Jennifer A. Byford

Affordable terahertz components using 3D printing

This paper presents the design and characterization of 3D printed photonic crystal filter (quasi optic component) and dielectric ridge waveguide (integrated component). Commercially available 3D printer was used to print polymer based components. Design and characterization of these devices is carried out over a frequency range of 0.15 - 0.5 THz. The photonic crystal filter shows a stop band from 0.25 - 0.35 THz. Also a very narrow defect mode (notch filter) was introduced by altering the structure of photonic crystal. The dielectric ridge waveguide shows broadband THz propagation characteristics. The transmission loss was determined to be largely dominated by the loss characteristics of the polymer material used.

Demonstration of RF and Microwave Passive Circuits Through 3-D Printing and Selective Metalization

The ultimate goal of this paper is to print radio frequency (RF) and microwave structures using a 3-D platform and to pattern metal films on nonplanar structures. To overcome substrate losses, air core substrates that can readily be printed are utilized. To meet the challenge of patterning conductive layers on complex or nonplanar printed structures, two novel self-aligning patterning processes are demonstrated. One is a simple damascene-like process, and the other is a lift-off process using a 3-D printed lift-off mask layer. A range of microwave and RF circuits are designed and demonstrated between 1 and 8 GHz utilizing these processes. Designs are created and simulated using Keysight Advanced Design System and ANSYS High Frequency Structure Simulator. Circuit designs include a simple microstrip transmission line (T-line), coupled-line bandpass filter, circular ring resonator, T-line resonator, resonant cavity structure, and patch antenna. A commercially available 3-D printer and metal sputtering system are used to realize the designs. Both simulated and measured results of these structures are presented.

Metamaterial inspired periodic structure used for microfluidic sensing

A novel metamaterial inspired resonating structure coupled with a microfluidic channel has been evaluated for sensing applications in the microwave frequency range. The structure is based on an open split ring resonator (OSRR) design, was simulated in a finite element analysis tool (Ansys HFSS®) and tested using a Vector Network Analyzer to detect changes in resonant frequency, amplitude, and phase due to dielectric loading from different chemicals in the microfluidic channel. The sensor was tested as a single unit cell, in a three cell aperiodic array and as an array of three different frequencies. Different concentrations of water-isopropanol (IPA) and watermethanol were used to characterize the sensor. Additionally, a biosensor application was demonstrated in detecting glucose-d concentration in deionized water.

3D printed metalized-polymer UWB high-gain Vivaldi antennas

This paper introduces a UWB high gain Vivaldi antenna fabricated with a polymer-based 3D printer. 3D printing technology allows for simple fabrication that is easier, faster, and lower cost compared to traditional microfabrication and metal fabrication techniques. Two 3D printed designs are presented, the first of which is a simple Vivaldi notch antenna with a radiating slotline cavity. The second design consists of a bilateral Vivaldi with a partially covered cavity, which increases the bandwidth and gain of the antenna. Both designs are printed with an acrylic-based polymer, blanket metalized with a thin copper layer, and fed with a 50 Ω coaxial feed. Both antennas show an extremely wide bandwidth of approximately 14 GHz from 4 to 18 GHz. In addition, the maximum gain of the antennas is approximately 12 dB. The measured results match well with the simulated results, showing the potential for these antennas as low cost, wideband, high gain alternatives which could be used in modern UWB communication systems.

Ultra-wideband hybrid substrate integrated ribbon waveguides using 3D printing

A new wave guiding structure and fabrication technique is introduced for high speed, low loss, ultra-wideband interconnects. It is a hybrid between a dielectric ribbon and a substrate integrated waveguide design. In this structure, a high dielectric constant valued core is surrounded by a low dielectric constant valued cladding which in turn is surrounded by a metal layer. Both cylindrical and rectangular waveguide designs are presented. Simulation and measurement results show that ultra-wide band interconnects with low-dispersion can be designed using this hybrid approach. Fabrication of the cladding layer was carried out using 3D plastic printing. Simulated and measured results are discussed as well as fabrication techniques.

Fabrication of Terahertz Components Using 3D Printed Templates

A new fabrication process for passive terahertz components is introduced. Molds are 3D printed on a commercially available 3D printer using rigid opaque material Vero White. An injection molding machine is used to melt low density polyethylene (LDPE) and high density polyethelene (HDPE) pellets to fill the molds. Sample components are designed in ANSYS HFSS and fabricated using the new process including a set of lenses, various dielectric ridge waveguides, a photonic crystal filter, and probes. Samples are then measured using a frequency domain terahertz system and compared to their expected performance from simulation.

Investigation of modulation-capable silicon waveguides for efficient on-wafer terahertz interconnects

In this paper, silicon-based waveguides are investigated for on-wafer THz interconnect applications. A silicon based dielectric ribbon and ridge waveguide are both shown through HFSS modeling and simulation to have very low-loss transmission characteristics as low as .3dB/mm in the THz frequency spectrum. In addition, the modulation properties of both waveguides are investigated through a Drude model analysis as well as EM simulation. Several silicon ridge waveguide samples are fabricated using a simple silicon wet-etching technique. These waveguides are shown to efficiently transmit THz radiation, especially when the ridge is narrow. The low-loss nature of these waveguides shows the potential of silicon-based interconnects with built-in modulation capabilities for THz integrated circuit applications.

Common misunderstandings and challenges in learning Gauss’s Law in a junior level electromagnetic engineering course

Common misunderstandings when learning Gauss’s Law in a college junior level electromagnetic engineering course are identified by observing normal course assessments and conducting one on one student interviews. Additionally, the extent to which students in this course struggle to translate prior mathematics is investigated by codifying student performance on normal assessments using a rubric developed by the authors based on Accreditation Board for Engineering and Technology (ABET) Criterion 3 (a) and (e). Five misconceptions are identified, three of which agree with physics educational literature, as well as a need for better scaffolding the translation of calculus II and multidimensional calculus material. Future work and possible intervention strategies are discussed.

3D Printed High Frequency Coaxial Transmission Line Based Circuits

This work presents a coaxial transmission line constructed with additive manufacturing (3D printing) technologies. The coaxial structure is primarily air dielectric and, thus, is relatively low loss and is capable of high frequency transmission, demonstrating good transmission above 10~GHz. Additionally, a first order band-pass filter is demonstrated along with a comparison to an equivalent planar (microstrip) filter. This process provides a template for designing coaxial interconnects which is far cheaper and flexible for the designer than traditional methodologies. The loss of the completed design is measured to be 0.78~dB in a 50~mm long section at 10~GHz (0.16~dB/cm). Simulated and measured results are shown.

Aerosol-Jet Printed Quasi-Optical Terahertz Filters

This paper presents the design, simulation, and characterization of metamaterial-inspired terahertz filters, fabricated by aerosol-jet printing. Filters are designed for operation at 230, 245, and 510 GHz, for both band-pass and bandstop operation. Operation of each printed filter is compared to structures fabricated from copper metal using a photolithographic process. Each of the aerosol jet printed filters are found to have performance comparable to those fabricated using lithographic techniques, demonstrating the applicability of aerosol-jet printing to the fabrication of components operating in the terahertz regime.