Crystal Ring Research Articles

The flagellar motor protein FliL forms a scaffold of circumferentially positioned rings required for stator activation

The flagellar motor stator is an ion channel nanomachine that assembles as a ring of the MotA5MotB2 units at the flagellar base. The role of accessory proteins required for stator assembly and activation remains largely enigmatic. Here, we show that one such assembly factor, the conserved protein FliL, forms an integral part of the Helicobacter pylori flagellar motor in a position that colocalizes with the stator. Cryogenic electron tomography reconstructions of the intact motor in whole wild-type cells and cells lacking FliL revealed that the periplasmic domain of FliL (FliL-C) forms 18 circumferentially positioned rings integrated with the 18 MotAB units. FliL-C formed partial rings in the crystal, and the crystal structure-based full ring model was consistent with the shape of the rings observed in situ. Our data suggest that each FliL ring is coaxially sandwiched between the MotA ring and the dimeric periplasmic MotB moiety of the stator unit and that the central hole of the FliL ring has density that is consistent with the plug/linker region of MotB in its extended, active conformation. Significant structural similarities were found between FliL-C and stomatin/prohibitin/flotillin/HflK/C domains of scaffolding proteins, suggesting that FliL acts as a scaffold. The binding energy released upon association of FliL with the stator units could be used to power the release of the plug helices. The finding that isolated FliL-C forms stable partial rings provides an insight into the putative mechanism by which the FliL rings assemble around the stator units.

Design of ring resonator based comparator using 2-D photonic crystal

Optical comparators are a key element in optical systems that are vital for the construction of all optical digital frameworks used in optical data processing. The framework for constructing a one-bit optical comparator using photonic crystal ring resonators is presented for maximum throughput. The photonic crystal resonator rings can be linear or nonlinear, depending on the application. Silicon rods in air are employed to create the resonant cavity in the structure for comparator design. The cylindrical rods are made from silicon, which are used in the design of the comparator. Ring resonator structure has been utilized in designing the 2D photonic crystal-based comparator. The input wavelength of 1.5 µm has been applied to both the input ports of comparator for simulating the structure and the quality factor of 648 has been achieved for presented design. The proposed design compares two signals applied at both the input ports of the comparator and generates the signal at the output port.

Role of PET-CT (Positron Emission Tomography-Computed Tomography) in Cancer Evaluation and Treatment

Context: Positron emission tomography is a nuclear medicine imaging that deals with physiological function using radioisotopes. With the most PET (Positron Emission Tomography) scanners in integration with the CT scanners of late, this technology has registered phenomenal growth. The small amount of radioactive material is called Radiotracers. Objective: Like 18F- Fluro-deoxy-2-glucose has widely used. In this article, the author introduced clinical applications of PET out of 25 patients who studied hypermetabolic lesions in lymph nodes. Methods: PET imaging is coincidence imaging which is different from the other imaging technique PET image formed from multiple rings of detector crystals. Each decay positron travel in tissue annihilation reaction is going on. FDG is the most commonly used radiotracer to detect and stage various types of malignancies. Result: The field of PET/CT imaging cares for many oncology patients. PET improved localization of malignant lesions. It improved staging biopsy and therapy. Conclusion: Finally, studies to data showed 4% to 10% improvement in the overall accuracy of staging/restaging in lesions. If we use Monte Carlo simulation, OLINDA/EXM software may improve further with widely used.

High-Q slow light and its localization in a photonic crystal microring

We introduce a photonic crystal ring cavity that resembles an internal gear and unites photonic crystal (PhC) and whispering gallery mode (WGM) concepts. This `microgear' photonic crystal ring (MPhCR) is created by applying a periodic modulation to the inside boundary of a microring resonator to open a large bandgap, as in a PhC cavity, while maintaining the ring's circularly symmetric outside boundary and high quality factor ($Q$), as in a WGM cavity. The MPhCR targets a specific WGM to open a large PhC bandgap up to tens of free spectral ranges, compressing the mode spectrum while maintaining the high-$Q$, angular momenta, and waveguide coupling properties of the WGM modes. In particular, near the dielectric band-edge, we observe modes whose group velocity is slowed down by 10 times relative to conventional microring modes while supporting $Q~=~(1.1\pm0.1)\times10^6$. This $Q$ is $\approx$50$\times$ that of the previous record in slow light devices. Using the slow light design as a starting point, we further demonstrate the ability to localize WGMs into photonic crystal defect (dPhC) modes for the first time, enabling a more than 10$\times$ reduction of mode volume compared to conventional WGMs while maintaining high-$Q$ up to (5.6$\pm$0.1)$\times$10$^5$. Importantly, this additional dPhC localization is achievable without requiring detailed electromagnetic design. Moreover, controlling their frequencies and waveguide coupling is straightforward in the MPhCR, thanks to its WGM heritage. By using a PhC to strongly modify fundamental properties of WGMs, such as group velocity and localization, the MPhCR provides an exciting platform for a broad range of photonics applications, including sensing/metrology, nonlinear optics, and cavity quantum electrodynamics.

