Silicon Rods Research Articles

Design and optimization of all-optical demultiplexer using photonic crystals for optical computing applications

Abstract In this work, photonic crystal (PhC) based all-optical 1 × 2 demultiplexer is designed for optical computing and optical signal processing. The structure is implemented with two-dimensional PhCs using T-shaped waveguides with an optimized silicon rod radius of 0.2a. Performance of the proposed structure is verified and analyzed by using the finite-difference time-domain method. The design of all-optical demultiplexer is operated based on optical interference effect at a wavelength of 1550 nm. Proposed design occupies less area of 8.4 × 5.4 µm, provides a contrast ratio of 18.53 dB, 94.52% of minimum and 100% of maximum transmission ratio and it has less insertion loss of 0.017 dB; therefore, the proposed device is suitable for photonic integrated devices.

Design of all-optical D flip-flop using photonic crystal waveguides for optical computing and networking.

The performance of an ultra-compact all-optical D flip-flop using photonic crystal waveguides is numerically analyzed and examined by optimized parameters such as refractive index and silicon rod radius. In the field of optical networking and computing, flip-flops are used to reduce the complexity of digital circuits. The phenomenon of optical interference effect is used to implement a D flip-flop at a wavelength of 1550 nm. This structure is designed using T-shaped waveguides without using non-linear material. The proposed design is small, has low insertion losses of 0.087 dB when operated at low power level, and provides high contrast ratio of 25 dB and transmission ratio of more than 96%.

Alternating Current Heating Model of Rods Located in Siemens Reactor▴

AbstractThe energy of a Siemens reduction furnace is provided by the current heating of silicon rods. Further, owing to the temperature gradient in the silicon rod, its center temperature is considerably higher than its surface temperature. The skin effect of alternating current (AC) reduces the temperature gradient within the silicon rod. Therefore, this study essentially establishes an AC heating model of 24 pairs of rod Siemens reactor based on electromagnetic theory. The calculation results are consistent with the industrial production data, indicating that the model is accurate. The results demonstrate that when the AC frequency exceeds 50 kHz, the current density at the center of the silicon rod becomes very small, tending to zero. As the frequency continues to increase, the area where the current density is close to zero expands; further, when the AC frequency exceeds 50 kHz, there exists a constant temperature zone near the central region of the silicon rod, and as the frequency of the AC increases, the range of the constant temperature zone gradually expands outward from the center of the silicon rod. The temperature difference inside the silicon rod increases with the reactor wall emissivity.

Evaluation of Mehta's modification of the Crawford technique for Frontalis Sling Surgery with Silicon rod in Severe Ptosis

Background: Ptosis is the drooping of the upper lid margin below its normal anatomic position due to the levator complex dysfunction. In this condition, the aesthetic and functional abnormality is obvious and is accompanied by severe visual field defect. Ptosis surgery is one of the most common oculoplastic procedures with different surgical procedures. The decision for an appropriate surgical procedure and the material used to minimize the incidence of complication depends on proper evaluation of the patient. Aims of study: To evaluate Mehta's Modification of the Crawford technique for frontalis sling surgery with silicon rod in sever ptosis. Patients and Methods: We considered 10 patients (12 lids) who were treated between February 2017 and June 2018. There were seven males and three females; two patients were bilateral and three patients had negative Bell's phenomenon, which was surgically treated with Mehta's modification of the Crawford technique for frontalis sling surgery with silicon rod. The patients’ age ranged from 4 to 30 years; they all had severe eyelid ptosis (>4mm) with poor levator function (≤4 mm). Results: Our patients' postoperative results were good, functional, and aesthetic, showing a clear visual field, with smooth and regular eyelid margin and no notching. Nine out of 10 patients achieved good results according to the above-mentioned criteria, and in addition to that, both patient and parents' satisfaction were taken into consideration. Only one patient had developed recurrence (1- month postop.) Conclusions: Mehta's modification of the Crawford technique for frontalis sling surgery with silicon rod in sever ptosis used for the treatment of severe ptosis with poor levator excursion is an easy and simple procedure that promises good postoperative results. Keywords: Eyelid ptosis, Silicon rod, Mehta's Modification of Crawford technique.

