Silicon Rods Research Articles

Open investigation on the interaction length between a terahertz wave and an embedded dielectric ZRIM structure, and also phase tuning.

In this paper, we have focused on the near field behaviour of 2D Photonic Crystal-based dielectric zero refractive index metamaterial lattices with cylindrical silicon rods embedded in THz waveguides having PMC sidewalls. An "interaction length" is expected in both input and output sides of a ZRIM lattice, after illumination of a TE polarized THz electromagnetic wave. In other words, by getting closer than a specific distance to the ZRIM lattice area from both input and output sides, which is called the interaction length, the wave profile will be affected significantly. Studying the field profile variation in the output side of the ZRIM lattice, we have considered two separate cascaded 2D PC-based ZRIM lattices in a THz waveguide with the same conditions and computed spatial phase shifts, and also the transmission and reflection coefficients versus the displacement between the two ZRIM lattices. This small limited distance led us to an almost 34° phase shift tuning between THz waves in two (multiple) THz waveguide systems.

A novel proposal for all optical 1-bit comparator based on 2D linear photonic crystal

We employ seven optical waveguides based on two-dimensional linear photonic crystal (LPhC) to realize an all optical comparator (AOCMP). The proposed 1-bit AOCMP has a very simple structure with a footprint of 356 μm2 which is composed of 31 × 33 cubic lattice of silicon rods immersed in air. This LPhC comparator comprises two input ports and two output ports. The functionality of the proposed 1-bit AOCMP is based on constructive and destructive interference phenomenon of optical beams and phase shift keying technique. The finite difference time domain (FDTD) procedure based on Yee’s Algorithm is used to compute the propagation of optical waves in this structure. The FDTD simulation results of suggested 1-bit AOCMP indicate that the minimum and maximum values of the normalized power at ON and OFF states for output ports are 62% and 10%, respectively. Also, the ON–OFF contrast ratio, bit rate, rise and fall times (Tr and Tf) of the suggested design are about 7.92 dB, 2.22 Tb/S, 0.15 ps and 0.05 ps, respectively.

Comparison of silicone rod versus prolene 4/0 suture in frontalis suspension surgery for simple congenital ptesis.

Objective: To compare the frequency of good functional outcome of frontalis suspension surgery using silicone rod versus prolene 4/0 suture in simple congenital ptosis. Study Design: Hospital Based Comparative Study. Setting: Department of Ophthalmology, Khyber Teaching Hospital, Peshawar. Period: June to August 2018. Material & Methods: This study was performed on 70 randomly selected patients divided in two groups (A and B) having 35 patients in each group. Patients with poor levator function (≤5mm), moderate to severe ptosis and good Bell’s phenomenon of either gender having age range of 5-25 years were included in the study. Good functional outcome was considered as achieved when the marginal reflex distance is more than or equal to 1 mm, and was considered as not achieved when the marginal reflex distance is less than 1 mm on physical examination after 3 months of the procedure. Results: In Group A, mean age recorded was 12+6.31 while mean duration of procedure was 52+3.08. In Group B, mean age was 15+4.76 and mean duration of procedure was 55+1.82. A total of 88.5% and 62.85% patients achieved good functional outcome in Group A and B respectively. Stratification of good functional outcome with respect to age shows that good functional outcome is statistically significant in the age group of 16-25 years. Conclusion: In simple congenital ptosis, prolene 4/0 suture achieved good functional outcome and an excellent safety profile in comparison to frontalis suspension using silicon rod.

Rozov and Kessler Tendon Sutures: Common Properties and Differences

Background. The Kessler suture is one of the most common tendon repair techniques and can be found schematically in most manuals of hand surgery, along with Bunnel and Tsuge sutures. In our country, the seam proposed by V.I. Rozov, while a number of authors believe that Rozov and Kessler sutures are very similar. Both techniques, both the Rozovs suture and the Kessler suture, have a large number of modifications that differ significantly from the originals, but retain the authors names, which confuses and hinders the analysis of the use of various methods for restoring the integrity of the tendons.
 The aim to find the correct authors description of Rozovs suture and Kesslers suture, test original techniques on a tendon model, compare techniques, analyze common properties and differences.
 Methods. Information was searched in domestic and foreign publications, manuals on traumatology and orthopedics, monographs, methodical letters, materials of congresses, Internet resources. Approbation of the methods was carried out on a tendon model, which was a silicone rod with a diameter of 1 cm.
 Results. The first image of the Rozovs suture discovered by us, dates back to 1958, the original grasping technique of flexor tendon repair was proposed by I. Kessler in 1969. These techniques have a number of significant differences in the location of nodes, methods of fixation and planes of threads in the thickness of the tendon.
 Conclusion. The data of this study give reason to believe that V.I. Rozov and I. Kessler proposed two different ways of applying a tendon suture.

