MedWorm.com provides a medical RSS filtering service. Over 6000 RSS medical sources are combined and output via different filters. This feed contains the latest items from the 'Research Letters in Optics' source. Sat, 12 Mar 2011 02:23:33 +0100 http://www.hindawi.com/journals/ijo/2010/978763.html The solubility of potassium dihydrogen phosphate (KDP) was determined for five different temperatures. Metastable zone width of aqueous solutions of KDP saturated at different temperatures was determined by nucleation method in pure form and adding a well-known chelating agent ethylenediaminetetraacetic acid (0.5 mol% EDTA). The induction period τ was measured, experiments were performed at selected degrees of supersaturation (C/C*), and the critical nucleation parameters like interfacial energy (σ) were calculated, based on the classical theory of nucleation. The structural and optical properties of the grown crystals have been investigated. FTIR analysis has been carried out to characterize the grown crystals. Band gap has been calculated from transmission spectr... Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=4330434 Tue, 11 Jan 2011 01:48:31 +0100 4330434 http://www.hindawi.com/journals/ijo/2010/802385.html Two patterns of functionally graded materials (FGMs) were successfully fabricated whose compositions gradually varied from 100% stainless steel 316L to 100% Inconel718 superalloy using laser engineered net shaping process. The microstructure characterization, composition analysis, and microhardness along the graded direction were investigated. The comparison revealed the distinctions in solidification behavior, microstructure evolution of two patterns. In the end, the abrasive wear resistance of the material was investigated. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=4304746 Mon, 03 Jan 2011 14:54:25 +0100 4304746 http://www.hindawi.com/journals/ijo/2010/601675.html A novel study has been undertaken for the coupling efficiency enhancement on planar (refractive and diffractive) microlenses as coupling elements with various geometrical shapes in fibre optics communication. When the dispersion of the planar diffractive microlens is expressed in terms of an Abbe number, it is easy to solve for the refractive and diffractive power coupling efficiency that result in a single material. Coupling loss is reduced with microlens used as coupler even when increasing wavelength of the Gaussian beam. A slight difference of power coupling efficiency is observed with the different direction of electric polarisation for a Gaussian beam of large spot size at its waist due to coupling property has been discussed and shown to agree well with theoretical model. (Source: R... Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=4304745 Mon, 03 Jan 2011 14:54:25 +0100 4304745 http://www.hindawi.com/journals/ijo/2010/137572.html A rigorous and consistent approach is demonstrated to develop a model of the 4M structure (the four-media structure of a film on a substrate of finite thickness). The general equations obtained for the reflectance and transmittance spectra of the 4M structure are simplified by employing a procedure of the so-called device averaging to reduce them to a succinct form convenient for processing of experimental spectra for the structures with a thick substrate. The newly derived equations are applied to two special cases: (i) an arbitrary film on highly absorbing substrates and (ii) a slightly absorbing film on transparent substrates. The reflectance and transmittance spectra represented in the simplified (with the device averaging) form have a practical application for determining the film thi... Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=4300300 Fri, 31 Dec 2010 08:42:45 +0100 4300300 http://www.hindawi.com/journals/ijo/2010/261420.html Ta and N co-doped SrTiO3 was synthesized by microwave-assisted solvothermal reaction using SrCl2⋅6H2O, Ti(OC3H7)4, TaCl5, and HMT (hexamethylenetetramine) in KOH and oleic acid mixed solutions. The products were characterized by XRD, TG-DTA, BET surface area measurement, TEM, EDX, DRS, PL-Spectra, and XPS. The nanoparticles of perovskite-type SrTi1-xTaxO3-yNy (x=0−0.1) were successfully synthesized. The photocatalytic activity of SrTiO3 for DeNOxability in the visible light region could be improved by the codoping of Ta5+ and N3-. The excellent visible light photocatalytic activity of this substance may be due to the generation of a new band gap by doping nitrogen that enables the absorption of visible light as well as a decrease in the incidence of the lattice defects, which... Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=4293418 Wed, 29 Dec 2010 04:18:00 +0100 4293418 http://www.hindawi.com/journals/ijo/2010/201305.html We present a remote, differential method for measuring the prescription of aspheric mirrors using null interferometry in the center-of-curvature configuration. The method requires no equipment beyond that used in a basic interferometery setup (i.e., there are no shearing elements or absolute distance meters). We chose this configuration because of its widespread use. However, the method is generalizable to other configurations with an adjustment of the governing equation. The method involves taking a series of interferograms before and after small, known misalignments are applied to the mirror in the interferometry setup and calculating the prescription (e.g., radius of curvature and conic constant) of the mirror, based on these differential measurements, using a nonlinear regression. We a... Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=4284828 Fri, 24 Dec 2010 02:10:00 +0100 4284828 http://www.hindawi.com/journals/ijo/2008/480362.html This paper presents a numerical study of parabolic pulse generation in tapered microstructured optical fibres (MOFs). Based on our results and the algorithms presented, one can determine the linear taper profile (starting and finishing pitch values and taper length) needed to achieve parabolic pulse shaping of an initial Gaussian pulse shape with different widths and powers. We quantify the evolution of the parabolic pulse using the misfit parameter and show that it is possible to reach values significantly better than those obtained by a step index fibre. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=4164189 Sun, 14 Nov 2010 23:35:28 +0100 4164189 http://www.hindawi.com/journals/ijo/2008/239037.html This paper presents a numerical study of high birefringence induced by four types (Type 1–4) of different sizes of elliptical air holes in photonic crystal fibers (PCFs). The numerical simulation is carried out by using the finite element method. The statistical correlations between the birefringence and the various parameters are obtained. Based on our results, the birefringence is found to be largely dependent on the variation of the normalized frequency, size ratio, effective area of the circular and elliptical air holes, and the ring number of cladding. Two of our suggested structures, Type 1 and Type 3, can considerably enhance the birefringence in PCFs leading to values as high as 7.697×10−3 and 8.002×10−3, respectively, which are much higher than th... Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=4164188 Sun, 14 Nov 2010 23:35:28 +0100 4164188 http://www.hindawi.com/journals/ijo/2009/926810.html We present a unifying description of localized states observed in systems with coexistence of two spatially periodic states, called bi-pattern systems. Localized states are pinned over an underlying lattice that is either a self-organized pattern spontaneously generated by the system itself, or a periodic grid created by a spatial forcing. We show that localized states are generic and require only the coexistence of two spatially periodic states. Experimentally, these states have been observed in a nonlinear optical system. At the onset of the spatial bifurcation, a forced one-dimensional amplitude equation is derived for the critical modes, which accounts for the appearance of localized states. By numerical simulations, we show that localized structures persist on two-dimensional systems ... Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=4164187 Sun, 14 Nov 2010 23:35:28 +0100 4164187 http://www.hindawi.com/journals/ijo/2009/181467.html We overview our recent developments in the theory of dispersion-managed (DM) solitons within the context of optical applications. First, we present a class of localized solutions with a period multiple to that of the standard DM soliton in the nonlinear Schrödinger equation with periodic variations of the dispersion. In the framework of a reduced ordinary differential equation-based model, we discuss the key features of these structures, such as a smaller energy compared to traditional DM solitons with the same temporal width. Next, we present new results on dissipative DM solitons, which occur in the context of mode-locked lasers. By means of numerical simulations and a reduced variational model of the complex Ginzburg-Landau equation, we analyze the influence of the different dissip... Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=4164186 Sun, 14 Nov 2010 23:35:28 +0100 4164186 http://www.hindawi.com/journals/ijo/2009/371974.html We present optical phase conjugation based on the degenerate four-wave mixing (DFWM) arrangement in gelatin films doped with acid blue 3 dye (FAST GREEN FCF) using He-Ne laser of total power 50 mW. Various parameters which influence the phase-conjugate (PC) signal during the DFWM process were studied (angle of between the forward pump and the probe beam, transition of gelatin film, reflectivity as a function of forward and backward beam). A maximum phase-conjugate beam reflectivity of about 0.02% has been observed in these dye-doped gelatin films. PACS: 42.65.-k, 42.65.Hw. