Showing papers in "Journal of Modern Optics in 2014"
TL;DR: In this article, a singular 1-soliton solution for optical metamaterials is derived and two integration approaches that obtains the solution are the ansatz approach and the simplest equation approach.
Abstract: This paper derives singular 1-soliton solution for optical metamaterials. There are two integration approaches that obtains the solution. These are the ansatz approach and the simplest equation approach. The second method also leads to an additional set of solutions that emerge as a by-product. These are topological soliton, rational solution and singular periodic solution. The constraint conditions for the existence of these solutions are also exhibited. The numerical simulation of a topological 1-soliton solution is also exhibited.
97 citations
TL;DR: In this article, solitons in nonlinear directional couplers in non-Kerr law media, with spatio-temporal dispersion, were studied for both twin-core and multiple-core coupler solutions.
Abstract: This paper addresses solitons in nonlinear directional couplers in non-Kerr law media, with spatio-temporal dispersion. Both twin-core couplers as well as multiple-core couplers are studied. The nonlinearities studied are Kerr law, power law, parabolic law, dual-power law and log law. Bright, dark and singular soliton solutions of the governing equation are studied.
88 citations
TL;DR: In this paper, the authors developed silicon SPADs with active area diameters as large as 500μm in a fully standard CMOS process, which can be used with on-chip integrated quenching circuitry to reduce the afterpulsing probability, or with external circuits to achieve even better photon-timing performances.
Abstract: Many demanding applications require single-photon detectors with very large active area, very low noise, high detection efficiency, and precise time response. Single-photon avalanche diodes (SPADs) provide all the advantages of solid-state devices, but in many applications other single-photon detectors, like photomultiplier tubes, have been preferred so far due to their larger active area. We developed silicon SPADs with active area diameters as large as 500 μm in a fully standard CMOS process. The 500 μm SPAD exhibits 55% peak photon detection efficiency at 420 nm, 8 kcps of dark counting rate at 0°C, and high uniformity of the sensitivity in the active area. These devices can be used with on-chip integrated quenching circuitry, which reduces the afterpulsing probability, or with external circuits to achieve even better photon-timing performances, as good as 92 ps FWHM for a 100 μm diameter SPAD. Owing to the state-of-the-art performance, not only compared to CMOS SPADs but also SPADs developed in custom...
86 citations
TL;DR: In this article, the perturbed nonlinear Schrodinger equation, describing an ultra-short optical pulse propagate along the parabolic law nonlinear fibers with Raman effect and self-steepening, has been investigated using the sub-equation expansion method.
Abstract: The perturbed nonlinear Schrodinger equation, describing an ultra-short optical pulse propagate along the parabolic law nonlinear fibers with Raman effect and self-steepening, has been investigated using the sub-equation expansion method. The dark and singular optical solitons are obtained. Furthermore, the modulational instability (MI) is analyzed based on the standard linear-stability analysis. The MI gain is got. These results have important application features in the area of telecommunications.
62 citations
TL;DR: The proposed cryptosystem decreases the volume of data to be transmitted and simplifies the keys for distribution simultaneously and numerical experiments verify the validity and security of the proposed algorithm.
Abstract: We propose a novel image encryption algorithm based on compressive sensing (CS) and chaos in the fractional Fourier domain. The original image is dimensionality reduction measured using CS. The measured values are then encrypted using chaotic-based double-random-phase encoding technique in the fractional Fourier transform domain. The measurement matrix and the random-phase masks used in the encryption process are formed from pseudo-random sequences generated by the chaotic map. In this proposed algorithm, the final result is compressed and encrypted. The proposed cryptosystem decreases the volume of data to be transmitted and simplifies the keys for distribution simultaneously. Numerical experiments verify the validity and security of the proposed algorithm.
60 citations
TL;DR: In this paper, the authors studied the Kerr nonlinearity of a four-level double-V-type quantum system near a two-dimensional array of metal-coated dielectric nanospheres.