Novel add-drop filter based on serial and parallel photonic crystal ring resonators (PCRR)

Abstract Photonic crystal ring resonators (PCRR) as momentous candidates for future photonic crystal integrated circuits (PCICs) draw worldwide attention. In this paper, different configurations are proposed based on single, parallel, and serial PCRRs. To be precise, the different coupling lengths and alignments have been discussed in double and triple PCRRs in parallel and serial configurations to achieve the highest efficiency concerning the desired applications such as an add-drop filter (ADF) and a power splitter. Moreover, in the achieved optimum double and triple PCRRs, the effect of coupling radius change has been discussed.

A Hollow-Core Photonic-Crystal Fiber-Optic Gyroscope Based on a Parallel Double-Ring Resonator.

A novel system structure of resonant fiber optical gyroscope using a parallel double hollow-core photonic crystal fiber ring resonator is proposed, which employs the double closed loop and reciprocal modulation–demodulation technique to solve the problem of the length mismatch between rings. This structure can suppress the residual amplitude modulation noise and laser frequency noise, essentially eliminating the influence of the Rayleigh backscattering noise and dramatically reduce the Kerr-effect-induced drift by three orders of magnitude. Thanks to its excellent noise suppression effect, the sensitivity of this novel system can approach the shot-noise-limited theoretical value of 8.94 × 10−7 rad/s assuming the length of the fiber ring resonator is 10 m.

Performance analysis of all optical 2 × 1 multiplexer in 2D photonic crystal structure

Abstract In optical processing systems, multiplexer is used to design optical devices such as arithmetic logic unit (ALU) and shift register (SR). Through this paper, we investigate the application of nonlinear photonic crystal ring resonator (PhCRR) based on nonlinear Kerr effect for realizing an all optical 2 × 1 multiplexer. The structure consists of two PhCRRs and five optical waveguides using hexagonal lattice silicon (Si) rods with a background of air. Performance of all optical 2 × 1 multiplexer is replicated with the help of finite difference time domain (FDTD) procedure at a wavelength of 1571 nm, and simulations presented an ultra-compact optical structure with ultra-fast switching speed.

Photonic crystal-based biosensor for detection of human red blood cells parasitized by plasmodium falciparum

In this paper, a biosensors based on a two-dimensional photonic crystal (2D PhC) waveguide including a ring resonator is designed and simulated based on refractive index changes of red blood cells. The proposed biosensor structure consists of an elliptical photonic crystal ring resonator and two linear waveguides containing silicon nitride rods in a 2D rectangular lattice with circular rods. The biosensor is utilized to detect the stages of the Plasmodium falciparum cycle in red blood cells and to diagnose malaria disease. The proposed design distinguishes with high sensitivity between normal red blood cells and cells infected with Plasmodium falciparum. This biosensor is very compact, consists of gold rods in the air background and works very well at two input central wavelengths of 0.514 and 1.55 μm. The finite-difference time-domain (FDTD) method is used to simulate and investigate the device. The biosensor is extremely compact which is very suitable for lab-on-chip applications and exhibits higher sensitivity at both input central wavelengths compared with that of previously reported sensors.

Nonlinear optical decoder based on photonic quasi crystal ring resonator structure

Abstract Using two nonlinear photonic crystal ring resonators we proposed and designed an all optical decoder. 2D 12 fold quasicrystal was used as the core section of the resonant rings. In order to make use of advantages of nonlinear Kerr effect, we put 24 dielectric rods between the core and outer shell of the resonant ring. The linear refractive index and nonlinear Kerr coefficient of these rods are n 0 = 1.4 and n 2 = 10−14 m2/W. In the proposed structure port I was used to switch the optical beams coming from BIAS between O1 and O2 output ports. The optical intensity required for performing the switching task is about 0.1 kW/μm2.

