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This article provides a review of current information about periodontal bacteria, their activities within dental plaque biofilm, their interactions with the host immune system, and the infections with which they are associated. Periodontal disease, plaque formation, and the host immune response are also discussed, as are antimicrobial measures used to control the bacteria and the disease.

We show that the authors of the preceding Comment [Schurmann and Serov, preceding Comment, Phys. Rev. A 100, 057801 (2019)10.1103/PhysRevA.100.057801] have not found a more general family of solutions of the generalized nonlinear Schrodinger equation (NLSE) with higher-order dispersions. Moreover, the necessary and sufficient conditions for the existence of the bounded traveling solutions presented by Kruglov (arXiv:1905.00960v1; arXiv:1905.00960v2) differ from the appropriate conditions in the preceding Comment. We have found (see the work by Kruglov) a regular method which yields the traveling-wave solutions of the generalized NLSE. This method differ from the approach presented in the preceding Comment. Moreover, our method yields a periodic bounded solution which is expressed in terms of elliptic Jacobi functions.

An exact solitary wave solution is presented for the nonlinear Schrodinger equation governing the propagation of pulses in optical fibers including the effects of second, third and fourth order dispersion. The stability of this soliton-like solution with sech2 shape is proven by the sign-definiteness of the operator and an integral of the Sobolev type. The main criteria governing the existence of such stable localized pulses propagating in optical fibers are also formulated. A unique feature of these soliton-like optical pulses propagating in a fiber with higher order dispersion is that their parameters satisfy efficient scaling relations. The main soliton solution term given by perturbation theory is also presented when absorption or gain is included in the nonlinear Schrodinger equation. We anticipate that this type of stable localized pulses could find practical applications in communications, slow-light devices and ultrafast lasers., 4 pages 3 Figures

The drying behavior of polyamide-imide (PAI)/graphene-oxide nanosheets (GO) in dimethylacetamide (DMAc) with and associated anisotropy development were determined using a real-time measurement system that tracks weight loss, thickness, in and out of plane birefringence. Initially optically isotropic cast films develop out of plane optical anisotropy at a critical solvent concentration. For PAI/DMAc solution the decrease of initial casting thickness lead to earlier onset of out of plane birefringence development caused primarily by increased depletion rate of solvent. Addition of GO content resulted in increased evaporation rate caused by reduction of hygroscopicity of DMAc in the presence of GO as shown by contact angle measurements. Planar orientation of nanosheets resulted in excellent helium-barrier properties even at very small GO concentrations.

A major step in our understanding of brain function is to determine how neural circuits are altered in their function by signaling molecules or neuromodulators. Neuromodulation is the neurochemical process that modifies the computations performed by a neuron or network based on changing the functional needs or behavioral state of the subject. These modulations have the effect of altering the responsivity to synaptic inputs. Early sensory processing areas, such as the main olfactory bulb, provide an accessible window for investigating how neuromodulation regulates the functional states of neural networks and influences how we process sensory information. Olfaction is an attractive model system in this regard because of its relative simplicity and because it links primary olfactory sensory neurons to higher olfactory and associational networks. Likewise, centrifugal fibers from higher order brain centers target neurons in the main olfactory bulb to regulate synaptic processing. The neuromodulatory systems that provide regulatory inputs and play important roles in olfactory sensory processing and behaviors include the endocannabinoid system, the dopaminergic system, the cholinergic system, the noradrenergic system and the serotonergic system. Here, we present a brief survey of neuromodulation of olfactory signals in the main olfactory bulb with an emphasis on the endocannabinoid system.

We demonstrate an improved configuration of an all-fibre laser that incorporates three separate gain sections. This gives 5 nJ pulses that can be compressed to 200 fs and are suitable as a seed for a high power CPA system.

Multifunctional single and triple-layer films exhibiting flexibility, enhanced modulus and gas barrier properties were developed using a soluble polyamide-imide (PAI) in dimethylacetamide (DMAc) with ammonium-modified montmorillonite (MMT, Cloisite 30B) mineral clay. The drying behavior and associated anisotropy development were determined real-time, using a newly developed real-time measurement system. Out-of-plane birefringence development takes place earlier for thinner neat samples caused primarily by increased depletion rate of solvent. Addition of organoclay content resulted in a decrease in evaporation rate of solvent due to planar orientation of well exfoliated nanoplatelets as shown by TEM images and WAXS. This is in agreement with the out-of-plane anisotropy development observed during drying. Beyond a critical solid wt%, out-of-plane birefringence started to increase earlier with organoclay addition. In the case of multi-layer organoclay reinforced PAI films, the drying behavior of each individual layer was tracked and a complementary drying model is proposed. Planar orientation of nanoplatelets resulted in high helium-barrier properties.

