Adel Shaaban Awad Elsharkawi

A compact phase-engineering method for generating zero-order Bessel beams with uniform on-axis intensity from femtosecond lasers exhibiting asymmetric Gaussian inputs (w _x ≠ w _y ) is presented. An axicon phase combined with Gaussian phase modulation (GPM) was encoded on a spatial light modulator (SLM) to correct beam ellipticity and axial decay. Analytical expressions derived using the stationary-phase method reveal the effects of asymmetry, while numerical GPM tuning ensures axial uniformity. Theoretical, simulated, and experimental results at 1030 nm show strong agreement, even for a small asymmetry ( δ _w = w _y /w _x ≈ 0.95–1.05). The technique provides a simple and practical route to high-fidelity Bessel beams for ultrafast laser microfabrication.

This work focuses on a novel, to the best of our knowledge, analytical form of the phase retardation function for achieving a uniform axial intensity of Bessel beams. Traditional methods of generating Bessel beams often result in significant oscillations in the intensity along the beam’s axial path, which limits their practical applications. However, the proposed phase retardation function in this study overcomes these limitations by ensuring consistent beam creation regardless of factors such as the beam waist size, wavelength, or axicon angle. By implementing the proposed spatial phase function, a fundamental Gaussian laser beam, thereby generating a Bessel beam with an elongated and constant axial intensity profile, supports our theoretical predictions. The functionality of this new phase retardation function was further scrutinized using different wavelengths and beam waist sizes to confirm that the axial intensity remained uniform profile. Additionally, when contrasting our phase function with those from earlier researches, it was observed that our findings are consistent with both theoretical models and experimental outcomes.

This paper is devoted to studying the Bessel beam propagation in cylindrical coordinates using the Hankel transform beam propagation method (HT-BPM) and their behavior in different scenarios in the microscale and meter scale of propagation distances. The study compares the results obtained from the HT-BPM with another fast Fourier transform beam propagation method (FFT-BPM) to validate the accuracy and effectiveness of the HT-BPM in modeling Bessel beam propagation. The axial intensity of Bessel beam propagation is analyzed using the HT-BPM. The simulation results obtained from the HT-BPM are compared with those from the FFT-BPM to evaluate the agreement and consistency between the two methods in predicting the axial intensity of Bessel beam propagation. The results show that the HT-BPM is numerically faster than the FFT-BPM by ten times for different sampling points, furthermore, the FFT-BPM accuracy for evaluating the Bessel beam spot radius is 89.9% of the analytical value, while the HT-BPM is 99% relative to analytical value. The prediction of the axial intensity of the Bessel beam has been tested at different types of phase functions and different propagation distances: micrometer, centimeter, and meter scales. The results of the HT-BPM are matched with the analytical and experimental values. Finally, the HT-BPM is tested when the input light source takes different profiles.

This study introduces a cutting-edge fiber-optic dosimetry (FOD) sensor designed for measuring radiation in biological settings. The accuracy and precision of dosimeters for small animals, particularly prolonged exposure to nonuniform radiation fields, are always challenging. A state-of-the-art in-vivo dosimeter utilizing glass-encapsulated Thermoluminescence cylindrical detector (TLD) was introduced. The FODs are implanted into the rat during a prolonged irradiation scenario involving ¹³⁷Cs where the rat has the freedom to move within a heterogeneous radiation domain. The implantation surgery was verified with X-ray computed tomography (CT) in addition to biochemical and pathological tests to assess the biocompatibility of FOD in vivo. A versatile FOD is designed for industrial and medical fields, which demand accurate and resilient radiation dosimeters. The dose measurements are associated with precise two-dimensional (2D) radiation distribution imaging. Three cylindrical FODs and three standards TLD_100 for each rat were tested. The measurements of peak irradiation before and after exposure reveal greater stability and superior sensitivity when compared to standard thermo-luminescence detectors in an in-vivo animal test. To the best of our knowledge, FOD testing on live animals is presented for the first time in this paper. Regarding the safety and biocompatibility of FOD, no morphological signs with any kind of inflammation or sensitivity toward the FOD material have been remarked. Moreover, with the current FOD, there is no oedema between the epidermal, dermal, and subdermal sections at the site of implantation. The results also show the stable levels of white blood cells (lymphocytes, granulocytes, MID) as blood inflammatory markers before surgery and at the time of extraction of the implanted dosimeters, thus confirming the biocompatibility for each optical fiber cylinder dosimeter. As a result, the new dosimeters have excellent biocompatibility in living tissues and have 100% accurate reusability intensity of the delivered radiation doses compared to TLD_100 which demonstrated a 45% reduction in its intensity accuracy.

In this paper, we propose a novel fiber-optical dosimetry sensor for radiation measurement in biological applications. A two-dimensional (2D) fiber-optical dosimeter (FOD) for radiation measurement is considered. The sensors are arranged as a 2D array in a tailored holder. This FOD targets accurate industrial and medical applications which seek more tolerant radiation dosimeters. In this paper, the FOD sensors are subjected to gamma-ray radiation facilities from the ¹³⁷Cs gamma-ray irradiator type for low doses and ⁶⁰Co gamma-ray irradiator for high doses. For better evaluation of radiation effects on the FOD sample, the measurements are performed using eight sensors (hollow cylinder shape) with two samples in each dose. The sensors were measured before and after each irradiation. To the author’s knowledge, the measurements of FOD transplanted inside animals are presented for the first time in this paper. A 2D simulation program has been implemented for numerical simulation based on the attenuation factors from the absorbed dose inside the in vivo models. A comparison between the FOD and the standard thermo-luminescence detector is presented based on the test of in vivo animal models. The results indicate that the proposed FOD sensor is more stable and has higher sensitivity.

