| 1. |
- Dai, Daoxin, et al.
(författare)
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Silicon Multimode Photonic Integrated Devices For On-Chip Mode-Division-Multiplexed Optical Interconnects
- 2013
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Ingår i: Progress In Electromagnetics Research. - 1070-4698 .- 1559-8985. ; 143, s. 773-819
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Tidskriftsartikel (refereegranskat)abstract
- Multimode spatial-division multiplexing (SDM) technology has attracted much attention for its potential to enhance the capacity of an optical-interconnect link with a single wavelength carrier. For a mode-multiplexed optical-interconnect link, the functional elements are quite different from the conventional ones as multiple modes are involved. In this paper we give a review and discussion on multimode photonic integrated devices for mode-multiplexed optical-interconnects. Light propagation and mode conversion in tapered waveguides as well as bent waveguides are discussed first. Recent progress on mode converter-(de)multiplexers is then reviewed. The demands of some functional devices used for mode-multiplexed optical-interconnects are also discussed. In particular, the fabrication tolerance is analyzed in detail for our hybrid demultiplexer, which enables mode-/polarization-division-(de)multiplexing simultaneously.
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| 2. |
- Dai, Daoxin, et al.
(författare)
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Accurate two-dimensional model of an arrayed-waveguide grating demultiplexer and optimal design based on the reciprocity theory
- 2004
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Ingår i: Journal of the Optical Society of America A: Optics and Image Science, and Vision. - 1084-7529. ; 21:12, s. 2392-2398
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Tidskriftsartikel (refereegranskat)abstract
- An accurate two-dimensional (2D) model is introduced for the simulation of an arrayed-waveguide grating (AWG) demultiplexer by integrating the field distribution along the vertical direction. The equivalent 2D model has almost the same accuracy as the original three-dimensional model and is more accurate for the AWG considered here than the conventional 2D model based on the effective-index method. To further improve the computational efficiency, the reciprocity theory is applied to the optimal design of a flat-top AWG demultiplexer with a special input structure.
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| 3. |
- Dai, Daoxin, et al.
(författare)
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Analysis of characteristics of bent rib waveguides
- 2004
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Ingår i: Journal of the Optical Society of America A. - 0740-3232. ; 21:1, s. 113-121
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Tidskriftsartikel (refereegranskat)abstract
- With a perfectly matched layer boundary treatment, a semivectorial finite-difference method is used to calculate the eigenmodes of a single-mode (SM) or multimode (MM) bent rib waveguide. A detailed analysis is given for the dependence of the bending losses (including the pure bending loss and the transition loss) on geometrical parameters of the bent rib waveguide such as the rib width, the rib height, and the bending radius. The characteristics of the higher-order modes are analyzed. It is shown that the bending loss of the fundamental mode can be reduced effectively by increasing the width and height of the rib. For an integrated device, undesired effects due to the higher-order modes of a MM bent waveguide can be removed by appropriate choice of the geometrical parameters. An appropriately designed MM bent waveguide is used to reduce effectively the bending loss of the fundamental mode, and a low-loss SM propagation in a MM bent waveguide is realized when the bending losses of the higher-order modes are large enough.
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| 4. |
- Dai, Daoxin, et al.
(författare)
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Analysis of the birefringence of a silicon-on-insulator rib waveguide
- 2004
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Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 43:5, s. 1156-1161
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Tidskriftsartikel (refereegranskat)abstract
- A detailed analysis of the polarization characteristics (birefringence) of a silicon-on-insulator (SOI) rib waveguide is given. The fundamental TE- and TM-polarized modes of the SOI rib waveguide are calculated by a semivectorial finite-difference method. The rib width and the slab height of the SOI rib waveguide are normalized with respect to the total height of the silicon layer. A general relation between the two normalized parameters for a nonbirefringent SOI rib waveguide is obtained. According to this relation a nonbirefringent SOI rib waveguide can easily be designed. The fabrication tolerance for a nonbirefringent SOI rib waveguide is also analyzed, revealing that the tolerance can be increased by use of a larger total height of the silicon layer.
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| 5. |
- Dai, Daoxin, et al.
(författare)
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Compact silicon-based wavelength-selective photonic integrated devices and the applications
- 2009
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Ingår i: SILICON PHOTONICS IV. - : SPIE-INT SOC OPTICAL ENGINEERING. - 9780819474667
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Konferensbidrag (refereegranskat)abstract
- In wavelength-division multiplexing systems, it is important to develop various wavelength-selective components to have flexible and reconfigurable nodes. When using conventional optical waveguides with low index contrast, the sizes of these wavelength-selective components are usually several cm(2), which is too large to integrate more components in a single wafer or chip. In order to improve the integration density and reduce the cost, it is desirable to minimize the component sizes. In our case, two kinds of strongly-confined optical waveguides on silicon wafer are considered for compact wavelength-selective devices. One is the popular silicon-on-insulator (SOI) nanowire and the other is SU-8 strip optical waveguide with an air cladding and a SiO2 insulator layer on a Si substrate. In this paper, we give a review of our recent work on wavelength-selective photonic integrated devices based on these two kinds of silicon-based optical waveguides with strong-confinements. Arrayed-waveguide grating (AWG) and microring resonator (MRR), which are two typical wavelength-selective components are included. First we give a review for several new layouts for SOI-nanowire AWG to have a further size-reduction and our novel designs for diminishing the polarization dependency of AWGs. Secondly we present the design and fabrication of multimode interference (MMI) couplers for MRRs. A novel design method for tapered MMI couplers is presented and the diminishment of polarization in a MMI coupler is proposed by optimizing the tapered MMI section. We also present our experimental results on optical sensor combining MRRs and micro-fluid channel. The measured sensitivity is about 180nm/RIU.
