Optical force between two lossless waveguides has been described by two approaches. One approach is the explicit description of the force by the Maxwell stress tensor. Another approach is to describe the modal force i...
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Optical force between two lossless waveguides has been described by two approaches. One approach is the explicit description of the force by the Maxwell stress tensor. Another approach is to describe the modal force in terms of the derivative of the eigenmode frequency with respect to the distance variation. Here, we analytically prove the equivalence of these two approaches for lossless waveguides having arbitrary cross sections through the use of transformation optics formalism. Our derivation is applicable to both pressure and shear forces. We also show that these two approaches are not equivalent in the presence of loss. (C) 2019 Optical Society of America
In this dissertation a fabrication process is developed to reliably create suspended waveguides with optical grating features. Two potential applications for suspended waveguides with optical gratings are described, e...
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In this dissertation a fabrication process is developed to reliably create suspended waveguides with optical grating features. Two potential applications for suspended waveguides with optical gratings are described, evanescent field sensors and stimulated Brillouin scattering lasers, along with procedures for design and fabrication of the devices. Development the of fabrication process is described in detail, to explain each choice of material and fabrication method. The optimized fabrication process is presented along with the full parameters and fabrication techniques used. Suspended optical gratings are fabricated successfully using this method, reliably creating suspensions of up to 1mm in length, ranging from 1 μm to 5 μm in width, and 400–450 nm thick. The waveguides are optically characterized, revealing significant spectral features as a result of optically induced defects on the waveguides. These defects and their effects are thoroughly characterized through numerical modeling. Two methods to bypass the issues caused by these defects are presented: increased lithography resolution to create single mode or defect free waveguides, or the use of a high index cladding layer to force even large scale waveguides into single mode operation. Time resolved transmission measurements, using the defects to create stochastic spectral features, are completed as a proof of concept for these structures use as evanescent field sensors.
A fiber-to-chip spot size converter (SSC), fully compatible with silicon-on-insulator technology and optimized for efficient coupling in the O-band, is proposed, designed, and experimentally demonstrated. The SSC is b...
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A fiber-to-chip spot size converter (SSC), fully compatible with silicon-on-insulator technology and optimized for efficient coupling in the O-band, is proposed, designed, and experimentally demonstrated. The SSC is based on a parabolic inverted taper structure in between two lateral air trenches. The proposed air trenches only require one extra etch step after the silica cladding deposition and allow improving the optical confinement and therefore minimize the coupling losses. An optical bandwidth of 60 nm across the O-band and coupling losses as low as 2 dB at the wavelength of 1310 nm have been experimentally demonstrated.
The local modification of the composition of glasses by high repetition femtosecond laser irradiation is an attractive method for producing photonic devices. Recently, the successful production of waveguides with a re...
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The local modification of the composition of glasses by high repetition femtosecond laser irradiation is an attractive method for producing photonic devices. Recently, the successful production of waveguides with a refractive index contrast (Delta n) above 10(-2) by fs-laser writing has been demonstrated in phosphate glasses containing La2O3 and K2O modifiers. This large index contrast has been related to a local enrichment in lanthanum in the light guiding region accompanied by a depletion in potassium. In this work, we have studied the influence of the initial glass composition on the performance of waveguides that are produced by fs-laser induced element redistribution (FLIER) in phosphate-based samples with different La and K concentrations. We have analyzed the contribution to the electronic polarizability of the different glass constituents based on refractive index measurements of the untreated samples, and used it to estimate the expected index contrast caused by the experimentally measured local compositional changes in laser written guiding structures. These estimated values have been compared to experimental ones that are derived from near field images of the guided modes with an excellent agreement. Therefore, we have developed a method to estimate before-hand the expected index contrast in fs-laser written waveguides via FLIER for a given glass composition. The obtained results stress the importance of considering the contribution to the polarizability of all the moving species when computing the expected refractive index changes that are caused by FLIER processes.
The dynamic behavior of the class of periodic waveguides whose unit cells are generated through a quasicrystalline sequence can be interpreted geometrically in terms of a trace map that embodies the recursive rule obe...
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The dynamic behavior of the class of periodic waveguides whose unit cells are generated through a quasicrystalline sequence can be interpreted geometrically in terms of a trace map that embodies the recursive rule obeyed by traces of the transmission matrices. We introduce the concept ofcanonical quasicrystalline waveguides, for which the orbits predicted by the trace map at specific frequencies, calledcanonical frequencies, are periodic. In particular, there exist three families of canonical waveguides. The theory reveals that for those (i) the frequency spectra are periodic and the periodicity depends on the canonical frequencies, (ii) a set of multiple periodic orbits exists at frequencies that differ from the canonical ones, and (iii) perturbation of the periodic orbit and linearization of the trace map define a scaling parameter, linked to the golden ratio, which governs the self-similar structure of the spectra. The periodicity of the waveguide responses is experimentally verified on finite specimens composed of selectedcanonicalunit cells.
This paper explores the use of additive manufacturing as a low-cost method to integrate coaxial SubMiniature version A (SMA) connectors with waveguides operating at X-band. The integration of coaxial connectors into t...