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=4164185 Sun, 14 Nov 2010 23:35:28 +0100 4164185 http://www.hindawi.com/journals/ijo/2010/897829.html We present fiber-coupled dielectric-loaded plasmonic waveguides for 1.55 μm telecom wavelength fabricated by two-photon polymerization and nanoimprint lithography. The waveguide structures include 100-μm-long plasmonic waveguides connected on both ends to tapered dielectric waveguides used for end-fire coupling with optical fibers. The excitation of plasmonic waveguides is verified via polarization-resolved measurements of the overall transmission, demonstrating thereby that this technology is suitable in principle for the integration of plasmonic components into fiberoptics. Loss mechanisms are investigated and improvements suggested to reduce transmission losses and consequently increase the viability of practical application. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=3798197 Thu, 29 Jul 2010 08:06:36 +0100 3798197 http://www.hindawi.com/journals/ijo/2010/275910.html The exact solutions of the Schrödinger equation for quantum damped oscillator with modified Caldirola-Kanai Hamiltonian are evaluated. We also investigate the cases of under-, over-, and critical damping. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=3595245 Tue, 25 May 2010 15:25:10 +0100 3595245 http://www.hindawi.com/journals/ijo/2010/626583.html We have demonstrated the Šolc-type wavelength filters in a 52 mm long periodically poled Ti-diffused lithium niobate channel waveguide which has a domain period of 16.6 μm. At room temperature, the center wavelength and the full-width at half maximum of the filter were about 1272.49 nm and 0.23 nm, respectively. The nearest side-lobe is about 7 dB. New structure of optical add/drop multiplexer (OADM) utilizing Šolc-type TE↔TM mode converters was proposed for the first time. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=3459884 Mon, 12 Apr 2010 15:40:54 +0100 3459884 http://www.hindawi.com/journals/ijo/2008/919403.html Wide wavelength tuning by a variable reflective output coupler is demonstrated in high-power double-clad Tm3+-doped silica fiber lasers diode-pumped at ∼790  nm. Varying the output coupling from 96% to 5%, the laser wavelength is tuned over a range of 106  nm from 1949 to 2055  nm. The output power exceeds 20  W over 90-nm range and the maximum output power is 32  W at 1949  nm for 51-W launched pump power, corresponding to a slope efficiency of ∼70%. Assisted with different fiber lengths, the tuning range is expanded to 240  nm from 1866 to 2107  nm with the output power larger than 10  W. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=2962819 Thu, 05 Nov 2009 16:15:34 +0100 2962819 http://www.hindawi.com/journals/ijo/2008/253634.html The data pulse delay based on slow light induced by stimulated Brillouin scattering (SBS) in a nonuniform dispersion decreasing fiber (DDF) is demonstrated experimentally, and the distortions of data pulses at different beat frequencies are studied. We found that a delay exceeding a pulse width can be achieved at particular beat frequency, and the DDF has larger delay versus gain slope coefficient with much better output pulse quality than single-mode fiber. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=2962818 Thu, 05 Nov 2009 16:15:34 +0100 2962818 http://www.hindawi.com/journals/ijo/2008/613986.html The transmission speed of optical network strongly depends on the impact of higher order dispersion. In presence of coherent crosstalk, which cannot be otherwise controlled by optical filtering, the impact of higher order dispersions becomes more pronounced. In this paper, the general expressions, that describe pulse deformation due to second- and fourth-order dispersions in a single-mode fiber, are given. The responses for such even-order dispersions, in presence of coherent crosstalk, are characterized by waveforms with long trailing edges. The transmission quality of optical pulses, due to both individual and combined influence of second- and fourth-order dispersions, is studied in this paper. Finally, the pulse shape and eye diagrams are obtained. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=2962817 Thu, 05 Nov 2009 16:15:34 +0100 2962817 http://www.hindawi.com/journals/ijo/2008/204828.html The role of Fermi resonance in formation of valence band of water Raman scattering was investigated. Simultaneous measurement of characteristics of bending and valence bands of water in D2O solutions, KBr, and KCl and using genetic algorithms in conjunction with variation methods allowed increasing accuracy of estimation of Fermi resonance coupling constant and of Fermi resonance contribution into formation of water Raman valence band. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=2962816 Thu, 05 Nov 2009 16:15:34 +0100 2962816 http://www.hindawi.com/journals/ijo/2008/865092.html We report on hybrid mode-locked laser operation of a tapered semiconductor amplifier in an external ring cavity, generating pulses as short as 0.5 ps at 88.1 MHz with an average power of 60 mW. The mode locking is achieved through a combination of a multiple quantum well saturable absorber (>10% modulation depth) and an RF current modulation. This designed laser has 20 nm tuning bandwidth in continuous wave and 10 nm tuning bandwidth in mode locking around 786 nm center wavelength at constant temperature. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=2962815 Thu, 05 Nov 2009 16:15:34 +0100 2962815 http://www.hindawi.com/journals/ijo/2008/163937.html A newly proposed strong harmonic-expansion method is applied to the laser-Lorenz equations to analytically construct a few typical solutions, including the first few expansions of the well-known period-doubling cascade that characterizes the system in its self-pulsing regime of operation. These solutions are shown to evolve in accordance with the driving frequency of the permanent solution that we recently reported to illustrate the system. The procedure amounts to analytically construct the signal Fourier transform by applying an iterative algorithm that reconstitutes the first few terms of its development. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=2962814 Thu, 05 Nov 2009 16:15:34 +0100 2962814 http://www.hindawi.com/journals/ijo/2009/981620.html We demonstrated a novel technique for all-optical 2-to-4 level amplitude-shift keying (ASK) coding based on a fiber optical parametric amplifier. A 20-Gb/s signal is realized by multiplexing two 10-Gb/s data streams. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=2962813 Thu, 05 Nov 2009 16:15:34 +0100 2962813 http://www.hindawi.com/journals/ijo/2009/481010.html The spectral behavior of single and multiple phase shifts tilted fiber Bragg gratings has been experimentally investigated. To this aim, a simple and cost-effective postprocessing technique based on local thermal treatment was used to create arbitrary phase shifts along the tilted grating structure. In particular, UV written tilted fiber Bragg gratings were treated by the electric arc discharge to erase the refractive index modulation in well-defined regions. We demonstrate that these defects give rise to interference pattern for all modes, and thus defect states can be achieved within all the attenuation bands, enabling a simple wavelength independent spectral tailoring of this class of devices. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=2962812 Thu, 05 Nov 2009 16:15:34 +0100 2962812 http://www.hindawi.com/journals/ijo/2009/276538.html We present for the first time a theoretical model of Er3+-Tm3+-Pr3+ codoped fiber pumped with both 800 nm and 980 nm lasers to explore possibility of this co-doped system as all-wave fiber amplifier. The rate and power propagation equations of the model are solved numerically and the dependence of the gains at 1310, 1470, 1530, 1600, 1650 nm windows on fiber length is calculated. The results show that with pump power of 200 mW/200 mW, when the concentrations of Pr3+, Tm3+, Er3+ are around 1.7×1024, 3.9×1024, 1.2×1024 (ions/m3), respectively, the signals at 1310, 1470, 1530, 1600, 1650 nm may be nearly equally amplified with gain of 13–16.0 dB in the active fiber with length of 23.5 m; the co-doping concentra... Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=2962811 Thu, 05 Nov 2009 16:15:34 +0100 2962811 http://www.hindawi.com/journals/ijo/2009/475941.html Effects of size, morphology, and composition of gold and silver nanoparticles on surface plasmon resonance (SPR) and surface enhanced Raman spectroscopy (SERS) are studied with the purpose of optimizing SERS substrates. Various gold and silver films made by evaporation and subsequent annealing give different morphologies and compositions of nanoparticles and thus different position of the SPR peak. SERS measurements of 4-mercaptobenzoic acid obtained from these films reveal that the proximity of the SPR peak to the exciting laser wavelength is not the only factor leading to the highest Raman enhancement. Silver nanoparticles evaporated on top of larger gold nanoparticles show higher SERS than gold-silver alloyed nanoparticles, in spite of the fact that the SPR peak of alloyed nanoparticles... Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=2962810 Thu, 05 Nov 2009 16:15:34 +0100 2962810 http://www.hindawi.com/journals/ijo/2009/387580.html The twin photons produced by a type-II spontaneous parametric down conversion are well know as a potential source of photons for quantum teleportation due to the strong entanglement in polarization. This strong entanglement in polarization, however, depends on the spectral composition of the pump photon and the nature of optical isotropy of the crystal. By exact numerical calculation of the concurrence, we have shown that how pump photons spectral width and the birefringence nature of the crystal directly affect the degree of polarization entanglement of the twin photons. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=2962809 Thu, 05 Nov 2009 16:15:34 +0100 2962809 http://www.hindawi.com/journals/ijo/2009/730165.html A simple truncated fused silica elliptical cavity is proposed to enhance the output performance of solar-pumped solid-state lasers. The imaging property of the truncated elliptical cavity ensures an enhanced absorption distribution within an Nd:YAG rod. Optimum pumping parameters are found through ZEMAX nonsequential ray-tracing and LASCAD laser cavity analyses. Compared with the output laser performance of a 3D-compound parabolic concentrator-2D-compound parabolic concentrator (3D-CPC-2D-CPC) cavity, the truncated cavity provides 11% more multimode and 72.7% more TEM00 laser powers. A laser beam of high beam quality can be produced efficiently. The standard tracking error for multimode laser power is also reduced to only 4.0% by the truncated cavity. (Source: Research Letters ... Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=2962808 Thu, 05 Nov 2009 16:15:34 +0100 2962808 http://www.hindawi.com/journals/ijo/2009/896208.html Accurate estimation of the axial position of a molecule using a single lateral image remains a challenge in fluorescent single particle tracking. Here, a principled algorithm for the Bayesian estimation of the axial position of a molecule in three-dimensional astigmatism-based particle tracking is proposed. This technique uses the data from a calibration image set to derive the position without assuming a functional form for the abberated defocusing curve. Using a calibration image set from forty 57 nm beads, the axial position is calculated, and the error associated with position estimation is discussed. This method is compared to previously published algorithms. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=2962807 Thu, 05 Nov 2009 16:15:34 +0100 2962807 http://www.hindawi.com/journals/rlo/2009/387580.html The twin photons produced by a type-II spontaneous parametric down conversion are well know as a potential source of photons for quantum teleportation due to the strong entanglement in polarization. This strong entanglement in polarization, however, depends on the spectral composition of the pump photon and the nature of optical isotropy of the crystal. By exact numerical calculation of the concurrence, we have shown that how pump photons spectral width and the birefringence nature of the crystal directly affect the degree of polarization entanglement of the twin photons. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=2641208 Mon, 27 Jul 2009 12:19:41 +0100 2641208 http://www.hindawi.com/journals/rlo/2009/475941.html Effects of size, morphology, and composition of gold and silver nanoparticles on surface plasmon resonance (SPR) and surface enhanced Raman spectroscopy (SERS) are studied with the purpose of optimizing SERS substrates. Various gold and silver films made by evaporation and subsequent annealing give different morphologies and compositions of nanoparticles and thus different position of the SPR peak. SERS measurements of 4-mercaptobenzoic acid obtained from these films reveal that the proximity of the SPR peak to the exciting laser wavelength is not the only factor leading to the highest Raman enhancement. Silver nanoparticles evaporated on top of larger gold nanoparticles show higher SERS than gold-silver alloyed nanoparticles, in spite of the fact that the SPR peak of alloyed nanoparticles... Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=2560342 Wed, 01 Jul 2009 18:31:07 +0100 2560342 http://www.hindawi.com/journals/rlo/2008/919403.html Wide wavelength tuning by a variable reflective output coupler is demonstrated in high-power double-clad Tm3+-doped silica fiber lasers diode-pumped at ∼790  nm. Varying the output coupling from 96% to 5%, the laser wavelength is tuned over a range of 106  nm from 1949 to 2055  nm. The output power exceeds 20  W over 90-nm range and the maximum output power is 32  W at 1949  nm for 51-W launched pump power, corresponding to a slope efficiency of ∼70%. Assisted with different fiber lengths, the tuning range is expanded to 240  nm from 1866 to 2107  nm with the output power larger than 10  W. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=2468387 Wed, 10 Jun 2009 05:16:39 +0100 2468387 http://www.hindawi.com/journals/rlo/2008/253634.html The data pulse delay based on slow light induced by stimulated Brillouin scattering (SBS) in a nonuniform dispersion decreasing fiber (DDF) is demonstrated experimentally, and the distortions of data pulses at different beat frequencies are studied. We found that a delay exceeding a pulse width can be achieved at particular beat frequency, and the DDF has larger delay versus gain slope coefficient with much better output pulse quality than single-mode fiber. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=2468386 Wed, 10 Jun 2009 05:16:39 +0100 2468386 http://www.hindawi.com/journals/rlo/2008/613986.html The transmission speed of optical network strongly depends on the impact of higher order dispersion. In presence of coherent crosstalk, which cannot be otherwise controlled by optical filtering, the impact of higher order dispersions becomes more pronounced. In this paper, the general expressions, that describe pulse deformation due to second- and fourth-order dispersions in a single-mode fiber, are given. The responses for such even-order dispersions, in presence of coherent crosstalk, are characterized by waveforms with long trailing edges. The transmission quality of optical pulses, due to both individual and combined influence of second- and fourth-order dispersions, is studied in this paper. Finally, the pulse shape and eye diagrams are obtained. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=2468385 Wed, 10 Jun 2009 05:16:39 +0100 2468385 http://www.hindawi.com/journals/rlo/2008/204828.html The role of Fermi resonance in formation of valence band of water Raman scattering was investigated. Simultaneous measurement of characteristics of bending and valence bands of water in D2O solutions, KBr, and KCl and using genetic algorithms in conjunction with variation methods allowed increasing accuracy of estimation of Fermi resonance coupling constant and of Fermi resonance contribution into formation of water Raman valence band. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=2468384 Wed, 10 Jun 2009 05:16:39 +0100 2468384 http://www.hindawi.com/journals/rlo/2008/865092.html We report on hybrid mode-locked laser operation of a tapered semiconductor amplifier in an external ring cavity, generating pulses as short as 0.5 ps at 88.1 MHz with an average power of 60 mW. The mode locking is achieved through a combination of a multiple quantum well saturable absorber (>10% modulation depth) and an RF current modulation. This designed laser has 20 nm tuning bandwidth in continuous wave and 10 nm tuning bandwidth in mode locking around 786 nm center wavelength at constant temperature. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=2468383 Wed, 10 Jun 2009 05:16:39 +0100 2468383 http://www.hindawi.com/journals/rlo/2008/163937.html A newly proposed strong harmonic-expansion method is applied to the laser-Lorenz equations to analytically construct a few typical solutions, including the first few expansions of the well-known period-doubling cascade that characterizes the system in its self-pulsing regime of operation. These solutions are shown to evolve in accordance with the driving frequency of the permanent solution that we recently reported to illustrate the system. The procedure amounts to analytically construct the signal Fourier transform by applying an iterative algorithm that reconstitutes the first few terms of its development. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=2468382 Wed, 10 Jun 2009 05:16:39 +0100 2468382 http://www.hindawi.com/journals/rlo/2009/981620.html We demonstrated a novel technique for all-optical 2-to-4 level amplitude-shift keying (ASK) coding based on a fiber optical parametric amplifier. A 20-Gb/s signal is realized by multiplexing two 10-Gb/s data streams. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=2468381 Wed, 10 Jun 2009 05:16:39 +0100 2468381 http://www.hindawi.com/journals/rlo/2009/481010.html The spectral behavior of single and multiple phase shifts tilted fiber Bragg gratings has been experimentally investigated. To this aim, a simple and cost-effective postprocessing technique based on local thermal treatment was used to create arbitrary phase shifts along the tilted grating structure. In particular, UV written tilted fiber Bragg gratings were treated by the electric arc discharge to erase the refractive index modulation in well-defined regions. We demonstrate that these defects give rise to interference pattern for all modes, and thus defect states can be achieved within all the attenuation bands, enabling a simple wavelength independent spectral tailoring of this class of devices. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=2468380 Wed, 10 Jun 2009 05:16:39 +0100 2468380 http://www.hindawi.com/journals/rlo/2009/276538.html We present for the first time a theoretical model of Er3+-Tm3+-Pr3+ codoped fiber pumped with both 800 nm and 980 nm lasers to explore possibility of this co-doped system as all-wave fiber amplifier. The rate and power propagation equations of the model are solved numerically and the dependence of the gains at 1310, 1470, 1530, 1600, 1650 nm windows on fiber length is calculated. The results show that with pump power of 200 mW/200 mW, when the concentrations of Pr3+, Tm3+, Er3+ are around 1.7×1024, 3.9×1024, 1.2×1024 (ions/m3), respectively, the signals at 1310, 1470, 1530, 1600, 1650 nm may be nearly equally amplified with gain of 13–16.0 dB in the active fiber with length of 23.5 m; the co-doping concentra... Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=2468379 Wed, 10 Jun 2009 05:16:39 +0100 2468379 http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2009/481010 The spectral behavior of single and multiple phase shifts tilted fiber Bragg gratings has been experimentally investigated. To this aim, a simple and cost-effective postprocessing technique based on local thermal treatment was used to create arbitrary phase shifts along the tilted grating structure. In particular, UV written tilted fiber Bragg gratings were treated by the electric arc discharge to erase the refractive index modulation in well-defined regions. We demonstrate that these defects give rise to interference pattern for all modes, and thus defect states can be achieved within all the attenuation bands, enabling a simple wavelength independent spectral tailoring of this class of devices. