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A multiple quantum well (MQW) transistor vertical-cavity surface- emitting laser (T-VCSEL) is designed and numerically modeled. The impor- tant physical models and parameters are discussed and validated by modeling a conventional VCSEL and comparing the results with the experiment. The quantum capture/escape process is simulated using the quantum-trap model and shows a signicant eect on the electrical output of the T-VCSEL. The parameters extracted from the numerical simulation are imported into the an- alytic modeling to predict the frequency response and simulate the large-signal modulation up to 40 Gbps.

Fourier domain mode locked (FDML) lasers are a class of frequency-swept lasers that are used to generate optical pulses with a wide sweep range, high repetition rate, and a low instantaneous bandwidth. They are commonly used in sensing and imaging applications, especially in optical coherence tomography. Ideally, the aspired features in the design of FDML lasers include a high coherence length, large sweep bandwidth, adjustable output power, and a high signal to noise ratio (SNR). However, the SNR of the output signal of FDML lasers is often lower than desired due to the presence of several irregularities in the output signal pattern, most notably because of the frequent occurrence of sharp power dips, also known as holes. These power dips originate due to the nonlinear gain dynamics of the semiconductor optical amplifier (SOA) that is employed in FDML lasers, while the occurrence frequency and strength of these dips are determined by the interaction of the FDML laser components, which involve the SOA, the tunable Fabry–Perot filter, and the optical delay fiber. Suppressing these power dips not only increases the output signal quality in terms of SNR, but also precludes the accumulation of phase offsets between subsequent roundtrips and facilitates convergence. As both current and future applications of FDML lasers are likely to require a higher signal power, in this paper, we are going to investigate the effect of self-phase modulation (SPM) in the optical fiber on dip formation and convergence. Since fiber nonlinearity, intracavity signal power, and fiber length all contribute to SPM, investigation of the effect of SPM on the formation of power-dips and operational convergence is critical. More importantly, the phase-mismatch that is caused by fiber-based SPM cannot be compensated easily in an FDML laser as in the case of chromatic dispersion, which necessitates a strategy for minimizing fiber-based SPM to ensure operational convergence and to secure a lower limit for the SNR of the output signal of FDML lasers.

In this paper, we will study two various nonlinear models: the Atangana-Baleanu fractional system of equations for the ion sound and Langmuir waves (ISALWs) and Hirota Ramani equation to obtain variety of solitary wave solutions. We will obtain bright, dark, periodic wave and solitory wave for ISALWs equation. We will also retreived bell type, kink type, singular, Jacbion elliptic function, Weierstrass-elliptic function, hyperbolic functions, periodic functions and other solitary wave solutions for Hirota Ramani equation using Sub ODE technique under some constraint conditions. At the end we will present our solutions with the help of graphs in distinct dimensions.

To detach large vectorial full-wave electromagnetic scattering problems from the specific, dissimilar bases that are typically associated with the optical waveguiding structures comprising an optical interface, we propose and demonstrate the expansion of wavefields in a single universal Wilson basis. We construct a Wilson basis by following the derivation in the paper by Daubechies, Jaffard and Journé. This basis features exponentially decaying basis functions in both the spatial and spectral domain. The strong localization in phase-space, with basis functions that strongly resemble wavefields, allow for efficient expansions of high-frequency electromagnetic fields. In a Wilson basis, the interface scattering problem is effectively separated from the physical configuration. For the evaluation of multiple, laterally displaced interface configurations, one may reuse electromagnetic fields in the Wilson basis, because the translation operator is sparse and diagonally dominant. We consider actual reflection-transmission problems comprising optical fibers and homogeneous media in the Wilson basis framework in a companion paper. There, the localization in the spectral domain aids the conversion of the numerical scheme to generate electromagnetic fields in homogeneous media due to Wilson-basis discretized electromagnetic sources. In this paper, we review the Wilson basis construction, demonstrate the expansion of modal electromagnetic fields in an optical fiber, and complex-source beams that are tilted with respect to the optical axis. Even for largely tilted beams (up to 60°), despite being highly oscillatory in the cross-sectional plane, the fields are well represented by a finite number of higher-order Wilson basis functions.

In this paper, we design an all-optical Pseudo Random Binary Sequence (PRBS) generator in parallel configuration for operating rate multiplication purposes. The sequential circuit comprises of several clocked D flip-flops, XOR gates and multiplexers implemented using microring resonator (MRR)-based switches. The proposed design is demonstrated and validated through simulations for 500 Gb/s and 400 Gb/s rate doubling and quadrupling, respectively, of a 5-bit degree PRBS. The MRR critical operating parameters are also optimized against performance metrics through numerical investigation.

