Reduction of the linewidths of deep luminescence centers in 28Si reveals fingerprints of the isotope constituents.

Dramatic reductions of the linewidths of well-known deep centers in 28Si reveal "isotopic fingerprints" of the constituents. The approximately 1014 meV Cu center, thought to be either a Cu pair or an isolated Cu, is shown to contain four Cu atoms, and the approximately 780 meV Ag center is shown to contain four Ag. The approximately 944 meV ;{*}Cu center, thought to be a different configuration of a Cu pair, in fact contains three Cu and one Ag, and a new two-Cu two-Ag center is found. The approximately 735 meV center, previously assigned to Fe, actually contains Au and three Cu. This suggests a family of four-atom (Cu, Ag, Au) centers.

Optical detection and ionization of donors in specific electronic and nuclear spin States.

We resolve the remarkably sharp bound exciton transitions of highly enriched 28Si using a single-frequency laser and photoluminescence excitation spectroscopy, as well as photocurrent spectroscopy. Well-resolved doublets in the spectrum of the 31P donor reflect the hyperfine coupling of the electronic and nuclear donor spins. The optical detection of the nuclear spin state, and selective pumping and ionization of donors in specific electronic and nuclear spin states, suggests a number of new possibilities which could be useful for the realization of silicon-based quantum computers.

Raman band intensities of tellurite glasses.

Raman spectra of TeO2-based glasses doped with WO3, ZnO, GeO2, TiO2, MoO3, and Sb2O3 are measured. The intensity of bands in the Raman spectra of MoO3-TeO2 and MoO3-WO3-TeO2 glasses is shown to be 80-95 times higher than that for silica glass. It is shown that these glasses can be considered as one of the most promising materials for Raman fiber amplifiers.

High-Power As-S Glass Fiber Delivery Instrument for Pulse YAG:Er Laser Radiation.

A 3-mum laser-generation delivery instrument that uses chalcogenide fibers with a unique damage threshold and conical radiation input has been developed for medical applications. A new purification and synthesis scheme has been elaborated that yields fibers with a heterophase inclusion content of less than 10(4) cm(-3). In such fibers the damage threshold is 350 J/cm(2) at an average power density of 0.5 kW/cm(2) in a YAG:Er laser operating in the repetitive pulse free-running regime with a pulse duration of 350 ms. 1-3 x 10(4) laser pulses were transmitted at a repetition rate of 3 Hz and an average output power of 1 W under the condition of a 15% decrease in the output power.