Mid-Infrared Soliton and Raman Frequency Comb Generation in Silicon Microrings

We numerically study the mechanisms of frequency comb generation in the mid-infrared spectral region from cw pumped silicon microring resonators. Coherent soliton comb generation may be obtained even for a pump with zero linear cavity detuning, through suitable control of the effective lifetime of free-carriers from multiphoton absorption, which introduces a nonlinear cavity detuning via free-carrier dispersion. Conditions for optimal octave spanning Raman comb generation are also described

Dynamics of microresonator frequency comb generation: models and stability

Microresonator frequency combs hold promise for enabling a new class of light sources that are simultaneously both broadband and coherent, and that could allow for a profusion of potential applications. In this article, we review various theoretical models for describing the temporal dynamics and formation of optical frequency combs. These models form the basis for performing numerical simulations that can be used in order to better understand the comb generation process, for example helping to identify the universal combcharacteristics and their different associated physical phenomena. Moreover, models allow for the study, design and optimization of comb properties prior to the fabrication of actual devices. We consider and derive theoretical formalisms based on the Ikeda map, the modal expansion approach, and the Lugiato-Lefever equation. We further discuss the generation of frequency combs in silicon resonators featuring multiphoton absorption and free-carrier effects. Additionally, we review comb stability properties and consider the role of modulational instability as well as of parametric instabilities due to the boundary conditions of the cavity. These instability mechanisms are the basis for comprehending the process of frequency comb formation, for identifying the different dynamical regimes and the associated dependence on the comb parameters. Finally, we also discuss the phenomena of continuous wave bi- and multistability and its relation to the observation of mode-locked cavity solitons

Dynamics of microresonator frequency comb generation: models and stability

Microresonator frequency combs hold promise for enabling a new class of light sources that are simultaneously both broadband and coherent, and that could allow for a profusion of potential applications. In this article, we review various theoretical models for describing the temporal dynamics and formation of optical frequency combs. These models form the basis for performing numerical simulations that can be used in order to better understand the comb generation process, for example helping to identify the universal combcharacteristics and their different associated physical phenomena. Moreover, models allow for the study, design and optimization of comb properties prior to the fabrication of actual devices. We consider and derive theoretical formalisms based on the Ikeda map, the modal expansion approach, and the Lugiato-Lefever equation. We further discuss the generation of frequency combs in silicon resonators featuring multiphoton absorption and free-carrier effects. Additionally, we review comb stability properties and consider the role of modulational instability as well as of parametric instabilities due to the boundary conditions of the cavity. These instability mechanisms are the basis for comprehending the process of frequency comb formation, for identifying the different dynamical regimes and the associated dependence on the comb parameters. Finally, we also discuss the phenomena of continuous wave bi- and multistability and its relation to the observation of mode-locked cavity solitons

Differential Proteome Analysis of the Preeclamptic Placenta Using Optimized Protein Extraction

The human placenta is a difficult tissue to work with using proteomic technology since it contains large amounts of lipids and glycogen. Both lipids and glycogen are known to interfere with the first step in the two-dimensional polyacrylamide gel electrophoresis (2D-PAGE), the isoelectric focusing. In order to gain the best possible protein separation on 2D-PAGE, an optimized sample preparation protocol for placental proteins was developed. Two different buffers, urea/CHAPS and Hepes, were used for solubilization in combination with six different precipitation methods. The removal of glycogen from the samples by centrifugation was crucial for the final proteome maps. Solubilization with urea/CHAPS in combination with dichloromethane/methanol or acidified acetone proved to be the best precipitation procedures. When applied to clinical placenta samples apolipoprotein A1 was found to be accumulated in the preeclamptic placenta, where it may either have a nutritional effect or act as a modifier of signal transduction

Control of Kerr Cavity Soliton Combs by Chirped Pumping

Pumping a dispersive Kerr cavity with chirped pump pulses permits to control the trapping position of temporal cavity soliton combs. Stability of single-cavity soliton generation is greatly enhanced by pump chirping