This paper demonstrates the structure and working principle of an optical 2-bit multiplier using lithium niobate (LiNbO3) based Mach–Zehnder interferometer (MZI). The powerful ability of MZI structures to switch the optical signal from one output port to the other output port has been used in the implementation of the proposed 2-bit multiplier. The paper constitutes the mathematical description of the 2-bit multiplier and thereafter compilation using MATLAB. The study is carried out by simulating the proposed device with Beam propagation method (BPM).

In this paper, a novel frequency reconfigurable microstrip antenna is presented. The proposed antenna has four photoconductive switches. These switches are mounted across two rectangular shape slots etched on the radiation patch. According to the incident light, the physical properties of these switches can be changed from an insulator state (OFF state) to a near-conducting state (ON state). The incident light is then coupled to the photoconductive switches using a reconfigurable optical router. The design in this paper yields an ultra-wideband that extends from 2.83 to 13.0 GHz with switchable single notched bands of 3.3–3.9 and 4.8–5.8 GHz for WiMAX and WLAN applications, respectively. Further, another two bands of 3.3–3.9 and 5.6–6.1 GHz can be eliminated from the whole frequency band. The suggested design is fabricated using photolithographic technique and the measured results have very good agreement with the simulated ones.

This paper reveals a complete spectrum of soliton solutions that emerges from the governing model studied with anti-cubic law of nonlinear refractive index. Jacobi’s elliptic function scheme shall be implemented followed by a limiting approach for the corresponding modulus of ellipticity. The existence criteria for such solitons are also enumerated.

In this paper, stochastic Fornberg–Whitham and a stochastic Camassa–Holm (CH) type equations are studied. A Galilean transformation which previously used for a stochastic KdV equation is employed to transform the equations into their deterministic counterparts. Then $$(1/G')$$ -expansion method is used to obtain analytical solutions. 2D, 3D, and contour graphs representing the peakon solutions have been plotted by assigning special values to the constants in the solutions via computer software. In addition, by giving different random values to the external noise, the effect of the noise on the wave-forms has been exhibited. The obtained results have been discussed in detail.

In this paper, we considered the nonlinear Schrodinger equation modeling cubic optical solitons in a polarization-preserving fiber with Kerr law. Using the improved $$tan(\varphi /2)$$ -expansion method, a powerful and effective method, we constructed exact solutions including the hyperbolic function solution, the trigonometric function solution, the exponential solution and the rational solution with free parameters. The geometrical shapes for some of the obtained results are depicted for various choices of the free parameters that appear in the results. The obtained solutions are entirely new and can be considered as generalization of the existing results in the ordinary derivative case.

In this paper we present a novel, time-delay approach using a copper-coated fiber. Piezo optical-fiber stretchers and temperature-controlled fiber spools are normally used for a conventional time-delay lines. A copper-coated fiber preserves the performance of a standard single-mode optical fiber, while at the same time acting as an electrical wire, which can be effectively heated by applying an electrical current. As a result of the significant temperature change, the signal (group) delay can be properly adjusted and controlled. Compared to piezo optical-fiber stretchers and temperature-controlled fiber spools, much shorter lengths of fiber are required and a faster response time can be achieved. This paper also proposes a simple, lumped thermal model and thus a copper-coated fiber can be included in the heat-transfer and response-time calculations of a realistic system that involves surrounding elements (e.g., heatsinks).

Illuminance uniformity and illuminating efficiency are always the key problems of light emitting diode (LED) lighting system design. Based on the new design of the reflection optical module, illuminance uniformity and illuminating efficiency are investigated simultaneously in this paper. At the first stage, a reflector with various profile designs is installed to improve the uniformity and efficiency of irradiances collected through the receiver. Using the macro commands, an effective process is presented through the optimal design of the reflector geometries, and the merit function is used as the optical quality objective to find the optimal design value of $$K2$$ and $$R2$$ parameters of the reflector. At the second stage, based on the optimal design result, the displacement between LED source and reflector is further adjusted automatically by the macro commands too. The results from the ray tracing simulation indicate that the optimal design can be achieved through the compromise of Illuminance uniformity and illuminating efficiency. Finally, we obtain the merit function value of $$1.81$$ with $$K2=-1.09, R2=1.11\,\hbox {mm}$$ , and the source position $$Z1= 1.68\,\hbox {mm}$$ . The results shown in this paper could be beneficial for machine vision systems which are heavily demanded in the light source applications for the uniform and efficient illuminance.

