Experimental exploration of longitudinal modes in spherical shells at 220 GHz – 330 GHz: applications to corneal sensing

Zarrinkhat, Faezeh; Lamberg, Joel; Baggio, Mariangela; Tamminen, Aleksi; Ala‐Laurinaho, Juha; Khaled, Elsayed Esam M.; Rius, Josep; Robert, Jordi Romeu; Taylor, Zachary D.

doi:10.1109/cleo/europe-eqec52157.2021.9541679

Cited by 2 publications

(5 citation statements)

References 1 publication

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“…The M 1 , N 1 , M 3 , and N 3 are vector spherical harmonics of first and third kind [18]. A through details of the theory can be found in [11,12,[15][16][17]19].…”

Section: Theory Based On Fourier Optic and Vector Spherical Harmonicsmentioning

confidence: 99%

“…Each cornea coupling coefficient is computed with Equation (3) and calibrated against the coupling coefficient of the same size steel sphere, which is accurately located in the cornea location (called Cal 0 ), for the frequency range from 100 GHz to 600 GHz. Targets are illuminated by a Gaussian beam in a way that the beam focus on the sub-confocal point introduced in [10,12], shown in Figure 1. Figure 2 compares calibrated efficiency with the stratified medium theory which models the cornea as a planar half-space illuminated by plane wave [8] at the frequency range of 100-600 GHz.…”

Section: Correctly Calibrated Corneamentioning

confidence: 99%

“…The nominal cornea dimension (0.5 mm corneal phantom sitting on a 7.5 mm aqueous core) manifests as a lossy thin film at THz frequencies, hence the extraction of corneal central thickness (CCT), corneal anterior water content (CAWC), and corneal posterior water content (CPWC) is achievable through the coupling of longitudinal modes via broadband reflectometry [7]. Given the cornea anatomy acting as a half-space structure in THz band, back-scattered field from the cornea is achievable by stratified medium theory [8][9][10], although some challenges such as phase matching in peripheral areas needed to be addressed. A study based on Fourier optics and vector spherical harmonics enables accurate calculation of back-scattered field from the cornea, by modelling cornea as a layered sphere under Gaussian illumination [11,12].…”

Section: Introductionmentioning

confidence: 99%

“…Given the cornea anatomy acting as a half-space structure in THz band, back-scattered field from the cornea is achievable by stratified medium theory [8][9][10], although some challenges such as phase matching in peripheral areas needed to be addressed. A study based on Fourier optics and vector spherical harmonics enables accurate calculation of back-scattered field from the cornea, by modelling cornea as a layered sphere under Gaussian illumination [11,12]. In practice, the two-way propagation through the reflectometer quasioptics is frequency-dependent, and calibrator targets with known reflectivity are necessary.…”

Section: Introductionmentioning

confidence: 99%

“…In practice, the two-way propagation through the reflectometer quasioptics is frequency-dependent, and calibrator targets with known reflectivity are necessary. The studies suggest using a PEC sphere identical to the cornea radius of curvature (ROC) and center of curvature (COC) for calibration [9,12], but reaching this identical situation comes with challenges.…”

Section: Introductionmentioning

confidence: 99%

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Calibration Alignment Sensitivity in Corneal Terahertz Imaging

Zarrinkhat

Baggio

Lamberg

et al. 2022

Sensors

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Improving the longitudinal modes coupling in layered spherical structure contributes significantly to corneal terahertz sensing, which plays a crucial role in the early diagnosis of cornea dystrophies. Using a steel sphere to calibrate reflection from the cornea sample assists in enhancing the resolution of longitudinal modes. The requirement and challenges toward applying the calibration sphere are introduced and addressed. Six corneas with different properties are spotted to study the effect of perturbations in the calibration sphere in a frequency range from 100 GHz to 600 GHz. A particle-swarm optimization algorithm is employed to quantify corneal characteristics considering cases of accurately calibrated and perturbed calibrated scenarios. For the first case, the study is carried out with signal-to-noise values of 40 dB, 50 dB and 60 dB at waveguide bands WR-5.1, WR-3.4, and WR-2.2. As expected, better estimation is achieved in high-SNR cases. Furthermore, the lower waveguide band is revealed as the most proper band for the assessment of corneal features. For perturbed cases, the analysis is continued for the noise level of 60 dB in the three waveguide bands. Consequently, the error in the estimation of corneal properties rises significantly (around 30%).

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“…The M 1 , N 1 , M 3 , and N 3 are vector spherical harmonics of first and third kind [18]. A through details of the theory can be found in [11,12,[15][16][17]19].…”

Section: Theory Based On Fourier Optic and Vector Spherical Harmonicsmentioning

confidence: 99%

Section: Correctly Calibrated Corneamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Calibration Alignment Sensitivity in Corneal Terahertz Imaging

Zarrinkhat

Baggio

Lamberg

et al. 2022

Sensors

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185–215 GHz CMOS Frequency Doubler with a Single Row Staggered Distribution Layout Design

Dong

You

2023

Electronics

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This paper presents a 220 GHz × 2 amplifier–doubler chain composed of a rat-race balun, a 6-stage driver amplifier, and a frequency doubler. The presented amplifier–doubler chain was fabricated in commercial 40 nm bulk CMOS technology. The maximum cutoff frequency fmax for the NMOS transistor produced by this manufacturing process was 290 GHz. The saturation output power of the six-stage driver amplifier at 110 GHz was 11.5 dBm. The transistor of the frequency doubler consisted of a single-row interleaved Poly-Diffusion Contact balancing structure. Theoretically, the single-row interleaved Poly-Diffusion Contact balancing structure was able to effectively avoid parasitic components. The simulated results demonstrate that the presented structure achieves a higher output than the conventional designs. Based on these measured results, the presented amplifier–doubler chain provides a peak output power of 7.9 dBm at 200 GHz and a 3-dB bandwidth of 30 GHz. Based on the comparison with other reported results, the presented amplifier–doubler chain provides the highest output power among reported frequency doublers fabricated in CMOS technology.

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Experimental exploration of longitudinal modes in spherical shells at 220 GHz – 330 GHz: applications to corneal sensing

Cited by 2 publications

References 1 publication

Calibration Alignment Sensitivity in Corneal Terahertz Imaging

Calibration Alignment Sensitivity in Corneal Terahertz Imaging

185–215 GHz CMOS Frequency Doubler with a Single Row Staggered Distribution Layout Design

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