arXiv subjects

Levi Smith

Publications and source records attributed to Levi Smith.

8 recordsLinked to original sources

arXiv2026

Design and Verification of a Terahertz Bandpass Filter using a Spoof Surface Plasmon Polariton Waveguide with Gapped Unit Cells

This paper presents the experimental verification of a planar guided-wave terahertz (THz) spoof surface plasmon polariton (SSPP) bandpass filter (BPF) using a coplanar stripline (CPS) with internal grooves and periodic gaps. The proposed BPF operates by combining the low-pass behavior from the SSPP's band edge and the high-pass behavior from the gaps that act as series capacitors. The higher and lower cut-off frequencies can be tailored by the appropriate selection of the unit cell geometry. For demonstration, a BPF with a center frequency of approximately 1 THz and a bandwidth of 0.25 THz was designed, fabricated, and experimentally validated. The passband around 1 THz is observed in the measurements, along with the lower and higher cut-off frequencies at approximately 0.91 THz and 1.16 THz, respectively, in agreement with simulation results.

physics.optics↗

arXiv2026

A Terahertz Bandpass Filter Using a Capacitive Transition Circuit and a Spoof Surface Plasmon Polariton Waveguide

This paper presents a novel terahertz (THz) bandpass filter (BPF) based on a spoof surface plasmon polariton (SSPP) waveguide with a center frequency of 1 THz and a 3 dB bandwidth of 0.3 THz. The proposed BPF comprises cascaded high-pass and low-pass elements. The high-pass element is a capacitive gap in the SSPP transition circuit, and the low-pass element is the SSPP waveguide itself. We find that the measurement results, including cut-off frequencies, align well with the theoretical predictions and simulations. To the authors' knowledge, the proposed SSPP BPF is the first of its kind.

physics.optics↗

arXiv2025

Genetic Algorithm-Based Inverse Design of Guided Wave Planar Terahertz Filters

We present a genetic algorithm (GA)-based inverse design framework for synthesizing high-performance planar terahertz (THz) filters integrated with coplanar striplines (CPSs). The method efficiently explores high-dimensional design spaces to generate filter geometries matching user-defined S-parameter magnitude and phase responses, while enforcing structural connectivity for compatibility with terahertz system-on-chip (TSoC) platforms. To accelerate optimization, filter performance is evaluated using the ABCD matrix method, providing a significant computational advantage over full-wave simulations. Final validation is performed through finite element method (FEM) simulations. As a proof of concept, we design band-stop filters with center frequencies of 0.6, 0.8, and 1.0 THz, each with a 150 GHz target bandwidth, and demonstrate tunable rejection depths within a constant physical footprint. Optimization is guided by minimizing the root-mean-square error (RMSE) between simulated and target S-parameters.

physics.app-ph↗

arXiv2025

Demonstration of a planar multimodal periodic filter at THz frequencies

This paper presents a planar multimodal periodic filter that is constructed from alternating sections of coplanar stripline and the odd-mode of a finite-ground plane coplanar waveguide constructed on a 1 um silicon nitride substrate to facilitate operation at THz frequencies. The multimode configuration differs from standard single-mode periodic filters and enables flexible designs and the possibility for active control of the filter characteristics. For this proof-of-concept, we present the relevant theory and design procedures required to develop a band-stop filter that has a center frequency of fc = 0.8 THz and a bandwidth of df = 0.07 THz. We find good agreement between theory, simulation, and experiment.

physics.app-ph↗

arXiv2024

On-Chip Glucose Sensing at Terahertz Frequencies

This paper demonstrates an on-chip anhydrous D-glucose sensor based using a coplanar stripline (CPS) on a thin (1 um) silicon nitride membrane at terahertz (THz) frequencies. A thin layer (~10 um) of D-glucose was placed in close proximity to the CPS and the transmission response was measured using a modified THz-TDS setup. The D-glucose introduces frequency-dependent changes to the effective permittivity of the CPS resulting in a modified spectral response at the receiver. Measurement results show absorption signatures at 1.42 THz and 2.07 THz corresponding to the first two significant resonances beyond 1 THz for D-glucose allowing for label-free detection. The frequency-dependent attenuation coefficient was estimated by simulation for several D-glucose layer thicknesses using a modified Lorentz model. Measurement results align with simulations and other literature that use free-space THz radiation. This work verifies on-chip THz sensing of D-glucose and presents a pathway towards on-chip sensing of other materials at THz frequencies.

physics.app-ph↗

arXiv2024

Terahertz Bandstop Filter Using Varying Radii Split-Ring Resonators

In this letter we report a proof-of-concept terahertz band-stop filter constructed from split-ring resonators that has a center frequency of 1.06 THz and a -3 dB bandwidth of 0.36 THz. The design consists of nine split ring resonators of varying radii (3 x 13 um, 3 x 14 um, 3 x 15 um) that are placed between the conductors of a coplanar stripline transmission line. The response of the filter is measured using a modified terahertz time-domain spectrometer and we find reasonable agreement between simulation and experiment. This work demonstrates the viability of using varying-radii split-ring resonators as discrete sub-wavelength filter elements for terahertz systems.

physics.optics↗

arXiv2023

Demonstration of an Integrated Planar Guided-wave Terahertz Synthesized Filter

At terahertz (THz) frequencies there are few experimental works which demonstrate filter synthesis to obtain a desired filter response (i.e., Chebyshev, Butterworth, Bessel, etc.). Currently, the majority of literature perform THz filter analysis, that is, characterizing the filter response after design procedure. In this paper, we apply filter synthesis methods from microwave engineering to design several integrated planar low-pass filters fc = 0.8 THz). We find that the transmission characteristics align with theory and simulation.

physics.app-ph↗

arXiv2023

Demonstration of an Integrated Terahertz Band-Stop Filter Using an Apodized Bragg Grating

This paper presents the demonstration of an on-chip integrated Terahertz (THz) Apodized Bragg grating (TABG) which functions as band-stop filter with a center frequency of 0.8 THz and a bandwidth of 200 GHz. For experimentation, we integrate the TABG into our THz System-on-Chip to enable wideband (DC - 1.5 THz) device characterization. Using this methodology, we measure the signal transmission through the TABG and find the experimental results align with simulation and theory provides a rejection of approximately 20 dB across the stop-band.

physics.app-ph↗