In this paper, we report a new design of an all-optical filter using photonic crystal microstructure. Ring resonators, line defects, scatterer rods, microcavities, and coupling rods are used to form the filter in order to extract specific wavelengths at the output channels. The well-known plane wave expansion method is used to calculate the photonic band diagram. The widely used finite-difference time-domain method is also applied to study the light propagation inside the filter. Our numerical results demonstrate that the proposed structure has high transmission power, high-quality factor, and low cross-talk. They reveal an optical signal centered at 1522 nm exits the first output channel, which has an output-to-input ratio (OIR) of 95 % with a bandwidth (FWHM) of 0.4 nm, and an optical signal centered at 1520.8 nm exits the second output channel with an OIR of 98 % and an FWHM of 0.5 nm. The third output channel can exit the optical signal centered at 1518.2 nm with an OIR of 78 % and an FWHM of 0.4 nm. Furthermore, the fourth channel will exit the optical signal at 1519.3 nm with an OIR of 56 % and an FWHM of 0.4 nm. Therefore, the quality factors of the first to fourth outputs of the filter are equal to 3805, 3041, 3795, and 3798, respectively. The first to fourth outputs’ cross-talk values are also − 37 dB, − 36 dB, − 41 dB, and − 38 dB, respectively, which confirm the least interference between output channels. Besides, linear dielectric rods form the filter design that leads to the filter’s appropriate performance at a low input power that is the most important benefit of this work compared to other recently published articles. The maximum rise time of the proposed filter for all output ports is less than 8 ps. The structure also has ​​375.84 µm2, which makes the filter easy to use in photonic integrated circuits.

To attain secure fiber-optic transmissions at a high rate, a realizable scheme is proposed in this paper, that can achieve 10-Gsymbol/s quantum noise encryption based on intensity modulation. Specifically, a dual digital-to-analog converter (DAC) is used to drive a single-drive Mach–Zehnder modulator. Then, to demonstrate the advantage of this scheme, a trial of 10-Gsymbol/s single-channel transmissions over 30 km are confirmed at 4096 intensity levels. Furthermore, specific indicators that affect secure transmissions are analysed, such as the number of modulation levels and noise masking. Finally, experimental results show that a masking number of 370 is achieved to resist direct detection attacks at the 4096 signal levels. Multilevel optical signals are hidden in the quantum noise. It is also apparent that the proposed modulation method realizes highly secure fiber-optic transmission.

In this paper, a 3 × 1 Multiplexer/Demultiplexer (MUX/DEMUX) Photonic Crystal (PhC) based structure is presented. This is achieved by carefully considering the coupling length of the propagating wave and accurately engineering the geometrical design of the microcavities. The design is highly selective, such that, a microcavity embedded between two waveguides selects a particular wavelength to couple from one waveguide into an adjacent waveguide. The numerical technique used for the designs throughout this paper is the Complex Envelope Alternating Direction Implicit Finite Difference Time Domain (CE-ADI-FDTD).

This paper presents optical packet switch architecture with large buffering capacity for the contention resolution of the packets. The main feature of the architecture is no requirement of Demux/Mux and splitter/combiner which are used in most of the other loop buffer based switch architectures. Therefore physical loss of the architecture is very less, and switch performance is not limited by the physical degradation of the signal. In the buffer, TWCs/SOAs are replaced by Tunable Fiber Bragg Gratings (TFBGs). The use of TFBGs inside the buffer is a novel approach towards buffering structure. The architecture presented here can be modeled as output queue buffer scheme. This paper investigates the advantages of the proposed architecture over the earlier architecture. The performance of the architecture in terms of physical layer parameters (loss analysis, power analysis and noise analysis), packaging volume and optical cost is done.

In our paper we modify the Jacobi elliptic function expansion method to obtain solutions to the Davey–Stewartson system of equations. Two categories of nonsingular solutions are obtained for both traveling and solitary waves and both with and without chirp. In both cases there is an arbitrary term in the mean flow field, meaning one can obtain solutions for arbitrary forms of the mean flow field.

In this paper, we present results about electronic spectra and optical properties of one-electron spherical quantum dot-quantum well (QDQW) structure. Investigated structure consists of CdSe core surrounded by ZnS shell and caped by infinitely high electron potential barrier which can be a good model for any high enough potential barriers. This specific QDQW structure is determined by CdSe and ZnS properties (effective masses and conductive band offset) and the core size and the shell thickness. We present calculation results for one-electron ground (1s) state and the first excited (1p) state transition. For this transition we have calculated oscillator strengths and linear and third-order nonlinear intersubband optical absorption coefficients for various core and shell size i.e. different CdSe core radii and ZnS barrier thickness. Change in core and shell dimensions induces change in one-electron wave function i.e. electron energy states and localization for both 1s and 1p states. As a result, intersubband 1s–1p transition of this system is greatly dependent on the core and shell size. For very small core radii, less than 0.7 nm, and core radii over 1.5 nm the most probable intersubband transition is 1s–1p, but in the region between 0.7 and 1.5 nm core radii, transitions from 1s to other p states dominates. Investigated properties depend mostly on the core radius. These results connect the dot structure and the optical properties of this particular structure. This behavior is than an illustration of similar systems.

