| 11. |
- Tang, Yongbo, et al.
(författare)
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Proposal for a Grating Waveguide Serving as Both a Polarization Splitter and an Efficient Coupler for Silicon-on-Insulator Nanophotonic Circuits
- 2009
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Ingår i: IEEE Photonics Technology Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1041-1135 .- 1941-0174. ; 21:1-4, s. 242-244
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Tidskriftsartikel (refereegranskat)abstract
- A grating waveguide is introduced and designed to serve as both a polarization splitter and an efficient vertical coupler between a fiber and a silicon-on-insulator (SOI) nanophotonic waveguide. Through this grating waveguide, the light from the fiber can be efficiently coupled into an SOI chip where the two orthogonally polarized waves are separated to travel towards the opposite directions along the waveguide. According to our simulations, the optimized structure can give a high coupling efficiency of about 50% for both polarizations, as well as a large bandwidth of over 70 nm and a very low polarization crosstalk below -22 dB at the output ports.
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| 12. |
- Tang, Yongbo
(författare)
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Study on electroabsorption modulators and grating couplers for optical interconnects
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Decades of efforts have pushed the replacement of electrical interconnects by optical links to the interconnects between computers, racks and circuit boards. It may be expected that optical solutions will further be used for inter-chip and intra-chip interconnects with potential benefits in bandwidth, capacity, delay, power consumption and crosstalk. Silicon integration is emerging to be the best candidate nowadays due to not only the dominant status of silicon in microelectronics but also the great advantages brought to the photonic integrated circuits (PICs). Regarding the recent breakthroughs concerning active devices on silicon substrate, the question left is no longer the feasibility of the optical interconnects based on silicon but the competitiveness of the silicon device compared with other alternatives. This thesis focuses on the study of two key components for the optical interconnects, both especially designed and fabricated for silicon platform. One is a high speed electroabsorption modulator (EAM), realized by transferring an InP-based segmented design to the hybrid silicon evanescent platform. The purpose here is to increase the speed of the silicon PICs to over 50 Gb/s or more. The other one is a high performance grating coupler, with the purpose to improve the optical interface between the silicon PICs and the outside fiber-based communication system. An general approach based on the transmission line analysis has been developed to evaluate the modulation response of an EAM with a lumped, traveling-wave, segmented or capacitively-loaded configuration. A genetic algorithm is used to optimize its configuration. This method has been applied to the design of the EAMs on hybrid silicon evanescent platform. Based on the comparison of various electrode design, segmented configuration is adopted for the target of a bandwidth over 40 GHz with as low as possible voltage and high extinction ratio. In addition to the common periodic analysis, the grating coupler is analyzed by the antenna theory assisted with an improved volume-current method, where the directionality of a grating coupler can be obtained analytically. In order to improve the performance of the grating coupler, a direct way is to address its shortcoming by e.g. increasing the coupling efficiency. For this reason, a nonuniform grating coupler with apodized grooves has been developed with a coupling efficiency of 64%, nearly a double of a standard one. Another way is to add more functionalities to the grating coupler. To do this, a polarization beam splitter (PBS) based on a bidirectional grating coupler has been proposed and experimentally demonstrated. An extinction ratio of around -20 dB, as well as a maximum coupling efficiency of over 50% for both polarizations, is achieved by such a PBS with a Bragg reflector underneath.
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| 13. |
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| 14. |
- Wang, Zhechao, et al.
(författare)
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Experimental demonstration of an ultracompact polarization beam splitter based on a bidirectional grating coupler
- 2009
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Ingår i: 2009 Asia Communications and Photonics Conference and Exhibition, ACP 2009. - 9781557528773 ; , s. 5377257-
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Konferensbidrag (refereegranskat)abstract
- A bidirectional grating serving both as a polarization beam splitter and a vertical coupler for Silicon on Insulator nanophotonic circuits is fabricated and characterized. The measured coupling efficiency is as high as 43%. The demonstrated device has a large 3-dB bandwidth and a high extinction ratio between two orthogonal polarizations.
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| 15. |
- Wang, Zhechao, et al.
(författare)
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High Efficiency Grating Couplers for Silicon-on-Insulator Photonic Circuits
- 2010
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Ingår i: 36th European Conference and Exhibition on Optical Communication, ECOC 2010. - : IEEE Communications Society. - 9781424485369 - 9781424485345
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Konferensbidrag (refereegranskat)abstract
- We have experimentally demonstrated two methods for improving the coupling efficiency of grating couplers. A grating coupler-polarization splitter is measured to have over 50% efficiency for both polarizations. 68% efficiency for single polarization is achieved by a nonuniform grating coupler.
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| 16. |
- Wang, Zhechao, et al.
(författare)
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Ultracompact low-loss coupler between strip and slot waveguides
- 2009
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 34:10, s. 1498-1500
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Tidskriftsartikel (refereegranskat)abstract
- We present both theoretical and experimental results of an ultracompact waveguide coupler that is capable of highly efficient coupling of light from strip waveguides to slot waveguides, and vice versa. By optimizing the geometrical parameters, it is possible to achieve extremely low-loss coupling. A coupling efficiency of 97% has been obtained experimentally while keeping the overall size down to the range below 10 mu m. Further analysis shows that the proposed coupler has relatively high tolerance to fabrication errors and is wavelength insensitive. (C) 2009 Optical Society of America
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| 17. |
- Wosinski, Lech, et al.
(författare)
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Coupling of silicon nanophotonic circuits to optical fibers
- 2010
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Ingår i: Asia Communications and Photonics Conference and Exhibition, ACP 2010. - : IEEE Communications Society. - 9781424471119 ; , s. 421-422
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Konferensbidrag (refereegranskat)abstract
- Silicon-based nanophotonic waveguides and components fabricated in silicon-on-insulator technology build a platform for high density photonic integrated circuits, where active III-V devices can be incorporated using evanescent field coupling. These circuits can be fabricated with standard CMOS technology processing, allowing for low cost mass production in applications such as optical networks, computer interconnects and sensing. Connecting of these integrated structures to the real world of optical fibers appears is an important problem to be solved. In this paper we discuss some solutions and present some of fabricated devices including a grating coupler-polarization splitter with over 50% efficiency for both polarizations and a nonuniform grating coupler with 68% efficiency for single polarization. To the best of our knowledge, they are the highest coupling efficiencies obtained by regular SOI grating couplers for both, single polarization and polarization splitting.
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| 18. |
- Wosinski, Lech, et al.
(författare)
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Interfacing of Silicon-on-insulator nanophotonic circuits to the real world
- 2010
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Ingår i: 2010 12th International Conference on Transparent Optical Networks (ICTON). - : IEEE Communications Society. - 9781424477999 - 9781424477975 ; , s. 5549268-
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Konferensbidrag (refereegranskat)abstract
- Silicon-on-insulator material structure allows for very high light confinement in the silicon core due to its high refractive index. The advantages of this technology include the possibility to miniaturize devices and integrate different functions on a single chip, reduction of optical loss and power consumption and potential perspectives for low cost mass production in CMOS technology line. Together with these advantages some new problems appear in comparison to weakly guided light in silica-on-silicon components, causing additional challenges for researchers to be solved. Besides much higher demands for fabrication accuracy, high refractive index contrast introduces additional optical input/output coupling problems as well as much higher polarization sensitivity of nanophotonic structures. Here we will propose some solutions for these problems and illustrate them with designed and fabricated components
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