An ultra-small heterostructure wavelength division multiplexer (WDM) with the ability to select two wavelengths from the s-band

In this article, a photonic crystal channel drop filter (CDF) based on \(2\times 3\) ring resonators is presented. At first, the effects of changing the radius of lattice rods and the lattice dielectric constant on the dropping efficiency of a 3-port CDF with one resonator are investigated. Then by developing this base structure, a new 4-port heterostructure CDF composed of two regions with rods made of silicone and germanium is presented, which can operate in the ‘S’ band of the communication window. The photonic crystal heterostructure CDF consists of a horizontal waveguide and two ring resonators that have been installed, in symmetry to the horizontal axis, in two regions with different refractive indices. These ring resonators act as energy couplers and capture at their resonant frequencies the electromagnetic energy which is propagated in the bus waveguide. For the analysis of transmission characteristics and the band structure of the filter, two methods have been employed: the two-dimensional Finite–difference time domain method and the Plane Wave Expansion method. In the final structure, dropping efficiencies of 97 and 89 % can be achieved at ports D and B, respectively, and also an acceptable quality factor can be obtained in the communication window. The overall size of this device is 174.14  \(\upmu \hbox {m}^{2}\) . Due to its small size, this structure can be used in Wavelength Division Multiplexer applications in the Optical Integrated Circuits.     

A new design of tunable four-port wavelength demultiplexer by photonic crystal ring resonators

A four-channel wavelength demultiplexer based on photonic crystal ring resonators (PCRR), which can be used for photonic integrated circuits, is designed. Dropping efficiency and Q factor of single improved ring are 100% and 842, respectively. In order to achieve the structure of demultiplexer, three improved rings have been used, that every ring has an individual inner rod radius; it means that each ring has a varying resonant wavelength. The results of simulation using finite-difference time-domain (FDTD) method in our proposed structure reveals an average transmitted power higher than 90% for each output port, Channel spacing is about 8 nm and bandwidth for each individual channel is about 2.8 nm. The mean value of the crosstalk between output channels and the area of the proposed structure are about −29 dB and 317 μm², respectively. By changing the radius of inner rods, various wavelengths can be chosen, therefore this device is tunable.     

Channel drop filter using photonic crystal ring resonators for CWDM communication systems

In this paper, a new optical channel drop filter (CDF) using photonic crystal ring resonators (PCRRs) is presented. Using the two-dimensional (2D) finite-difference time-domain (FDTD) method in triangular lattice photonic crystal (PC) silicon rods, 100% forward dropping efficiency and a quality factor of more than 1000 can be achieved in third communication window while the resonant wavelength is 1550 nm. Through this novel (CDF), a multi-CDF operation with 100% drop efficiencies across all channels can be obtained. The proposed device could be used in future coarse wavelength division multiplexing (CWDM) communication systems.     

T-shaped channel drop filter based on photonic crystal ring resonator

Photonic crystal ring resonators are promising candidates for realizing all optical filters with acceptable transmission efficiency and quality factor values. In this paper, by putting a12-fold quasi crystal at the middle of on 7 × 7 square cavity we created a ring resonator structure and designed a T-shaped channel drop filter. The drop wavelength of our filter is at 1551 nm, with transmission efficiency and quality factor equal to 90% and 387. Our structure is composed of dielectric rods immersed in air. Because in this kind of structures the dominant band gap is in TM mode, all of our simulations have been done in TM mode. The total footprint of our filter is 242.4 μm², which makes it suitable for all optical integrated circuits.     

Demonstration of temperature resilient properties of 2D silicon carbide photonic crystal structures and cavity modes

In this paper, photonic crystal (PhC) based on two dimensional (2D) square and hexagonal lattice periodic arrays of Silicon Carbide (SiC) rods in air structure have been investigated using plane wave expansion (PWE) method. The PhC designs have been optimized for telecommunication wavelength (λ = 1.55 μm) by varying the radius of the rods and lattice constant. The result obtained shows that a photonic band gap (PBG) exists for TE-mode propagation. First, the effect of temperature on the width of the photonic band gap in the 2D SiC PhC structure has been investigated and compared with Silicon (Si) PhC. Further, a cavity has been created in the proposed SiC PhC and carried out temperature resiliency study of the defect modes. The dispersion relation for the TE mode of a point defect A1 cavity for both SiC and Si PhC has been plotted. Quality factor (Q) for both these structures have been calculated using finite difference time domain (FDTD) method and found a maximum Q value of 224 for SiC and 213 for Si PhC cavity structures. These analyses are important for fabricating novel PhC cavity designs that may find application in temperature resilient devices.     