Recently, unusual properties of novel two-dimensional materials like graphene have revolutionized many branches of science and technology. Adequate numerical simulations of photonic devices comprising graphene layers require new approaches or modified methods. In this paper we present comparison of results obtained with three representations of a graphene monolayer: (1) an infinitely thin sheet with a finite surface complex conductivity, (2) a thin layer of a finite thickness exhibiting uniaxially anisotropic complex permittivity, and (3) anisotropic permittivity perturbation in an infinitely small volume. Numerical solutions of rigorous dispersion equations were compared to each other and also with the results obtained with several commercial as well as proprietary software packets. Under proper conditions, all approaches provide comparable results.

In this paper, we have reported the far-field intensity distribution for a varied configuration of air holes in the cladding region of the solid-core single-mode photonic crystal fibers (PCFs). Recently, an analytical approach based on the normalized frequency (V parameter) and normalized attenuation constant (W parameter) has been developed for index-guided PCF. Parameters V and W are frequently used in the design of conventional optical fibers. Using the empirical relations for the V parameter as well as W parameter of PCF, the dependence of the far-field intensity distribution on two structural parameters—the air hole diameter and the air hole pitch is calculated and presented. The results displayed here can find their utilization in the design and development of a sensor system based on PCFs for potential applications involving structural health monitoring, medicine, environmental monitoring sensors, and in certain areas of biology and chemistry.

This paper covers the absolute spectral power responsivity calibration of spectralon-coated Integrating Sphere Radiometer (ISR) equipped with 3 mm diameter InGaAs photodiode to be used as a transfer standard in fiber optic power measurements against Electrical Substitution Cryogenic Radiometer (ESCR) in Optics Laboratory of National Metrology Institute (TUBITAK UME) of Turkey. The initial uncertainty arising from the use of the Electrically Calibrated Pyroelectric Radiometer (ECPR) as a transfer standard in radiometric scale is 0.5% (k=2), which particularly comes from irregularity in the surface homogeneity of ECPR. In order to eliminate the ECPR step as well as its initial uncertainty contribution in fiber optic power measurements, the calibration application herein was carried out. Moreover power stabilization measurements of DFB laser sources at both 1309.1 nm and 1549.0 nm, the beam size determinations, and spectral analyses of these laser sources as well as spatial and angular dependence of spectral responsivities of the ISR were presented in this paper. The total expanded uncertainties were calculated as 0.283% and 0.315% in the determination of absolute spectral power responsivities of the ISR for 1309.1 nm and 1549.0 nm wavelengths respectively (k=2).

The intra-channel collision of optical solitons, with parabolic law nonlinearity, is studied in this paper by the aid of quasi-particle theory. The perturbation terms that are considered in this paper are the nonlinear gain and saturable amplifiers along with filters. The suppression of soliton-soliton interaction, in presence of these perturbations terms, is achieved. The numerical simulations support the quasi-particle theory.

A new designed and analyzed silicon-on-insulator (SOI) waveguide Michelson interferometer (SMI) sensor is proposed in this paper. The authors compare an optical SMI sensor, a silicon-on-insulator Bragg waveguide grating (SBG) sensor, and a fiber Bragg grating sensor (FBG) for temperature sensing in medicine applications. The SMI sensor has 20 times sensing more accuracy than the FBG sensor. Moreovr, the full width at half maximum (FWHM) of the pass-band frequency responses of our proposed SMI can be designed much narrower than FBG and SBG sensors for sensing resolution enhancement. Further, the improved characteristics of the SMI demonstrated in this paper could pave the way for future high density temperature monitoring medicine applications.

The propagation of solitons through optical couplers is studied here in this paper. Both the twin-core couplers as well as the multiple-core couplers are considered here in this paper. The parameter dynamics of the solitons that are governed by the coupled generalized nonlinear Schrodinger's equation, due to non-Kerr law nonlinearity, has been obtained for such couplers.

Lasers essentially consist of single-mode optical cavities containing two-level atoms with a supply of energy called the pump and a sink of energy, perhaps an optical detector. The latter converts the light energy into a sequence of electrical pulses corresponding to photo-detection events. It was predicted in 1984 on the basis of Quantum Optics and verified experimentally shortly thereafter that when the pump is non-fluctuating the emitted light does not fluctuate much. Precisely, this means that the variance of the number of photo-detection events observed over a sufficiently long period of time is much smaller than the average number of events. Light having that property is said to be'sub-Poissonian'. The theory presented rests on the concept introduced by Einstein around 1905, asserting that matter may exchange energy with a wave at angular frequency ω only by multiples of ħω. The optical field energy may only vary by integral multiples of ħω as a result of matter quantization and conservation of energy. A number of important results relating to isolated optical cavities containing two-level atoms are first established on the basis of the laws of Statistical Mechanics. Next, the laser system with a pump and an absorber of radiation is treated. The expression of the photo-current spectral density found in that manner coincides with the Quantum Optics result. The concepts employed in this paper are intuitive and the algebra is elementary. The paper supplements a previous tutorial paper (J. Arnaud, Opt. Quantum. Electron., 27 1995) in establishing a connection between the theory of laser noise and Statistical Mechanics.

