Use Of Waveguides Research Articles

Synthesized All-Pass Waveguide for Ultrafast Electronics

Ultrashort pulse transmission has been recognized as a primary problem that fundamentally hinders the development of ultrafast electronics beyond the current nanosecond timescale. This requires a transmission line or waveguide that exhibits an all-pass frequency behavior for the transmitted ultrashort pulse signals. However, this type of waveguiding structure has not yet been practically developed; groundbreaking innovations and advances in signal transmission technology are urgently required to address this scenario. Herein, we present a synthesized all-pass waveguide that demonstrates record guided-wave controlling capabilities, including eigenmode reshaping, polarization rotation, loss reduction, and dispersion improvement. We experimentally developed two waveguides for use in ultrabroad frequency ranges (direct current (DC)-to-millimeter-wave and DC-to-terahertz). Our results suggest that the waveguides can efficiently transmit picosecond electrical pulses while maintaining signal integrity. This waveguide technology is an important breakthrough in the evolution of ultrafast electronics, providing a path towards frequency-engineered ultrashort pulses for low-loss and low-dispersion transmissions.

Design and analysis of all-optical 1 × 4 demultiplexer based on 2D photonic crystal

Abstract In this paper, an all-optical 1 × 4 demultiplexer (DEMUX) has been designed by employing 2D photonic crystal (PhC) waveguides for use in optical networking and signal processing. The proposed structures consist of four T-shaped and one Y-shaped waveguide using 15a × 15a rectangular lattice silicon rods in ambient air. All-optical DEMUX has been simulated using the finite-difference-time-domain (FDTD) method and the results have been verified by distributing the optical field at a wavelength of 1.90 μm. Analysis of the device has been carried out for distinctive crystal and lattice designs with the achievement of a transmission ratio of more than 2.05 in presence of select input.

Design of a cylindrical corrugated waveguide for a collinear wakefield accelerator

We present the design of a cylindrical corrugated waveguide for use in the A-STAR accelerator under development at Argonne National Laboratory. A-STAR is a high gradient, high bunch repetition rate collinear wakefield accelerator that uses a 1-mm inner radius corrugated waveguide to produce a $90\text{ }\text{ }\mathrm{MV}\text{ }{\mathrm{m}}^{\ensuremath{-}1}$, 180-GHz accelerating field when driven by a 10-nC drive bunch. To select a corrugation geometry for A-STAR, we analyze three types of corrugation profiles in the overmoded regime with $a/\ensuremath{\lambda}$ ranging from 0.53 to 0.67, where $a$ is the minor radius of the corrugated waveguide and $\ensuremath{\lambda}$ is the free-space wavelength. We find that the corrugation geometry that optimizes the accelerator performance is a rounded profile with vertical sidewalls and a corrugation period $p\ensuremath{\ll}a$. Trade-offs between the peak surface fields and thermal loading are presented along with calculations of pulse heating and steady-state power dissipation. In addition to the ${\mathrm{TM}}_{01}$ accelerating mode, properties of the ${\mathrm{HEM}}_{11}$ mode and contributions from higher order modes are discussed.

SiN half-etch horizontal slot waveguides for integrated photonics: numerical modeling, fabrication, and characterization of passive components.

This work presents a "half-etch" horizontal slot waveguide design based on SiN, where only the upper SiN layer is etched to form a strip that confines the mode laterally. The numerical modeling, fabrication, and characterization of passive waveguiding components are described. This novel slot waveguide structure was designed with on-chip light amplification in mind, for example with an Er-doped oxide spacer layer. Proof-of-concept racetrack resonators were fabricated and characterized, showing quality factors up to 50,000 at critical coupling and residual losses of 4 dB/cm at wavelengths away from the N-H bond absorption peak in SiN, demonstrating the high potential of these horizontal slot waveguides for use in active integrated photonics.

A 110–170-GHz Non-Galvanic Interface for Integrating Silicon Micromachined Chips With Metallic Waveguide Systems

We report on the development of a non-galvanic transition from a silicon micromachined to metallic rectangular waveguide for use in integrated waveguide systems at D-band (110-170 GHz). This transition overcomes the limitations of current solutions that require proper ohmic (galvanic) contact between both waveguides, and thus relaxes tolerance requirements in assembly and manufacturing. The transition uses an in-plane design which enables low-loss integration of micromachined waveguide components, as it eliminates the need for waveguide bends and complex multi-layer structures. We describe the RF design, analyze the EM simulation results, and explain the operating principle of the transition. To verify the concept, dedicated silicon micromachined and metallic waveguides are designed and fabricated. Characterization of the assembled samples shows good agreement with simulation. The transition achieves a typical insertion loss of 0.3 dB and return loss above 20 dB over most of the D-band. Measurement of multiple samples and repeated assemblies results in a variation of S21 of less than ±0.1 dB over the whole band, demonstrating good robustness and repeatability. By removing the need for galvanic connection, automated tools can then be used during system assembly, which enables industrial scale applications such as wireless communications.