Design of ultra compact 4:2 encoder using two dimensional photonic crystals

In this paper all optical ultra compact 4:2 encoder is proposed and designed using two dimensional photonic crystals (PC). The proposed structure has silicon rods of refractive index 3.4 embedded in air host by creating line defects in hexagonal lattice platform. The analysis of the design is done for various experimental values of radius, lattice constant and pitch values using finite difference time domain (FDTD) and plane wave expansion (PWE) method of licensed OptiFDTD software tool. The structure is optimised to get maximum power confinement at the output of the two ports of the 4:2 encoder by inserting extra rods which interns acts like a resonator to couple the power to the two output waveguides. The structure is chosen in such a way that ( $$\frac{a}{\lambda }$$ ) will fall around 1550 nm wavelength only and is good for long distance transmission application as it is having low attenuation constant and high contrast ratio. Further, the proposed 4:2 encoder is operated at 1550 nm and it provides a high contrast ratio of 9.25 dB, propagation delay 33.1 fs and foot print of the structure is 119.34 $$\mu$$ m $$^2$$ . Hence it is highly advisable for photonic integrated circuits and optical signal processing.

Study on Deposition Conditions in Coupled Polysilicon CVD Furnaces by Simulations

Electronic-grade polysilicon is the cornerstone of the information industry. Considering the demand for this material in the semiconductor industry, any technological improvement has great potential benefits. Due to the quality requirements of electronic polysilicon, its preparation process is characterized by low raw material utilization and high cost. Simply increasing the deposition rate by increasing the chemical reaction rate will easily lead to a reduction in the proportion of dense materials. For the first time, a coupled furnace scheme is proposed to improve the utilization of raw materials while maintaining the same deposition quality. The deposition conditions on the surface of silicon rods with different base plate designs were modeled and analyzed using the software PolySim, and a design characterized by a high flow rate and the use of 9 mm and 15 mm nozzles was selected for the coupling scheme. In coupling mode, the simulation results show that the utilization of raw materials is increased by 17.5%, and the deposition rate is increased by 44.9%, while the deposition quality and uniformity remain approximately unchanged. The results show that the coupling scheme with high feed flow is beneficial for significantly improving the deposition conditions and the utilization rate of raw materials, which also provides guidance for material preparation processes with similar principles.

Highly sensitive refractive index sensor based on photonic crystal ring resonators nested in a Mach–Zehnder interferometer

Today, with the rapid development of photonics, optical sensors are being considered as efficient tools for detecting environmental variations and have been regarded as one of the most important fields in photonic research. In this study, we have proposed a two-dimensional photonic crystal refractive index sensor using a combination of Mach–Zehnder interferometers and two ring resonators. Our goal is to increase the sensitivity and figure of merit of the sensor, so that the output transmission spectrum can be considerably shifted by changing the refractive index of the simulated analytes. The proposed photonic crystal sensor consists of a hexagonal array of silicon rods on a SiO2 substrate. The finite difference time domain method is used for the numerical simulation of the structure. In this regard, to validate the simulation results, two different commercial software have been used. The quality-factor and the sensitivity of the proposed structure are 1535 and 1658 nm/RIU, respectively, where RIU stands for the refractive index unit. In general, the structure has advantages such as low fabrication cost, high sensitivity to changes in refractive index and a high Q-factor.

Ultra-fast tunable optoelectronic full-adder based on photonic crystal ring resonators covered by graphene nanoshells

