Impact of dispersion on pulse dynamics in chirped-pulse fiber lasers

Cataloged from PDF version of article.We report on a systematic study of an environmentally stable mode-locked Yb-doped fiber laser operating in the chirped-pulse regime. The linear cavity chirped-pulse fiber laser is constructed with a saturable absorber mirror as nonlinear mode-locking mechanism and a nonlinearity-free transmission-grating-based stretcher/compressor for dispersion management. Mode-locked operation and pulse dynamics from strong normal to strong anomalous total cavity dispersion in the range of +2.5 to -1.6 ps(2) is experimentally studied. Strongly positively chirped pulses from 4.3 ps (0.01 ps(2)) to 39 ps (2.5 ps(2)) are obtained at normal net-cavity dispersion. In the anomalous dispersion regime, the laser generates average soliton feature negatively chirped pulses with autocorrelation pulse durations from 0.8 ps (-0.07 ps(2)) to 3.9 ps (-1.6 ps(2)). The lowered peak power due to the pulse stretching allows one to increase the double pulse threshold. Based on the numerical simulation, different regimes of mode locking are obtained by varying the intra-cavity dispersion, and the characteristics of average soliton, stretched-pulse, wave-breaking-free and chirped-pulse regimes are discussed

Soliton excitation in waveguide arrays with an effective intermediate dimensionality

We reveal and observe experimentally significant modifications undertaken by discrete solitons in waveguide lattices upon the continuous transformation of the lattice structure from one-dimensional to two-dimensional. Light evolution and soliton excitation in arrays with a gradually increasing number of rows are investigated, yielding solitons with an effective reduced dimensionality residing at the edge and in the bulk of the lattice.Comment: 14 pages, 5 figures, to appear in Physical Review Letter

High speed laser drilling of metals using a high repetition rate, high average power ultrafast fiber CPA system

We present an experimental study on the drilling of metal targets with ultrashort laser pulses at high repetition rates (from 50 kHz up to 975 kHz) and high average powers (up to 68 Watts), using an ytterbium-doped fiber CPA system. The number of pulses to drill through steel and copper sheets with thicknesses up to 1 mm have been measured as a function of the repetition rate and the pulse energy. Two distinctive effects, influencing the drilling efficiency at high repetition rates, have been experimentally found and studied: particle shielding and heat accumulation. While the shielding of subsequent pulses due to the ejected particles leads to a reduced ablation efficiency, this effect is counteracted by heat accumulation. The experimental data are in good qualitative agreement with simulations of the heat accumulation effect and previous studies on the particle emission. However, for materials with a high thermal conductivity as copper, both effects are negligible for the investigated processing parameters. Therefore, the full power of the fiber CPA system can be exploited, which allows to trepan high-quality holes in 0.5mm-thick copper samples with breakthrough times as low as 75 ms. © 2008 Optical Society of America

Observation of two-dimensional surface solitons in anisotropic waveguide arrays

We report on the experimental observation of two-dimensional surface waves localized at the edge or in the corner of femtosecond laser-written waveguide arrays in fused silica. Increasing the power of the input beam allows one to observe a clear transition from a linear diffraction pattern to localized nonlinear surface states, which can exist at the interface only above a certain power threshold.Comment: 13 pages, 4 figure

Experimental demonstration of a suspended diffractively coupled optical cavity

All-reflective optical systems are under consideration for future gravitational wave detector topologies. One approach in proposed designs is to use diffraction gratings as input couplers for Fabry–Perot cavities. We present an experimental demonstration of a fully suspended diffractively coupled cavity and investigate the use of conventional Pound–Drever–Hall length sensing and control techniques to maintain the required operating condition

Anderson cross-localization

We report Anderson localization in two-dimensional optical waveguide arrays with disorder in waveguide separation introduced along one axis of the array, in an uncorrelated fashion for each waveguide row. We show that the anisotropic nature of such disorder induces a strong localization along both array axes. The degree of localization in the cross-axis remains weaker than that in the direction in which disorder is introduced. This effect is illustrated both theoretically and experimentally.Comment: 4 pages, 4 figures, to appear in Optics Letter

Diffraction-managed solitons and nonlinear beam diffusion in modulated waveguide arrays

We present the first experimental observation of nonlinear beam diffusion and formation of diffraction-managed solitons in periodically-curved arrays of coupled optical waveguides created using femtosecond laser writing in silica glass, and titanium indiffusion in LiNbO3 crystals

Compact surface fano states embedded in the continuum of waveguide arrays

We describe theoretically and observe experimentally the formation of a surface state in a semi-infinite waveguide array with a side-coupled waveguide, designed to simultaneously achieve Fano and Fabry-Perot resonances. We demonstrate that the surface mo

Transição da pessoa com doença oncológica avançada de oncologia para cuidados paliativos: O papel do enfermeiro especialista em enfermagem de saúde mental e psiquiátrica

Este relatório de estágio procura estruturar o percurso desenvolvido durante o 2º Estágio do 2º Mestrado em Associação de Enfermagem de Saúde Mental e Psiquiátrica e assim demonstrar a aquisição das Competências Especificas do Enfermeiro Especialista em Enfermagem de Saúde Mental e Competências de Mestre. Grande parte das pessoas com doença oncológica avançada não têm acesso de forma sistemática às intervenções de Cuidados Paliativos. Foi utilizada a metodologia de projeto para dar resposta ao problema identificado: “A transição da pessoa com doença avançada para CP é muitas vezes realizada de forma abrupta e sem preparação gradual”. Ao longo do trabalho foi evidenciado o papel do Enfermeiro Especialista em Enfermagem de Saúde Mental e Psiquiátrica como uma mais valia nesta transição pois, além das competências de avaliação das necessidades em saúde mental, só ele poderá intervir com cuidados psicoterapêuticos, sócio-terapêuticos, psicossociais e psicoeducacionais permitindo assim promover a melhoria da qualidade dos cuidados de saúde

Ultra-large mode area fibers for high power lasers

The most recent advances on ultra-large mode area fibers for high-power operation will be presented. Moreover, an approach to synthetize ultra-large mode area fibers that circumvents technical limitations by using multi-core fibers will be discussed