Abstract: We present a theoretical study for the Kerr nonlinearity of a four-level double-V-type quantum system near a two-dimensional array of metal-coated dielectric nanospheres. In the quantum system under study one V-type transition is influenced by the interaction with surface plasmons while the other V-type transition interacts with free-space vacuum. The quantum system interacts with a linearly polarized weak laser field that couples the lowest state with the upper states in the free-space transitions. We show that the Kerr nonlinearity is strongly influenced by the presence of the plasmonic nanostructure and is particularly sensitive to the distance between the quantum system and the plasmonic nanostructure.
50 citations
TL;DR: In this article, the authors compare two approaches to open quantum systems, namely, the non-Hermitian dynamics and the Lindblad master equation, and propose the unified master equation that combines the characteristics of both of these approaches.
Abstract: We compare two approaches to open quantum systems, namely, the non-Hermitian dynamics and the Lindblad master equation. In order to deal with more general dissipative phenomena, we propose the unified master equation that combines the characteristics of both of these approaches. This allows us to assess the differences between them as well as to clarify which observed features come from the Lindblad or the non-Hermitian part, when it comes to experiment. Using a generic two-mode single-atom laser system as a practical example, we analytically solve the dynamics of the normalized density matrix operator. We study the two-level model in a number of cases (depending on parameters and types of dynamics), compute different observables and study their physical properties. It turns out that one can not only able to describe the different types of damping in dissipative quantum optical systems but also mimic the undamped anharmonic oscillatory phenomena which happen in quantum systems with more than two levels (w...
50 citations
TL;DR: In this paper, the authors recall the explicit form taken by the helicity of light within classical electromagnetic theory and reflect upon some of its remarkable characteristics, including its relation to the spin of light.
Abstract: Helicity is a property of light which is familiar from particle physics but less well-known in optics. In this paper we recall the explicit form taken by the helicity of light within classical electromagnetic theory and reflect upon some of its remarkable characteristics. The helicity of light is related to, but is distinct from, the spin of light. To emphasise this fact, we draw a simple analogy between the helicity of light and electric charge and between the spin of light and electric current. We illustrate this and other observations by examining various superpositions of plane waves explicitly.
43 citations
TL;DR: In this paper, the effect of temperature on a two-dimensional square lattice photonic crystal composed of Si rods arranged in an air background was investigated theoretically using the plane-wave expansion method.
Abstract: The effect of temperature on a two-dimensional square lattice photonic crystal composed of Si rods arranged in an air background was investigated theoretically using the plane-wave expansion method...
42 citations
TL;DR: In this paper, a plasmonic splitter based on subwavelength metal-insulator-metal (MIM) waveguides with tooth-shaped structures is proposed and numerically researched by using the finite-difference time-domain (FDTD) method in visible and near infrared frequencies.
Abstract: A plasmonic splitter based on subwavelength metal–insulator–metal (MIM) waveguides with tooth-shaped structures is proposed and numerically researched by using the finite-difference time-domain (FDTD) method in visible and near infrared frequencies. The splitter is regarded as two zigzag-shaped MIM waveguides, which naturally stretch out two tooth structures in bending corners. Each tooth forms a resonant cavity. The transmission of the zigzag-shaped waveguide is close to zero at some resonant wavelength of the tooth cavity. The same-order resonant wavelength has an approximately linear relationship with the depth of the tooth. When the geometric parameters of the two zigzag-shaped waveguides of teeth are suitably initialized, both frequency splitter and power splitter can be simply achieved.
39 citations
TL;DR: In this article, a new efficient binary optimization method based on teaching-learning-based optimization (TLBO) algorithm is proposed to design an array of plasmonic nano bi-pyramids in order to achieve maximum absorption coefficient spectrum.