This paper reports a novel design of a tunable optoelectronic full-adder using two photonic crystal ring resonators (PCRRs). Every PCRR consists of a matrix of silicon rods surrounded by silica rods coated with graphene nanoshells (GNSs). The proposed full-adder is formed by three input ports, two PCRRs, and two output ports for ‘SUM’ and ‘CARRY’. The plane wave expansion technique is used to study the photonic band structure of the fundamental photonic crystal (PhC) microstructure, and the finite-difference time-domain method is also employed in the final design for solving Maxwell's equations to analyze the light propagation inside the structure. We can tune the PhC resonant mode for our desired application by setting the chemical potential of GNSs with an appropriate gate voltage. The numerical results reveal that when the chemical potential of GNSs changes, the switching mechanism occurs and manages the coupling and propagation direction of the input beam inside the structure. We systematically study the effects of physical parameters on the transmission, reflection, and absorption spectra . Our numerical results also demonstrate that the maximum delay is about 0.8 ps. The 663 μm 2 area of the proposed full-adder based on two-dimensional materials makes it a building block of every photonic integrated circuit used for data processing systems. • A fast and compact all-optical full-adder using photonic crystal ring resonators (PCRRs). • A maximum steady-state time of about 0.8 ps and the structure's total size of 663 μm 2 . • There is no need to increase the input intensity for the appearance of the nonlinear effect. • The ON-OFF contrast ratios for Sum and Carry are 16 dB and 14 dB, respectively. • The full-adder is applicable in optical integrated circuits for high-speed signal processing.

Two-stage tendoplasty of the flexor digitorum profundus in a small child

BACKGROUND: Injuries to the flexor tendons of the fingers are uncommon in young children, and chronic injury is an extremely rare injury. Many issues of damage diagnosis, surgical intervention and rehabilitation techniques remain unresolved. In this regard, the treatment of chronic damage to the flexor tendons of the fingers in young children has practical and theoretical significances.
 CLINICAL CASE: A 16-month old underwent a two-stage treatment of chronic damage to the flexor tendons of the small finger. At the first stage, scars were removed from the fibro-synovial canal, and a silicone rod was inserted into the canal. At the second stage, the silicone spacer was replaced by a tendon autograft. The surgical treatment and postoperative management of the patient was described in detail. The full range (270 degrees) of active and passive motion was restored five months after the second stage of tendoplasty. Two years after the operation, good hand function.
 DISCUSSION: The analyzed publications mainly present the results of treatment of patients older than 1 year and 4 months. Only in the study by S.L. Piper et al. (2019) the youngest patient at the time of injury was 7 months old, at the time of first stage of tendoplasty 1 year and 3 months. The final volume of active motion was 160 degrees. In our case, the functional result was higher. Considering the undoubted rarity of damage uncharacteristic for this age, we intend to continue monitoring the patient.
 CONCLUSIONS: Comprehensive long-term treatment of a serious injury to the hand, considering the anatomical and physiological characteristics of a small child, made it possible to obtain a good functional result.

Mathematical modeling of the gettering process for a cylindrical region

The paper considers a mathematical model of the technical process of external gettering of silicon rods. The purpose of this process is to remove unwanted impurities from silicon. The model of this process is an initial-boundary value problem for a linear partial differential equation of parabolic type. A feature of this problem is the presence of a nonlocal in time boundary condition, which reflects the law of conservation of mass (matter). For numerical modeling, an algorithm based on difference approximations of differential operators of the 1st and 2nd order is proposed. The classical sweep method is used to find a solution to a discrete problem.

Super strong wide TM Mie bandgaps tolerating disorders

This study demonstrates the appearance of super intense and wide Mie bandgaps in metamaterials composed of tellurium, germanium, and silicon rods in air that tolerate some disordering of rod position and rod radius under transverse magnetic (TM) polarized light waves. Tellurium metamaterials reveal {mathrm{TM}}_{01}, {mathrm{TM}}_{11}, {mathrm{TM}}_{21}, {mathrm{TM}}_{02}, {mathrm{TM}}_{12} Mie bandgap modes in which {mathrm{TM}}_{01}, {mathrm{TM}}_{11}, and {mathrm{TM}}_{21} tolerate high rod-position disordering of 50% and rod-radius disordering of 34 and 27%, respectively. Results for germanium metamaterials show Mie bandgap modes {mathrm{TM}}_{01}, {mathrm{TM}}_{11}, and {mathrm{TM}}_{21}, in which {mathrm{TM}}_{01} and {mathrm{TM}}_{11} tolerate rod-position disordering of 50%, and rod-radius disordering of 34 and 20%, respectively. Using these characteristics of {mathrm{TM}}_{11} in germanium metamaterials under position and radius disordering, ultra-narrow straight, L-shaped, and crossing waveguides that contain 14, four, and two rows of germanium rods in air are designed. Also, it is shown that {mathrm{TE}}_{01} Mie bandgap appears in metamaterials containing a high refractive index, and disappears in metamaterials with a lower refractive index such as silicon; in contrast, a new phenomenon of intense and broadband {mathrm{TM}}_{01}, {mathrm{TM}}_{11}, and {mathrm{TM}}_{21} in metamaterials with a lower refractive index such as silicon appear. In silicon-based metamaterials, {mathrm{TM}}_{01} tolerates high rod-position and rod-radius disordering of 40% and 34%, respectively, and {mathrm{TM}}_{11} shows robustness to rod-position and rod-radius disordering of 20%. This strong tolerance of disordering of TM modes in tellurium, germanium, and silicon metamaterials opens a new way to design small, high-efficient, and feasible fabrication optical devices for optical integrated circuits.