An ultra-narrowband all-optical filter based on the resonant cavities in rod-based photonic crystal microstructure

In view of the large scientific and technical interest in the frequency-selective all-optical devices, and some optical filters limitations, we focus on the design and analysis of a novel ultra-narrowband all-optical filter. The proposed structure consists of input/output waveguides and a resonator in a microstructured photonic crystal that encompasses silicon rods. We study the effects of the variations of rod radius, the lattice constant, and the refractive index of the filter on the resonance wavelength, quality factor, transmission, and full width at half maximum (FWHM) by solving Maxwell’s equations using the finite-difference time-domain method. The numerical results show that the proposed filter with a lattice constant of a = 540 nm, central resonant rod radius of 216 nm, and the rod radius of r = 0.2a has a resonant wavelength of λr = 1253 nm, the quality factor of Qf = 3288, FWHM of 0.26 nm and broad free spectral range of FSR = 790 nm while this filter for r = 0.26a has λr = 1552 nm, Qf = 5542, FWHM of 0.28 nm, and FSR = 720 nm. Some promising characteristics, such as its short propagation time and a small area of 102.6 µm2 make this optical filter an interesting candidate for use in photonic integrated chips.

Flexor pollicis longus tendon retrieval using silicone rods; is it worth it?

The hand represents one of the most common sites for injuries in a trauma setting. Hand mobility, the arc of motion away from the body, and being involved in many of the daily activities add to this high incidence. Thumb injuries carry a substantial burden on hand function due to its mobility, distinctive motion patterns, and particular purposes it attains. This is a prospective case-control study for cases presented to the emergency department at Kasr Al-Ainy, school of medicine, Cairo University, for the period between January 2018 and July 2019, with zone II (T2) flexor pollicis longus (FPL) tendon injuries. Patients were divided into two groups: one group had FPL retrieved with the aid of silicone rods using a different wrist incision and the other group had a retrieval done through the same site of injury without the use of rods. Patients were followed up paying attention to their rehabilitation progress, return-to-work time, and complications (e.g., rupture and infections). Patients with comorbidities (e.g., diabetes mellitus), hand infections, or associated fractures were excluded from the study. One hundred patients were included in this study. Randomly, 50 patients were assigned to group A and 50 patients to group B. The age range was 16 to 75 years. Eighty percent of the patients were males, and the remaining 20% were females. Follow-up period ranged from 3 months to 1 year with a mean follow-up period of 8 months. Group A showed shorter operative time (P value < 0.001), faster return to work (P value < 0.001), and lower complication rates (P value < 0.07) than group B. The use of silicone rods represents a suitable method for FPL tendon repair with faster recovery, lower complication rates, and shorter operative times. Level of evidence: Level IV, therapeutic study.

Multiparameter-detecting biosensors based on the surface and waveguide modes of the two-dimensional photonic crystal slab

The refractive index sensing characteristics of the two-dimensional photonic crystal (PhC) slab are studied. The proposed symmetric and asymmetric PhC structures are composed of finite-height silicon rods sandwiched by two glass substrates immersed in the liquid environment, so it is suitable to the real-time and dynamic detection of protein’s concentration. For the symmetric PhC structure, owing to the interaction of surface and waveguide modes, the resonant wavelengths and the corresponding light transmittances can be influenced by the slight thickness alteration at specific locations within a finite-size photonic crystal slab, while the localized modes work more independently for the other structure. A value of the resonant mode’s quality factor more than 1000 is achieved and a slight alteration of the protein’s thickness less than 20 nm can be distinguished.

