Showing papers on "Waveguide (optics) published in 2004"
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
1,891 citations
TL;DR: A novel silicon waveguide structure for guiding and confining light in nanometer-wide low-refractive-index material is experimentally demonstrated and it is shown that the structure can be implemented in highly integrated photonics.
Abstract: We experimentally demonstrate a novel silicon waveguide structure for guiding and confining light in nanometer-wide low-refractive-index material. The optical field in the low-index material is enhanced because of the discontinuity of the electric field at high-index-contrast interfaces. We measure a 30% reduction of the effective index of light propagating in the novel structure due to the presence of the nanometer-wide low-index region, evidencing the guiding and confinement of light in the low-index material. We fabricate ring resonators based on the structure and show that the structure can be implemented in highly integrated photonics.
740 citations
TL;DR: In this paper, the authors show that a metal-insulator-metal geometry is necessary and sufficient condition for subwavelength confinement of the optical mode, and the resulting trade-off between propagation and confinement for surface plasmons is discussed.
Abstract: Plasmonic waveguides can guide light along metal-dielectric interfaces with propagating wave vectors of greater magnitude than are available in free space and hence with propagating wavelengths shorter than those in vacuum. This is a necessary, rather than sufficient, condition for subwavelength confinement of the optical mode. By use of the reflection pole method, the two-dimensional modal solutions for single planar waveguides as well as adjacent waveguide systems are solved. We demonstrate that, to achieve subwavelength pitches, a metal-insulator-metal geometry is required with higher confinement factors and smaller spatial extent than conventional insulator-metal-insulator structures. The resulting trade-off between propagation and confinement for surface plasmons is discussed, and optimization by materials selection is described.
705 citations
TL;DR: In this paper, the authors demonstrate how to design a 90° bend in a two-dimensional photonic crystal waveguide with a transmission loss of less than 0.3% in almost the entire frequency range of the guided mode.
Abstract: Topology optimization is a promising method for systematic design of optical devices. As an example, we demonstrate how the method can be used to design a 90° bend in a two-dimensional photonic crystal waveguide with a transmission loss of less than 0.3% in almost the entire frequency range of the guided mode. The method can directly be applied to the design of other optical devices, e.g., multiplexers and wave splitters, with optimized performance.
324 citations
TL;DR: In this article, the transmission, group delay time and quadratic dispersion properties of the four basic building blocs of optical filters built using ring resonators are described, and explicit expressions to compute the complex amplitude of the circulating wave in the ring, the Q factor, the finesse and the insertion loss are also given.
Abstract: This tutorial describes the transmission, group delay time and quadratic dispersion properties of the four basic building blocs of optical filters built using ring resonators. These building blocs are single-ring resonators in either two-port (all-pass) or four-port (add/drop filter) configuration. The effect of waveguide and coupler loss is included throughout. Explicit expressions to compute the complex amplitude of the circulating wave in the ring, the Q factor, the finesse and the insertion loss are also given. Attention is drawn to the similarities between the ring resonator the Fabry-Pe/spl acute/rot resonator and the Gires-Tournois interferometer. Material properties and fabrication technology are not reviewed.
319 citations
Patent•
16 Jul 2004
TL;DR: In this paper, a waveguide core and a nanocomposite material optically coupled to the waveguide was described. But the authors did not specify the number of quantum dots.
Abstract: The invention relates to an optical device. The optical device comprises a waveguide core and a nanocomposite material optically coupled to the waveguide core. The nanocomposite material includes a plurality of quantum dots. The nanocomposite material has a nonlinear index of refraction γ that is at least 10 −9 cm 2 /W when irradiated with an activation light having a wavelength λ between approximately 3×10 −5 cm and 2×10 −4 cm.
222 citations
TL;DR: In this article, a double-pulse measurement technique based on the Fresnel reflection from the fibre tip is used for measurements of the refractive indices of various liquids at wavelengths of 1310 and 1551 nm.
Abstract: A fibre optic technique based on the Fresnel reflection from the fibre tip is used for measurements of the refractive indices of various liquids at wavelengths of 1310 and 1551 nm. Reflection signals from liquid?fibre interface are compared with reflection signals from air?fibre interface to obtain the refractive index. Values of refractive indices for distilled water measured by this technique compare very well with known values at both wavelengths only if the fibre effective waveguide index is used. Applying the double-pulse measurement technique, it is shown that a measurement resolution of about 2.5 ? 10?5 can be achieved.
217 citations
TL;DR: In this article, high refractive index contrast optical microdisk resonators fabricated from silicon-on-insulator wafers are studied using an external silica fiber taper waveguide as a wafer-scale optical probe.