A repetition rate of 506 kHz is achieved in an all-fibre laser, mode-locked with a nonlinear amplifying loop mirror. The laser produces 7 nJ pulses with a broad 7.5 nm spectral width, compressible to 540 fs.

We report on an environmentally stable, Yb-doped, all-normal dispersion, mode-locked fibre laser that is capable of creating broadband pulses with ultra-low repetition rates. Specifically, through careful positioning of fibre sections in an all-PM-fibre cavity mode-locked with a nonlinear amplifying loop mirror, we achieve stable pulse trains with repetition rates as low as 506 kHz. The pulses have several nanojules of energy and are compressible down to ultrashort (< 500 fs) durations., 5 pages, 4 figures, optics letters submission

Topic: Optical information and image processing; International audience; This paper provides the analysis of wavelength converted pulses obtained with a simple semiconductor optical amplifier (SOA)-based wavelength conversion scheme, which exploits cross phase modulation (XPM) in an SOA in conjunction with shifted filtering. The analysis includes experimental measurements of the back-to-back system performances as well as frequency-resolved optical gating (FROG) characterisations of the wavelength converted pulses. These measurements are implemented at different bit rates up to 80 Gbit/s and for both red and blue-shifted filtering, particularly showing different patterning effect dependencies of red and blue-shifting techniques. This analysis is developed by the addition of a numerical study which corroborates the experimental results. A further understanding of the different performances of red and blue filtering techniques, presented in the literature, can thus be proposed. The placement of the filter to undertake red-shifted filtering (RSF) allows us to achieve very short pulse widths but high bit rate operation is limited by pattern effects. The blue-shifted filtering (BSF) technique shows optimum performance as regards to patterning effects even if the wavelength converted pulses can be larger.

Optical parametric amplification is an important nonlinear process in photonic crystal fibres driven by the small effective area and the special dispersion characteristics of these fibres. Aside from its role in supercontinuum generation, parametric amplification can lead to efficient wavelength conversion, limited primarily by the uniformity of the diameter of currently available fibres. The related Bragg scattering process can be used for both wavelength conversion and optical switching, again limited by the physical characteristics of the fibres used.

Recently, metal complexes of the isomers and analogs of porphyrin have become important model compounds for heme enzymes and proteins. While the chemistry of metalloporphyrins as heme models still attracts attention, the isomers and analogs of porphyrins provide insight into the biological choice of porphine as the macrocycle of choice and also help model reactive intermediates, such as high valent oxidation states. In this mini-review, we discuss the heme-relevant chemistry of N-confused porphyrin, an isomer of porphyrin with an inverted pyrrole ring, and focus on the chemistry of manganese, iron, and cobalt. The metallation chemistry of this macrocycle is more diverse than normal porphyrin, and involves tautomerization, C–H bond activation, the Lewis basicity of the external nitrogen, and issues with nucleophilic sensitivity. Despite the challenges posed by N-confused porphyrin, significant progress has been made toward generating heme-model complexes with this macrocycle.

The issue of how best to cleave PMMA microstructured polymer optical fibres (mPOF) is addressed. The impact of the following parameters on the cleaving process is considered: (i) temperature of the cutting blade, (ii) temperature of the platen holding the fibre, (iii) time allowed for thermal equilibration between fibre and platen, (iv) blade speed, and (v) blade condition. The strong influence of a temperature-dependent phase transition in the polymer on the cleaving process is established. Optically acceptable mPOF end-faces can be achieved but only over a limited range of cleavage conditions.

Two high resolution single X-ray crystal structures of meso-substituted free-base corroles are presented: 5,10,15-triphenylcorrole (1) and 5,10,15-tris(pentafluorophenyl)corrole (2). The internal NH protons are clearly assignable to different nitrogens, which represents the two tautomer limits of corrole.