Optical sensor based on two-dimensional photonic crystals for measuring glucose in urine

The design and simulation of two bio-optical sensors for the noninvasive measurement of glucose levels in urine of diabetic patients are presented. While the sensors are of the same shape and structure, their quality factors (QFs), sensitivities, and sizes are different. The structure developed is based on two-dimensional (2D)-hexagonal-latticed photonic crystals containing silicon rods immersed in urine. By creating line and point defects in the structure, two resonant modes are localized in the photonic bandgap (the photonic bandgap is a frequency range corresponding to mirror action for incident light of frequency within that range). Sensor 1 design was based on localized resonant mode 1, while sensor 2 uses localized resonant mode 2. The mechanism of these sensors relies on the change of the refractive index of urine as a result of the change in glucose concentration, which in turn causes shifts in resonant modes of the sensors. For tuning in the wavelength of 1.55 μm, the scaling method is utilized. The major difference between the proposed sensors and previously reported bio-optical sensors is the determination of glucose level based on the shift in resonant wavelengths. Previous works relied on the change of the amplitude of emerging waves for the same purpose. Consequently, the sensors presented here exhibit a higher QF and operate within the wavelength window of 1.55 μm. QF calculations and sensitivity simulations for sensor 1 yielded approximate values of 3800 and 500 nm/refractive index unit (RIU), respectively. For sensor 2, QF and sensitivity were 5540 and 500 nm / RIU, respectively. The sizes of sensor 1 and sensor 2 are 14.93 × 8.8 μm2 and 15.7 × 9.47 μm2, respectively. The 2D finite difference time domain and plane wave expansion methods were relied upon in the simulations.

Performance analysis of all-optical NAND, NOR, and XNOR logic gates using photonic crystal waveguide for optical computing applications

All-optical photonic integrated devices have gained great attention in the field of optical computing and large-scale integration. All-optical logic gates are useful for optical signal processing and optical communication network. The flexible devices presented here satisfy the functionality of NAND (NOT-AND), NOR (NOT-OR), and XNOR (exclusive NOR) logic gates using only one structure with proper changes in the phase of an applied light signal. The design of all-optical logic gates is implemented with photonic crystal waveguides using square lattice silicon rods. The performance of the structure is simulated, verified, and analyzed by the finite-difference time-domain method, with the principle of interference effect at a wavelength of 1550 nm. The contrast ratio (CR) of NAND, NOR, and XNOR logic gates is 17.59, 14.3, and 10.52 dB, respectively, with an optimized size of 7.2 μm × 5.4 μm.

Intelligent cooling structure design of "Z-pins like" silicon rods to enhance the ablation resistance of C/C-ZrC-SiC composites above 2500 °C

In order to improve the ablation resistance of C/C-ZrC-SiC composites by reducing the damage of the protective oxide layer, novel "Z-pins like" silicon rods, which were designed and fabricated by liquid phase sintering, were utilised as a dissipative agent. The microstructure evolution and thermal dissipation behaviour were investigated after ablating above 2500 °C for 300 s. After the "Z-pins like" silicon rods were implanted, the anti-ablative property of the C/C-ZrC-SiC composites was drastically improved by the dissipative thermal protection mechanism. The linear ablation rate of the "Z-pins like" silicon rod-reinforced C/C-ZrC-SiC composite was -0.28 μm/s, which is 112.72% lower than the unmodified composite. Additionally, the actual ablative temperature dropped approximately 357 °C, which enabled abundant SiO2 to remain in the ablation centre. Furthermore, a dense SiO2-rich oxide layer with a low oxygen diffusion coefficient is formed that covers the entire ablative surface.

Ordinary PVC feeding tube: A low-cost alternative to silicon rod for staged flexor tendon reconstruction in zone II of hand

BackgroundStaged flexor tendon reconstruction is most appropriate treatment for delayed zone II flexor tendon injuries of hand. The Hunter’s silicon rod used in this procedure is costly and not simply available. The aim of this study was to evaluate the results using PVC feeding tube as a cheaper and readily available alternative. Materials and methodsthis study include 6 patients(8 digits) were treated by the staged flexor tendon reconstruction using PVC feeding tube for first stage followed by tendon graft in second stage and the patients were followed for mean period of 6 months. ResultsExcellent results were seen in 5 digits and good results in 3 digits, according to both LaSalle system and Strickland-Glogovac grading system. ConclusionsPVC feeding tube is a cost effective, simply accessible and an effective alternative to Hunter’s silicon rod for staged flexor tendon reconstruction.