In this paper we analyse the second harmonic generation of TM polarisation in a planar waveguide with a non-linear anisotropic substrate using the coupled mode theory under the non-depleted pump approximation. It is an extention of our previous paper in which we treated TE polarisation. Moreover, both guided waves and Cerenkov radiation are now taken into account simultaneously. It is shown both analytically and numerically that the Cerenkov efficiency peak follows the L3/2 dependence on the interaction length L also for TM polarisation. In an anisotropic KTP/Si3N4/SiO2 waveguide, higher maximum attainable second harmonic generation (SHG) efficiency was calculated for the TM polarisation than for the optimum TE case.

In this paper, we present experimental results of current-induced polarization change and transverse mode change in mid-infrared quantum cascade lasers. The polarization of laser beam was determined by measuring of far-field distributions of polarization projection on the linear polarization basis. The measured amount of TE-polarized light is associated with transversal mode structure, which was determined based on the far-field power distributions. The TE polarized light contribution in the beams varies from 6 to 19%. This quantity is anti-correlated to the fundamental transverse mode contribution.

This paper focuses on the problem of lowest-order mode (LOM) transmission in multimode S-bends given LOM input. Total loss calculations in S-bends using the finite difference beam propagation method (FDBPM) are compared with analytical results. Sine and cosine shaped slab S-bend geometries are studied to determine if mode conversion (to higher-order modes) can be controlled and/or suppressed altogether. Reduction of bending losses for the overall structure is also sought. It is also shown that loss rates for a fixed radius of curvature and total loss in an S-bend are not sensitive to the substrate index. Thus results determined in this paper are applicable to a range of substrate indices. Specifically, it is shown that the results are applicable to ion-exchange glass waveguides.

In the physics of two-dimensional materials, notion semi-Dirac dispersion denotes electronic dispersion which is Dirac-like along one direction in the reciprocal space, and quadratic along the orthogonal direction. In our earlier publication (Damljanovic and Gajic in J Phys Condens Matter 29:185503, 2017) we have shown that certain layer groups are particularly suitable for hosting semi-Dirac dispersion in the vicinity of some points in the Brillouin zone (BZ). In the present paper we have considered tight-binding model up to seventh nearest neighbors, on a structure belonging to layer group Dg5. According to our theory, this group should host semi-Dirac dispersion at A and B points in the BZ. The structure has four atoms per primitive cell, and it is isostructural with sublattice occupied by phosphorus atoms in the layered material SnPSe $$_3$$ . While the first order perturbation theory of double degenerate level gives two pairs of semi-Dirac cones and correctly reproduces dispersion in the Dirac-like direction, exact diagonalisation of four-by-four tight-binding Hamiltonian shows node lines caused by accidental degeneracy in the band structure. We discuss these degeneracies in the context of von Neumann–Wigner theorem, and conclude that although dispersion remains semi-Dirac in the exact diagonalisation method, the band structure does not necessarily form cones. In order to get full picture of behavior of bands in the vicinity of semi-Dirac points, first order perturbation theory may not be sufficient and one may need higher order corrections.

In this paper we joined plasmonics and microreactors for photocatalytic optofluidic devices. To this purpose we consider the use of subwavelength texturing of plasmonic films applied to microreactor channel bottom to ensure SPP localization and field enhancement. The small volume of the microchannel is ideal for the enhancement of photocatalytic processes using localized evanescent fields. A great advantage of our approach is that it is highly compatible with the standard chemical bulk micromachining techniques which are commonly used in fabrication of the microreactors i.e. standard photolithography can be used to define microchannels, and radiofrequent sputtering to deposit a gold film as a plasmonic material over the roughened surface. Subwavelength surface texturing can be obtained by varying etching techniques and parameters and the microreactor building materials. We show using ab initio FEM modeling that the stochastic surface profile ensures broadband coupling of visible light as well as enables us to merge plasmonic sensors and microreactors into a single device.

In this paper we compare results of the eigenmode analysis of the third-order add/drop filter with the transfer functions (S-parameters) calculated in wide spectral range covering telecommunication C band. Both type of calculations are performed using 2D finite elements (FEM) method. The computational domain is closed using standard perfectly matched layer method. Also, the model of add/drop microring filter based on the temporal coupled mode is presented, since such models are usually used as a starting point in filter design procedure. The obtained results show excellent agreement between the two approaches. It is well known that when single microring is coupled to access waveguides or another rings, the resonance frequency will deviate from its original isolated resonator value. This effect, known as coupling-induced resonance frequency shift, causes resonance frequency mismatches between individual resonators and thus significantly impacts eigen spectra, as well as transfer characteristics, of the coupled-resonator systems. FEM calculations show that this effect has no significant importance when coupling between the access waveguide and the microring is strong enough, i.e. when the conditions for flat filter response are satisfied.