The characteristics of 40-Gbit/s pulses generated by exploiting the nonlinear characteristics of a Mach-Zender Lithium Niobate modulator are presented. A high spectral resolution frequency resolved optical gating apparatus has been developed to allow for the complete characterization of the intensity and phase of these pulses. The use of these measurements to simplify the design and optimization of an 80-Gbit/s pulse source, based on this 40-Gbit/s source followed by a nonlinear fiber compressor and multiplexer, is also demonstrated.

Since its discovery as a side product in acid catalyzed condensations in 1994, the metal chemistry of N-confused porphyrins has grown exponentially. Due to the location of an external nitrogen on the porphyrin skeleton, different binding modes are being discovered for N-confused porphyrin as compared to tetraphenylporphyrin. In this paper, the metal chemistry of N-confused porphyrin is discussed, reviewing coordination modes and literature on the metal complexes to date.

Pulse propagation in high gain optical fiber amplifiers with normal group velocity dispersion is studied using numerical simulations of a generalized nonlinear Schrodinger equation including a complex Lorentzian gain profile. In particular, when the bandwidth of the input pulse is significantly less than that of the amplifier transition, an initial period of propagation where parabolic pulse characteristics are observed is followed by a solitary wave regime where the pulse temporal and spectral widths are stabilized by the limiting effect of the transition. The intensity and chirp characteristics of the resulting solitary pulse are considered in detail and dimensional analysis yields an empirical expression for the solitary wave peak power in excellent agreement with simulations.

This paper reviews the use of frequency-resolved optical gating (FROG) to characterize mode-locked lasers producing ultrashort pulses suitable for high-capacity optical communications systems at wavelengths around 1550 nm, Second harmonic generation (SHG) FROG is used to characterize pulses from a passively mode-locked erbium-doped fiber laser, and both single-mode and dual-mode gain-switched semiconductor lasers. The compression of gain-switched pulses in dispersion compensating fiber is also studied using SHG-FROG, allowing optimal compression conditions to be determined without a priori assumptions about pulse characteristics. We also describe a fiber-based FROG geometry exploiting cross-phase modulation and show that it is ideally suited to pulse characterization at optical communications wavelengths. This technique has been used to characterize picosecond pulses with energy as low as 24 pJ, giving results in excellent agreement with SHG-FROG characterization, and without any temporal ambiguity in the retrieved pulse.

The ultrashort pulse measurement technique of frequency-resolved optical gating (FROG) has been used to characterize the propagation of picosecond pulses at wavelengths around 1550 nm in a variety of different optical fibers used in communications applications. In this paper, we review the use of the FROG technique for ultrashort pulse measurements, discussing in particular several practical issues of importance for accurate results at wavelengths around 1550 nm. We describe the use of FROG measurements to characterize pulse distortion in standard, dispersion-shifted, and erbium-doped optical fiber, and show how they provide direct measurements of complex intensity and phase evolution arising from the interplay of fiber nonlinearity and dispersion. We also discuss the application of the FROG technique to accurately measure the dispersive and the nonlinear parameters of optical fibers, and we present results for standard single-mode fiber in good agreement with specifications.

We present results from both theoretical and experimental studies of the noise characteristics of mode-locked superfluorescent lasers. The results show that observed macroscopic broadband amplitude noise on the laser pulse train has its origin in quantum noise-initiated ''phase-wave'' fluctuations, and we find an associated phase transition in the noise characteristics as a function of laser cavity detuning.

A series of experiments and numerical simulations have been carried out studying the transition between stable and unstable behaviour observed in a mode-locked argon laser when the cavity length is decreased from the optimum value associated with stable operation. Good qualitative agreement is found between the experiments and the numerical simulations, and the pulse characteristics in this regime are found to be determined by the interplay of the coherent atom - field interaction, the cavity detuning, the time-varying loss of the mode-locker and the recovery of the atomic inversion due to repumping.

Polarization modulation instability (PMI) has been utilised to generate amplitude modulated light pulses where the modulation frequency is continuously tuneable from 3.5 THz to 7.0 THz. The tuneability is achieved by varying the tension in a low-birefringent single-mode fiber which is wrapped around a spool.