A Computational Comparative Study of the Lithium Diffusion in Amorphous Silicon Spheres, Rods, and Circular Disks

Abstract We study through extensive finite element analysis the lithium diffusion in small elements of Si anodes under the forms of spheres, rods, and circular disks for Li-ion batteries. Elastoplastic properties of the amorphous silicon are assumed to be lithium concentration-dependent. Effects of the normalized flux of Li-ions on the lithium concentrations, stresses, and total equivalent plastic strains are considered. Effects of the disk's thickness are also included. At a given normalized flux, the heterogeneity of the lithiation, stresses, and plastic deformation increases in the order: disk, sphere, and rod. The thinner disk the better performance is. Below a critical value of the normalized flux of Li-ions, silicon spheres and disks exhibit linear elasticity and homogeneous distribution of Li-ions, whereas silicon rods undergo always plastic deformation after lithiation. When the radii of these three structures are smaller than several micrometers and the normalized flux is taken as 95% of their critical value, the charge time falls in the range from minutes to several hours. Our findings will help to optimize the charge and geometrical parameters for silicon anodes.

Surface plasma resonance characteristics of cylindrical multilayer metal‐coated silicon nanoparticles

AbstractIn this article, the light scattering properties of cylindrical, three‐layer, silver‐coated silicon nanoparticles of the same size are investigated. Based on the T‐matrix methods, the light transmission and reflection characteristics of the multilayer structure are strictly derived. The scattering cross section (SCS) of the system and the near‐field Hz distribution are numerically calculated. The results show that surface plasmas (SPs) with different frequencies in the outer interface between the metal shell and air can be excited by the incident light and were resonant in different cavities formed by the silver‐coated silicon nanoparticles. When the incident light has higher frequencies, the SPs are excited at the inner interface between the silver shell and the silicon rod by the penetration of the light into the metal shell, and are resonant in the internal dielectric nuclei. These special SPs resonant phenomena have broad applications in the fields of surface plasma resonance sensors and detector.

Research on detection and location of weak edge signals

In order to be able to control the growth rate of industrial polycrystalline silicon rods well and reduce energy consumption, it is necessary to accurately locate the boundaries of the silicon rods and measure the diameter of the silicon rod during growth. In this paper, a weak edge signal detection method based on small area is proposed for the problem of weak boundary signal in the late growth stage of polycrystalline silicon rods. The method increases the gradient of the edge by projecting the boundary signal in the column direction. In addition, the method further enhances the gradient information of the weak boundary signal by improving the classical difference operator. In the experimental part, the improved difference operator increases the weak difference signal value from 304 to 686. Finally, the effectiveness of the algorithm is proved by two groups of experimental results.

Photonic Crystal-Based All-Optical Half Adder with High Contrast Ratio

Abstract Photonic crystal waveguides provide a way to manipulate the performance of an optical signal in an ultra-small volume and are quite viable in designing chip-based components that will work all-optically. Here, in this article an all-optical half adder is proposed. It is based on a square lattice photonic crystal waveguide in which silicon rods are arranged periodically. The photonic crystal offers a wide photonic band-gap in the desired region of telecommunication wavelength (i. e. near λ = 1550 nm. The performance of half Adder is measured using the contrast ratio and response time. The contrast ratio for sum and carry is 5.2 dB and 16.7 dB, respectively. The proposed half adder is miniaturized in size and having a footprint of 49 µm2 only. The total response time of the proposed adder is 1.4 picoseconds only. So, the device offers a high bit rate of 0.714 Tb/sec. The proposed half adder is an optimum choice for its application in on-chip optical integrated circuits.

