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- Lourdudoss, Sebastian, et al.
(författare)
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Heteroepitaxy and selective epitaxy for discrete and integrated devices
- 2006
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Ingår i: 2006 CONFERENCE ON OPTOELECTRONIC AND MICROELECTRONIC MATERIALS & DEVICES. - NEW YORK : IEEE. - 9781424405770 ; , s. 309-311
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Konferensbidrag (refereegranskat)abstract
- We present first results on heteroepitaxy of InP on silicon on insulator (SOI). We also demonstrate InP nanopillar fabrication by means of selective epitaxy. Selective epitaxy is also exploited to fabricate advanced photonic integrated devices for Optical Code Division Multiplex Access (OCDMA) networking applications.
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| 3. |
- Qiu, Min, et al.
(författare)
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Negative refraction in semiconductor photonic crystals
- 2005
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Ingår i: SEMICONDUCTOR AND ORGANIC OPTOELECTRONIC MATERIALS AND DEVICES. - : SPIE. ; , s. 345-352
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Konferensbidrag (refereegranskat)abstract
- The coupling efficiency between external plane waves and the Bloch waves in photonic crystals are investigated. It is found that the coupling coefficient is highly angular dependent even for an interface between air n=l and a photonic crystal with effective index -1. It is also shown that, for point imaging by a photonic crystal slab owing to the negative refraction, the influence of the surface termination to the transmission and the imaging quality is significant. Finally, we present results demonstrating experimentally negative refraction in a two-dimensional photonic crystal.
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| 4. |
- Benisty, H., et al.
(författare)
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Low-loss photonic-crystal and monolithic InP integration : Bands, bends, lasers, filters
- 2004
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Ingår i: Photonic Crystal Materials and Devices II. - : SPIE - International Society for Optical Engineering. - 0819452688 ; , s. 119-128
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Konferensbidrag (refereegranskat)abstract
- Practical realizations of 2D (planar) photonics crystal (PhC) are either on a membrane or etched through a conventional heterostructure. While fascinating objects can emerge from the first approach, only the latter approach lends itself to a progressive integration of more compact PhC's towards monolithic PICs based on InP. We describe in this talk the various aspects from technology to functions and devices, as emerged from the European collaboration "PCIC". The main technology tour de force is deep-etching with aspect ratio of about 10 and vertical sidewall, achieved by three techniques (CAIBE, ICP-RIE, ECR-RIE). The basic functions explored are bends, splitters/combiners, mirrors, tapers, and the devices are filters and lasers. At the end of the talk, I will emphasize some positive aspects of "broad" multimode PhC waveguides, in view of compact add-drop filtering action, notably.
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| 9. |
- Grancharov, Volodya, et al.
(författare)
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Robust spectrum quantization for LP parameter enhancement
- 2015
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Ingår i: European Signal Processing Conference. - : European Signal Processing Conference, EUSIPCO. ; , s. 1951-1954
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Konferensbidrag (refereegranskat)abstract
- In this paper, we investigate the denoising properties of robust vector quantization of the speech spectrum parameters in combination with a Kalman filter. The underlying assumption is that the high-energy speech regions can be used to reconstruct the low-energy regions destroyed by noise. This can be achieved through vector quantization with a properly weighted distortion measure. The performance of the proposed system, Kalman filtering with prior vector quantization, is compared with existing schemes for parameter estimation used in Kalman filtering. The results indicate significant improvement over the reference systems in both objective and subjective tests.
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| 10. |
- Guruswami, V., et al.
(författare)
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Super-polylogarithmic hypergraph coloring hardness via low-degree long codes
- 2014
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Ingår i: Proceedings of the Annual ACM Symposium on Theory of Computing. - New York, NY, USA : ACM. - 9781450327107 ; , s. 614-623
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Konferensbidrag (refereegranskat)abstract
- We prove improved inapproximability results for hypergraph coloring using the low-degree polynomial code (aka, the"short code" of Barak et. al. [FOCS 2012]) and the techniques pro-posed by Dinur and Guruswami [FOCS 2013] to incorporatethis code for inapproximability results. In particular, we prove quasi-NP-hardness of the following problems on n-vertex hypergraphs: • Coloring a 2-colorable 8-uniform hypergraph with 2 2Ω(√log log n) colors. • Coloring a 4-colorable 4-uniform hypergraph with 22Ω(√ log log n) colors. • Coloring a 3-colorable 3-uniform hypergraph with (log n) Ω(1√ log log log n) colors. In each of these cases, the hardness results obtained are (at least) superpolynomially stronger (if not exponentially stronger as in the third case) than what was previously known for the respective cases. In fact, prior to this result, (log n)O(1) colors was the strongest quantitative bound on the number of colors ruled out by inapproximability results for O(1)-colorable hypergraphs. The fundamental bottleneck in obtaining coloring in approximability results using the low-degree long code was a ultipartite structural restriction in the PCP construction of Dinur-Guruswami. We are able to get around this restriction by simulating the multipartite structure implicitly by querying just one partition (albeit requiring 8 queries), which yields our result for 2-colorable 8-uniform hypergraphs. The result for 4-colorable 4-uniform hypergraphs is obtained via a "query doubling" method exploiting additional properties of the 8-query test. For 3-colorable 3-uniform hyper-graphs, we exploit the ternary domain to design a test with an additive (as opposed to multiplicative) noise function, and analyze its efficacy in killing high weight Fourier coefficients via the pseudorandom properties of an associated quadratic form. The latter step involves extending the key algebraic ingredient of Dinur-Guruswami concerning testing binary Reed-Muller codes to the ternary alphabet.
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