Analytical modal analysis of bent slot waveguides.
01 Nov 2009-Journal of The Optical Society of America A-optics Image Science and Vision (Optical Society of America)-Vol. 26, Iss: 11, pp 2321-2326
TL;DR: In this article, a multilayer formulation of the well-known classical analytical model of bent waveguides based on the Bessel-Hankel functions is proposed to characterize the optimal slot position inside the bent core to maximize the field enhancement in the slot.
Abstract: We analyze modal properties of dielectric optical bent slot waveguides by using the multilayer formulation of the well-known classical analytical model of bent waveguides based on the Bessel-Hankel functions. Unlike the previously studied approximate model based on the Airy functions, this model is valid for all values of bend radii. The present approach allows quick and accurate computations of propagation constants, mode profiles, and field-power densities for the 2D bent slot waveguides with very small radii. Using this model we characterize the optimal slot position inside the bent core to maximize the field enhancement in the slot. Such modal analysis is quite useful for the design of devices involving bent slot waveguides. Moreover the results obtained by the present 2D rigorous analytical model can also be used for benchmarking other numerical tools.
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TL;DR: The use of nanometer scale guiding structure where optical mode is confined in a low-index region permits a very compact sensor with high optical intensity in the region, which makes it possible to detect minimum refractive index change, and offers higher sensitivities.
Abstract: A finite element method based on the full-vectorial H-field formulation has been employed to achieve the maximum field penetration in the sensing medium of the slot-waveguide-based ring resonator biosensor. The use of nanometer scale guiding structure where optical mode is confined in a low-index region permits a very compact sensor with high optical intensity in the region, which makes it possible to detect minimum refractive index change, and offers higher sensitivities. We analyze the change in effective refractive index of mode, sensitivity, and power confinement of the proposed slot-waveguide-based ring resonator biosensor for the detection of DNA hybridization. The biosensor exhibited theoretical sensitivity of 856 nm per refractive index unit (RIU) and a detection limit of 1.43×10−6 RIU.
64 citations
TL;DR: The waveguide sensitivity of silicon slot microring sensors and single- and double-slot microrings is analyzed using a combination of the effective index and the Airy-functions-based mode matching methods and illustrates that double- slots offer wider fabrication tolerance than single-slot ones.
Abstract: The waveguide sensitivity of silicon slot microring sensors and single- and double-slot microrings is analyzed using a combination of the effective index and the Airy-functions-based mode matching methods. The sensing properties of these two cases are investigated under a variety of geometries. The trends of the waveguide sensitivity on each geometrical parameter are obtained. In addition, the influence of asymmetry on the waveguide sensitivity is also investigated. Calculation also illustrates that double-slot microrings offer wider fabrication tolerance than single-slot ones. These results provide a guideline and insights for designing microring geometry to satisfy the desired sensing requirements and performance.
48 citations
TL;DR: This work investigates light propagation in a waveguide-resonator system where the resonators consist of slotted ring cavities via a frequency-domain spatial Coupled-Mode Theory (CMT) approach, and compares its results with a Discontinuous Galerkin Time-Domain (DGTD) solver that is equipped with curvilinear finite elements.
Abstract: Optical devices with a slot configuration offer the distinct feature of strong electric field confinement in a low refractive index region and are, therefore, of considerable interest in many applications. In this work we investigate light propagation in a waveguide-resonator system where the resonators consist of slotted ring cavities. Owing to the presence of curved material interfaces and the vastly different length scales associated with the sub-wavelength sized slots and the waveguide-resonator coupling regions on the one hand, and the spatial extent of the ring on the other hand, this prototypical system provides significant challenges to both direct numerical solvers and semi-analytical approaches. We address these difficulties by modeling the slot resonators via a frequency-domain spatial Coupled-Mode Theory (CMT) approach, and compare its results with a Discontinuous Galerkin Time-Domain (DGTD) solver that is equipped with curvilinear finite elements. In particular, the CMT model is built on the underlying physical properties of the slotted resonators, and turns out to be quite efficient for analyzing the device characteristics. We also discuss the advantages and limitations of the CMT approach by comparing the results with the numerically exact solutions obtained by the DGTD solver. Besides providing considerable physical insight, the CMT model thus forms a convenient basis for the efficient analysis of more complex systems with slotted resonators such as entire arrays of waveguide-coupled resonators and systems with strongly nonlinear optical properties.
16 citations
TL;DR: In this article , a chalcogenide slot waveguide was theoretically studied, and the highest power confinement factors of the slot region and the cladding region were obtained to be 36.3% and 56.7%, respectively.
