ABSTRACT
We have developed a technique for laser tuning at rates of 100 kHz or more using a pair of acousto-optic modulators. In addition to all-electronic wavelength control, the same modulators also can provide electronically variable Q-switching, cavity length and power stabilization, chirp and linewidth control, and variable output coupling, all at rates far beyond what is possible with conventional mechanically tuned components. Tuning rates of 70 kHz have been demonstrated on a radio-frequency-pumped CO2 laser, with random access to over 50 laser lines spanning a 17% range in wavelength and with wavelength discrimination better than 1 part in 1000. A compact tuner and Q-switch has been deployed in a 5-10-kHz pulsed lidar system. The modulators each operate at a fixed Bragg angle, with the acoustic frequency determining the selected wavelength. This arrangement doubles the wavelength resolution without introducing an undesirable frequency shift.
ABSTRACT
The operating principles of a wave-front shearing interferometer designed by Murty are described. The interferometer has simple, independent adjustment for both phase and shear and is stable mechanically. It has been used to assess the quality of cryogenic laser-fusion targets immediately prior to their irradiation by a high-power laser. It has also been used to study the changes in cryogenic targets caused by energy emitted by the high-power laser prior to the main pulse.
ABSTRACT
The ability to directly measure and evaluate ultrafast processes with unprecedented time resolution and reliability has greatly extended our knowledge about the kinetics of primary processes in chemistry and allied physical and biological sciences. Improvements in the reliability and versatility of picosecond techniques should lead to an increase in the experimental information about basic interactions in atomic and molecular systems.
Subject(s)
Bacteriorhodopsins , Carotenoids , Lasers , Retinal Pigments , Rhodopsin , Chemical Phenomena , Chemistry , Chloroplasts , Coloring Agents , Electrons , Kinetics , Photosynthesis , Vision, OcularABSTRACT
We have excited detergent-solubilized bovine rhodopsin at room temperature with 530-nm light pulses from a mode locked laser, and have observed the appearance and decay of a transient species that absorbs more strongly at 560 nm than does ground-state rhodopsin. Our data show that the absorbing intermediate appears in a time that is at least as short as the experimental resolution (about 6 psec) and decays with a life time of about 30 nsec. The extremely fast risetime supports the hypothesis that prelumirhodopsin is the product of the primary photoprocess.
