Analysis of photonic spot profile converter and bridge structure on SOI platform for horizontal and vertical integration
23 Aug 2017-Vol. 10382, pp 1038203
TL;DR: In this paper, the authors used the semi-analytical matrix method to analyze horizontal and vertically integrated photonic circuits for both TE and TM modes at 1550 nm wavelength using the semi analytical matrix method which is simple and fast in computation time and memory.
Abstract: Horizontal spot size converter required for horizontal light coupling and vertical bridge structure required for vertical integration are designed on high index contrast SOI platform in order to form more compact integrated photonic circuits. Both the structures are based on the concept of multimode interference. The spot size converter can be realized by successive integration of multimode interference structures with reducing dimension on horizontal plane, whereas the optical bridge structure consists of a number of vertical multimode interference structure connected by single mode sections. The spot size converter can be modified to a spot profile converter when the final single mode waveguide is replaced by a slot waveguide. Analysis have shown that by using three multimode sections in a spot size converter, an Gaussian input having spot diameter of 2.51 μm can be converted to a spot diameter of 0.25 μm. If the output single mode section is replaced by a slot waveguide, this input profile can be converted to a flat top profile of width 50 nm. Similarly, vertical displacement of 8μm is possible by using a combination of two multimode sections and three single mode sections in the vertical bridge structure. The analyses of these two structures are carried out for both TE and TM modes at 1550 nm wavelength using the semi analytical matrix method which is simple and fast in computation time and memory. This work shows that the matrix method is equally applicable for analysis of horizontally as well as vertically integrated photonic circuit.
Citations
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05 May 2019
TL;DR: In this paper, a low temperature fabrication process of vertical MMI a:Si-H waveguides for multi-layer photonic integrated circuits was demonstrated, where measured MMI loss of 1.97dB/MMI and vertical light coupling of TE polarization at 1550nm wavelength have been achieved.
Abstract: We successfully demonstrated low temperature fabrication process of vertical MMI a:Si-H waveguides for multi-layer photonic integrated circuit. Measured MMI loss of 1.97dB/MMI and vertical light coupling of TE polarization at 1550nm wavelength have been achieved.
Cites methods from "Analysis of photonic spot profile c..."
...The design and fabrication of vertical MMIs have been previously demonstrated [1-3]....
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References
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TL;DR: The underlying self-imaging principle in multimode waveguides is described using a guided mode propagation analysis and it is shown that multimode interference couplers offer superior performance, excellent tolerance to polarization and wavelength variations, and relaxed fabrication requirements when compared to alternatives such as directional coupling.
Abstract: This paper presents an overview of integrated optics routing and coupling devices based on multimode interference. The underlying self-imaging principle in multimode waveguides is described using a guided mode propagation analysis. Special issues concerning the design and operation of multimode interference devices are discussed, followed by a survey of reported applications. It is shown that multimode interference couplers offer superior performance, excellent tolerance to polarization and wavelength variations, and relaxed fabrication requirements when compared to alternatives such as directional couplers, adiabatic X- or Y-junctions, and diffractive star couplers. >
2,477 citations
"Analysis of photonic spot profile c..." refers background in this paper
...The beat length can be defined in terms of the two lowest order modes [7] as...
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...The field profile will vary along the length of multimode section and will be similar to the input field profile (termed self imaging) when the length of the multimode section is equal to 6Lπ[7]....
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...It is already known that for a multimode step index waveguide that has width WM , core refractive index nr , cladding refractive index nc and supporting M lateral modes at working wavelength λ0, will have an effective width, Wev , due to the lateral penetration of each mode field which can be expressed as [7] 2 1 2 2 2 c r r c o M e n n n n W W ...
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...Multimode Interference (MMI) couplers [7] are therefore ideal for such horizontal and vertical integration....
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TL;DR: It is shown that by use of a novel waveguide geometry the field can be confined in a 50-nm-wide low-index region with a normalized intensity of 20 microm(-2), approximately 20 times higher than what can be achieved in SiO2 with conventional rectangular waveguides.
