Femtosecond diode-pumped Nd:glass laser with more than 1 W of average output power

We have demonstrated 175-fs pulses with 1 W and 300-fs pulses with 1.2 W of average output power at a pulse repetition rate of 117 MHz from a Nd:phosphate (Schott LG 760) glass laser pumped by a 1-cm-wide, 20-W diode laser bar. Stable soliton mode locking was achieved by use of an intracavity semiconductor saturable absorber mirror. We obtained more than 2 W of average power without mode locking. Using cylindrical cavity mirrors, we adapted the laser mode inside the Nd:glass to the highly elliptical pump beam in both dimensions (tangential and sagittal axes) while maintaining a nearly ideal circular TEM(00) output beam with M(2) approximately 1.2 . Overpumping the laser mode in the tangential plane and efficient unidirectional heat removal in the sagittal plane using a 0.8-mm thin Nd:glass also contributed to the good output-beam quality.     

Jaspamides M-P: new tryptophan modified jaspamide derivatives from the sponge Jaspis splendans

Four new jaspamide derivatives with antimicrofilament activity were isolated from the marine sponge Jaspis splendans. Their structures were elucidated by NMR and MS analysis. A structure-activity relationship analysis on all natural jaspamides is also reported here.     

240-fs pulses with 22-W average power from a mode-locked thin-disk Yb:KY(WO(4))(2) laser

We demonstrate what is to our knowledge the first passively mode-locked thin-disk Yb:KY(WO(4))(2) laser. The laser produces pulses of 240-fs duration with an average power of 22 W at a center wavelength of 1028 nm. At a pulse repetition rate of 25 MHz, the pulse energy is 0.9microJ , and the peak power is as high as 3.3 MW. The beam quality is very close to the diffraction limit, with M(2)=1.1 .     

Photoconductivity in trans (CH)x: A proof for the existence of solitons?

The optical absorption spectrum has been measured on trans (CH)_x upon simultaneous illumination of the sample with a second light source. No additional mid-gap absorption has been observed nor have the characteristic i.r. peaks been found which are known to show up at 0.11 and 0.17 eV upon doping. On the other hand photoconductivity has been detected, and, from its size, one would expect that the i.r. features should appear provided that the electron-hole pairs preferentially decay into soliton-antisoliton pairs, as predicted by theory. The negative results thus suggests that photo-generated carriers do not relax into solitonic states.     

Gel permeation chromatographic studies of the degradation of polyethylene with fuming nitric acid. II. Bulk polyethylene

Preliminary results are reported on the use of gel permeation chromatography in morphological studies of bulk polymers and fibres. Several samples of bulk isotropic and drawn polyethylene were analyzed by gel permeation chromatography following nitric acid oxidation. In all cases suitable samples showed two peaks in the molecular weight distribution, suggesting a qualitative similarity with results for single crystals. It is concluded that the present data are consistent with chain folding in bulk polymers, both in the isotropic and oriented states, with a less degree of regularity than exists in single crystals.