Temporal dynamics of semiconductor lasers with optical feedback

Includes bibliographical references (page 5539).We measure the temporal evolution of the intensity of an edge emitting semiconductor laser with delayed optical feedback for time spans ranging from 4.5 to 65 ns with a time resolution from 16to 230 ps, respectively. Spectrally resolved streak camera measurements show that the fast pulsing of the total intensity is a consequence of the time delay and multimode operation of the laser. We experimentally observe that the instabilities at low frequency are generated by the interaction among different modes of the laser

Spatio-temporal dynamics in vertical cavity surface emitting lasers excited by fast electrical pulses

Includes bibliographical references (pages 320-321).We have measured the time average spatial intensity distribution and the spatio-temporal evolution of the spectrally resolved radiation emitted from broad-area vertical cavity surface emitting lasers (VCSEL) when pumped by a fast current pulse. We show that an intrinsic symmetry break exists due to geometrical asymmetry of the device structure and that the frequency separation between different modes allows the evaluation of the asymmetry factor. The space-time behavior shows the appearance of higher-order modes coexisting or alternating in time. The dynamical behavior shows a chirping infrequency

Temporal dynamics of semiconductor lasers with optical feedback

We measure the temporal evolution of the intensity of an edge emitting semiconductor laser with delayed optical feedback for time spans ranging from 4.5 to 65 ns with a time resolution from 16 to 230 ps, respectively. Spectrally resolved streak camera measurements show that the fast pulsing of the total intensity is a consequence of the time delay and multimode operation of the laser. We experimentally observe that the instabilities at low frequency are generated by the interaction among different modes of the laser.We acknowledge support of the European Community TMR program, the NSF Optoelectronic Computing System Center, the NSF (ECS 95-02888), CICYT Project No. TIC95-0563, and DGICYT Project No. SAB95-0674.Peer Reviewe

Volume extreme ultraviolet holographic imaging with numerical optical sectioning

Includes bibliographical references (pages 10622-10623).Three dimensional images were obtained using a single high numerical aperture hologram recorded in a high resolution photoresist with a table top λ = 46.9 nm laser. Gabor holograms were numerically reconstructed over a range of image planes by sweeping the propagation distance in the numerical reconstruction algorithm, allowing numerical optical sectioning. A robust three dimension image of a test object was obtained with numerical optical sectioning, providing a longitudinal resolution of approximately 2 μm and a lateral resolution of 164 nm

Sub 400 nm spatial resolution extreme ultraviolet holography with a table top laser

Includes bibliographical references (pages 9636-9637).We report sub-400 nm spatial resolution with Gabor holography obtained using a highly coherent table top 46.9 nm laser. The hologram was recorded in high resolution photoresist and subsequently digitized with an atomic force microscope. The final image was numerically reconstructed with a Fresnel propagator. Optimal reconstruction parameters and quantification of spatial resolution were obtained with a wavelet analysis and image correlation

Methodological framework for an integrated multi-scale vulnerability and resilience assessment

The deliverable illustrates the methodological framework to assess vulnerability and resilience across different temporal and spatial scales, acknowledging the different domains where the latter may manifest, and in particular in the natural and the built environment, allocating a large importance to the so called “critical infrastructures”, in social and economic systems. A set of four matrices has been developed to identify what aspects should be looked at before the impact, that is to say what shows the potential ability or inability to cope with an extreme; at the impact, addressing in particular the capacity (or incapacity) to sustain various types of stresses (in the form of acceleration, pressure, heat…); in the time immediately after the impact, as the ability (or inability) to suffer losses and still continue functioning; and in the longer term of recovery, as the capacity to find a new state of equilibrium in which the fragilities manifested during and after the impact are addressed. Developing the framework, a particular attention has been paid to the relationships among systems within the same matrix and among matrices, across spatial and temporal scales. A set of matrices has been developed for different natural hazards, including in particular landslides and floods, trying to include as much as possible what past cases, the international literature and prior experience of involved partners have indicated as relevant parameters and factors to look at. In this regard, the project builds on the state of the art, embedding what has been learned until now in terms of response capacity to a variety of stresses and in the meantime identifying gaps to be addressed by future research

Ablation and transmission of thin solid targets irradiated by intense extreme ultraviolet laser radiation

The interaction of an extreme ultraviolet (EUV) laser beam with a parylene foil was studied by experiments and simulation. A single EUV laser pulse of nanosecond duration focused to an intensity of 3 × 1010 W cm−2 perforated micrometer thick targets. The same laser pulse was simultaneously used to diagnose the interaction by a transmission measurement. A combination of 2-dimensional radiation-hydrodynamic and diffraction calculations was used to model the ablation, leading to good agreement with experiment. This theoretical approach allows predictive modelling of the interaction with matter of intense EUV beams over a broad range of parameters

Table top nanopatterning with extreme ultraviolet laser illumination

Includes bibliographical references (pages 723-724).Patterning with extreme ultraviolet light generated by a compact, bright laser source operating at a wavelength of 46.9 nm is demonstrated using two complementary approaches: multiple beam interferometric lithography and de-magnifying projection. Features with sizes ranging from 370 nm to 60 nm were printed in a few seconds in poly-methyl methacrylate resist. These proof-of-principle experiments demonstrate practical table-top nanopatterning tools based on extreme ultraviolet lasers for nanotechnology applications

Nanometer-scale ablation with a table-top soft x-ray laser

Includes bibliographical references (page 3617).Ablation of holes with diameters as small as 82 nm and very clean walls was obtained in poly(methyl methacrylate) focusing pulses from a Ne-like Ar 46.9 nm compact capillary-discharge laser with a freestanding Fresnel zone plate diffracting into third order. These results demonstrate the feasibility of using focused soft x-ray laser beams for the direct nanoscale patterning of materials and the development of new nanoprobes