Abstract: A new efficient binary optimization method based on Teaching–Learning-Based Optimization (TLBO) algorithm is proposed to design an array of plasmonic nano bi-pyramids in order to achieve maximum absorption coefficient spectrum. In binary TLBO, a group of learners consisting of a matrix with binary entries controls the presence (‘1’) or the absence (‘0’) of nanoparticles in the array. Simulation results show that absorption coefficient strongly depends on the localized position of plasmonic nanoparticles. Non-periodic structures have more appropriate response in term of absorption coefficient. This approach is useful in optical applications such as solar cells and plasmonic nano antenna.
TL;DR: The Morris-Shore transformation as discussed by the authors generalizes this procedure to replace the description of an elaborate linkage pattern of an -state Hamiltonian in the rotating-wave approximation by a set of independent two-state systems.
Abstract: Descriptions of coherent excitation of multi-state quantum systems model changes through coupled ordinary differential equations that become more cumbersome as the number of involved quantum states increases. It is always useful to find simplifications of the equations, ideally involving exact analytic solutions. The ultimate simplification is to a set of independent pairs of quantum states. Such sets of independent two-state linkages occur naturally when we describe the excitation between two sets of degenerate Zeeman sublevels by a field that is linearly or circularly polarized. The Morris–Shore (MS) transformation, a Hilbert-space coordinate change, generalizes this procedure to replace the description of an elaborate linkage pattern of an -state Hamiltonian in the rotating-wave approximation by a set of independent two-state systems – a basis of paired bright states and excited states supplemented with dark states and spectator states. The three-state lambda-linkage found in stimulated Raman transitio...
TL;DR: In this article, the authors investigated the gain spectrum of a nonlinear optical coupler with a negative-index metamaterial channel whose nonlinear response includes third and fifth-order terms.
Abstract: We are motivated by recent studies in medium formed by two tunnel-coupled waveguides. One of the waveguides is manufactured from an ordinary dielectric, while the second has negative refraction. We present an investigation of the gain spectrum permitting modulation instability in the nonlinear optical coupler with a negative-index metamaterial channel whose non-linear response includes third- and fifth-order terms. The principal motivation for our analysis stems from the impact of the inevitable presence of the effective cubic–quintic nonlinearity. We emphasize the influence of higher order nonlinear terms, over the MI phenomena, and the outcome of its development achieved by using linear stability analysis. Gain spectrum investigation has been carried out for both anomalous and normal dispersion regime in the focusing and defocusing cases of nonlinearity and near-zero dispersion regime where higher order linear dispersive effects emerge. Our results show that the MI gain spectra consist of multiple spect...
TL;DR: In this paper, a novel fringe analysis method is proposed that uses a new optical system, which uses a plane wave as the reference beam of the speckle interferometer.
Abstract: Speckle interferometry is an important deformation measurement method for an object with a rough surface. In this paper, a novel fringe analysis method is proposed that uses a new optical system, which uses a plane wave as the reference beam of the speckle interferometer. When the optical system is employed in fringe analysis, the deformation information and the bias components of the speckle patterns are clearly separated in the frequency domain. Therefore, the deformation information can be readily extracted using a Fourier transform, which gives a pair of real and imaginary components concerning the information. The specklegram is calculated using such a pair of components, and the phase map is obtained from the specklegram. Experimental results confirmed that the resolution power of this measurement method is higher than 1/261 of the wavelength of the light source of the optical system.
TL;DR: In this article, the authors reported the lifetime of an OPV cell in ambient laboratory condition whose active layer is composed of PTB7:PCBM blend, and the degradation of OPV cells generally depends on the nature of the semiconductor polymer used in the preparation of the devices.
Abstract: The short life span of organic photovoltaic (OPV) cell in an ambient laboratory condition is one of the challenges hindering the realization of organic-based devices. The presence of moisture and oxygen in conjugated polymer matrix is the major factors responsible for the degradation of organic molecules. The chemical degradation of OPV cell generally depends on the nature of the semiconductor polymer used in the preparation of the devices. However, the lifespan of unprotected OPV cells often ranges in the order of few hours in simple laboratory environment. We are reporting here the lifetime of organic photovoltaic cell in ambient laboratory condition whose active layer is composed of PTB7:PCBM blend.