Intensity and phase encoding for realization of integrated Pauli X, Y and Z gates using 2D photonic crystal

Nano-scale all-optical logic gates systems are desirable for the all-optical computing and signal processing applications. All-optical Quantum computing offers excellent computational abilities and lossless operations. The Pauli X, Y and Z gates are vital quantum logic gates for all-optical systems. In this paper, the integrated all-optical Pauli X, Y, Z gate is realized using a square lattice 2D photonic crystal of silicon rods. The phase encoding and intensity encoding techniques have been used simultaneously for the integrated operation. Pauli X, Y, Z logic gate truth table has been verified at the operating wavelength of 1.55 µm.The system offers a linear operation, compact size, low power requirement, and high contrast ratio of 10.4 dB. The footprint of the proposed structure is about 70µm x 70µm and demonstrates a fast response time of 2 ps, bit rate of 0.25 Tbps, which makes it suitable for photonic integrated circuits (PICs).

Designing a Circuit for High-Speed Optical Logic Half Subtractor

In this paper, a high-speed optical subtractor has been designed and simulated. This circuit is based on a photonic crystal structure with silicon rods embracing a circular cross-section in the air platform. This structure was performed based on the photonic band gap. The best performance of this subtractor is in the highly-usable telecommunication wavelength of 1550, laying in the range of the photonic band gap of this structure. To design the circuit, two inputs with optical sources and two outputs have been used for difference and borrow bit. The features of this logic half subtractor encompassed simple structure, small dimensions, and appropriate level of the outputs 1 and 0.

Logic gate and optical half-adder designed by photonic crystal based on BPSK signals

We design a logic gate and an optical half-adder based on photonic crystal using BPSK signals. The logic gate is composed of a silicon rod array and a microcavity containing a SiO2 dielectric column, which can realize XOR and XNOR logic. The optical half adder is formed by introducing a reference beam with a fixed initial phase to the proposed logic gate. The initial phase of incident light determines the logic state of the BPSK signals. The intensity of the output light determines the output logic state. We use the plane wave expansion and finite element methods to analyze logic gates and optical half adders. The proposed logic gate and optical half-adder cover 160 µm2 and 270 µm2, the response time is 0.6 ps and 0.9 ps, respectively, and the margin difference of the output signals is 103% and 81%, respectively. Their compact structure, short response time, and large margin difference of the output signals have potential application prospects in all-optical information processing.

Design and simulation of a 2 × 1 All-Optical multiplexer based on photonic crystals

Photonic crystals are alternating structures widely used to design various types of logic circuits. In this paper, a 2 × 1 multiplexer is designed and simulated based on two-dimensional photonic crystals with a cubic lattice. Silicon rods in the air were used to design this multiplexer. Only linear defects were considered in the design of the structure. In other words, none of the rods were changed and all Si rods were the same, which is one of the advantages of this structure. Optical sources with a wavelength of 1.55 µm were utilized in the inputs and select line. The size of the structure was 12.16 µm × 12.16 µm. The small dimension and the simplicity of the structure make it a suitable candidate in optically integrated circuits.

The Combined Use of Silicone and Green Braided Polyester ‎Suture (Ethibond) versus ‎Silicone or Ethibond Alone for Frontalis ‎Suspension Surgery in Children.

