Femtosecond

Abstract: A topical review of numerical and experimental studies of supercontinuum generation in photonic crystal fiber is presented over the full range of experimentally reported parameters, from the femtosecond to the continuous-wave regime. Results from numerical simulations are used to discuss the temporal and spectral characteristics of the supercontinuum, and to interpret the physics of the underlying spectral broadening processes. Particular attention is given to the case of supercontinuum generation seeded by femtosecond pulses in the anomalous group velocity dispersion regime of photonic crystal fiber, where the processes of soliton fission, stimulated Raman scattering, and dispersive wave generation are reviewed in detail. The corresponding intensity and phase stability properties of the supercontinuum spectra generated under different conditions are also discussed.

Abstract: We stabilized the carrier-envelope phase of the pulses emitted by a femtosecond mode-locked laser by using the powerful tools of frequency-domain laser stabilization. We confirmed control of the pulse-to-pulse carrier-envelope phase using temporal cross correlation. This phase stabilization locks the absolute frequencies emitted by the laser, which we used to perform absolute optical frequency measurements that were directly referenced to a stable microwave clock.

Abstract: With the goal of being able to create optical devices for the telecommunications industry, we investigated the effects of 810-nm, femtosecond laser radiation on various glasses. By focusing the laser beam through a microscope objective, we successfully wrote transparent, but visible, round-elliptical damage lines inside high-silica, borate, soda lime silicate, and fluorozirconate (ZBLAN) bulk glasses. Microellipsometer measurements of the damaged region in the pure and Ge-doped silica glasses showed a 0.01–0.035 refractive-index increase, depending on the radiation dose. The formation of several defects, including Si E′ or Ge E′ centers, nonbridging oxygen hole centers, and peroxy radicals, was also detected. These results suggest that multiphoton interactions occur in the glasses and that it may be possible to write three-dimensional optical circuits in bulk glasses with such a focused laser beam technique.

Abstract: Laser ablation of solid targets by 0.2–5000 ps Ti: Sapphire laser pulses is studied. Theoretical models and qualitative explanations of experimental results are presented. Advantages of femtosecond lasers for precise material processing are discussed and demonstrated.

Abstract: This paper introduces and discusses the main aspects of ultrashort laser pulse filamentation in various transparent media such as air (gases), transparent solids and liquids. The properties of femtosecond filaments and their applications are presented. Theoretical models developed to explain filaments and the main predictions inferred from these models are reviewed. The various techniques to observe filaments and to measure their characteristics are described. The main measurements of filament features performed so far are reviewed.