Employing polymethine dyes as saturable absorbers and intracavity Fabry-Perot interferometers, a flashlamp-pumped cresyl-violet dye laser has been mode locked to produce picosecond pulses (3–5 psec) frequency tunable from 644 to 704 nm. The frequency tuning ranges of mode-locked rhodamine 6G and rhodamine B dye lasers have also been extended to cover 584 to 645 nm.
The buildup of picosecond pulses in a passively mode-locked rhodamine 6G dye laser has been directly studied with a picosecond streak camera. It is shown how a single isolated picosecond pulse evolves from the initial intensity fluctuations.
The UNESCO Active Learning in Optics and Photonics project is designed for the benefit of teachers of introductory university physics from developing countries. Initial implementation has taken place in two African nations, Ghana and Tunisia. The training curriculum includes student materials to teach topics in geometrical and physical optics in an active way with a high level of student involvement in the learning process. The curriculum makes use of simple, inexpensive materials. A conceptual learning assessment instrument is being developed as part of the project. Follow-up activities are planned. Experiences of the international group of workshop trainers are reported.
Picosecond pulses of transform-limited durations (Δt∼3 psec; ΔtΔν∼0.5) have been obtained from a passively mode-locked Rhodamine 6G dye laser, frequency tuned over a range of 230 Å with an intracavity Fabry-Perot filter. Self-phase-modulation frequency broadening at higher powers has also been measured giving a value n2 = 10−18 cm2V−2 for the nonlinear refractive index of the ethanol dye solvent.
Hands-On Optics (HOO) is a collaborative four-year National Science Foundation fundedprogram (Principal Investigator A. Johnson) designed to create a sustainable science education program to excite students about science by actively engaging them in optics activities. It will reach underrepresented middle school students in after-school programs and at hands-on science centers across the United States. The project creates and distributes educational modules and provides professional development for educators and optics resource volunteers.
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