Production of intense subnanosecond pulses by cavity dumping

Three experimental realizations of a technique for generating intense laser pulses with continuously variable and precisely controllable durations in the subnanosecond and nanosecond range are described. Laser pulses with durations ranging from 0.5 to 2.0 ns at power levels up to 0.3 MW have been generated. Applications of the technique to optical pulse shaping, cavity dumping of mode-locked pulses, and optical isolation of amplifiers are discussed.     

Pulse stretching utilizing two-photon-induced light absorption

The effect of inserting an element exhibiting induced absorption into aQ-switched laser cavity is investigated theoretically and experimentally. The rate equations are solved assuming two types of nonlinear loss, one being proportional to the square of the laser intensity and the other being proportional to the product of laser intensity and density of excited electrons in the nonlinear absorber. Experiments are performed with a rotating-prism ruby laser with a CdS crystal in its cavity. It is established that two-photon absorption takes place, and as predicted by the theory that the output intensity and output energy both decrease and pulse length increases as compared with the normalQ-switched case. In addition, the output pulse has an oscillatory behavior, and it is suggested that this is caused by loss due to the excited electrons, which are found to have a lifetime of approximately 24 ns.     

Structure Studies on 6a-Thiathiophthenes and Related Compounds

The results from structure studies on 6a-thiathiophthenes show that different substituent groups perturb the bonding in the three-sulphur sequence to different degrees. Both equal and unequal S? S bonds occur in symmetrically as well as in unsymmetrically substituted derivatives. The specific effect of methyl and phenyl substituents on the sulphur-sulphur bonding may be described by the results from CNDO/2 calculations on mono-methyl and mono-phenyl substituted 6a-thiathiophthenes. Molecular packing and intermolecular close contacts also seem to affect the S? S bonding. The structures of equally substituted 6a-thiathiophthene analogues with and show, when compared with the equivalent 6a-thiathiophthene, that and cause a pronounced change in the S? S bonding, while the perturbation caused by is negligible. In symmetrical 6a-thiathiophthene analogues with and , the average bond length in the linear three-atom sequence is 9 – 12% longer than the respective single bond.     

Stability of IR transparent fluoride glasses in humid air studied by auger electron spectroscopy

The effects of humid air on freshly cleaved samples of IR-transparent fluorohafnate and fluorozirconate glasses have been investigated by means of Auger electron spectroscopy. The study reveals that the oxygen content at the surface increases with increasing temperature and humidity. But the penetration into the bulk progresses relatively slowly as shown in a long-term test where samples were exposed to 50°C and 80% RH for six months. However, if water condenses on the glass surface a rapid and penetrating corrosion takes place.     

Time behavior of stimulated Raman scattering

The time relationship between the 1st Stokes, 2nd Stokes, 3rd Stokes, 1st anti-Stokes radiations, and the exciting laser radiation for stimulated Raman scattering in self-focusing liquids has been investigated theoretically and experimentally. A model is presented for calculating the output power and time behavior of the different orders of Stokes radiation when self-focusing occurs. Experimentally, good agreement is found between predicted and measured output powers, but some apparent anomalies are observed in the time behavior for the 2nd and 3rd Stokes radiations and 1st anti-Stokes radiation, especially in carbon disulfide. There are strong indications of dielectric breakdown occurring in the liquids, and it is shown qualitatively that the observed time behavior of the higher order Stokes radiation can be caused by the dielectric breakdown.     

Loss mechanisms in single-mode fibers jacketed with a loose jelly-filled tube

A study has been made of temperature induced losses in single-mode fibers with a loose jelly-filled jacket. It has been found that at low temperatures where the fiber has to buckle to fit into the tube, the losses have the character of macrobend losses. At high temperatures where the fiber is pressed against the tube wall, the losses are of the microbending type.