An ultrafast all-optical half adder using nonlinear ring resonators in photonic crystal microstructure

Half adder and half subtractor are the basic building blocks of an arithmetic logic unit used in every optical central processing unit (CPU) to provide computational operators. In this paper, we aim to design an ultrafast all-optical half adder based on nonlinear ring resonators. The proposed structure consists of the concurrent designs of the AND and XOR logic gates inside a rod-based photonic crystal microstructure. The linear dielectric rods made of silicon and nonlinear dielectric rods composed of doped glass are used to design the nonlinear ring resonators as the fundamental blocks of a half adder. We demonstrate as the intensity of the incoming light increases, the nonlinear Kerr effect appears, and the total refractive index increases. It diverts the direction of light propagation to the desired nonlinear ring resonator depending on the signal wavelength, the radius of rods and lattice constant. Finally, after several resonances, the light is coupled to the output. Our numerical simulations using a two-dimensional finite-difference time-domain method reveal depending on the light intensity, the maximum and minimum transmissions of the half adder are 100% and 96%, respectively. The calculations also show the delay of the designed half adder is 3.6 ps. Due to the small area of 249.75 µm2, the proposed half adder is an appropriate candidate for photonic integrated circuits used in the next generation of all-optical CPUs.

Long-Term in vivo Release Profile of Dexamethasone-Loaded Silicone Rods Implanted Into the Cochlea of Guinea Pigs.

Glucocorticoids are used intra-operatively in cochlear implant surgeries to reduce the inflammatory reaction caused by insertion trauma and the foreign body response against the electrode carrier after cochlear implantation. To prevent higher systemic concentrations of glucocorticoids that might cause undesirable systemic side effects, the drug should be applied locally. Since rapid clearance of glucocorticoids occurs in the inner ear fluid spaces, sustained application is supposedly more effective in suppressing foreign body and tissue reactions and in preserving neuronal structures. Embedding of the glucocorticoid dexamethasone into the cochlear implant electrode carrier and its continuous release may solve this problem. The aim of the present study was to examine how dexamethasone concentrations in the electrode carrier influence drug levels in the perilymph at different time points. Silicone rods were implanted through a cochleostomy into the basal turn of the scala tympani of guinea pigs. The silicone rods were loaded homogeneously with 0.1, 1, and 10% concentrations of dexamethasone. After implantation, dexamethasone concentrations in perilymph and cochlear tissue were measured at several time points over a period of up to 7 weeks. The kinetic was concentration-dependent and showed an initial burst release in the 10%- and the 1%-dexamethasone-loaded electrode carrier dummies. The 10%-loaded electrode carrier resulted in a more elevated and longer lasting burst release than the 1%-loaded carrier. Following this initial burst release phase, sustained dexamethasone levels of about 60 and 100 ng/ml were observed in the perilymph for the 1 and 10% loaded rods, respectively, during the remainder of the observation time. The 0.1% loaded carrier dummy achieved very low perilymph drug levels of about 0.5 ng/ml. The cochlear tissue drug concentration shows a similar dynamic to the perilymph drug concentration, but only reaches about 0.005–0.05% of the perilymph drug concentration. Dexamethasone can be released from silicone electrode carrier dummies in a controlled and sustained way over a period of several weeks, leading to constant drug concentrations in the scala tympani perilymph. No accumulation of dexamethasone was observed in the cochlear tissue. In consideration of experimental studies using similar drug depots and investigating physiological effects, an effective dose range between 50 and 100 ng/ml after burst release is suggested for the CI insertion trauma model.