Design and analysis of photonic MEMS based micro ring resonators for pressure sensing application

The proposed work consists of a ring resonator-based pressure sensor. Double and triple ring photonic crystal resonators are configured in series and in parallel combinations. The sensing layer is designed and simulated for a varying pressure of 3–9 MPa using ansys workbench to obtain the stress and deformation experienced by the sensor. The equivalent refractive index value for every stress is computed and shift in wavelength is determined by simulation of the photonic crystal ring resonator (PCRR) structures in the optical tool. Finite-difference time-domain results show that ‘three rings coupled in parallel’ PCRR structure have the best sensitivity and good quality factor than other sensing configurations. A maximum sensitivity of 49.77 nm MPa−1 and a quality factor of 3260.25 is observed for the triple-ring parallel PCRR. The proposed type of sensor has remarkable biosensing applications.

Modeling and analysis of all‐optical pressure sensor using photonic crystal based micro ring resonator

AbstractThe paper illustrates a photonic crystal micro ring resonator based pressure sensor utilizing the variation of refractive index of the material and the structural deformation. FEM is employed for reformed structure analysis. Structural deformation and change in refractive index are taken as input variables in FDTD simulation and the external pressure is measured by analyzing shift in resonance wavelength. A comparative study of the rod type and the hole type photonic crystal micro ring resonator based pressure sensor is reported in this paper. Both the structures are ultra compact and can be used for compact photonic integrated circuits.

A proposal for four channel demultiplexer based on phoxonic crystal ring resonators

The complete phononic and photonic bandgap have been obtained which can manage the sound and TM polarized light waves through the forbidden band. The matrix is made of nylon and the inclusions are filled with molybdenum. The proposed phoxonic structure acts as a phononic and photonic demultiplexer which can separate four frequencies and wavelengths. This separation is done simultaneously without coupling between light and sound, or even without interfering and scattering. The proposed structure contains triangular ring resonators with significant advantages such as high transfer of sound and light waves from input to outputs with high quality factor.

Realization of all-optical logic gates using a single design of 2D photonic band gap structure by square ring resonator

The interference method is used to achieve all-optical logic gate operations. This has been realized with a single design of photonic crystal ring resonator at different wavelengths rather than designing separate for all the logic gates. Such a single design can be used to perform all optical operations as AND, OR, and XOR logic gates at different wavelengths. Further operating wavelength, contrast ratio (CR), response time (RT), and bit rate have been analyzed for all three logic gates. The highest CR is obtained as about 22.06 dB with fast RT about 0.14 ps and high bit rate of 7.14 Tb / s for proposed XOR logic gate in comparison to all the other logic gates with single-design structure, which may lead us to construct on-chip logic circuits.

High Sensitivity Temperature Sensor Based on Two-Dimensional Photonic Crystal

In this work, a two-dimensional photonic crystal ring resonator based temperature sensor is investigated. The device consists of a hexagonal array of air holes surrounded by the base material of germanium (Ge). The sensing mechanism is based on the shifting of transmission peak with refractive index changes in Ge induced by variation of temperature. Simulation results are obtained using finite difference time domain method (FDTD). The photonic band gap is studied by plane wave expansion method (PWE). The sensor has high sensitivity of 270 pm/K and high quality factor of 2028.86 with` wide range of temperature detection between 300 K to 800 K. The size of the structure is 112.91 (µm)2 and appropriate for sensing applications in nanotechnology.

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

This paper reports a new design of a tunable optoelectronic half adder/subtractor. Two photonic crystal (PhC) ring resonators are used to realize the proposed structure. Several silicon rods surrounded by silica rods covered with graphene nanoshells (GNSs) form every PhC ring resonator. Setting the chemical potential of GNS with an appropriate gate voltage, we can tune the PhC resonant mode as desired. The plane wave expansion technique is used to study the photonic band structure of the fundamental PC microstructure, and the finite-difference time-domain method is employed in the final design for solving Maxwell's equations to analyze the light propagation inside the structure. We systematically study the effects of physical parameters on the transmission reflection and absorption spectra. By optimizing the geometric dimensions, resonant absorption peaks can be excited at the same time for GNSs. Our numerical results also reveal the maximum time response is about 0.8 ps. The 200 µm2 area of the proposed half adder/subtractor makes it the building block of every photonic integrated circuit. Also, the design of various fast signal processing systems in optical communication networks is possible due to using tunable GNSs in PhC ring resonators. This study can introduce the use of two-dimensional materials in the design and implementation of logic circuits.