Abstract: We present a novel waveguide geometry for enhancing and confining light in a nanometer-wide low-index material. Light enhancement and confinement is caused by large discontinuity of the electric field at highindex-contrast interfaces. We show that by use of such a structure the field can be confined in a 50-nm-wide low-index region with a normalized intensity of 20 mm 22 . This intensity is approximately 20 times higher than what can be achieved in SiO2 with conventional rectangular waveguides. © 2004 Optical Society of America OCIS codes: 030.4070, 130.0130, 130.2790, 230.7370, 230.7380, 230.7390, 230.7400. Recent results in integrated optics have shown the ability to guide, bend, split, and f ilter light on chips by use of optical devices based on high-index-contrast waveguides. 1–5 In all these devices the guiding mechanism is based on total internal ref lection (TIR) in a highindex material (core) surrounded by a low-indexmaterial (cladding); the TIR mechanism can strongly confine light in the high-index material. In recent years a number of structures have been proposed to guide or enhance light in low-index materials, 6–1 1 relying on external ref lections provided by interference effects. Unlike TIR, the external ref lection cannot be perfectly unity; therefore the modes in these structures are inherently leaky modes. In addition, since interference is involved, these structures are strongly wavelength dependent. Here we show that the optical field can be enhanced and conf ined in the low-index material even when light is guided by TIR. For a high-index-contrast interface, Maxwell’s equations state that, to satisfy the continuity of the normal component of electric f lux density D, the corresponding electric field (E-field) must undergo a large discontinuity with much higher amplitude in the low-index side. We show that this discontinuity can be used to strongly enhance and confine light in a nanometer-wide region of low-index material. The proposed structure presents an eigenmode, and it is compatible with highly integrated photonics technology. The principle of operation of the novel structure can be illustrated by analysis of the slab-based structure shown in Fig. 1(a), where a low-index slot is embedded between two high-index slabs (shaded regions). The novel structure is hereafter referred to as a slot waveguide. The slot waveguide eigenmode can be seen as being formed by the interaction between the fundamental eigenmodes of the individual slab waveguides. Rigorously, the analytical solution for the transverse E-field profile Ex of the fundamental TM eigenmode of the slab-based slot waveguide is
1,716 citations
"Analysis of photonic spot profile c..." refers background or methods in this paper
...The structure of Fig 1(a) can be modified to a spot profile converter by replacing the SM section with a slot waveguide [13] which is shown in Fig....
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...For high index contrast guide, the modes are more confined within the waveguide itself [13]....
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TL;DR: This paper discusses challenges of codesign and cosimulation of complex photonic and electronic circuits, tolerance to variability, and verification algorithms that can handle photonic circuits, and gives an outlook on how tools need to evolve to address the needs of photonic-electronic IC designers.
Abstract: Silicon photonics is rapidly gaining maturity in high-bandwidth optical communication, with applications in datacom, access networks, and I/O for bandwidth-intensive electronics. Also, applications are emerging in spectroscopy and sensing. To get the best performance out of the photonics, co-integration with electronics is needed: side-by-side, stacked, or on the same chip. However, the combination of photonics and electronics introduces a range of new problems on the design side: Codesign and cosimulation of complex photonic and electronic circuits, tolerance to variability, and verification algorithms that can handle photonic circuits. We will discuss these challenges and give an outlook on how tools need to evolve to address the needs of photonic-electronic IC designers.
172 citations
"Analysis of photonic spot profile c..." refers methods in this paper
...Usually high index contrast SOI platform is used for this dense light confinement [6] which is also CMOS compatible....
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TL;DR: In this paper, the eigenvalue equations for a slab three-guide coupler were solved and the power transfer efficiency was calculated when the coupler was used as a power divider and to transfer power from one outside guide to another.
Abstract: The eigenvalue equations for a slab three-guide coupler were solved and the power-transfer efficiency was calculated when the coupler is used as 1) a power divider and 2) to transfer power from one outside guide to another. In the first case, two modes take part in the power transfer, and unless the guides are very tightly coupled, periodic beats with high power transfer are obtained at multiples of the coupling length as in a two-guide coupler. In the second case, three modes take part in the power transfer, and periodic beats and high power-transfer efficiency can only be obtained if the propagation velocities of the three modes are related to each other in a simple way. This condition will occur only if the guides of a three-guide coupler made up of identical guides are much more loosely coupled than guides generally used in a two-guide coupler.
67 citations
"Analysis of photonic spot profile c..." refers background in this paper
...Mathematically the overlap integral is defined as [12]...
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TL;DR: In this article, the theoretical analysis of rib channel waveguides as well as the results of experimental research on slab and single mode rib channels were presented, where the waveguide films were selectively masked with a photoresist.
53 citations
"Analysis of photonic spot profile c..." refers methods in this paper
...e, refractive index variation along vertical (y) and horizontal (x-axis) directions, is converted to 1D effective refractive index neff (x) at any x along the horizontal direction using the dispersion equation given in [11]....
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