PurposeThis study aimed to report the outcomes of correcting severe congenital blepharoptosis by frontalis suspension using combined silicone tube and 2–0 green braided polyester suture (Ethibond), and to compare the results with those of silicone rod alone and Ethibond suture alone.Patients and MethodsThe medical records of patients below 16 years who underwent frontalis suspension were retrospectively reviewed. Three groups of patients were identified; group I (16 patients: 22 eyelids) had frontalis suspension surgery using silicone suspension set, group II (18 patients: 25 eyelids) underwent the surgery using Ethibond suture, and group III (15 patients: 23 eyelids) was operated on using combined silicone and Ethibond suture. The primary outcome measures were postoperative marginal reflex distance-1 (MRD-1) and postoperative symmetry, and the secondary outcome measures were the occurrence of complications; mainly recurrence and wound-related complications. The follow-up data were collected after 1 week, 1 month, 6 months, 12 months and every 6 months thereafter.ResultsThe follow-up period ranged from 18 to 36 months. By the last follow-up visit, 13 eyelids in silicone group (59%), 11 eyelids in the Ethibond group (44%), and 13 eyelids in the double sling group (57%) achieved good surgical correction with MRD1 ≥3mm; these differences were not statistically significant. The difference in symmetry among the three groups was not significant. The highest rates of recurrence (44%) and wound-related problems (8%) were encountered in the Ethibond group, while the silicone group had no cases of wound-related problems. The lowest recurrence rate (26.1%) was in the double sling group but those differences were not significant.ConclusionCombined use of silicone and Ethibond suture in frontalis suspension surgery could offer lower recurrence rate and good final surgical outcome when compared to silicone rod or Ethibond suture alone.

Frontalis Sling Using a Silicone Rod for Ptosis in Third Nerve Palsy: Cosmesis versus Safety.

PurposeTo evaluate the results of the frontalis sling operation using a silicone rod for the correction of ptosis in patients with third nerve palsy with a focus on corneal safety.MethodsPatients with third nerve palsy who underwent the frontalis sling operation using a silicone rod between 2008 and 2019 were included in this study. The medical records of all patients were reviewed, and their clinical characteristics and postoperative outcomes were analyzed. In this retrospective, interventional case series, the main outcome measures were eyelid contour, eyelid height by margin reflex distance, and corneal status.ResultsTwenty-four eyes of 18 patients (12 male and six female patients) were included. The mean age at the time of surgery was 35.1 years (range, 5–64 years). Twelve patients underwent a unilateral ptosis operation, and six patients received a bilateral ptosis operation. The mean follow-up period was 32.1 months (range, 2–87 months). Most patients (21 of 24 eyes, 88%) showed poor Bell’s phenomenon on preoperative examination. Satisfactory eyelid height and eyelid contour were achieved in almost all patients (mean postoperative margin reflex distance, +1.2 mm) postoperatively. Although corneal erosions were detected for several months in eight of 24 eyes after surgery, these findings were well controlled medically with artificial tear eye drops and ointments.ConclusionsFrontalis sling surgery using a silicone rod can safely and effectively correct ptosis without severe corneal complications in patients with third nerve palsy. Our study outlines a new method to define the postoperative safety outcome by specifically focusing on categorized corneal status.

Optimized design of an all-optical XOR gate with high contrast ratio and ultra-compact dimensions

In this work, an optimized structure for an all-optical XOR gate with high contrast ratio and extremely compact dimension is proposed based on a photonic crystal platform. The above structure employs silicon rods in a hexagonal lattice configuration. The design works purely on linear interference effect between the incoming light signals without utilizing any non-linear materials. To study the propagation of light within the structure and to generate the bandgap diagram, the Finite Difference Time Domain technique and Plane Wave Expansion methods are utilized. After optimization of the various design parameters, a contrast ratio of 31.76 dB is attained by the proposed structure along with a response time of 0.46 ps and a footprint of 42.24 μm2. The device can be operated in the C Band with optimum performance at 1550 nm, which is the telecommunication wavelength. The operating bit rate for the proposed structure is 2.17 Tbps. The all-optical XOR gate plays a crucial role as the building blocks of various sequential and combinational logic designs suitable for application in optical computing and telecommunication systems.

Investigation on ultra-compact, high contrast ratio 2D-photonic crystal based all optical 4 × 2 encoder

Optical encoder is playing an essential starring role in optical communication and computing applications. This paper presents a new structure for 4 × 2 optical encoder based on two dimensional photonic crystals. The proposed structure consists of silicon rods in background of air using hexagonal lattice. The proposed structure is composed of four input waveguides and two outputs. The band structure is examined by plane wave expansion method and the performance parameters of the 4 × 2 encoder, namely, normalized output power, footprint, contrast ratio, response time and bit rate are analyzed using finite difference time domain method. The proposed encoder is operated at 1550 nm. The low response time, and small footprint have shown that the encoder is exceptionally suitable for high performance optical networks and photonic computational integrated devices.

Convective Heat Transfer Across Silicon Rods Under Uniform Wall Heat Flux in a Laboratory-Scale Siemens Reactor

Convective Heat Transfer Across Silicon Rods Under Uniform Wall Heat Flux in a Laboratory-Scale Siemens Reactor