DEMUX with low crosstalk and compact channel drop filter based on photonics crystals ring resonator with high quality factor

Abstract The optical components based on photonic crystal had a wide range of applications fields these last years. In this work, we propose a configuration of photonic crystal structure of Channel Drop Filter (CDF). The proposed filter study by finite difference numerical method in the time domain FDTD makes it possible to ensure an average detected modal transmission rate of 95.30%, an average quality factor of order 3149.12 and a compact size of 144.65 μm2 with high sensitivity to small variation of refractive index, period and radius of rods. Thus, we designed demultiplexer with four channels, which has a low average crosstalk of −30.73 dB. The transmission and the quality factor are 90.94% and 2221.13 respectively, with channel spacing 4.2 nm and a size of 405.6 μm2. These properties make our model of the proposed filter and demultiplexer well adapted for the realization of optical integrated circuit.

High-Performance Eight-Channel Photonic Crystal Ring Resonator–Based Optical Demultiplexer for DWDM Applications

High-Performance Eight-Channel Photonic Crystal Ring Resonator–Based Optical Demultiplexer for DWDM Applications

A novel design of all-optical high speed and ultra-compact photonic crystal AND logic gate based on the Kerr effect

In this study, we have designed and simulated a photonic crystal (PhC) nonlinear AND logic gate. First, a suitable photonic crystal ring resonator (PhCRR) structure is designed and simulated that can be used for obtaining the switching power intensity after applying the nonlinear Kerr effect. In this structure, GaAs dielectric rods have been used in the air. The plane wave expansion (PWE) method is used to obtain the guided modes in the proposed structure and the two-dimensional finite-difference time-domain (2D-FDTD) method is also employed to simulate the structure. According to the results obtained from the numerical calculations, the minimum switching power intensity for the structure is equal to 800 W/μm2. Using the designed PhCRR and the obtained switching power intensity, an optimal compact photonic crystal AND logic gate based on the Kerr effect is designed and simulated which exhibits a good performance. The minimum contrast ratio, the response time, and the total area of the structure are 11.04 dB, 1.8 ps, and 194.56 μm2, respectively.

ICES: an innovative crosstalk-efficient 2 × 2 photonic-crystal switch

Crosstalk and insertion loss are the crucial determinants of ring resonated routers. A novel 2 × 2 optical switch is proposed through a combination of broadband waveguide crossing and X-shape photonic crystal ring resonators. The main goal of the proposed design is to demonstrate the switching wavelengths based on changing the refractive index and reduce the level of the crosstalk and insertion loss. The performance of the proposed structure is analyzed using two-dimensional finite difference time domain and plane-wave expansion methods. Results show that crosstalk noise and insertion loss can be significantly reduced by using optimized crossbar waveguide and novel structure with bending elimination, thereby allowing higher network scalability and better performance and utility for future many-core architectures. Maximum crosstalk and insertion loss of −37.41 and 0.3 dB are obtained at 1570.5 nm, respectively. The size of the proposed structure is 18.69 × 19.6 μm2, which can be used for photonic integrated circuits design due to its compactness.

Formation of Metallic Polyferrocene Chains under Pressure.

The effect of pressure on the structural reorganization of ferrocene, Fc = (C5H5)2Fe, is studied using density functional theory (DFT) calculations assisted by evolutionary crystal structure prediction algorithms based on USPEX code. Pressure brings the individual molecules in close contact, and above 220 GPa, the 18-electron closed-shell molecular unit undergoes polymerization through the formation of quasi-one-dimensional (1D) chains, [(C5H5)2Fe]∞, termed as polyferrocene (p-Fc). Pressure induced polymerization (PIP) of Fc causes significant deviations from the 5-fold symmetry of the cyclopentadiene (Cp, C5H5 rings) and loss of planarity due to the onset of envelope-like distortions. This triggers distortions within the multidecker sandwich structures and σ(C-C) bond formation between the otherwise weak noncovalently interacting Cp rings in Fc crystals. Pressure gradually reduces the band gap of Fc, and for p-Fc, metallic states are found due to increased electronic coupling between the covalently linked Cp rings. Polyferrocene is significantly more rigid than ferrocene as evident from the 5-fold increase in its bulk modulus. Pressure dependent Raman spectra show a clear onset of polymerization in Fc at P = 220 GPa. Higher mechanical strength coupled with its metallicity makes p-Fc an interesting candidate for high pressure synthesis.