TL;DR: In this article, the properties of photonic band structures in two-dimensional superconductor photonic crystals were investigated by various parameters such as filling factor, the lattice constant alteration, threshold frequency of the super-conductor, and shape of the rods as well.
Abstract: In this paper, by means of frequency-dependent plane wave expansion method we investigate the properties of photonic band structures in two-dimensional superconductor photonic crystals. Effects of cut-off frequency are investigated by various parameters such as filling factor, the lattice constant alteration, threshold frequency of the superconductor, and shape of the rods as well. We show that the cut-off frequency can be efficiently tuned by the operating temperature. Moreover, it can be tailored by changing the dielectric constant of the background and the threshold frequency of the superconductor material.
TL;DR: In this paper, the authors reformulate the Liouville equation by defining a vector corresponding to the elements of the density operator, and determining the corresponding time-evolution matrix for a system of N energy levels.
Abstract: The Liouville equation governing the evolution of the density matrix for an atomic/molecular system is expressed in terms of a commutator between the density matrix and the Hamiltonian, along with terms that account for decay and redistribution. To find solutions of this equation, it is convenient first to reformulate the Liouville equation by defining a vector corresponding to the elements of the density operator, and determining the corresponding time-evolution matrix. For a system of N energy levels, the size of the evolution matrix is N2 × N2. When N is very large, evaluating the elements of these matrices becomes very cumbersome. We describe a novel algorithm that can produce the evolution matrix in an automated fashion for an arbitrary value of N. As a non-trivial example, we apply this algorithm to a 15-level atomic system used for producing optically controlled polarization rotation. We also point out how such a code can be extended for use in an atomic system with arbitrary number of energy levels.
TL;DR: In this paper, the authors reported on the manipulation of the particles elliptical shapes and the underlying refractive indices with respect to a maximally confined power distribution in the resulting nanojet which has been parameterized according to both, the beam waist and the beam divergence.
Abstract: Elliptically shaped particles with different size and refractive indices have been studied under plane wave illumination using simulation tools such as 2D-FDTD, 2D-MMP, and 3D-MMP. Owing to careful manipulation, the power distribution in the vicinity of the particles opposite boundary resulted in a tightly focused photonic nanojet. Their waists are significantly smaller than the diffraction limit while propagating over several optical wavelengths without significant divergence. In this paper, we report on the manipulation of the particles elliptical shapes and the underlying refractive indices with respect to a maximally confined power distribution in the resulting nanojet which has been parameterized according to both, the beam waist and the beam divergence. The result that elliptical particles (i.e. oblate spheroids) turned out to be superior to spherical ones was underpinned within a highly accurate and fast 3D-MMP simulation using ring multipoles.
TL;DR: In this article, the authors studied the dependence of the electron yield with respect to the static electric field applied to the tip of a tungsten nanotip and showed that photoelectron spectra are recorded using a retarding field spectrometer and peaks separated by the photon energy are observed with a 45% contrast.
Abstract: We present an experiment studying the interaction of a strongly focused 25 fs laser pulse with a tungsten nanotip, investigating the different regimes of laser-induced electron emission. We study the dependence of the electron yield with respect to the static electric field applied to the tip. Photoelectron spectra are recorded using a retarding field spectrometer and peaks separated by the photon energy are observed with a 45% contrast. They are a clear signature of above threshold photoemission (ATP), and are confirmed by extensive spectrally resolved studies of the laser power dependence. Understanding these mechanisms opens the route to control experiment in the strong-field regime on nanoscale objects.
TL;DR: In this paper, an optical fiber humidity sensor was fabricated using a hydrophilic gel (agarose) deposited on the tapered plastic optical fiber (POF), which can absorb and exude moisture from/to the ambience and changing its ability to modulate the intensity of light that propagates through the fiber.