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=2328435 Thu, 16 Apr 2009 11:12:51 +0100 2328435 http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2009/981620 We demonstrated a novel technique for all-optical 2-to-4 level amplitude-shift keying (ASK) coding based on a fiber optical parametric amplifier. A 20-Gb/s signal is realized by multiplexing two 10-Gb/s data streams. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=2297161 Sun, 29 Mar 2009 07:45:40 +0100 2297161 http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2008/163937 A newly proposed strong harmonic-expansion method is applied to the laser-Lorenz equations to analytically construct a few typical solutions, including the first few expansions of the well-known period-doubling cascade that characterizes the system in its self-pulsing regime of operation. These solutions are shown to evolve in accordance with the driving frequency of the permanent solution that we recently reported to illustrate the system. The procedure amounts to analytically construct the signal Fourier transform by applying an iterative algorithm that reconstitutes the first few terms of its development. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=1838189 Tue, 30 Sep 2008 16:38:05 +0100 1838189 http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2008/919403 Wide wavelength tuning by a variable reflective output coupler is demonstrated in high-power double-clad Tm3+-doped silica fiber lasers diode-pumped at ∼790  nm. Varying the output coupling from 96% to 5%, the laser wavelength is tuned over a range of 106  nm from 1949 to 2055  nm. The output power exceeds 20  W over 90-nm range and the maximum output power is 32  W at 1949  nm for 51-W launched pump power, corresponding to a slope efficiency of ∼70%. Assisted with different fiber lengths, the tuning range is expanded to 240  nm from 1866 to 2107  nm with the output power larger than 10  W. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=1618360 Mon, 14 Jul 2008 14:02:58 +0100 1618360 http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2008/253634 The data pulse delay based on slow light induced by stimulated Brillouin scattering (SBS) in a nonuniform dispersion decreasing fiber (DDF) is demonstrated experimentally, and the distortions of data pulses at different beat frequencies are studied. We found that a delay exceeding a pulse width can be achieved at particular beat frequency, and the DDF has larger delay versus gain slope coefficient with much better output pulse quality than single-mode fiber. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=1618359 Mon, 14 Jul 2008 14:02:58 +0100 1618359 http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2008/613986 The transmission speed of optical network strongly depends on the impact of higher order dispersion. In presence of coherent crosstalk, which cannot be otherwise controlled by optical filtering, the impact of higher order dispersions becomes more pronounced. In this paper, the general expressions, that describe pulse deformation due to second- and fourth-order dispersions in a single-mode fiber, are given. The responses for such even-order dispersions, in presence of coherent crosstalk, are characterized by waveforms with long trailing edges. The transmission quality of optical pulses, due to both individual and combined influence of second- and fourth-order dispersions, is studied in this paper. Finally, the pulse shape and eye diagrams are obtained. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=1618358 Mon, 14 Jul 2008 14:02:58 +0100 1618358 http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2008/204828 The role of Fermi resonance in formation of valence band of water Raman scattering was investigated. Simultaneous measurement of characteristics of bending and valence bands of water in D2O solutions, KBr, and KCl and using genetic algorithms in conjunction with variation methods allowed increasing accuracy of estimation of Fermi resonance coupling constant and of Fermi resonance contribution into formation of water Raman valence band. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=1618357 Mon, 14 Jul 2008 14:02:58 +0100 1618357 http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2008/865092 We report on hybrid mode-locked laser operation of a tapered semiconductor amplifier in an external ring cavity, generating pulses as short as 0.5 ps at 88.1 MHz with an average power of 60 mW. The mode locking is achieved through a combination of a multiple quantum well saturable absorber (>10% modulation depth) and an RF current modulation. This designed laser has 20 nm tuning bandwidth in continuous wave and 10 nm tuning bandwidth in mode locking around 786 nm center wavelength at constant temperature. (Source: Research Letters in Optics) Research Letters in Optics journals http://www.medworm.com/rss/comments.php?id=1618356 Mon, 14 Jul 2008 14:02:58 +0100 1618356