Abstract: High refractive index contrast optical microdisk resonators fabricated from silicon-on-insulator wafers are studied using an external silica fiber taper waveguide as a wafer-scale optical probe. Measurements performed in the 1500 nm wavelength band show that these silicon microdisks can support whispering-gallery modes with quality factors as high as 5.2×10^5, limited by Rayleigh scattering from fabrication induced surface roughness. Microdisks with radii as small as 2.5 µm are studied, with measured quality factors as high as 4.7×10^5 for an optical mode volume of 5.3 (lambda/n)^3.
187 citations
TL;DR: In this article, a flexible optical waveguide film with integrated optoelectronic devices (vertical-cavity surface-emitting laser and p-i-n photodiode arrays) for fully embedded board-level optical interconnects was demonstrated.
Abstract: This paper demonstrates a flexible optical waveguide film with integrated optoelectronic devices (vertical-cavity surface-emitting laser (VCSEL) and p-i-n photodiode arrays) for fully embedded board-level optical interconnects. The optical waveguide circuit with 45/spl deg/ micromirror couplers was fabricated on a thin flexible polymeric substrate by soft molding. The 45/spl deg/ couplers were fabricated by cutting the waveguide with a microtome blade. The waveguide core material was SU-8 photoresist, and the cladding was cycloolefin copolymer. A thin VCSEL and p-i-n photodiode array were directly integrated on the waveguide film. Measured propagation loss of a waveguide was 0.6 dB/cm at 850 nm.
178 citations
Book•
1 Jan 2004
TL;DR: In this paper, the authors present a system of units for optical Fibers and planar waveguides, as well as a software package for time domain switching and optical switch.
Abstract: Preface.1. Optical Fibers.2. Passive Fiber Components.3. Active Fiber Components.4. Planar Waveguides.5. Semiconductor Lasers and Amplifiers.6. Optical Modulators.7. Photodetectors.8. WDM Components.9. Optical Switching.10. Time-Domain Switching.Appendix A: System of Units.Appendix B: Software Package.Appendix C: Acronyms.Index.
167 citations
TL;DR: In this article, a low loss elliptical intersection of Si photonic wire waveguides on a silicon-on-insulator substrate was fabricated, achieving an insertion loss of less than 0.1 dB at a wavelength of 1.55 µm.
Abstract: We fabricated a low loss elliptical intersection of Si photonic wire waveguides on a silicon-on-insulator substrate. An insertion loss of less than 0.1 dB was achieved at a wavelength of 1.55 µm. The experimental loss characteristic closely agreed with the theoretical one. We also used this intersection as a suspension of an air-bridge-type waveguide and evaluated a low loss characteristic similar to that mentioned above.
TL;DR: In this paper, a low-loss rib waveguide (WG) was fabricated in silicon-on-insulator with a small effective core area of ∼1.57μm2 and measured the stimulated Raman scattering gain in the WG.
Abstract: We fabricated a low-loss (∼0.22dB∕cm) rib waveguide (WG) in silicon-on-insulator with a small effective core area of ∼1.57μm2 and measured the stimulated Raman scattering gain in the WG. We obtained 2.3dB Raman gain in a 4.8-cm-long S-shaped WG using a 1455nm pump laser with a cw power of 0.9W measured before the WG. In addition, we observed nonlinear dependence of Raman gain and optical propagation loss as a function of the pump power. Our study shows that this mainly is due to two-photon absorption (TPA) induced free carrier absorption in the silicon WG. We experimentally determined the TPA induced free carrier lifetime of 25ns, which agrees well with our modeling.
TL;DR: In this paper, the authors present a successful design, realisation and characterisation of single-mode TE00-TM00 rib optical waveguides composed of SU-8 polymer.
TL;DR: In this article, a Y splitter has been fabricated in LN and the output optical fields through the channel waveguide and Y-splitter were measured and compared with theoretical simulation results, and the refractive index change of /spl sim/6/spl times/10/sup -4/ was obtained with the transmitted-beam near field method.
Abstract: Using a tightly focused femtosecond laser of microjoule energy per pulse, we produced optical waveguide inside the pure Lithium Niobate (LN) substrate. This technique has the potential to generate not only channel waveguide but three-dimensional photonic devices. In this letter, a Y splitter has been fabricated in LN. The output optical fields through the channel waveguide and Y splitter were measured and compared with theoretical simulation results. The refractive index change of /spl sim/6/spl times/10/sup -4/ was obtained with the transmitted-beam near-field method. The properties of channel waveguide and Y splitter were discussed for further study.
