Hana Medhat

Institute of Photonic Sciences

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Frank Gunzer

German University in Cairo

Yintao Ma

Xi'an Jiaotong University

Björn Raupers

GEOMAR Helmholtz Centre for Ocean Research Kiel

Wassim Alexan

German University in Cairo

Vito Giovanni Lucivero

Institute of Photonic Sciences

Morgan W. Mitchell

Institute of Photonic Sciences

Jürgen Grotemeyer

Health Affairs

Hisham H. Hussein

Applied Science Private University

Chiara Mazzinghi

Institute of Photonic Sciences

A.A. Hamza

Mansoura University

Cooperative Institutions

Institute of Photonic Sciences

German University in Cairo

Kiel University

Clinical Research Center Kiel

American University in Cairo

Institute of Science and Technology

Barcelona Institute for Science and Technology

Shanghai Institute for Science of Science

Xi'an Jiaotong University

Huazhong Agricultural University

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Performance of photonic crystal based gas sensors under the influence of losses

Hana Medhat Frank Gunzer

Photonic crystals have attracted a great amount of research work in the last 20 years. Initially, their application possibilities concentrated on communications. In recent years, a lot of research has shown the capability of using these crystals in the form of photonic crystal micro cavities (PCM) in gas sensing applications for e.g. environmental monitoring. Since these crystals exhibit so called photonic bands, they allow only certain frequencies to propagate through the structure while blocking other frequencies. These bands depend on a variety of parameters including the refractive indices forming the crystal structure; most importantly, they show a strong response towards refractive index changes. Thus, it is possible to create gas sensors with high selectivity that even react to the small refractive index changes of different gaseous analytes. These structures are often proposed to be used as chemical sensors, since they allow for very high Q values and thus very high selectivity. The performance of such sensors can be easily simulated with help of numerical approaches such as Finite Elements Method (FEM). Previous research that aimed at studying PCM sensors typically neglected losses due to signal attenuation in such simulations. In this paper we subsequently show how the Q values and the related gas sensing performance change with the imaginary refractive index of the crystal structure.

Crystal (programming language)

SIGNAL (programming language)

10.1109/eesms.2017.8052676

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Citations (1)

Influence of the trap length on the performance of Cassinian ion traps: A simulation study

International Journal of Mass Spectrometry (2018)

Björn Raupers Hana Medhat Frank Gunzer Jürgen Grotemeyer

Trap (plumbing)

Truncation (statistics)

Quadrupole ion trap

10.1016/j.ijms.2018.12.017

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Citations (4)

Sequence-Based Bit-Cycling in Double Layer Message Security

Wassim Alexan Hana Medhat Ahmed Hamza Hisham H. Hussein

This paper proposes two different implementations of a double-layer message security scheme. In both schemes, the first layer is of a cryptographic nature, employing the AES-256, while the second layer is of a steganographic nature, employing a number of mathematical sequences that determine the color-plane cycling for least significant bit (LSB) embedding. Arithmetic and geometric sequences are employed for the first and the second schemes, respectively, to determine the location of embedding, whereas the specific color plane where the embedding occurs in the RGB pixel is based on a derived form of the Rudin-Shapiro sequence. Performance is measured in terms of the mean squared error (MSE), the peak signal to noise ratio (PSNR), histogram analysis and entropy values. Numerical results show that the proposed techniques are superior to some of the recurring approaches in the literature.

Peak signal-to-noise ratio

RGB color model

10.1109/rtuwo.2018.8587872

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Citations (16)

Analysis of the mercury induced fragmentation of certain n-alkanes in pulsed ion mobility spectrometry with Gold's Algorithm

Hana Medhat Frank Gunzer

Ion mobility is a well know technique offering the analysis of gaseous substances in e.g. environmental monitoring applications. The advantages are a portable instrument size, very high sensitivity in the ppbv range, fast response time in the range of a few seconds, but limited selectivity due to its relatively low resolving power. Typically, an ion mobility spectrum has maximum two peaks per analyte if dimer formation takes place; often only one peak per analyte is observable. Normally, analyte fragmentation is not observed. However, in a previous study, we reported strong fragmentation of n-decane and n-undecane when mercury is present in the device. In this paper, we employed de-convolution with help of Gold's Algorithm to reduce the peak width in these spectra with the goal to obtain further information regarding this fragmentation.

Ion-mobility spectrometry

Fragmentation

Mercury

10.1109/eesms.2017.8052677

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An AES Double–Layer Based Message Security Scheme

Wassim Alexan A.A. Hamza Hana Medhat

Nowadays, the Achilles heel of any software system that deals with data communication and/or storage on a cloud is the security of information being handled. However, modern cryptographic methods were proven vulnerable to brute force and side channel attacks, and thus were dubbed insufficient to be used in a secure system. Security is effected by using the cryptographic methods in proactive contexts, one of which is the use of a cryptography/steganography hybrid multi-layer system. Cryptography would be responsible for the secrecy of data whereas steganography would be responsible for the secrecy of communication. In this work, we propose two possible hierarchies which are common in that they are both double-layered and that they employ AES-256 for the cryptographic layer. As for the steganographic layer, we propose using the least significant bit (LSB) embedding by means of color-plane cycling in bitmap images. The cycling follows a prime number sequence in one method and the Fibonacci sequence in the other. We compute the mean squared error (MSE) and the peak signal to noise ratio (PSNR) for both techniques for comparison and we show the superiority of the Fibonacci sequence. We also compare our results with the results reported in the literature for some of the most commonly used LSB steganographic methods in hybrid systems and show the superiority of our proposed message security scheme.