Molecular structure of cyclopropenylidene,HCCCH from the millimeter wave spectra of its isotopomers

The rotational spectra of the two ¹³C and of the D monoisotopic substitutions of cyclopropenylidene C₃H₂ have been measured up to 300 GHz. The determination of the rotational and centrifugal distortion constants of four isotopomers has led to a complete substitution structure. The values of the two CC bond lengths which define the three-membered ring have been improved by using Watson's “mass-dependence” (r_m) method.     

Characteristics of Add Drop Filter using single and dual PCRR in square lattice

A Photonic Crystal Ring Resonator (PCRR) based Add Drop Filter is designed using two dimensional (2D) square lattice PC silicon rods in air host. The normalized transmission spectra for a single-ring and dual-ring configurations have been investigated using 2D Finite Difference Time Domain (FDTD). The filter characteristics such as coupling efficiency, dropping efficiency, resonant wavelength and Q factor are numerically analyzed for single ring and dual ring PCRR. It is noted that the coupling efficiency, dropping efficiency and Q factor of single ring circular PCRR with scatterer rod are 100%, 100% and 186.75, respectively. The backward dropping is observed in single ring PCRR whereas forward dropping are noticed in dual ring PCRR based ADF. The Photonic Band Gap (PBG) with respect to structural parameters such as the radius of the rod, lattice constant and refractive index difference, and propagation modes in periodic and nonperiodic structure are calculated by Plane Wave Expansion (PWE) method.     

The Brillouin zones and band gaps of a two-dimensional phononic crystal with parallelogram lattice structure

We present a detailed theoretical study on the acoustic band structure of two-dimensional(2D)phononic crystal.The 2D phononic crystal with parallelogram lattice structure is considered to be formed by rigid solid rods embedded in air.For the circular rods,some of the extrema of the acoustic bands appear in the usual high-symmetry points and,in contrast,we find that some of them are located in other specific lines.For the case of elliptic rods,our results indicate that it is necessary to study the whole first Brillouin zone to obtain rightly the band structure and corresponding band gaps.Furthermore,we evaluate the first and second band gaps using the plane wave expansion method and find that these gaps can be tuned by adjusting the side lengths ratio R,inclined angleθand filling fraction F of the parallelogram lattice with circular rods.The results show that the largest value of the first band gap appears atθ=90°and F=0.7854.In contrast,the largest value of the second band gap is atθ=60°and F=0.9068.Our results indicate that the improvement of matching degree between scatterers and lattice pattern,rather than the reduction of structural symmetry,is mainly responsible for the enhancement of the band gaps in the 2D phononic crystal.     

The thermal–optical effect due to varying the angle of incidence used for designing a tunable filter in photonic crystals

Tunable devices based on photonic-crystal (PhC) structures are employed in optical sources, detectors, and filters. We present the design and optimization of a wavelength-selective tunable filter with potential applications to the wavelength-division-multiplexing (WDM) systems. We analyze the design of a 1D tunable photonic-crystal filter, where tunability is achieved either by changing the temperature or the angle of incidence. The device is designed in a multilayered structure of silicon/silica (Si/SiO₂) with a defect in the middle. Based on the induced variation of optical parameters introduced by an external change of temperature, we analyze the effects of these changes in temperature on the transmission of the optical filter at different angles of incidence. We show that the position of the resonance peak has a linear dependence on temperature and the square of the angle of incidence. A linear regression provides a slope of d??/dT?=?+0.06?nm/°C and d??/d?? ²?=??0.104?nm/degree² around the transmission wavelength ???=?1.55???m. We obtain the corresponding field patterns and the transmission spectra using the transfer-matrix-method (TMM) simulations. We show the ability to tune the optical properties of the photonic-crystal filter elaborated by changing two parameters: the angle of incidence for selecting the wavelength and the temperature for fine tuning of the wavelength, which can be applied in integrated optics.     

Investigation on parameters affecting the performance of two dimensional photonic crystal based bandpass filter

A two dimensional Photonic Crystal based Bandpass Filter is designed by exploiting coupling between the quasi waveguides and the circular Photonic Crystal Ring Resonator (PCRR). The output efficiency, resonant wavelength and bandwidth of PCBPF are investigated by varying the dielectric constant of the structure. The normalized transmission spectra of circular PCRR are taken using 2D Finite Difference Time Domain method. The Photonic Band Gap is calculated by Plane Wave Expansion method. Close to 100% (Band II) output efficiency is observed over the wavelength range from 1,504 to 1,521?nm and 85% (Band I) is obtained at 1,420?nm through simulation. The full width half maximum bandwidth of these bands is 35 and 20?nm, respectively. Further, the parameters that affect the resonant wavelength, output efficiency and bandwidth of the filter such as size of the reflector, radius of the coupling rods, lattice constant, rod radius and number of rods in the structure are analyzed. The overall size of the proposed filter is 11.4?μm ×?10.2?μm, which is smaller than the filters already reported in the literature and highly desirable for Photonic Integrated Circuits.     