Single electron in spherical shell in infinite potential barrier is investigated. Schrodinger equation in effective mass approximation for this spherical heterosystem is solved to get eigenenergies and corresponding wave functions. In case of infinite potential barrier the ground state energy depends only on the shell width. Self-polarization potential is obtained by solving Poisson equation in three concentric spherical regions: core, shell and surrounding medium. Shell self-polarization energy depends on geometry (core and shell radius) and the dielectric mismatch at the quantum dot boundaries. Self-polarization energy is used as perturbation. One electron ground state energy results are presented in this paper. CdSe is placed in the shell. Surrounding medium is dielectric of smaller permittivity (vacuum or water), that is the most realistic case. The core dielectric permittivity influence on ground state energy is analysed. The self-polarization corrections to the ground state energy for different compositions, i.e. core and shell radius, are presented. For smaller core radius and the same shell thickness (which imply the same unperturbed ground state energy) bigger is the energy correction, i.e. perturbed energy state, for fixed value of the core dielectric permittivity. Increase of core dielectric permittivity produces decrease of energy correction.

In this paper, we report the analysis of the electromagnetic wave transmission having a wave length near infrared propagating in Fibonacci quasiperiodic multilayer structures made of fullerene and germanium materials. We observe that within the stop band the reflection phase difference changes smoothly and increases with the increasing of the incident angle. In the center of the gap the reflection phase difference remains almost unchanged in a broad wavelength band. Especially, at both the edges of the gap the reflection phase difference keeps zero in spite of the change of incident angle. Basing on our results, the supposed structure provides a convenient way to design very compact phase controllers such as phase retarders.

Fluctuation of current through alternating current operated light-emitting diodes (AC LEDs) make luminous flux simply equivalent to the product of power consumption and luminous efficiency unreasonable, unlike constant current scenario. Based on application model and average luminous efficiency introduced by this paper, relationship between AC LEDs luminous flux and its application circuit parameters, including balance resistor, threshold voltage and equivalent resistor of LED etc. was presented. Then method to design AC LEDs through single LED photoelectric characters to meet luminous flux requirement was given.

In this paper, a nonlinear photonic crystal structure is proposed in order to implement all-optical NOT and OR logic gates. The proposed structure includes combiners and limiters. The limiters are designed using ring resonator. Also, the combiners are optimized with changing the radius of rods near the crosspoint of waveguides in order to enhance the performance of structure. Nonlinear rods of proposed structure are made of silicon nanocrystal which has been used in order to create the frequency shift for different values of input power. Plane wave expansion and finite difference time domain methods have been utilized to simulate the performance of proposed logic gate. Simulation results show that the ON–OFF logic-level extinction ratio and bit rate are −18.7 dB and 333 Gbit/s, respectively.

In this paper, a coherent perfect absorption (CPA)-type NAND gate based on plasmonic nano particles is proposed. It consists of two plasmonic nano-sphere arrays on the top of two parallel arms with quartz substrate. The operation principle is based on the absorbable formation of a conductive path in the dielectric layer of a plasmonic nano-particle waveguide. Since the CPA efficiency depends strongly on the number of plasmonic nano-spheres and the locations of nano-spheres, an efficient binary optimization method based on the particle swarm optimization (PSO) algorithm is used to design an optimized array of the plasmonic nano-spheres in order to achieve the maximum absorption coefficient in the ‘off’ state and the minimum absorption coefficient in the ‘on’ state. In binary PSO, a group of birds consists a matrix with binary entries, control the presence (‘1’) or the absence (‘0’) of nano spheres in the array.

Terahertz time-domain spectroscopy system was used to measure the characteristic absorption spectra of 8 transgenic cotton seeds in the frequency range from 0.3 to 1.5 THz. Comparing the similarities and differences of THz absorption spectrum of eight kinds of transgenic cotton seeds, which is based on spectral analysis, and using principal component analysis to perform qualitative analysis, the relevant data of spectral analysis was obtained. Three principal component factors were extracted in this paper, which the cumulative percentage variance reached 71.537 %. Therefore, different categories of transgenic cotton seeds were clearly distinguished according to the principal component analysis score chart. The experimental results indicated that nondestructive testing of transgenic cotton seeds could be achieved by using Terahertz time-domain spectroscopy system technology, which could be widely applied in the fields of agricultural seed selection, agricultural security and so on.