TL;DR: In this article, a single-mode integrated optical waveguide with liquid cores is presented, which is based on antiresonant reflecting optical (ARROW) waveguides with hollow cores.
Abstract: We report the design, fabrication, and demonstration of single-mode integrated optical waveguides with liquid cores. The principle of the device is based on antiresonant reflecting optical (ARROW) waveguides with hollow cores. We describe design principles for waveguide loss optimization down to 0.1∕cm. Using a fabrication process based on conventional silicon microfabrication and sacrificial core layers, waveguides of varying widths and lengths with volumes covering the pico- to nanoliter range were fabricated. We observe confined mode propagation, measure waveguide losses of 2.4∕cm, and demonstrate that the waveguides possess tailorable wavelength selectivity. The potential for highly integrated, sensitive devices based on these properties of the ARROW waveguides is discussed.
TL;DR: A numerical differentiation algorithm, namely, the backward Taylor series expansion and the digital signal processing technique are employed, for the first time, to develop a generalized theory of a pth-derivative FIR optical differentiator, capable of processing Gaussian pulses with high accuracy.
TL;DR: In this article, single-crystal optical waveguides of 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST), an organic material with a large electro-optic coefficient, have been obtained.
Abstract: Single-crystal optical waveguides of 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST), an organic material with a large electro-optic coefficient, have been obtained. DAST decomposes at its melting temperature, making its growth from the melt difficult. However, graphoepitaxy allows for >1 mm s−1 growth, 1×105 times faster than conventional techniques, and produces crystals of the correct dimensions for optical waveguides, 1–15 μm on a side and 5–10 mm long. The crystals grow with the c-axis normal to the substrate, and with in-plane orientation determined by lithographic patterning. The electro-optic coefficient dn/dE is 600±300 pm V−1 at 1.55 μm wavelength. Optical losses are <10 dB cm−1.
Patent•
6 Feb 2004TL;DR: In this article, a pump array (8) for providing pump radiation (7), a first pump combiner (1), and a waveguide (3) were coupled into the waveguide via the first pump-combiner via a pump-combiner.
Abstract: Apparatus for providing optical radiation (10) comprising a pump array (8) for providing pump radiation (7), a first pump combiner (1), and a waveguide (3), wherein the pump radiation (7) from the pump array (8) is coupled into the waveguide (3) via the first pump combiner (1), and wherein the waveguide (3) comprises a pump guide (4) for guiding the pump radiation (7), and a gain medium (5) which emits the optical radiation (10) when it is pumped by the pump radiation (7).
TL;DR: In this paper, a variable semiconductor optical buffer based on the electromagnetically induced transparency in a quantum dot waveguide is theoretically investigated with feasible parameters for applications to a 40 Gbps optical network.
Abstract: A variable semiconductor optical buffer based on the electromagnetically induced transparency in a quantum dot waveguide is theoretically investigated with feasible parameters for applications to a 40 Gbps optical network. We show the refractive index and absorption spectra of the quantum dot waveguide at various pump levels, which exhibit an optimal pump power for maximum slow-down factor, in agreement with the previous experimental observation using a Pr-doped solid. The group velocity slow-down factor is theoretically analysed as a function of the pump intensity at different broadened linewidths. Inhomogeneous broadening in self-assembled quantum dots degrades the slow-down factor. In order to reduce the inhomogeneous broadening effects, we propose to use a resonant microcavity structure with quantum dots embedded in the active layer to enhance the slow-down factor.
Patent•
11 May 2004
TL;DR: In this paper, a planar optical waveguide having at least one set of diffractive elements is described. And the diffracted portion of the optical signal reaches the output port as a superposition of multiple transverse modes.
Abstract: A spectral filter comprises a planar optical waveguide having at least one set of diffractive elements. The waveguide confines in one transverse dimension an optical signal propagating in two other dimensions therein. The waveguide supports multiple transverse modes. Each diffractive element set routes, between input and output ports, a diffracted portion of the optical signal propagating in the planar waveguide and diffracted by the diffractive elements. The diffracted portion of the optical signal reaches the output port as a superposition of multiple transverse modes. A multimode optical source may launch the optical signal into the planar waveguide, through the corresponding input optical port, as a superposition of multiple transverse modes. A multimode output waveguide may receive, through the output port, the diffracted portion of the optical signal. Multiple diffractive element sets may route corresponding diffracted portions of optical signal between one or more corresponding input and output ports.