FRONTALIS SLING SURGERY USING SILICON ROD: RESULTS IN CONGENITAL UNILATERAL PTOSIS AMONG NORTH INDIAN POPULATION

ABSTRACT&#x0D; Purpose: To evaluate the results after frontalis sling surgery in congenital unilateral ptosis.&#x0D; Methods:&#x0D; This was a prospective study which included 27 eyes of patients with congenital unilateral ptosis and fair to poor levator action (&lt;8mm). A complete examination was performed including palpebral fissure height and width, lid-crease distance, margin reflex distance 1 (MRD 1) and margin reflex distance 2 (MRD 2), levator function. Fox pentagon technique was employed using silicon rod. Follow up was done at 2 weeks and at 3 months and based on the criteria recommended by Tarbet et al, the ptosis correction was catergorized into: ‘excellent’ if MRD1 measured more than 2mm or the difference in MRD1 between two eyelids was equal to or less than 1 mm, ‘good’ if MRD1 ranged from 1 to 2mm or if asymmetry was 1.5 to 2mm, and ‘poor’ if MRD1 measured less than 1 mm or if asymmetry was greater than 2mm in primary position of gaze.&#x0D; Results: A total of 27 eyelids of 27 patients underwent frontalis sling surgery with silicon rod. The correction was excellent in 20 patients (74%) on both first and second follow-up visits, shown in fig1. It was good in 5 patients (19%) and poor in 2 patients (7%) based on the above mentioned criteria. Lagophthalmos was present in all patients postoperatively which improved with time.&#x0D; Conclusion: This study shows that surgical repair using silicone sling is a safe and effective method of correcting congenital ptosis with poor to fair levator function.

Pseudospin states and topological phase transitions in two-dimensional photonic crystals made of dielectric materials

Based on the transmission properties of against backscattering and robustness against defects, photonic topological insulators have opened up a novel way to steer the propagation of electromagnetic wave. In order to construct the photonic analogs of the quantum spin Hall effect in an electronic system, we propose a simple two-dimensional photonic crystal made of dielectric materials to realize topologically protected edge states associated with the photonic pseudospin. The photonic crystal comprises a honeycomb array of equilateral-triangle-ring-shaped silicon rods embedded in an air host. By simply rotating the silicon rods around their respective centers by 60°, the band inversion between a twofold degenerated dipolar mode and a twofold degenerated quadrupolar mode is clearly observed in the Brillouin zone center. For the double twofold degenerated states, the chirality of the time-averaged Poynting vector surrounding the unit cell center (i.e., right-hand or left-hand circular polarizations) plays the role of the pseudospin degree of freedom in the present photonic system, and their point group symmetry can be utilized to construct a pseudo-time-reversal symmetry. By utilizing &lt;inline-formula&gt;&lt;tex-math id="M2"&gt;\begin{document}${{k}} \cdot {{p}}$\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20191962_M2.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20191962_M2.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; perturbation theory, we develop an effective Hamiltonian for the associated dispersion relation around the Brillouin zone center and calculate the spin Chen number, which indicates that the band inversion leads to a topological phase transition from a trivial to a nontrivial state. With numerical simulations, we unambiguously demonstrate that the unidirectional propagation of pseudospin-dependent edge state along the interface between a topologically nontrivial photonic crystal and a trivial one, and robustness of the edge states against different defects including sharp bend and cavity, regardless of the type of interface. The photonic system proposed by us consists of dielectric materials and the corresponding lattice structure is simple. And without changing the fill ratio or changing the positions of the silicon rods, a simple rotation of the silicon rods can generate the topological phase transition. So the potential applications of the pseudospin-dependent edge states based on our design are expected in more efficient way.

Simple and compact optical half-subtractor based on photonic crystal resonant cavities in silicon rods.

We propose a very simple and compact structure to realize the subtracting operation using resonant cavities in a photonic crystal structure. The cross section of the structure is ${103}\;\unicode{x00B5}{\rm m}^2$103µm2 and is desirable for integration based on popular planar technology. In the designed subtractor, the cavity was responsible for selecting the wavelength. By changing the boundary rods' cavity condition, the mode could resonate at the desired frequencies. To have resonant cavities, we introduce four defect rods between the input and the output waveguides. The results exhibit the true performance of the device. We used only silicon rods in the proposed device, and hence it is very simple to be fabricated. The finite-difference time-domain method was used for analyzing the proposed structure. The simulation results show that the contrast ratio of the device is 5 dB. The maximum rise and fall times are 1.5 and 0.5 ps, respectively.