Broadly tunable compact continuous-wave Cr(2+):ZnS laser

We report the development of a continuous-wave, room-temperature Cr(2+) ZnS laser that is compact and tunable over 700 nm. The laser is pumped by a diode-pumped Er-fiber laser and generates 0.7 W of linearly polarized radiation at 2.35microm , at up to 40% slope efficiency. Cr(2+) ZnS directly diode-pumped at 1.6microm yields polarized radiation that is tunable over 400 nm at up to 25 mW of output power. A comparison of Cr(2+) ZnS with Cr ZnSe (70 mW, 350 nm) in a similar setup is given. As opposed to Cr ZnSe, the Cr ZnS laser is intrinsically polarized. Finally, we observe sensitization of the output radiation by a few milliwatts of the visible (470-500-nm) and near-infrared (740-770-nm) radiation.     

A cw room-temperature Ho,Tm:YLF laser pumped at 1.682 μm

We present the results obtained with a Ho,Tm:YLF crystal grown at a new crystal growth facility in Pisa. The optical quality of the sample has been tested by studying its performance as the active medium of a laser operating at 2.06 μm. We employed three different pump laser sources: a Ti:sapphire, a diode (both tuned at 793 nm) and, for the first time, a continuous-wave Co:MgF₂ laser, tuned at 1.682 μm. At room temperature the best slope efficiency was 30 % in the case of “red” pumping, and 59 % in the case of “infrared” excitation. The typical lasing threshold is about 100 mW. Received: 14 March 2001 / Revised version: 15 June 2001 / Published online: 19 September 2001     

Reaction of 3,3-dimethyl- and 3-spirocyclohexyl-tetrahydroisoquinolines with alkynes*

It has been found that 2,3,3-trimethyl-1-phenyl- and 1,2-dimethyl-3-spirocyclohexyltetrahydro-isoquinolines react with activated alkynes in methanol with cleavage of the tetrahydropyridine ring to give methoxybenzyl- and methoxyethylbenzenes, and in boiling acetonitrile form N-butenoyl derivatives from N-methylspirocylohexyltetrahydroisoquinoline by its reaction with acetylacetylene.     

Synthesis of 3,5-diaroylpyridines

Previously unknown 3,5-diaroylpyridines have been synthesized by the condensation of 1,3-diketones according to the Hantzsch reaction.     

Continuous-wave tunable Cr2+:ZnS laser

We report the first continuous-wave tunable over ∼280 nm around 2.3 μm room-temperature operation of a chemical vapor transport-grown and diffusion-doped Cr²⁺:ZnS laser, pumped by a Co:MgF₂ laser at 1.67 μm and generating over 100 mW of output power at 16% slope efficiency. The self-consistent results of the laser and spectroscopic analysis demonstrate a large potential of this crystal as an active medium for diode-pumped tunable mid-infrared sources. Received: 7 January 2002 / Revised: 14 March 2002 / Published online: 2 May 2002     

A study of magnetic liquids with the help of a paramagnetic sensor

The paramagnetic sensor method was used to study local magnetic fields in a magnetite aqueous suspension. The sensor was 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl, a stable nitroxide radical. The lines in the EPR spectrum of the sensor were demonstrated to be broadened due to the dipole-dipole interaction with magnetite nanoparticles. It was established that no spin exchange occurred between sensor molecules and magnetite nanoparticles. The g-factor was found to decrease with the concentration of magnetite nanoparticles in the suspension. The mean strengths of the local magnetic fields calculated from changes in the EPR spectrum of the sensor proved to be substantially lower than the values determined from magnetic measurements. This difference was accounted for by the formation of linear aggregates of magnetite nanoparticles under the action of a magnetic field.     

Synthesis of furyl-, furylvinyl-, thienyl-, pyrrolinylquinazolines and isoindolo[2,1-<Emphasis Type="Italic">a</Emphasis>]quinazolines

A method for the synthesis of hydrogenated furyl-, furylvinyl-, thienyl-, and pyrrolinyl-substituted quinazolin-4-ones was developed. A possibility of the reaction of 2-furylquinazolines with maleic anhydride was demonstrated. A number of quinazolines obtained were subjected to a primary bioscreening on inhibition of acetylcholinesterase.