Purpose Kretschmann-configuration has been used as a subwavelength framework to detect tiny ‎alterations of the refractive index of biomaterials. However, most of the theoretical assessment of such configuration ‎is usually based on the plane wave excitation transfer matrix method (TMM) of prism-‎coupled to thin metal film supporting plasmonic modes. Accordingly, a better theoretical framework ‎than the plane wave approximation is indispensable for reliable and accurate assessments and ‎simulations. A reformulated form of the traditional FFT-BPM has been adapted to evaluate the performance and characteristics of surface plasmonic waveguide biosensor. Method Surface plasmon mode is excited by a sub-wavelength narrow light beam. The highly confined optical energy of that plasmonic mode enables an ‎efficient means to detect tiny variations in the composition of ‎the analyte in contact with the metallic layer of the surface plasmon ‎guide. The plasmonic guided power is detected thereafter electronically via an optical MOS capacitor. Results the guided plasmonic power has been used to assess the fundamental characteristics and performance of the sensor, namely the linearity, sensitivity, and figure of merit as well as the full width at half maximum (FWHM). Conclusion The proposed sensor could be integrated to a wide class of angular measurement system (for instance goniometer) or via electronic detection of the optical plasmonic guided power. we claim that this work is worthy of being shared with researchers and ‎developers interested in the experimentation and assessment of sensitive biosensors; especially in ‎case when complicated and sophisticated analysis tools represent an unpleasant burden.

A new perspective using Kretschmann configuration is presented to excite surface plasmon polaritons (SPP) at liquid crystal (LC)/metal interface. The excitation of SPP takes place through the electrical tuning of the prism refractive index instead of the commonly used angular interrogation. The results show that the proposed methodology is 30% superior to the traditional angular interrogation. The 5CB (4-pentyl-4’-cyanobiphenyl) is one of the best suited nematic LC material for the proposed detection framework. Its refractive index is linearly tunable in the range 1.55 ~ 1.78 (at wavelength 1.55 μm) via an external applied electric field. In that range of refractive index variation, the SPP modes are efficiently excited; and hence any minute variation in the analyte refractive index can be detected reliably and accurately through a simple tuning of the refractive index of the prism LC material. The fundamental characteristics of the sensor are assessed through the evaluation of the linearity, sensitivity (S), the full width at half maximum (FWHM) of the reflectivity curve and the figure of merit (FOM). The variation of these characteristics over a whole range of analyte refractive index (1.3–1.4) are presented as well. The electrical tuning provides a well-matched design with micro-scale devices.

This research proposed a new wearable device with microphone array and camera speech tracking and enhancement over a full range of 360-degree of a specific speaker. The proposed sensing method that combined computer vision and voice techniques to track the speech target in a flexible manner. The device could scan the specific speech source over 360°, and reduces the noise due to the interference, thus enhancing the auto-scan hearing-impaired process this helps students with hearing loss to concentrate more easily during the learning process in the class. The experimental results indicated that the proposed method could locate the noise source far from the target by more than 30°, regardless of whether the computer vision detected the human face or not. The measured positioning accuracy is greater than 83% within a range of 360-degree and the speech could be enhanced by at least 5.2 dB. The proposed wearable design for schoolchildren with speech recording also has the potential to be a tool for review class.

The feasibility of using coconut shell powder (CSP) and dog conch shell powder (DCSP) as carburizing media in the pack carburization of SCM 420 steel was investigated. The carbon content and surface hardness of the carburized specimens prepared with different CSP:DCSP ratios and carburizing durations were examined and compared. A CSP:DCSP ratio of 60%:40% and an extended carburizing time of 12 h were found to increase the carbon content of the carburized specimens to 1.14 ± 0.007 wt%. Furthermore, the surface hardness was significantly improved to 961.3 ± 4.918 HV following water quenching. Finally, the thickness of the carburized layer of the quenched specimens increased by around 2.5 times as the carburizing duration was increased from 3 to 12 h.

This study discusses whether the prism used in a Kretschmann-based surface plasmon sensor can be fabricated from a thermotropic liquid crystal (TLC) material. The refractive index of the TLC prism can be thermally tuned to match the excitation requirements for the surface plasmon modes along the metal–TLC interface of the proposed sensing platform. The TLC material was chemically prepared in vitro and was thermally and optically characterized. The measurements reported a wide mesophase temperature range ΔT (~35 °C) and a relatively high clearing temperature T_C (~84 °C) which constitutes a stable thermal control for the TLC optical parameters. The experimentally measured refractive indices of the TLC material reflect a linear change in line with the temperatures at several selected wavelengths in the visible region. A design of the surface plasmon sensor was proposed, which provided a linear response to the investigated analytes refractive index. This work highlights the importance of employing TLC material in designs compatible with detecting refractive index changes by thermal tuning and presents refractive index interrogation as an alternative method for exciting surface plasmon modes.