Generation of frequency shifted picosecond pulses with low temporal jitter

Transient stimulated Raman scattering is used for the generation of a frequency shifted picosecond light pulse; part of this Raman shifted pulse is subsequently coherently scattered at a material excitation of a second Raman cell. Starting with the second harmonic pulse (tp = 4 ps) of a mode-locked Nd : glass laser system, both the stimulated and the coherently produced pulses have durations of 2.3 ps at different wavelengths. By the appropriate choice of the Raman medium pulses between 13 000 and 21 000 cm-1 can be generated. The coherent generation process minimizes the temporal jitter between the two pulses and allows to obtain a high time resolution of better than 0.3 ps in excite and probe experiments

Energy relaxation of an excited electron gas in quantum wires: many-body electron LO-phonon coupling

We theoretically study energy relaxation via LO-phonon emission in an excited one-dimensional electron gas confined in a GaAs quantum wire structure. We find that the inclusion of phonon renormalization effects in the theory extends the LO-phonon dominated loss regime down to substantially lower temperatures. We show that a simple plasmon-pole approximation works well for this problem, and discuss implications of our results for low temperature electron heating experiments in quantum wires.Comment: 10 pages, RevTex, 4 figures included. Also available at http://www-cmg.physics.umd.edu/~lzheng

New Investigations of the Primary Processes of Bacteriorhodopsin and of Halorhodopsin

Halobacterium halobium contains two retinylidene protein units which show light induced ion pumping. We have studied the two systems, bacteriorhodopsin (bR)1 and halorhodopsin (hR)2, on the picosecond time scale.</jats:p

Generation of Infrared Picosecond Pulses Between 1.2 μm and 1.8 μm Using a Travelling Wave Dye Laser

Recently, the synthesis of infrared dyes of high photochemical stability became possible.1 One of these dyes was used to operate a synchronously pumped cw dye laser system tunable around 1.3 μm.2 Here, we demonstrate a new method for effective pumping of dyes with small fluorescence quantum yield (10–4). Laser emission up to 1.8 μm is now accessible by a travelling wave pumping system.</jats:p

Picosecond events in the photochemical cycle of the light-driven chloride-pump halorhodopsin

The early events in halorhodopsin after light excitation are studied with picosecond time resolution. Absorption and fluorescence measurements show that the electronically excited state of the incorporated retinal has a lifetime of 5 ps. Within that time a red-shifted photoproduct is formed that remains stable for at least 2 ns