Abstract: An optical fiber humidity sensor was fabricated using a hydrophilic gel (agarose) deposited on the tapered plastic optical fiber (POF). The sensing element, agarose, can absorb and exude moisture from/to the ambience, thereby altering its refractive index and changing its ability to modulate the intensity of light that propagates through the fiber. Thus, the operating principle of the sensor is based on the intensity modulation technique, which utilizes a tapered POF probe coated with agarose that is sensitive to humidity. The POF, which was fabricated using an etching method, has a waist diameter of 0.45 mm and tapering length of 10 mm. As the relative humidity varies from 50% to 80%, the output voltage of the sensor with agarose gel of 0.5% weight content decreases linearly from 2.24 mV to 1.55 mV. The agarose-based sensor produces a sensitivity of 0.0228 mV/%, with a slope linearity of more than 98.36%. The tapered fiber with agarose gel of 1% weight content produces a sensitivity of 0.0103 mV/% with a slope linearity of more than 94.95% and a limit of detection of 2.635%, while the tapered fiber with agarose gel of 1.5% weight content produces a sensitivity of 0.0079 mV/% with a slope linearity of more than 98.53% and a limit of detection of 6.853%. The fiber with agarose gel of 0.5% weight content shows higher sensitivity compared to that of 1% and 1.5% due to the effect of pore size, which changes with concentration. The results demonstrate that agarose-based optical fiber sensors are both sensitive and efficient for economical and flexible measurements of humidity.
TL;DR: This extension of image enhancement techniques based on the retinex theory achieves simultaneous dynamic range modification, color consistency, and lightness rendition without multi-scale Gaussian filtering which has a certain halo effect.
Abstract: In this paper, we extend image enhancement techniques based on the retinex theory imitating human visual perception of scenes containing high illumination variations. This extension achieves simultaneous dynamic range modification, color consistency, and lightness rendition without multi-scale Gaussian filtering which has a certain halo effect. The reflection component is analyzed based on the illumination and reflection imaging model. A new prior named Max Intensity Channel (MIC) is implemented assuming that the reflections of some points in the scene are very high in at least one color channel. Using this prior, the illumination of the scene is obtained directly by performing a gray-scale closing operation and a fast cross-bilateral filtering on the MIC of the input color image. Consequently, the reflection component of each RGB color channel can be determined from the illumination and reflection imaging model. The proposed algorithm estimates the illumination component which is relatively smooth and maintains the edge details in different regions. A satisfactory color rendition is achieved for a class of images that do not satisfy the gray-world assumption implicit to the theoretical foundation of the retinex. Experiments are carried out to compare the new method with several spatial and transform domain methods. Our results indicate that the new method is superior in enhancement applications, improves computation speed, and performs well for images with high illumination variations than other methods. Further comparisons of images from National Aeronautics and Space Administration and a wearable camera eButton have shown a high performance of the new method with better color restoration and preservation of image details.
TL;DR: In this article, all-optical nonlinear plasmonic ring resonator (PRR) switches containing 90o sharp and smooth bends have been proposed and numerically analyzed by the finite-difference time-domain method.
Abstract: In this paper, all-optical nonlinear plasmonic ring resonator (PRR) switches containing 90o sharp and smooth bends have been proposed and numerically analyzed by the finite-difference time-domain method Kerr nonlinear self-phase modulation (SPM) and cross-phase modulation (XPM) effects on the switching performance of the device have been studied By applying a high-power lightwave, the signal can switch from one port to the other port due to the ON/OFF resonant states of the ring We have shown that by utilizing the XPM effect, the output power ratio is improved by a factor of 25 and the required switching power is 31% of that of the case with only the SPM effect Moreover, by utilizing sharp bend square-shaped ring resonators, the switching power is 104% lower than that of the smooth ones The nonlinear PRR switches are suitable for application in photonic-integrated circuits as all-optical switches because of their nanoscale size and low required switching power
TL;DR: In this article, a detailed experimental investigation and theoretical analysis have been made in the V-type Rb atomic medium, and seven induced transparency windows, including a central double peak-structure, have been observed experimentally when a coupling field and a probe field are applied into the ground and first excited states.
