James D. Kafka

Generation and amplification of sub-picosecond pulses using a frequency-doubled neodymium YAG pumping source

Abstract Stable, tunable, sub-picosecond pulses have been obtained by synchronously pumping a Rhodamine 6G dye laser with a frequency-doubled CW modelocked neodymium YAG laser. Careful attention has been paid to minimize amplitude and timing instabilities, resulting in dye laser pulses shorter than 500 fs. The main advantage of this new pumping source over current synchronously pumped dye lasers is that it is particularly well suited to short pulse amplification. Using this technique amplification of 2 × 10 6 has been achieved.

Applications of synchronously pumped subpicosecond optical parametric oscillators (OPOs)

We review the design of an LBO optical parametric oscillator (OPO) synchronously pumped by a cw mode-locked Ti:sapphire laser. The synchronously pumped OPO produces 100 fsec pulses at 1.3 and 1.5 micrometers as well as near 600 nm using frequency doubling. We also demonstrate the synchronization of the pump, signal and idler pulses on the 100 fsec time scale. We then review applications that utilize these capabilities. These applications include studies of: InGaAs absorbers, GaAs quantum wells, electro-optic modulators, soliton-soliton interactions, energy transfer in photosynthetic bacteria, uncaging of biological molecules using confocal microscopy, electronic distributions and two photon fluorescence in dyes.

Electron Diffraction in the Picosecond Domain Steven Williamson and Gerard Mourou and Synchronous Amplification of 70 fsec Pulses Using a Frequency-Doubled Nd: YAG Pumping Source

With the exception of picosecond photoelectron switching recently demonstrated, streak camera tubes have been used exclusively as a fast optical and x-ray diagnostic tool. However, some of the most beautiful features of the image converter device used in the streak camera have been only partially exploited with this application. The image converter device produces a temporal and spatial monoenergetic photoelectron replica of the incident optical pulse. This replica is ultimately limited by the temporal and spatial resolution of the particular streak tube employed. Temporal and spatial resolution can be as good as subpicosecond and 100 μm respectively. It is also worth noting that this replica is accurately synchronized with the incident optical pulse. We have used this electron burst to generate an electron diffraction pattern, inferring that picosecond snap shots of laser induced structural changes in laser annealing or in the field of surface physics, can now be taken not only with a picosecond exposure, but also in picosecond synchronization with the laser induced kinetics. In the experiment (Fig.1) a demountable photochron II streak camera tube is used. The Al specimen of 150 Angstroms thickness is located in the drift space 1 cm behind the anode. The diffraction pattern is captured on a phosphor sreen and photographed using an image intensifier with a gain of 3×104 lens coupled to the film.