Narrowband optical filter design for DWDM communication applications based on Generalized Aperiodic Thue-Morse structures

We present here a novel proposal for multichannel narrowband DWDM filter design, based on Generalized Aperiodic Thue-Morse (GATM) multilayer structures. Transmission spectra of light propagation through these structures are studied in this article. Numerical simulations in this research show an ultra high efficiency and a very low crosstalk for this filter so that the total transmission of filter output channels is up to 100% and the range of output wavelength is 1550 nm which is suitable for DWDM communication systems. By studying the effects of parameters of GATM structure, we realized that by varying parameters such as number of layers, distance between layers, refractive index of layers, etc., a suitable DWDM filter can be accomplished, which is in accordance with the communication ITU-T standard. This narrowband DWDM filter has capability of changing the number of channels and the bandwidth of each channel, at the special wavelength. By changing the thickness of each layer, the transmittance wavelength of the filter will change. The main advantage of the Thue-Morse structure is the numbers of selective layers, which in our designed structure, we choose GATM(3,2) where m = 3 and n = 2 in B^mAⁿ, and for the first time we change both m and n simultaneously in the proposed structure to control optical properties of the introduced filter.     

Global study of electron–quark unparticle interactions

We perform a global fit on parity-conserving electron–quark interactions via spin-1 unparticle exchange. Besides the peculiar features of unparticle exchange due to non-integral values for the scaling dimension \(d_{\mathcal {U}}\) and a non-trivial phase factor \(\exp (-id_{\mathcal {U}}\pi)\) associated with a time-like unparticle propagator, the energy dependence of the unparticle contributions in the scattering amplitudes are also taken into account. The high energy data sets taken into consideration in our analysis are from (1) deep inelastic scattering at high Q ² from ZEUS and H1, (2) Drell–Yan production at Run II of CDF and DØ, and (3) e ⁺ e ^?→ hadrons at LEPII. The hadronic data at LEPII by itself indicated a 3–4 sigma preference of new physics over the Standard Model. However, when all data sets are combined, no preference for unparticle effects can be given. We thus deduce an improved 95% confidence level limit on the unparticle energy scale \(\varLambda_{\mathcal {U}}\).     

Tunable erbium-doped fiber ring laser for applications of infrared absorption spectroscopy

We fabricate a low noise erbium-doped fiber ring laser that can be continuously tuned over 102 nm by insertion of the fiber Fabry-Perot tunable filter (FFP-TF) in the ring cavity with a novel cavity structure and the optimal gain medium length. As an application of this fiber ring laser, we performed the absorption spectroscopy of acetylene (¹³C₂H₂) and hydrogen cyanide (H¹³C¹⁴N) and measure the absorption spectra of more than 50 transition lines of these gases with an excellent signal to noise ratio (SNR). The pressure broadening coefficients of four acetylene transition lines are obtained using this fiber ring laser and an external cavity laser diode.     

Optical channel drop filters based on photonic crystal ring resonators

A new optical channel drop filters (CDFs) configuration based on photonic crystals ring resonators (PCRRs) is provided. The transmission characteristics for single-ring and multiple-ring configurations have been investigated by using the two-dimensional (2D) finite-difference time-domain (FDTD) technique in triangular lattice photonic crystal (PC) silicon rods. Both forward and backward dropping were achieved in dual-ring PCRR structures. In this filter, 100% drop efficiency and acceptable quality factor can be obtained at 1550 nm. The present device can be used in the future photonic integrated circuits.     

New high negative dispersion photonic crystal fiber

A new high negative dispersion photonic crystal fiber is proposed. It has double-core structure. The inner core has a circle germanium-doped region. The outer core is formed by removing the 3rd ring air-holes around the core. There are two ring air-holes between the two cores, Diameter of the 1st ring air holes is bigger than that of the 2nd ring air-holes, this can make mode coupling between inner mode and outer mode and showed that the high negative PCF is the result of this structure characteristics. There are honeycomb photonic lattice in the PCF's cladding. The influence of the structure parameters deviated from the design those on the chromatic dispersion are evaluated. When the structure parameters Λ=1.50 μm, d_core=2.10 μm, d₁=0.90 μm, d₂=0.44 μm and d₃=1.04 μm, the dispersion coefficient D is −1320 ps/(nm·km) at 1550 nm. This is a new kind of chromatic dispersion compensation PCF.     