The activation spectrum of the photosensitising agent aluminium phthalocyanine chloride (ClAlPc) was determined using cultured meningioma cells as the biological target. Cells were irradiated with tunable lasers over the wavelength range 605–1000 nm and photocytotoxicity was measured 24 h later by a tetrazolium assay. The photoactivation spectrum was found to be relatively narrow with a sharply defined maximum at 675–680 nm, a readily accessible wavelength for commercially available diode lasers. The absorption spectrum of ClAlPc in aqueous solution was broad and featureless, contrasting markedly with the activation spectrum. However, as the content of an organic solvent (dimethylsulphoxide) was increased, the absorption spectrum progressively resembled the activation spectrum. It is concluded that the absorption spectrum of ClAlPc in aqueous solution is determined by drug aggregation, which can be prevented by an organic environment. This implies that the active form of ClAlPc in cells is the monomeric species probably located in cellular membranes.

Modulation instability can occur in the normal dispersion regime only via cross-phase modulation. In a high birefringence fiber, cross-phase modulation between the pump waves on the two principal axes of the fiber generates two modulation instability sidebands separated by a frequency which is primarily determined by the birefringence and dispersion of the fiber, with a secondary dependence on the pump power. The superposition of these sidebands can generate an amplitude modulated pulse with modulation frequencies of up to 16 THz.

We present approximate but nevertheless highly accurate similariton solutions to the generalized nonlinear Schr\"odinger equation (NLSE) with varying parameters describing pulses propagating in fiber amplifiers and lasers with normal and anomalous dispersion. We also derive the analytical similariton solutions of the NLSE for the case when the pulses have a rectangular or ``smooth rectangular'' shape and when they have a kink and antikink shape. Numerical simulations are in excellent agreement with these analytical solutions describing self-similar linearly chirped pulses showing that they can be observed in realistic fiber geometries.

Polymer optical fibres (POF) have historically focused on applications in data transmission over short distances, using highly multimode step-index or graded-index fibre designs. This paper will focus on a qualitatively different type of polymer fibres - microstructured polymer optical fibres (mPOF) - which allow a wider variety of fibre designs and optical properties to be achieved. Fibres with similar properties to conventional step- and graded-index POF can be made for data transmission applications, as well as single-mode fibres which can be used for grating inscription and gratingbased sensing. The use of microstructures can also be extended to longer wavelengths for the transmission of THz radiation, and both solid-core and hollow-core mPOF-based THz waveguides have been demonstrated. Finally, the development and extension of mPOF to form metal-dielectric structures for the manufacture of metamaterials using fibre-drawing methods will be discussed. Such drawn-metamaterials with electric and magnetic responses at THz frequencies have been demonstrated.

This talk discusses theoretical and experimental investigations of self similar solutions of the equation governing pulse propagation in optical fibre amplifiers. Several such similariton solutions have been discovered and experimentally realized in the last decade.

Cross-phase modulation has been harnessed to construct a modulation instability laser operating at 514.5 nm. The laser output consists of orthogonally polarized upshifted and downshifted sideband pulses separated in wavelength by 2.1 nm from the pump. The laser configuration has been found to generate a much more stable source of terahertz modulated light pulses than the single-pass configuration previously used to demonstrate modulation instability in the visible. The extra stability arises from the feedback, which provides a seed for the modulation, and hence a reduction in the pump power necessary compared with the single-pass configuration, which in turn reduces the Raman gain, and the asymmetry of the sideband amplitudes. The sideband pulses can be combined to generate a modulated envelope of 4-THz oscillations with a duration of 10-15 ps. >

We develop a theory for pulses propagating in normal dispersion fiber amplifiers with constant and varying gain, and for dispersion-decreasing fibers, including the effect of third-order dispersion. These solutions of the generalized nonlinear Schr\"odinger equation are based on asymptotical methods, first-order perturbation theory, and a renormalization procedure. We have also found an explicit equation for the critical length corresponding to pulse breakup and a criterion which ensure the accuracy of the asymptotic solutions. This criterion is confirmed numerically, showing that the analytical description of the pulses and the critical length formulas developed here for fiber amplifiers and dispersion-decreasing fibers with third-order dispersion are very accurate.

We present an analytical solution for parabolic similaritons with saturation effects and new self-similar linearly chirped pulses generated in normal dispersion fibers with fast decaying gain, the Hyper-Gaussian pulse, suitable for low energy systems.

