand its offerings
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