Bend- and Twist-Insensitive Flexible Multimode Polymer Optical Interconnects

Polymer multimode optical waveguides can enable high-speed short-reach optical interconnection at low cost within high performance electronic systems. The formation of such waveguides on flexible substrates can offer important additional advantages such as light weight, ability to be tightly bent, and reconfigurability which are particularly important in environments where space, weight, and shape conformity are critical, for instance in vehicles and aircraft. The ability of such flexible optical interconnects to be tightly bent and twisted with low excess loss is crucial in enabling their use in systems with limited space and with movable parts. As a result, in this work, we present a new design of such flexible polymer multimode waveguides that achieves improved bending loss performance over the conventional waveguide design. It is experimentally shown that the proposed design achieves a very low excess loss of 0.5 dB for a 3 mm radius bend under a 50 μm MMF launch. In comparison, flexible waveguides with the conventional design exhibit a 2 dB excess loss under the same launch and bend conditions. Additionally, useful rules that associate the twisting loss performance of flexible polymer waveguide samples with their geometric characteristics are derived. It is shown that negligible twisting losses (<0.1 dB for a 50 μm MMF input) can be achieved when the dimensions of the waveguide samples are appropriately selected. The results demonstrate the strong potential of such bend- and twist-insensitive flexible polymer waveguides for use in next-generation vehicles and aircraft.

Thermoforming of planar polymer optical waveguides for integrated optics in smart packaging materials

Abstract The innovations in smart packaging will open up a wide range of opportunities in the future. This work describes the processing of additive manufactured and planar integrated polymer optical waveguides for use in smart packaging products. The previously published combination of flexographic and Aerosol Jet printing is complemented by thermoforming and thus creates three-dimensional integrated multimode waveguides with optical attenuation of 1.9 dB/cm ± 0.1 dB/cm @ 638 nm. These properties will be the basis to develop smart applications in packaging materials.

High-birefringence direct UV-written waveguides for use as heralded single-photon sources at telecommunication wavelengths.

Direct UV-written waveguides are fabricated in silica-on-silicon with birefringence of (4.9 ± 0.2) × 10-4, much greater than previously reported in this platform. We show that these waveguides are suitable for the generation of heralded single photons at telecommunication wavelengths by spontaneous four-wave mixing. A pulsed pump field at 1060 nm generates pairs of photons in highly detuned, spectrally uncorrelated modes near 1550 nm and 800 nm. Waveguide-to-fiber coupling efficiencies of 78-91 % are achieved for all fields. Waveguide birefringence is controlled through dopant concentration of GeCl4 and BCl3 using the flame hydrolysis deposition process. The technology provides a route towards the scalability of silica-on-silicon integrated components for photonic quantum experiments.

Characterization of Ge Quantum Dot Optical Waveguides for High Speed Optical Modulators

Quantum Dot (QD) Optical Modulators can provide high speed modulation in low cost indirect bandgap materials. Si based optical modulators can be realized with the inclusion of self-assembled Ge QDs to provide low cost, high speed CMOS compatible optical devices. In this paper, we present the optical characterization of a novel Ge-QD Si-SiO2 based waveguide for use in as an optical modulator. Optical performance figures of merit are investigated including insertion loss (IL) measurements, and Wavelength dependent loss (WDL). We present a multimode waveguide fabricated with conventional CMOS processing. The waveguide provides 4.43dB/cm loss and individual discrete absorption regimes corresponding to the unique minibands produced by superlattice properties of the self-assembled Ge QDs in the IR regime. Absorption properties of the Ge QDs are demonstrated and verified against the QD superlattice bandgap model. Analysis and simulation is presented to qualitatively compare the QD bandgap energies with the reported optical properties. The QD functionalized structure demonstrates the fundamental optical principles of a QD waveguide, setting the foundation for a active modulation testing of this QD based optical modulator.