Abstract: A detailed experimental investigation and theoretical analysis have been made in the V-type Rb atomic medium. Seven induced transparency windows, including a central double-peak-structure, have been observed experimentally when a coupling field and a probe field are applied into the ground and first excited states. By taking into account the hyperfine splitting of the excited state, our theoretical analysis gives good explanation for the observed phenomena.
TL;DR: In this article, an experimental demonstration of the Klyshko advanced-wave picture using a time-gated camera in an image-based coincidence measurement is presented, showing an excellent agreement between the spatial distributions as predicted by the klyshka picture and those obtained using the SPDC photon pairs.
Abstract: The Klyshko advanced-wave picture is a well-known tool useful in the conceptualisation of parametric down-conversion (SPDC) experiments. Despite being well-known and understood, there have been few experimental demonstrations illustrating its validity. Here, we present an experimental demonstration of this picture using a time-gated camera in an image-based coincidence measurement. We show an excellent agreement between the spatial distributions as predicted by the Klyshko picture and those obtained using the SPDC photon pairs. An interesting speckle feature is present in the Klyshko predictive images due to the spatial coherence of the back-propagated beam in the multi-mode fibre. This effect can be removed by mechanically twisting the fibre, thus degrading the spatial coherence of the beam and time-averaging the speckle pattern, giving an accurate correspondence between the predictive and SPDC images.
TL;DR: This review focusses on the history and state-of-the-art of optical read-out strategies for centrifugal microfluidic platforms, arising (commercial) application potential and future opportunities.
Abstract: Centrifugal microfluidic systems have become one of the principal platforms for implementing bioanalytical assays, most notably for biomedical point-of-care diagnostics. These so-called ‘lab-on-a-disc’ systems primarily utilise the rotationally controlled centrifugal field in combination with capillary forces to automate a range of laboratory unit operations (LUOs) for sample preparation, such as metering, aliquoting, mixing and extraction for biofluids as well as sorting, isolation and counting of bioparticles. These centrifugal microfluidic LUOs have been regularly surveyed in the literature. However, even though absolutely essential to provide true sample-to-answer functionality of lab-on-a-disc platforms, systematic examination of associated, often optical, read-out technologies has been so far neglected. This review focusses on the history and state-of-the-art of optical read-out strategies for centrifugal microfluidic platforms, arising (commercial) application potential and future opportunities.
TL;DR: In this paper, Krotov's method allows simultaneously imposing temporal and spectral constraints without perturbing monotonic convergence, provided the constraints can be expressed as positive semi-definite quadratic forms.
Abstract: Shaped pulses obtained by optimal control theory often possess unphysically broad spectra. In principle, the spectral width of a pulse can be restricted by an additional constraint in the optimization functional. However, it has so far been impossible to impose spectral constraints while strictly guaranteeing monotonic convergence. Here, we show that Krotov’s method allows for simultaneously imposing temporal and spectral constraints without perturbing monotonic convergence, provided the constraints can be expressed as positive semi-definite quadratic forms. The optimized field is given by an integral equation which can be solved efficiently using the method of degenerate kernels. We demonstrate that Gaussian filters suppress undesired frequency components in the control of non-resonant two-photon absorption.
TL;DR: In this article, the authors investigate theoretically a system consisting of a one-dimensional Bose-Einstein condensate trapped inside the optical lattice of an optical cavity, and they show that using the nonlinear effect of atomic collisions, how one can manipulate and control the state of the Bogoliubov mode and produce squeezed states.