TL;DR: It is shown that the group index strongly depends on the number of cavities in the system, especially for operation at the center frequency, and the nonlinear phase sensitivity shows an enhancement proportional to the square of the groupIndex.
Abstract: In this paper, we derive the exact dispersion relation of one dimensional periodic coupled-resonator optical waveguides of finite length, from which the reduced group velocity of light is obtained. We show that the group index strongly depends on the number of cavities in the system, especially for operation at the center frequency. The nonlinear phase sensitivity shows an enhancement proportional to the square of the group index (or light slowing ratio). Aperiodic coupled ring-resonator optical waveguides with optimized linear properties are then synthesized to give an almost ideal nonlinear phase shift response. For a given application and bandwidth requirement, the nonlinear sensitivity can be increased by either decreasing resonator length or by using higher-order structures. The impact of optical loss, including linear and two-photon absorption is discussed in post-analysis.
TL;DR: Femtosecond time of flight measurements based on a Kerr shutter configuration show that the group velocity dispersion is small at a wavelength of 800 nm, confirming that dispersion may be neglected in the estimation of n2 so that a simplified theory can be used with good accuracy.
Abstract: Self-phase modulation has been observed for ultrashort pulses of wavelength 800nm propagating through a 1 cm-long Ta2O5 rib waveguide. The associated nonlinear refractive index n2 was estimated to be 7.23×10-19 m2/W, which is higher than silica glass by more than one order of magnitude. Femtosecond time of flight measurements based on a Kerr shutter configuration show that the group velocity dispersion is small at a wavelength of 800 nm, confirming that dispersion may be neglected in the estimation of n2 so that a simplified theory can be used with good accuracy.
TL;DR: Polarization-independent hollow optical waveguides were obtained with the hollow waveguide structure and a uniform propagation loss of the waveguide to be around 1.7dB/cm for C+L band was found for the TE and TM modes.
Abstract: In this study, a hollow optical waveguide with omni-directional reflectors in silicon-based materials was design, fabricated and characterized. By using dry etching technique, plasma-enhanced chemical vapor deposition for Si/SiO2 thin films and covering another wafer with omni-directional reflector together, the waveguides can be formed with an air core of 1.2microm x 1.3microm. A uniform propagation loss of the waveguide to be around 1.7dB/cm for C+L band was found for the TE and TM modes. Polarization-independent hollow optical waveguides were obtained with the hollow waveguide structure.
TL;DR: In this article, a direct fabrication of organic light-emitting diodes (OLEDs) and organic photodetectors (OPDs) on polymeric waveguide substrates to form flexile optical integrated devices is demonstrated.
Abstract: Direct fabrication of organic light-emitting diodes (OLEDs) and organic photodetectors (OPDs) on polymeric substrates, i.e., polymeric waveguide substrates to form flexile optical integrated devices is demonstrated. The OELD and OPD were fabricated by organic molecular beam deposition (OMBD) technique on a polymeric or a glass substrate, for comparison. The device fabricated on a polymeric substrate shows similar device characteristics to that on a glass substrate. Optical signals of faster than 100 MHz have been created by applying pulsed voltage directly to the OLED utilizing diamine derivative, or rubrene or porphine doped in 8-hydoxyquinolinum aluminum derivatives, as an emissive layer. Electrical signals are successively converted to optical signals for optical transmission of moving picture signals with OLED fabricated on a polymeric waveguide. OPDs utilizing phthalocyanines derivatives with superlattice structure provide increased pulse response with input optical signals, and the OPD with the cutoff frequency of more than 5 MHz has been realized.
TL;DR: In this paper, a multimode erbium and ytterbium (Yb3+) rare-earth ion codoped polymeric channel waveguides were fabricated using electron beam direct writing.
Abstract: Codoping of erbium (Er3+) and ytterbium (Yb3+) rare-earth ions in polymer was studied for optical amplifier applications. The absorption spectrum confirms that the presence of Yb3+ ions enhances the absorption efficiency of Er3+ ions. Typical Er3+ luminescence at ∼1540 nm wavelength was observed, and the full width at half maximum bandwidth is ∼47 nm wide. Multimode Er3+–Yb3+ codoped polymeric channel waveguides were fabricated using electron beam direct writing. With an input signal power of <−18 dB m, an optical gain of 13 dB at a wavelength of 1533 nm was measured in an 18 mm long multimode channel waveguide.
TL;DR: The effect of nonlinear transmission in coupled optical waveguide arrays is theoretically investigated and a realistic experimental setup is suggested and it is shown that the energy transfers from the boundary waveguide to the waveguide array above a certain threshold intensity of the injected beam.