Abstract: In this article, the chalcogenide slot waveguide is theoretically studied, and the highest power confinement factors of the slot region and the cladding region are obtained to be 36.3% and 56.7%, respectively. A high-sensitivity chalcogenide slot microring resonator sensor is designed and fabricated by electron-beam lithography and dry etching. The structure increases the sensitivity of the sensor compared with the conventional evanescent field waveguide sensor. The cavity has achieved a quality factor of 1 × 104 by fitting the resonant peaks with the Lorentzian profile, one of the highest quality factors reported for chalcogenide slot microring resonators. The sensor sensitivity is measured to be 471 nm/RIU, which leads to an intrinsic limit of detection of 3.3 × 10--4 RIU.
12 citations
TL;DR: In this article, an effective index based matrix method was used to analyze high-index contrast slab and slot optical waveguides, and the results were compared with results obtained from numerical techniques like finite element method, finite-difference time-domain, and beam propagation method.
Abstract: High-index contrast slab and slot optical waveguides have a high index variation both along the lateral and vertical interfaces and are usually analyzed numerically, requiring large computer memory and time. In this article, their analysis is done semianalytically using an effective-index based matrix method. This method, which is computationally very fast, was earlier used successfully for low-index profile waveguide structures only and is now suitably modified for use in high-index contrast structures. The electric field profile of the waveguide structures is plotted and the effective refractive index at different wavelengths is calculated. The results are compared with results obtained from numerical techniques like finite element method, finite-difference time-domain, and beam propagation method and they match very well. The dependence of their different optical characteristics with the waveguide parameters is also studied. These studies will help in obtaining improved sensitivity of slot waveguides for sensing applications.
12 citations
References
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46,339 citations
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
TL;DR: In this paper, a silicon-organic hybrid slot waveguide with a strong optical nonlinearity is demonstrated to perform ultrafast all-optical demultiplexing of high-bit-rate data streams.
Abstract: Integrated optical circuits based on silicon-on-insulator technology are likely to become the mainstay of the photonics industry. Over recent years an impressive range of silicon-on-insulator devices has been realized, including waveguides1,2, filters3,4 and photonic-crystal devices5. However, silicon-based all-optical switching is still challenging owing to the slow dynamics of two-photon generated free carriers. Here we show that silicon–organic hybrid integration overcomes such intrinsic limitations by combining the best of two worlds, using mature CMOS processing to fabricate the waveguide, and molecular beam deposition to cover it with organic molecules that efficiently mediate all-optical interaction without introducing significant absorption. We fabricate a 4-mm-long silicon–organic hybrid waveguide with a record nonlinearity coefficient of γ ≈ 1 × 105 W−1 km−1 and perform all-optical demultiplexing of 170.8 Gb s−1 to 42.7 Gb s−1. This is—to the best of our knowledge—the fastest silicon photonic optical signal processing demonstrated. A silicon–organic hybrid slot waveguide with a strong optical nonlinearity is demonstrated to perform ultrafast all-optical demultiplexing of high-bit-rate data streams. The approach could form the basis of compact high-speed optical processing units for future communication networks.
821 citations
TL;DR: In this article, light transmission through a curved dielectric rod of rectangular cross section embedded in different dielectrics is analyzed in closed-form, though approximate form, in three ranges: (i) small cross section guides such as a thin glass ribbon surrounded by air; making its width 1 percent of the wavelength, most of the power travels outside of the glass; the attenuation coefficient of the guide is two orders of magnitude smaller than that of glass; and the radius of curvature that doubles the straight guide loss is around 10,000Λ.
Abstract: Light transmission through a curved dielectric rod of rectangular cross section embedded in different dielectrics is analyzed in closed, though approximate form. We distinguish three ranges: (i) Small cross section guides such as a thin glass ribbon surrounded by air—Making its width 1 percent of the wavelength, most of the power travels outside of the glass; the attenuation coefficient of the guide is two orders of magnitude smaller than that of glass, and the radius of curvature that doubles the straight guide loss is around 10,000Λ. (ii) Medium cross section guide for integration optics—It is only a few microns on the side and capable of guiding a single mode either in low loss bends with short radii of curvature or in a high Q closed loop useful for filters. Q's of the order of 108 are theoretically achievable in loops with radii ranging from 0.04 to 1 mm, if the percentage refractive index difference between guide and surrounding dielectric lies between 0.1 and 0.01. (iii) Large cross section guides—They are multimode and are used in fiber optics. Conversion to higher order modes are found more significant than radiation loss resulting from curvature.
699 citations
TL;DR: This algorithm is a package of subroutines for Computing Bessel functions for orders v and complex z in −πz) and their double-precision counterparts are provided.
Abstract: This algorithm is a package of subroutines for Computing Bessel functions Hv(1)(z), Hv(2)(z), Iv(z), Jv(z), Kv(z), Yv(z) and Airy functions Ai(z), Ai′(z), Bi(z), Bi′(z) for ordersv≥0 and complex z in −p
236 citations