10.1109/itce.2019.8646461

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Citations (17)

Cavity-enhanced detection of spin polarization in a microfabricated atomic vapor cell

Physical Review Applied (2024)

M. Hernández Ruiz Yintao Ma Hana Medhat Chiara Mazzinghi Vito Giovanni Lucivero

We demonstrate continuous Pound-Drever-Hall (PDH) nondestructive monitoring of the electron spin polarization of an atomic vapor in a microfabricated vapor cell within an optical resonator. The two-chamber silicon and glass cell contains ${}^{87}$Rb and 1.3 amg of ${\mathrm{N}}_{2}$ buffer gas, and is placed within a planar optical resonator formed by two mirrors with dichroic dielectric coatings to resonantly enhance the coupling to phase-modulated probe light near the ${D}_{2}$ line at 780 nm. We describe the theory of signal generation in this system, including the spin-dependent complex refractive index, cavity optical transfer functions, and PDH signal response to spin polarization. We observe cavity transmission and PDH signals across approximately 200 GHz of detuning around the atomic resonance line. By resonant optical pumping on the 795-nm ${D}_{1}$ line, we observe spin-dependent cavity line shifts, in good agreement with theory. We use the saturation of the line shift versus optical pumping power to calibrate the number density and efficiency of the optical pumping. In the unresolved sideband regime, we observe quantum noise limited PDH readout of the spin polarization density, with a flat noise floor of 9\ifmmode\times\else\texttimes\fi{}${10}^{9}\phantom{\rule{0.1em}{0ex}}{\text{spins cm}}^{\ensuremath{-}3}\phantom{\rule{0.2em}{0ex}}{\text{Hz}}^{\ensuremath{-}1/2}$ for frequencies above 700 Hz. We note possible extensions of the technique.

10.1103/physrevapplied.21.064014

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Numerical analysis of trajectories in a Cassinian ion trap of second order with trap door ion inlet

European Journal of Mass Spectrometry (2021)

Björn Raupers Hana Medhat Jürgen Grotemeyer Frank Gunzer

Ion traps like the Orbitrap are well known mass analyzers with very high resolving power. This resolving power is achieved with help of ions orbiting around an inner electrode for long time, in general up to a few seconds, since the mass signal is obtained by calculating the Fourier Transform of the induced signal caused by the ion motion. A similar principle is applied in the Cassinian Ion Trap of second order, where the ions move in a periodic pattern in-between two inner electrodes. The Cassinian ion trap has the potential to offer mass resolving power comparable to the Orbitrap with advantages regarding the experimental implementation. In this paper we have investigated the details of the ion motion analyzing experimental data and the results of different numerical methods, with focus on increasing the resolving power by increasing the oscillation frequency for ions in a high field ion trap. In this context the influence of the trap door, a tunnel through which the ions are injected into the trap, on the ion velocity becomes especially important.

Orbitrap

Quadrupole ion trap

Trap (plumbing)

Oscillation (cell signaling)

Ion trapping

10.1177/1469066720984380

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Citations (3)

Cavity-resonated detection of spin polarization in a microfabricated atomic vapor cell

arXiv (Cornell University) (2023)

María Hernández Ruiz Yintao Ma Hana Medhat Vito Giovanni Lucivero Morgan W. Mitchell

We demonstrate continuous Pound-Drever-Hall (PDH) nondestructive monitoring of the electron spin polarization of an atomic vapor in a microfabricated vapor cell within an optical resonator. The two-chamber silicon and glass cell contains $^{87}$Rb and 1.3 amagat of N$_{2}$ buffer gas, and is placed within a planar optical resonator formed by two mirrors with dichroic dielectric coatings to resonantly enhance the coupling to phase-modulated probe light near the D$_2$ line at 780 nm. We describe the theory of signal generation in this system, including the spin-dependent complex refractive index, cavity optical transfer functions, and PDH signal response to spin polarization. We observe cavity transmission and PDH signals across $\approx 200$ GHz of detuning around the atomic resonance line. By resonant optical pumping on the 795 nm D$_1$ line, we observe spin-dependent cavity line shifts, in good agreement with theory. We use the saturation of the line shift vs. optical pumping power to calibrate the number density and efficiency of the optical pumping. In the unresolved sideband regime, we observe quantum-noise-limited PDH readout of the spin polarization density, with a flat noise floor of $9 \times 10^9$ spins cm$^{-3}$ Hz$^{-1/2}$ for frequencies above 700 Hz. We note possible extensions of the technique.

Optical Pumping

10.48550/arxiv.2312.12256

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