Pulse compression by filamentation in argon with an acoustic optical programmable dispersive filter for predispersion compensation

We have experimentally demonstrated pulses 0.4 mJ in duration smaller than 12 fs; with an excellent spatial beam profile by self-guided propagation in argon. The original 52 fs pulses from the chirped pulsed amplification laser system are first precompressed to 32 fs by inserting an acoustic optical programmable dispersive filter instrument into the laser system for spectrum reshaping and dispersion compensation, and the pulse spectrum is subsequently broadened by filamentation in an argon cell. By using chirped mirrors for post-dispersion compensation, the pulses are successfully compressed to smaller than 12 fs.

Splitting of femtosecond laser pulses by using a Dammann grating and compensation gratings

When a Dammann grating is used to split a beam of femtosecond laser pulses into multiple equal-intensity beams, chromatic dispersion will occur in beams of each order of diffraction and with different scale of angular dispersion because the incident ultrashort pulse contains a broad range of spectral bandwidths. We propose a novel method in which the angular dispersion can be compensated by positioning an m-time-density grating to collimate the mth-order beam that has been split, producing an array of beams that are free of angular dispersion. The increased width of the compensated output pulses and the spectral walk-off effect are discussed. We have verified this approach theoretically and validated it through experiments. It should be highly interesting in practical applications of splitting femtosecond laser pulses for pulse-width measurement, pump-probe measurement, and micromachining at multiple points. (c) 2005 Optical Society of America.

The Co-management Survey report: an executive summary

Co-management is typically known to be a resource management system that shares managerial responsibility between the state and other stakeholders of a resource. In the case of Lake Victoria, one would expect the state to be represented by the fisheries departments of Kenya, Uganda and Tanzania, while stakeholder groups may comprise fishing communities, fish processing factories and municipalities. Taking that into account, the survey's objectives were defined as: (a) To identify the difficulties and impracticalities inherent in implementing state-based regulations via a "top-down" management strategy. (b) To assess the prevalence of community-based institutions that either seek to regulate the fishery or have the potential to be used to regulate it. (c) To identify ways in which community-based regulatory and monitory systems may be established, and how these will fare over time. (d) To identify roles for national Fisheries Departments, industrial fish processors and other stakeholders. (e) To develop well-founded policy suggestions for the establishment of a co-management framework to manage the fisheries of Lake Victoria.

Analysis of dispersion compensation for position-dependence in externally modulated CATV lightwave systems by using chirped fiber grating

The dispersion compensation characteristics of the chirped fiber grating (CFG) for different dispersion compensation positions are analyzed in externally modulated cable television (CATV) lightwave system and the analytic expression of the composite second order (CSO) distortion is derived. The analyses give a reasonable explanation for the position-dependent effect of CFG dispersion compensator, which was found in practical systems. Moreover, the theoretical result is also verified by an experiment. It is believed that the theory will be helpful in designing optical CATV fiber links with nodes at proper positions both for intensity amplification and dispersion compensation.