Transition between gap waveguides for use in multilayer structures at millimeter-wave frequencies

This is the peer reviewed version of the following article: Carrera-Suarez, F., Navarro-Mendez, D., Baquero-Escudero, M. and Sanchez-Escuderos, D. (2016), Transition between gap waveguides for use in multilayer structures at millimeter-wave frequencies. Microw. Opt. Technol. Lett., 58: 102–106., which has been published in final form at http://dx.doi.org/10.1002/mop.29507. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.

Lithium niobate ridged waveguides with smooth vertical sidewalls fabricated by an ultra-precision cutting method.

This paper demonstrates the application of ultra-precision cutting to the fabrication of ridged LiNbO₃ waveguides for use in low-loss photonic integrated circuits. Ridged waveguides with sidewall verticality of 88° and ultra-smooth sidewalls were obtained in LiNbO₃ crystals using this technique. In addition, the possibility of fabricating bent ridged waveguides via this mechanical micromachining method was examined. The root mean square surface roughness of the machined sidewall was 4.5 nm over an area of 2.5 × 10 µm, which is sufficiently low so as to minimize scattering losses of guided light. The propagation loss of the ridged waveguide produced during this work was well below 1 dB/cm at a wavelength of 1550 nm. The present technique should have significant applicability to the micromachining of ferroelectric materials and the fabrication of highly confined optical waveguides such as ridged waveguides and photonic wires.

Plasmonic Terahertz Waveguide Based on Anisotropically Etched Silicon Substrate

We experimentally examine anisotropically etched silicon surfaces for terahertz (THz) plasmonic guided wave applications. Highly doped silicon surfaces are anisotropically etched to form a one-dimensional array of subwavelength concave pyramidal troughs. The plasmonic wave guides are found to support highly confined guided modes both in transverse and longitudinal directions. The resonant frequencies of the modes can be controlled by adjusting the geometrical parameters of the troughs. The existence of guided modes in plasmonic wave guides is also established through finite-element-based numerical simulations. These wave guides could provide a silicon-based alternative to metallic wave guides for use in future THz devices.

RETRACTED: Design of integrated optical circulator based on photonic crystals

Abstract Photonic crystals containing defects produce enhanced Faraday rotation. They have opened up the possibility of fabricating very compact magneto-optics structures. In this work, we have designed a two-dimensional photonic crystal waveguide for use in optical packaging and integrated optical circuits. For design purposes, a temporal coupled mode theory was utilized at the first step. It examined the coupling between cavity and optical ports. After acquiring a general solution, it would be applied to specific problem in hand. Then, optical characteristics of photonic crystal were investigated to design the practical parts such as cavity and waveguides which eventually a triangular crystal lattice of air holes in Bi:YIG (BIG) was considered to be the best candidate. Finally, the results of analytical investigations were evaluated using OptiFDTD software and then were confirmed.

Topical Developments in High-Field Dynamic Nuclear Polarization.

We report our recent efforts directed at improving high-field DNP experiments. We investigated a series of thiourea nitroxide radicals and the associated DNP enhancements ranging from ε = 25 to 82 that demonstrate the impact of molecular structure on performance. We directly polarized low-gamma nuclei including 13C, 2H, and 17O using trityl via the cross effect. We discuss a variety of sample preparation techniques for DNP with emphasis on the benefit of methods that do not use a glass-forming cryoprotecting matrix. Lastly, we describe a corrugated waveguide for use in a 700 MHz / 460 GHz DNP system that improves microwave delivery and increases enhancements up to 50%.

Characterization of Silver Halide Fiber Optics and Hollow Silica Waveguides for Use in the Construction of a Mid-Infrared Attenuated Total Reflection Fourier Transform Infrared (ATR FT-IR) Spectroscopy Probe

Advances in fiber optic materials have allowed for the construction of fibers and waveguides capable of transmitting infrared radiation. An investigation of the transmission characteristics associated with two commonly used types of infrared-transmitting fibers/waveguides for prospective use in a fiber/waveguide-coupled attenuated total internal reflection (ATR) probe was performed. Characterization of silver halide polycrystalline fiber optics and hollow silica waveguides was done on the basis of the transmission of infrared light using a conventional fiber optic coupling accessory and an infrared microscope. Using the fiber optic coupling accessory, the average percent transmission for three silver halide fibers was 18.1 ± 6.1% relative to a benchtop reflection accessory. The average transmission for two hollow waveguides (HWGs) using the coupling accessory was 8.0 ± 0.3%. (Uncertainties in the relative percent transmission represent the standard deviations.) Reduced transmission observed for the HWGs was attributed to the high numerical aperture of the coupling accessory. Characterization of the fibers/waveguides using a zinc selenide lens objective on an infrared microscope indicated 24.1 ± 7.2% of the initial light input into the silver halide fibers was transmitted. Percent transmission obtained for the HWGs was 98.7 ± 0.1%. Increased transmission using the HWGs resulted from the absence or minimization of insertion and scattering losses due to the hollow air core and a better-matched numerical aperture. The effect of bending on the transmission characteristics of the fibers/waveguides was also investigated. Significant deviations in the transmission of infrared light by the solid-core silver halide fibers were observed for various bending angles. Percent transmission greater than 98% was consistently observed for the HWGs at the bending angles. The combined benefits of high percent transmission, reproducible instrument responses, and increased bending tolerance indicated HWGs should be preferred in the construction of a fiber/waveguide-coupled ATR probe.