Abstract: The effect of nonlinear transmission in coupled optical waveguide arrays is theoretically investigated and a realistic experimental setup is suggested. The beam is injected in a single boundary waveguide, linear refractive index of which (${n}_{0}$) is larger than refractive indexes ($n$) of other identical waveguides in the array. Particularly, the effect holds if $\ensuremath{\omega}({n}_{0}\ensuremath{-}n)/cg2Q$, where $Q$ is a linear coupling constant between array waveguides, $\ensuremath{\omega}$ is a carrier wave frequency, and $c$ is a light velocity. Numerical experiments show that the energy transfers from the boundary waveguide to the waveguide array above a certain threshold intensity of the injected beam. This effect is due to the creation and the propagation of gap solitons in full analogy with a similar phenomenon in sine-Gordon lattice [F. Geniet and J. Leon, Phys. Rev. Lett. 89, 134102 (2002)].
TL;DR: In this paper, a slab waveguide structure that guides visible light in an air core was designed and analyzed using metal-dielectric nanostructures, which showed intriguing optical properties including total external reflection.
Abstract: Metamaterials composed of metal-dielectric nanostructures can be engineered to have the real part of the effective refractive index less than unity at optical wavelengths. These materials show intriguing optical properties including total external reflection. We utilize this effect to design and analyze slab waveguide structures that guide visible light in an air core.
Patent•
15 Jun 2004TL;DR: In this article, an anti-resonant reflecting optical waveguide (ARROW) is used to measure fluorescence characteristics associated with the sample material. But the non-solid core layer has an index of refraction lower than that of the surrounding solid-state material.
Abstract: An optical waveguide is constructed so as to comprise a non-solid core layer surrounded by a solid-state material. The non-solid core layer has an index of refraction which is lower than the index of refraction of the surrounding solid-state material, and light can be transmitted with low loss through the non-solid core layer. In an exemplary application, the non-solid core layer comprises a sample material whose light transmission, absorption, and/or interference characteristics are to be measured. In addition, a perpendicular waveguide portion may be included for use in injecting light into the core for measuring fluorescence characteristics associated with the sample material. Most preferably, the optical waveguide is generally structured as an anti-resonant reflecting optical waveguide (ARROW), which comprises a Fabry-Perot reflector adjacent to the core layer, whereby light is substantially prevented from leaking out of said core in a transverse direction.
TL;DR: In this paper, the development of the longest wavelength quantum-cascade laser (QCL) without the assistance of magnetic fields is reported, which uses a structure based on resonant-phonon depopulation, and a metal-metal waveguide to obtain high modal confinement.
Abstract: The development of quantum-cascade lasers (QCLs) at 21 THz (/spl lambda//spl sime/141 /spl mu/m), which is the longest wavelength QCL to date without the assistance of magnetic fields, is reported This laser uses a structure based on resonant-phonon depopulation, and a metal-metal waveguide to obtain high modal confinement with low waveguide losses Lasing was observed up to a heatsink temperature of 72 K in pulsed mode and 40 K in continuous-wave (CW) mode, and 12 mW of power was obtained in CW mode at 17 K
TL;DR: In this article, the upconversion emission of a Na2O-Al2O3-GeO2-PbO−PbF2 glass was investigated under 976-nm diode laser excitation.
Abstract: Yb3+/Er3+-codoped Na2O–Al2O3–GeO2–PbO–PbF2 glasses that are suitable for use in fiber lasers, amplifiers, and waveguide devices have been fabricated and characterized. The density, refractive indices, optical absorptions, Judd–Ofelt parameters, and spontaneous-transition probabilities of the glasses have been measured and calculated. Intense and broad 1.53-μm infrared fluorescence and visible upconversion luminescence were observed under 976-nm diode laser excitation. For the 1.53-μm emission band, the full widths at the half-maximum increase and the peak wavelengths are blueshifted with an increase of PbF2. The stimulated-emission cross sections were calculated from the measured-absorption cross section according to the McCumber theory. The monotonically reduced emission cross section arises from the decreased refractive indices of glasses and the increased linewidth of the infrared fluorescence spectrum. For the upconversion emissions centered at 524, 547, and 660 nm, the emission intensity changes remarkably with PbF2 contents from 0 to 15 mol.%. The quadratic dependence of the green and red emissions on excitation power indicates that a two-photon absorption process occurs under the 976-nm excitation. The relatively long lifetimes of the Er3+ 4S3/2 and 4F9/2 levels for the NAGF3 glass gives rise to a much more intense upconversion emission.