Abstract: In this paper, we investigate theoretically a system consisting of a one-dimensional Bose–Einstein condensate trapped inside the optical lattice of an optical cavity. In the weak-interaction regime and under the Bogoliubov approximation, the wave function of the Bose–Einstein condensate can be described by a classical field (condensate mode) having some quantum fluctuations (the Bogoliubov mode) about the mean value. Such a system behaves as a so-called atomic parametric amplifier, similar to an optical parametric amplifier, where the condensate and the Bogoliubov modes play, respectively, the roles of the pump field and the signal mode in the degenerate parametric amplifier and the s-wave scattering frequency of atom–atom interaction plays the role of the nonlinear gain parameter. We show that using the nonlinear effect of atomic collisions, how one can manipulate and control the state of the Bogoliubov mode and produce squeezed states.
TL;DR: In this article, a miniaturized microstrip patch antenna with a complementary split ring resonator (CSRR) was investigated for multiband operation, and the proposed structure has a CSRR loaded in the base of the antenna to improve its performance and make it a metamaterial.
Abstract: Following recent findings on metamaterials, a miniaturized microstrip patch antenna loaded with a complementary split ring resonator (CSRR) was investigated for multiband operation. The proposed structure has a CSRR loaded in the base of the antenna to improve its performance and to make it a metamaterial. Metamaterials exhibit qualitatively new electromagnetic response functions that cannot be found in nature. The CSRR-loaded base allows simultaneous operation over several frequencies. Here, a total of seven bands were achieved by loading the patch antenna with the CSRR. The seven bands were centered around frequencies of 4.33 GHz, 5.29 GHz, 6.256 GHz, 7.066 GHz, 7.846 GHz, 8.86 GHz, and 9.75 GHz. Design results were obtained by using a high-frequency structure simulator that is used for simulating microwave passive components.
TL;DR: In this article, a photovoltaic polymer solar cells with Ag and titanium dioxide were fabricated to improve the PV performance by increasing the amount of Ag in TiO2 (by 3, 5, 7, and 10%).
Abstract: Photovoltaic (PV) polymer solar cells with Ag and titanium dioxide were fabricated to improve the PV performance by increasing the amount of Ag in TiO2 (by 3, 5, 7, and 10%). Sol–gel method was used to obtain amorphous or crystalline form of titanium dioxide layers. The solar cells with poly(3-hexylthiophene) and [6,6]-phenyl-C61-butyric acid methyl ester active layer in two various positions of titanium dioxide in device were tested. Higher PV performance was received by introducing TiO2 with 5% of Ag between ITO and PEDOT:PSS in device and by heating the layer at 130 °C. The viscosity of applied PEDOT:PSS strongly influences the values of power conversion efficiency of the constructed polymer devices with titanium dioxide.
TL;DR: In this paper, a simple multi-wavelength passively Q-switched Erbium-doped fiber laser (EDFL) is demonstrated using low-cost multi-walled carbon nanotubes (MWCNTs)-based saturable absorber, which is prepared using polyvinyl alcohol as a host polymer.
Abstract: A simple multi-wavelength passively Q-switched Erbium-doped fiber laser (EDFL) is demonstrated using low-cost multi-walled carbon nanotubes (MWCNTs)-based saturable absorber, which is prepared using polyvinyl alcohol as a host polymer. The multi-wavelength operation is achieved based on non-linear polarization rotation effect by incorporating 50 m long photonic crystal fiber in the ring cavity. The EDFL produces a stable multi-wavelength comb spectrum for more than 14 lines with a fixed spacing of 0.48 nm. The laser also demonstrates a stable pulse train with the repetition rate increasing from 14.9 to 25.4 kHz as the pump power increases from the threshold power of 69.0 mW to the maximum pump power of 133.8 mW. The minimum pulse width of 4.4 μs was obtained at the maximum pump power of 133.8 mW while the highest energy of 0.74 nJ was obtained at the pump power of 69.0 mW.