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| 6. |
- Dai, Daoxin, et al.
(författare)
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Gain enhancement in a hybrid plasmonic nano-waveguide with a low-index or high-index gain medium
- 2011
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Ingår i: Optics Express. - 1094-4087. ; 19:14, s. 12925-12936
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Tidskriftsartikel (refereegranskat)abstract
- A theoretical investigation of a nano-scale hybrid plasmonic waveguide with a low-index as well as high-index gain medium is presented. The present hybrid plasmonic waveguide structure consists of a Si substrate, a buffer layer, a high-index dielectric rib, a low-index cladding, a low-index nano-slot, and an inverted metal rib. Due to the field enhancement in the nano-slot region, a gain enhancement is observed, i.e., the ratio partial derivative G/partial derivative g > 1, where g and G are the gains of the gain medium and the TM fundamental mode of the hybrid plasmonic waveguide, respectively. For a hybrid plasmonic waveguide with a core width of w(co) = 30nm and a slot height of h(slot) = 50nm, the intrinsic loss could be compensated when using a low-index medium with a moderate gain of 176dB/cm. When introducing the high-index gain medium for the hybrid plasmonic waveguide, a higher gain is obtained by choosing a wider core width. For the high-index gain case with h(slot) = 50nm and w(co) = 500nm, a gain of about 200dB/cm also suffices for the compensation of the intrinsic loss.
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| 7. |
- Dai, Daoxin, et al.
(författare)
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Silicon hybrid plasmonic submicron-donut resonator with pure dielectric access waveguides
- 2011
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Ingår i: Optics Express. - 1094-4087. ; 19:24, s. 23671-23682
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Tidskriftsartikel (refereegranskat)abstract
- Characteristic analyses are given for a bent silicon hybrid plasmonic waveguide, which has the ability of submicron bending (e.g., R = 500nm) even when operating at the infrared wavelength range (1.2 mu m similar to 2 mu m). A silicon hybrid plasmonic submicron-donut resonator is then presented by utilizing the sharp-bending ability of the hybrid plasmonic waveguide. In order to enable long-distance optical interconnects, a pure dielectric access waveguide is introduced for the present hybrid plasmonic submicron-donut resonator by utilizing the evanescent coupling between this pure dielectric waveguide and the submicron hybrid plasmonic resonator. Since the hybrid plasmonic waveguide has a relatively low intrinsic loss, the theoretical intrinsic Q-value is up to 2000 even when the bending radius is reduced to 800nm. By using a three-dimensional finite-difference time-domain (FDTD) method, the spectral response of hybrid plasmonic submicron-donut resonators with a bending radius of 800nm is simulated. The critical coupling of the resonance at around 1423nm is achieved by choosing a 80nm-wide gap between the access waveguide and the resonator. The corresponding loaded Q-value of the submicron-donut resonator is about 220.
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| 8. |
- Dai, Daoxin, et al.
(författare)
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Three-dimensional hybrid modeling based on a beam propagation method and a diffraction formula for an AWG demultiplexer
- 2007
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Ingår i: Optics Communications. - : Elsevier BV. - 0030-4018 .- 1873-0310. ; 270:2, s. 195-202
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Tidskriftsartikel (refereegranskat)abstract
- An efficient and accurate three-dimensional (3D) hybrid modeling, which combines a 3D beam propagation method (BPM) and the two-dimensional (2D) Kirchhoff-Huygens diffraction formula, is developed to simulate the field propagation in an arrayed waveguide grating (AWG) dernultiplexer. The 2D Kirchhoff-Huygens diffraction formula is used for the simulation of the light propagation in the free propagation regions (FPRs). A 3D BPM in a polar coordinate system is used to simulate the light propagation in the transition region between the input FPR and the arrayed waveguides so that the coupling coefficients for the arrayed waveguides are calculated conveniently and accurately. For the simulation in the transition region between the arrayed waveguides and the output FPR, only the central arrayed waveguide and several adjacent ones are needed in the computational window of a standard BPM and thus the computation efficiency is improved. Finally, a flat-top AWG is designed and fabricated to verify the reliability of the present simulation method. The calculated and measured spectral responses are in a good agreement.
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| 9. |
- Dai, Daoxin, et al.
(författare)
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Ultrasmall integrated devices based on silicon nanowires for optical communications
- 2008
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Ingår i: JOURNAL OF NANOPHOTONICS. - : SPIE-Intl Soc Optical Eng. - 1934-2608. ; 2, s. 021780-
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Tidskriftsartikel (refereegranskat)abstract
- Planar lightwave circuits (PLCs) based on Si nanowires exhibit several serious problems due to the small cross sections of the nanowires. These problems include large scattering loss, large coupling loss to a single-mode fiber, and high dependency on polarization. Several solutions to these problems have emerged. Recent progress on Si-nanowire-based passive PLC devices encompasses arrayed waveguide grating (de) multiplexers, microring resonators, and multimode interference couplers.
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| 10. |
- He, Sailing, et al.
(författare)
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Some progress in integrated photonics
- 2005
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Ingår i: OPTOELECTRONIC DEVICES AND INTEGRATION. - : SPIE. - 0819455997 ; , s. 405-413
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Konferensbidrag (refereegranskat)abstract
- A review is presented on some progress we have made recently in planar integrated photonics including arrayed-waveguide gratings (AWGs) and etched diffraction gratings (EDGs), multimode interference (MMI) couplers/splitters, and spot-size converters. Some novel structures and design methods are summarized and presented.
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