The top quark, others new phenomena observed at the CDF in {ie359-1} collisions at √s = 1.96 TeV (Review)

Upgraded Tevatron luminosity in Run-II (started 2001) has opened a new level of modern heavy-quark studies compared to that one of Run-I. Now top event samples contain hundreds of event statistics for investigation. This review mainly covers the mass measurements of the top quark produced at √s = 1.96 TeV in {ie359-2} collisions at the Collider Detector of Fermilab with the integrated luminosity samples up to 1 fb^?1. As an example of the top quark mass measurements we consider so-called Matrix Element method in “lepton + jets” and “dilepton” channels of the top-quark decay. The CDF top quark mass obtained in lepton +jets mode is the world most precise single measurement of this important physics parameter. The review summarizes the essential results of the CDF top-quark mass measurement achieved and published for the recent 2003–2008 period. We consider also b-quark baryon discoveries like Σ _b , Σ _b ^* , Θ _b as well as first observation of {ie359-3} oscillations. Let us mention here that a CDF/JINR-group created significant contribution to the new CDF complex and physics investigation.     

Performance analysis of an eight channel demultiplexer using a 2D-photonic crystal quasi square ring resonator

Recent years, the design of photonic crystal (PC) based optical devices is receiving keen interest in research and scientific community. In this paper, two dimensional (2D) PC based eight channel demultiplexer is proposed and designed and the functional characteristics of demultiplexer namely resonant wavelength, transmission efficiency, quality factor, spectral width, channel spacing and crosstalk are investigated. The demultiplexer is designed to drop the wavelength centred at 1537.6 nm, 1538.5 nm, 1539.4 nm, 1540.4 nm, 1541.2 nm, 1541.9 nm, 1542.6 nm and 1543.1 nm. The proposed demultiplexer is primarily composed of bus waveguide, drop waveguide and quasi square ring resonator. The quasi square ring resonator and square ring micro cavity (inner rods) are playing a vital role for a desired channel selection. The operating range of the devices is identified through a photonic band gap (PBG) which is obtained using a plane wave expansion (PWE) method. The functional characteristics of the proposed demultiplexer are attained using a 2D finite difference time domain (FDTD) method. The proposed device offers low crosstalk and high transmission efficiency with ultra-compact size, hence, it is highly desirable for DWDM applications.     

A Novel Proposal for an All-Optical “and” Logic Gate Using Two-Dimensional Photonic Crystals

We present a novel proposal for an all-optical AND logic gate. It is designed based on line and point defects in two-dimensional photonic crystal (PC) rods in air with square lattice. Material of the rods is silicon with dielectric constant 11.56. Dimension of the proposed device is equal to 12.155×12.155 μm. The device elaborated has a simple structure consisting of two inputs – a main output and two idler outputs. Bit rate of the device is equal to 3·10¹² bit/s. Maximum contrast ratio is 5.84 dB. It is a good candidate for optical integrated circuits.     

Easy Implementation of Selective Inverse Experiments with Chemical-Shift-Selective Filters

Several one-dimensional experiments for selective proton-carbon correlation are presented. The proposed experiments can be characterized as one-dimensional analogues of corresponding two-dimensional methods. Instead of the incremented t₁ period of 2D experiments, a carbon-chemical-shift-selective filter (¹³C CSSF) is introduced for the frequency selection. This approach provides better selectivity and has no extra hardware demands in comparison with 1D experiments which use soft carbon pulses.     

Modelling of magnetic satellite intensity in the neutron diffraction of an incommensurate helical structure: NiBr2 and Ni0.91Fe0.09Br2

We describe the application of a neutron multidetector diffractometer (D16, I.L.L.) to the study of the incommensurate helical magnetic structure of pure and Fe²⁺-doped single crystals of NiBr₂. Use of the multidetector permits detailed mapping of satellite intensity around 003_M arising from three magnetic domains, from which the magnitude and direction of the helix propagation vector τ are deduced. τ moves from [110] (0.0138(5) Å^?1) in NiBr₂ to [100] (0.0151(5) Å^?1) in Ni_0.91 Fe_0.09Br₂. The measured intensity profiles in (2θ, ω, v space are fitted to model profiles constructed by superimposing profiles measured at 003_M in the collinear phase at 28 K on a ring with radius τ, and optimizing the weighting of intensity around the ring.