We demonstrate error free data transmission at 9.5 Gb/s at 636 nm through a record length of 50 m of microstructured polymer optical fiber. We observe minimal modal dispersion and a power penalty of 1dB.

Self similar solutions of nonlinear partial differential equations have been found with applications in many areas of Physics. The techniques used to find these solutions have been recently been applied to develop solutions of the Nonlinear Schrodinger Equation (NLSE) governing optical pulse propagation, where they are known as similaritons. This talk will discuss not only the well known parabolic and hyperbolic similaritons but also self similar solutions appropriate to amplifiers with gain saturation, together with their applications in high power amplifiers, and similariton lasers.

Recent studies have revealed an important type of optical pulse (similaritons) with parabolic profiles and linear frequency chirps that propagate in optical fiber amplifiers with constant and distributed gain [1]. In recent papers the effect of third-order fiber dispersion (TOD) on similariton pulse propagation has been studied in fibre amplifiers, and in mode-locked lasers [2]. In fact, the impact of TOD on parabolic pulses propagation is to generate optical shock-type instabilities as shown in Fig.1 (a) [3, 4].

We demonstrate the transmission of a 9.5Gb/s data signal through a record length of 50m of microstructured polymer optical fiber. The signal suffers from minimal modal dispersion and a power penalty of 1dB.

This paper discusses recent experiments demonstrating dramatic improvements in the tunability and power output of fiber optical parametric amplifiers constructed utilising both conventional fibers and photonic crystal fibers.

The noise characteristics of cross-phase modulation instability visible light produced in high-birefringence fibres have been investigated. Noise measurements were made on single sidebands, and on the intensity difference between upshifted and downshifted sidebands using single pass and fibre-laser configurations. The intensity difference noise for the single pass configuration was reduced by more than 25 dB below the single sideband noise, which was typically 35 dB above shot noise. Under certain conditions the intensity difference noise of the modulation instability laser sidebands could be reduced to the shot noise level, while the single sideband noise from the modulation instability laser could be reduced to 2 dB above shot noise. Raman gain on the low frequency sideband and attenuation in the fibre limited the attainable noise reduction.

We present a novel analytical solution and the conditions leading to accurate description of propagating pulses and critical length describing pulse break-up for the generalized nonlinear Schrodinger equation with third-order fiber dispersion and constant gain.

The phase-matching curves for the four-wave mixing effect of Bragg scattering in two fibers with opposite sign β(4) dispersion coefficients have been measured experimentally. The measured phase-matching curves are in good agreement with theoretical expectations, and their dependence on several key parameters has been determined.

We present an analytical solution for propagating pulses in normal dispersion fiber amplifiers, including the effect of third-order dispersion. The solution of the generalized nonlinear Schrodinger equation is based on asymptotic methods, first-order perturbation theory, and a renormalization procedure and leads to determination of the critical length corresponding to pulse breakup. We have also found and confirmed numerically the condition on the parameters that govern the propagation, as is necessary to ensure a highly accurate analytical description of the pulses and critical lengths in fiber amplifiers with third-order dispersion.

We report here the first demonstration of a mode-locked fiber laser delivering parabolic pulses (similaritons) at 1534 nm. The use of a Raman-based gain medium potentially allows its implementation at any wavelength. The 22nJ output similariton pulses have a true parabolic shape both in the time and spectral domains and a linear chirp. Linear recompression close to Fourier limit is demonstrated allowing us to obtain 6 ps compressed pulses with a compression factor of 75.

We demonstrate 5Gb/s transmission in a microstructured PMMA fibre at visible wavelengths. The source used in this measurement is generated by sum frequency mixing a CW Nd-YAG laser with a modulated L Band signal.

Recent advances in the drawing of photonic crystal fibres have enabled the development of fibre optic parametric oscillators generating coherent light tunable over wide regions of the visible and near IR spectrum.

This paper discusses recent developments which have led to dramatic improvements in the performance of optical parametric amplifiers, utilising both highly nonlinear fibers and photonic crystal fibers.

We experimentally demonstrate the phase matching curve for the Four-Wave-Mixing effect of Bragg Scattering in two Highly-Nonlinear-Fibers with opposite sign 4th order dispersion coefficients. The experimental results are fitted to theoretical predictions with good agreement.