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This paper explores the use of additive manufacturing as a low-cost method to integrate coaxial SubMiniature version A (SMA) connectors with waveguides operating at X-band. The integration of coaxial connectors into the filter and waveguide designs via 3D printing eliminates the need for two additional bulky external SMA-to-waveguide transitions, and allows for customizable integrated SMA-to-waveguide transitions that minimize impedance mismatch. Four designs, including air-filled and polycarbonate (PC) dielectric-filled waveguides and two-pole filters, are modeled and manufactured using additive manufacturing to demonstrate this integrative approach. Placement of the coaxial connector in terms of depth and location is optimized in the designs for good match using simulation. PC dielectric posts are also incorporated into the device to provide additional reinforcement to the coaxial connectors without impacting the radio frequency (RF) performance. Good RF performance is achieved with the variation less than 0.39 dB between simulated and measured insertion loss results at the center of the device passband.
We study saturable absorption in graphene-comprising nanophotonic waveguides taking into account the finite relaxation time as well as the carrier diffusion due to the nonuniform, tightly confined spatial profile of t...
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We study saturable absorption in graphene-comprising nanophotonic waveguides taking into account the finite relaxation time as well as the carrier diffusion due to the nonuniform, tightly confined spatial profile of the guided modes. We discuss various details of graphene SA and comment on the necessary conditions that allow for directly comparing our model with available experimental. The mathematical framework is based on the nonlinear Schrödinger equation which provides a strict framework for our analysis and is developed for two optical channels. We explore the propagation of cw, long and short pulsed signals in a silicon slot waveguide and show the importance of our model in order to capture the ultrafast dynamics of graphene and the spatial distribution of guided modes. Finally, we demonstrate how cross absorption modulation can be exploited in order to imprint data from a high power optical channel to a low power channel.
A promising method to leverage near-field power densities without the use of nanoscale vacuum gaps is through hyperbolic metamaterial (HMM) waveguides. When placed between a hot and cold reservoir, an ideal HMM can tr...
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A promising method to leverage near-field power densities without the use of nanoscale vacuum gaps is through hyperbolic metamaterial (HMM) waveguides. When placed between a hot and cold reservoir, an ideal HMM can transmit surface waves across several microns, enabling an extension of near-field enhancements. However, when accounting for transmission loss due to realistic levels of absorption within the waveguide, previous studies have shown that the enhancements are significantly curtailed at wide separations. In our study, we investigate the role of internal sources within nonisothermal HMMs. We demonstrate that, in some cases, the emission from the HMM accounts for over 90% of the total radiative heat transfer to the receiver, and that these additional sources can largely compensate for optical losses associated with decreased transmission from the emitter to the receiver. Lastly, we investigate the spectral transport in a realistic three-body system that has mismatching optical properties between the boundaries (emitter and receiver) and the waveguide (HMM). Our model shows that the near-field thermal transport remains spectrally selective to the boundaries, even as major radiative contributions come from the waveguide. This work may enable the design of nonisothermal emitter-waveguide-receiver systems that transmit near-field power levels over wider separations.
Various recent experiments have proven the theoretical prediction that domain walls in planar magnetic structures can channel spin waves as magnonic waveguides, establishing a platform for building magnonic devices. R...
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Various recent experiments have proven the theoretical prediction that domain walls in planar magnetic structures can channel spin waves as magnonic waveguides, establishing a platform for building magnonic devices. Recently, three-dimensional nanomagnetism has been boosted and become a significant branch of magnetism, because three-dimensional magnetic structures expose much emerging physics hidden behind planar ones and will provide broader room for device engineering. Skyrmions and antiskyrmions, as natural three-dimensional magnetic configurations, are not considered yet in the context of spin-wave channeling and steering. Here, we show that skyrmion tubes can act as nonplanar magnonic waveguides, if excited suitably. An isolated skyrmion tube in a magnetic nanoprism induces spatially separate internal and edge channels of spin waves; the internal channel has a narrower energy gap, compared with that of the edge channel and, accordingly, can transmit signals at lower frequencies. Additionally, we verify that those spin-wave beams along the magnetic nanoprism are restricted to the regions of potential wells. Transmission of spin-wave signals in such waveguides results from the coherent propagation of locally driven eigenmodes of skyrmions, i.e., the breathing and rotational modes. Finally, we find that spin waves along the internal channels are less susceptible to the magnetic field than those along the edge channels. Our work will open up an arena for spin-wave manipulation and help to bridge between skyrmionics and magnonics.
TiO2 thin films have been deposited on glass substrates with and without ZnO underlayer by sol-gel dip coating process. XRD patterns show the formation of anatase phase with the diffraction lines (1 0 1) and (2 0 0) i...
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TiO2 thin films have been deposited on glass substrates with and without ZnO underlayer by sol-gel dip coating process. XRD patterns show the formation of anatase phase with the diffraction lines (1 0 1) and (2 0 0) in TiO2/glass sample. In TiO2/(ZnO/glass) sample, TiO2 is composed of anatase phase with the diffraction line (2 0 0) but the diffraction peaks of ZnO wurtzite are also well-defined. The determination of the refractive index and the thickness of the waveguiding layers has been performed by m-lines spectroscopy. The thickness of TiO2 thin films deduced by Rutheford Backscattering Geometry (RBS) agrees well with that obtained by m-lines spectroscopy. TiO2/glass sample exhibits one guided TE0 and TM0 polarized modes. In TiO2/(ZnO/glass) sample, only, TE0 single mode has been excited due to cutoff condition.
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