Novel generation schemes for stable soliton states in optical microcavities

The excitation of Kerr optical frequency combs(OFC) is frequently non-deterministic and remains a cumbersome problem in many practical situations. While standard techniques to generate Kerr solitons in passive resonators employ a continuous wave pump, recently pulsed pumping has also been proposed. In this study we individuate and classify OFC states in a phase space defined by an experimental set of coordinates and triggered by a general super-Gaussian chirped driving field. Our numerical analysis shows how the soliton drifts caused by the phase modulation of the input field accelerate the dynamics and convergence towards a stable soliton stat

Vacuum-assisted wound closure versus alginate for the treatment of deep perivascular wound infections in the groin after vascular surgery

BackgroundVacuum-assisted wound closure (VAC) therapy may heal wounds faster than conventional dressings after surgical debridement of perivascular groin infections after vascular surgery.MethodsPatients with deep infected wounds (Szilagyi grade III) were surgically revised and left open for secondary healing, then randomized to either VAC or alginate (Sorbalgon) therapy, between February 2007 and November 2011. To test the hypothesis, it was calculated that 42 patients needed to be included (90% power, 5% level of significance). It was decided to perform an interim analysis after inclusion of 20 patients.ResultsAmong 66 patients undergoing groin revision, 20 patients were included in this study. Patients were randomized to VAC (n = 10) or alginate (n = 10). The two groups were comparable in patient and wound characteristics. Time to full skin epithelialization was significantly shorter in the VAC group (median, 57 days) compared with the alginate group (median, 104 days; P = .026). The number of positive wound cultures of bacteria and C-reactive protein values decreased equally in both groups between surgical revision and day 21. One femur amputation was performed in each group as a consequence of the groin infection, one patient died during the in-hospital stay in the alginate group, and none died in the VAC group.ConclusionsVAC achieves faster healing than alginate therapy after wound debridement for deep perivascular wound infections in the groin after vascular surgery. This finding does not allow further inclusion of patients from an ethical point of view, and this study was, therefore, stopped prematurely

Nonlinear beam self-imaging and self-focusing dynamics in a GRIN multimode optical fiber: theory and experiments

Beam self-imaging in nonlinear graded-index multimode optical fibers is of interest for many applications, such as implementing a fast saturable absorber mechanism in fiber lasers via multimode interference. We obtain an exact solution for the nonlinear evolution of first and second order moments of a laser beam carried by a graded-index multimode fiber, predicting that the spatial self-imaging period does not vary with power. Whereas the amplitude of the oscillation of the beam width is power-dependent. We have experimentally studied the longitudinal evolution of beam self-imaging by means of femtosecond laser pulse propagation in both the anomalous and the normal dispersion regime of a standard telecom graded-index multimode optical fiber. Light scattering out of the fiber core via visible fluorescence emission and harmonic wave generation permits us to directly confirm that the self-imaging period is invariant with power. Spatial shift and splitting of the self-imaging process under the action of self-focusing are also emphasized

Organic Cultivation of Lemon Ballm (Melissa officinalis) in Macedonia

The possibility for perspective growing of medicinal, aromatic and spice plants, can be expected only if their cultivation is based on the principles of organic farming. The cultivation of this group of plants is usually associated with satisfactory yield level and raw materials with uniform quality. This paper contains the most important features of lemon balm (Melissa officinalis), and methods of cultivation. Data of two annual activities are presented and they are related with organic system of cultivation in the central part of Macedonia. The objective of this study is to analyze, determine and demonstrate the economic viability of lemon balm organic production with irrigation. In the first year, there were only two moving, yielding 500 kg/ha of above-ground plant dry mass. In the second year, there were three moving, yielding 6,775 kg/ha of above-ground plant dry mass. Economic analysis is proved that profitability in organically produced lemon balm is obtained in the second year of growing when the profit reached $6,150/ha. Key words: Organic, lemon balm, yield, pofitability