The present paper explains the design of imaging payload of remote sensing LEO satellites. The spectral band of this imager is visible band. Imaging payload includes panchromatic and multi-spectral camera that use linear imaging technique. Pushbroom imaging technique use the forward motion of a satellite to sweep a linear array of detectors oriented perpendicular to the ground track across a scene being imaged. Because of superior image quality and flexibility, CCD sensor are used in imaging payload. After amplifying CCD output signal, a high frequency A/D is used to sample the amplified signal. The imaging payload contains a powerful processor in order to do compression process, coding, encryption, and the framing. Then the radio frames are sent by transmitter to the ground station or stored on an on-board memory in remote sensing mode.

In this paper, quantitative study of the enhanced three wave mixing effects from periodic array of nano-scale golden cut-wires embedded in nonlinear dielectric is performed. Geometrical parameters of the considered structure are chosen so that the plasmonic resonance occurs in the wavelength 1.5 μm. Plasmonic resonance of this structure gives rise to the localization factor significantly larger than that of the cut-wire structures with no plasmonic resonance. Considering the surrounding medium of the cut-wire a typical second-order nonlinear optical medium, enhancement of the nonlinearity of this nonlinear medium is illustrated. Since the mentioned structure can be considered a homogeneous nonlinear medium with the effective nonlinear susceptibility, nonlinear retrieval method is used to determine the effective nonlinear susceptibility for all four frequency combinations. Maximum enhancement of the effective susceptibility is obtained for the second harmonic generation of the applied wave with the frequency corresponding to the plasmonic resonance, with the enhancement up to two orders of magnitude. Efficiency of the second harmonic generation in this resonant structure surrounded with nonlinear dielectric is calculated to be 30 times more than that of the nonlinear dielectric with the same dimensions.

This paper demonstrates 100 Gbps long reach coherent passive optical network (CPON) downstream transmission on a single wavelength over 100 km with 1:128 power split having acceptable performance. Here dual polarization-quadrature phase shift keying modulation format is utilized for transmission in the central office and digital signal processing (DSP) is utilized at the optical network unit (ONU) to compensate the linear impairments generated due to high speed optical signal transmission over standard single mode fiber. At the receiving end (ONU), homodyne coherent detection is utilized. The DSP is done using MATLAB and executes five functions that are analog to digital conversion, chromatic dispersion compensation, polarization demultiplexing, carrier phase estimation and digital to analog conversion. The results of proposed architecture are verified in terms of constellation diagrams and receiver sensitivity. The simulated results indicate that our proposed 100 Gbps long reach CPON downstream transmission is feasible and may be implemented in next generation high speed PONs.

Overall series resistance of the contact increases due to unwanted pores created during the time of contact formation in solar cell. Light induced plating is an industrial established process which is used to reduce the series resistance and to improve the contact resistance resulting in increase of fill factor of solar cell through modification of front side contact. In this paper a theoretical modeling is done to show how distributed pores affect the series resistance and solar cell performance. Here we explored several parameters like: series resistance, shunt resistance, fill factor, short circuit current, and external quantum efficiency. Through our experimental setup it is found that the short circuit current improves significantly and also it is observed that during the time of experiment due to unintentional deposition of silver nanoparticles, external quantum efficiency improved by 5.249 % and a reduction of reflectance by 2.03 %. An overall enhancement of solar cell efficiency of 1.65 % is obtained during the process.

Recent successes in unzipping carbon nanotubes have introduced a new member of graphene nanoribbons (GNRs) family known as chiral GNRs. In this paper, optical properties of chiral GNRs both in longitudinal and transverse polarizations of incident beam have been studied using Density Functional Theory. We have shown that the selection rules, which were previously reported for armchair and zigzag GNRs, are no longer valid due to breaking symmetries in this new family. However, we have demonstrated that the edge states play a critical role in the dielectric constant. It has been shown that, depending on the polarization of incident beam the absorption peaks are different, although they are spread in the same energy range. We also suggested that the absorption energy range is sensitive to the chiral vectors and the light polarization. Due to breaking symmetries in chiral GNRs, absorption peaks are changed becoming approximately 1000 nm, thus a new potential of GNRs for optoelectronic devices is introduced.

This paper investigates the transmission of an injection-locked optical orthogonal frequency-division multiplexing (ILO-OFDM) scheme over an optical fiber. In the ILO-OFDM system, an optically injection-locked semiconductor laser is utilized to directly modulate the OFDM signal on the optical carrier. With a sufficiently large injection strength and a negative shift of the detuning frequency, the modulation sidebands become asymmetric similar to a single sideband modulation (SSB). The SSB spectrum is advantageous for minimizing the chromatic dispersion-induced power variation. Using simulation we show that ILO-OFDM system can be used to compensate for chromatic dispersion in long-haul applications.