Design of a Ring Monopole Dual-Frequency Antenna Fed by Coplanar Waveguide

A printed ring-shaped monopole antenna fed by coplanar waveguide for use in the dual-band wireless communication system has been presented and investigated. By adding some branch strips inside the ring and changing its size, as well as the further optimization, the proposed antenna could work effectively within the scope of 2.4-2.484GHz and 5.15-5.825GHz frequency band. Practical antenna structure is fabricated. The details of the antenna design and both the theoretical and experimental results are discussed.

Design of Access-Tube TDR Sensor for Soil Water Content: Theory

Soil water measurement is important in water management for irrigation and hydrologic sciences. The purpose of this paper is to describe the design of a cylindrical access-tube mounted waveguide for use in time-domain reflectometry (TDR) for in-situ soil water content sensing. In order to optimize the design with respect to sampling volume and losses, we derived the electromagnetic fields produced by a TDR sensor with this geometry. Using this analytical derivation, the effects on sampling area, waveform shape, and losses while varying design and soil water content were examined. It was found that when the soil and tube substrate have identical dielectrics, then sampling area has a local extremum. Tube radius has the largest impact of any geometrical parameter on sampling area with increases in radius causing increases in sampling area. Increasing electrode separation angle increases the sampling area slightly. The effects on TDR waveform are greatest for soil water content, tube dielectric, and tube radius: where increasing any of these increase delay and dispersion.

Model Selection Under Limited Information Using a Value-of-Information-Based Indicator

Designers are continuously challenged by complexity, as well as by the excessive instantiation and execution times of models, particularly in the context of integrated product and materials design. In order to manage these challenges, a systematic strategy for evaluating and selecting models is presented in this paper. The systematic strategy is based on value-of-information for design decision making. It consists of a (i) process performance indicator (PPI) to quantify the impact of model refinement from a decision-centric perspective and (ii) a method involving model evaluation. Using this method, a least complex but valid model is evaluated, and, only if necessary, gradually refined it until the most appropriate one is selected. The systematic approach is particularly well suited for integrated product and materials design, and all other scenarios where the perfect knowledge of the true system behavior and bounds of error are not available throughout the design space. The proposed strategy is applied to the design of photonic crystal waveguides for use in a next-generation optoelectronic communication system. In this paper, it is shown that the systematic strategy based on the PPI is useful for evaluating and selecting models particularly when accuracy of the prediction or the associated error bounds are not known.

Numerical Analysis of Deep sub-wavelength integrated plasmonic devices based on Semiconductor-Insulator-Metal strip waveguides

We report the first study of nanoscale integrated photonic devices constructed with semiconductor-insulator-metal strip (SIMS) waveguides for use at telecom wavelengths. These waveguides support hybrid plasmonic modes transmitting through a 5-nm thick insulating region with a normalized intensity of 200-300 μm(-2). Their fundamental mode, unique transmission and dispersion properties are consistent with photonic devices for guiding and routing of signals in communication applications. It has been demonstrated using Finite Element Methods (FEM) that the high performance SIMS waveguide can be used to fabricate deep sub-wavelength integrated plasmonic devices such as directional couplers with the ultra short coupling lengths, sharply bent waveguides, and ring resonators having a functional size of ≈1 µm and with low insertion losses and nearly zero radiation losses.

Fabrication of surface plasmon waveguides on thin CYTOP membranes

The fabrication of a membrane supported long-range surface plasmon polariton waveguide for use as a biosensor is described. This type of device can be completely immersed in the sensing environments to create symmetrical waveguide surroundings. The membrane is created from the fluoropolymer CYTOP which has strong physical properties and a low index of refraction. The fabrication steps of this device are described along with examples of completed structures.