Abstract:We report emission from a bismuth doped chalcogenide glass which is flattened, has a full width at half maximum (FWHM) of 600 nm, peaks at 1300 nm and covers the entire telecommunications window. At cryogenic temperatures the FWHM reaches 850 nm. The quantum efficiency and lifetime were as high as 32% and 175 µs, respectively. We also report two new bismuth emission bands at 2000 and 2600 nm. Absorption bands at 680, 850, 1020 and 1180 nm were observed. The 1180 nm absorption band was previously unobserved. We suggest that the origin of the emission in Bi:GLS is Bi 45-50 (1996). 36. J. Ren, J. Qiu, D. Chen, C. Wang, X. Jiang, and C. Zhu, "Infrared luminescence properties of bismuth-doped barium silicate glasses,"

The authors describe the fabrication of buried waveguides in a highly nonlinear chalcogenide glass, gallium lanthanum sulfide, using focused femtosecond laser pulses. Through optical characterization of the waveguides, they have proposed a formation mechanism and provide comparisons to previous work. Tunneling has been identified as the dominant nonlinear absorption mechanism in the formation of the waveguides. Single mode guidance at 633 nm has been demonstrated. 3 This is because of its ability to cause nonlinear phase shifts over much shorter interaction lengths than conventional ͑silica based͒ devices. Various waveguiding structures such as fibers, proton beam written waveguides, continuous wave laser written waveguides, and femtosecond laser written waveguides could be used to realize such devices. Of these femtosecond laser writing is particularly attractive because as well as having rapid processing times waveguiding structures can be formed below the surface of the glass enabling three-dimensional structures to be fabricated. There have been several studies detailing the fabrication and characterization of waveguides using focused femtosecond laser pulses in phosphate glass, 4 chalcogenide glass, 5 and heavy metal oxide glass. 6 Of these chalcogenide glasses are especially attractive because they have a high nonlinear refractive index and enhanced IR transmission coupled with low maximum phonon energy. Of the chalcogenide glasses gallium lanthanum sulfide ͑GLS͒ is probably the most notable with respect to optical nonlinear devices as it has the highest nonlinear figure of merit ͑FOM͒ of any glass reported to date, 7 FOM= n 2 / ͑2␤͒, where is the wavelength, n 2 is the real part of the nonlinear refractive index, and ␤ is the two-photon absorption coefficient. In this letter we report the fabrication and characterization of buried waveguides written into GLS glass using focused femtosecond laser pulses.A sample of GLS was prepared by mixing 65% gallium sulfide, 30% lanthanum sulfide, and 5% lanthanum oxide ͑mol %͒ in a dry-nitrogen purged glove box. Gallium and lanthanum sulfides were synthesised in-house from high purity gallium and lanthanum precursors in a flowing H 2 S gas system; the lanthanum oxide was purchased commercially and used without further purification. The glass was melted in a dry-argon purged furnace at 1150°C for 24 h before being quenched and annealed at 400°C for 12 h, it was then cut and polished into a 12ϫ 12ϫ 5 mm 3 slab. To write the waveguides a Ti:sapphire laser ͑Coherent RegA͒ emitting a train of pulses with a duration of 150 fs, a repetition rate of 250 kHz, and a central wavelength of 800 nm was used. Pulse energy was varied using a variable neutral density filter. The laser beam was focused via a 50ϫ objective ͓numerical aperture ͑NA͒ = 0.55͔ around 200 m below the surface of the sample and had a focus spot diameter of around 2 m. The sample was mounted on a computer controlled linear motor translation stage which could move in three axes with a resolution of a few nanomete...

Carrier-type reversal to enable the formation of semiconductor p-n junctions is a prerequisite for many electronic applications. Chalcogenide glasses are p-type semiconductors and their applications have been limited by the extraordinary difficulty in obtaining n-type conductivity. The ability to form chalcogenide glass p-n junctions could improve the performance of phase-change memory and thermoelectric devices and allow the direct electronic control of nonlinear optical devices. Previously, carrier-type reversal has been restricted to the GeCh (Ch ¼ S, Se, Te) family of glasses, with very high Bi or Pb 'doping' concentrations (B5-11 at.%), incorporated during high-temperature glass melting. Here we report the first n-type doping of chalcogenide glasses by ion implantation of Bi into GeTe and GaLaSO amorphous films, demonstrating rectification and photocurrent in a Bi-implanted GaLaSO device. The electrical doping effect of Bi is observed at a 100 times lower concentration than for Bi melt-doped GeCh glasses.

We fabricated a series of glasses with the composition 94.7-GeO 2 -5Al 2 O 3 -0.3Bi 2 O 3 -PbO ͑ =0-24 mol. %͒. Characteristic absorption bands of bismuth centered at 500, 700, 800, and 1000 nm were observed. Adding PbO was found to decrease the strength of bismuth absorption. The addition of 3%-4% PbO resulted in a 50% increase in lifetime, a 20-fold increase in quantum efficiency, and a 28-fold increase in the product of emission cross section and lifetime on the 0% PbO composition. We propose that the 800 nm absorption band relates a different bismuth center than the other absorption bands.

A single carbon nanotube diode is reported, with Ti and Pd contacts, and split gates. Without gate bias the device displays strong rectification, with a leakage current (I0) of 6 × 10−16 A, and an ideality factor (η) of 1.38. When the gate above the Ti contact is biased negatively the diode inverts. When positive bias is then applied to the gate above the Pd contact minority carrier injection is suppressed. Configured such I0 and η were 2 × 10−14 A and 2.01, respectively. Electrical characterization indicates that the Schottky barrier height for electrons is lower for the Pd contact than the Ti contact.