Spatial optical beam-forming network (OBFN) is a superior structure than traditional ones in bandwidth adaptability, system complexity, and so forth. Compared with conventional beam-forming network, the output signal model of OBFN is different, making the previous direction of arrival (DOA) estimation methods improper for this structure. At present, DOA estimation method for this structure has not been sufficiently explored and there is no efficient algorithm. In this paper, the observation model of the network is established first, and then a new DOA estimation method is proposed. The new method makes use of the amplitude distribution of the fiber array to achieve direction finding. Sufficient numerical simulations are carried out to demonstrate the feasibility and efficiency of the proposed algorithm.

Multiphoton microscopy and nanoparticle-assisted photodynamic therapy are two important areas in biophotonics research. In this paper, we combined these two technologies together. Photosensitizer (HPPH) doped colloidal mesoporous silica nanoparticles were synthesized and systematically characterized. Based on a confocal microscope equipped with a 1560 nm femtosecond laser, we showed: (1) direct three-photon luminescence from HPPH doped nanoparticles, which were uptaken by tumor cells, and (2) cytotoxicity towards tumor cells by HPPH under three-photon excitation. Nanoparticle-assisted three-photon photodynamic therapy can be a promising technology for disease diagnosis and in vivo/clinical therapy.

In this paper, a method is proposed for conceptual design of remote sensing satellites, based on different levels of NIIRS (National Image Interpretability Rating Scales) and statistical analysis. The extraction method of these specifications is based on statistical data of remote sensing satellites that have been launched thus far, and includes the collected database of over 300 remote sensing satellites with different resolutions. In this method, first the essential parameters for designing optical remote sensing payloads were calculated based on the data and statistical relations, considering NIIRS criterion and the resolution related to each level. Moreover, weight and power consumption of these payloads were estimated and extracted considering payload specifications of satellite bus requirements, such as mass, power consumption, and stability accuracy.

Phase shifts extraction is an important research field of phase-shifting interferometry. In this paper, based on Gram–Schmidt orthonormalization of two vectors, a novel algorithm for phase shifts extraction is proposed. This algorithm can determine the phase shifts by using only two-frame phase-shifting interferograms, as well as the phase shifts among a sequence of interferograms by a loop program. To verify the performance of the proposed algorithm, we have employed this algorithm to the simulation fringe patterns and experimental interferograms to extract the phase shifts, both of the results prove that this algorithm can obtain the phase shifts with high precision rapidly. Comparing with other algorithms, it shows that the proposed algorithm is suitable for phase shifts extraction, especially in the situation of only two-frame interferograms.

In this paper, a theoretical model of a multimode optical fiber based fluorescence sensor was proposed and established with the aims to optimize specific physical parameters of the sensor including the refractive index of the fluorescent matrix, external diameter and the length of sensing fiber probe which were calculated using the beam propagation method. The plane wave at wavelengths of 395 or 505 nm was used as the excitation light source. The excitation light power in the coating layer was calculated to obtain more excitation fluorescence. The change of fluorescence intensity with structural differences of the parameters was analyzed. The theoretical results showed that for a pure silica fiber using a matrix of higher refractive index (>1.458) material was effective in improving fluorescence performance. The optimized external diameter of the sensing fiber probe was found to be >206 μm with a 200 µm fiber core diameter when the refractive index of the sensing layer is 1.49. Increasing the thickness of the sensing layer increased the level of fluorescence excitation. The fluorescence intensity excited by 395 nm light is stronger than that of light at 505 nm.

The photonic crystals (PhC) draw significant attention to build all optical logic devices and considered one of the solutions for the opto-electronic bottleneck via speed and size. The paper presents a novel all optical SR flip flop memory based on two optical NOR gates using 2D PhC. The design of optical Flip Flop is based on four nonlinear photonic crystal ring resonator and T-type waveguide. The total size of the proposed optical memory flip flop is equal to 30 μm × 30 μm. The structure has lattice constant ‘a’ is equal to 630 nm and bandgap range from 0.32 to 044. The flip flop design has a switching time in few Picoseconds and low power input of 50 mW. The PhC structure has a square lattice of silicon rod with refractive index of 3.39 in air. The overall design and the results are discussed through the experimental implementation and the numerically simulation to confirm its operation and feasibility.

In this paper, a multiscale approach coupling semi-classical drift-diffusion (DD) and the quantum mechanical non-equilibrium Green’s function (NEGF) formalism is established to simulate the full geometry of miniaturized GaN high electron mobility transistors (HEMTs). DD current flow is corrected locally in the HEMT channel, where electron transport represented by the NEGF is governed by quantum effects. As a result, simulated drain current–drain voltage and drain current–gate voltage curves are easily fitted to experimental data without fitting mobility. The variation of electric behavior predicted by our multiscale approach is in agreement with that expected from 2D electrostatics. This work indicates that it is practical and efficient to include NEGF in a DD solver, which is still the workhorse of the technology computer-aided design industry.