J. A. Medeiros Neto

Upconversion fluorescence spectroscopy of Er3+/Yb3+-doped heavy metal Bi2O3–Na2O–Nb2O5–GeO2 glass

Upconversion fluorescence emission of Er3+/Yb3+-doped Bi2O3–Na2O–Nb2O5–GeO2 heavy metal glass samples excited at 1.06 μm is experimentally investigated. The results reveal the existence of intense emission bands centered around 520, 545, and 655 nm. The germano-niobate based host glass presents high transparency in the region of 400–2700 nm, the capability of incorporating high dopant concentrations, high melting temperature, and large resistance to atmospheric moisture. The observed intensity of the green fluorescence emission, suggested that the niobium based host glass material plays an important role in the efficiency of the upconversion process. Emission lines centered at 425, 483, 503, 608, and 628 nm were also observed.

PROBING OF THE QUANTUM DOT SIZE DISTRIBUTION IN CDTE-DOPED GLASSES BY PHOTOLUMINESCENCE EXCITATION SPECTROSCOPY

We studied confinement effects in CdTe quantum dots by means of photoluminescence excitation spectroscopy. We show that by changing the detection energy we can resolve the spectrum of quantum dots of different sizes inside their much broader size distribution in CdTe‐doped glass. The spectra obtained show several well‐resolved lines. There is excellent agreement between the photoluminescence excitation spectra peak energies and calculations of the confined energy transitions based on a modified multiband envelope function model.

Quantum size effects on CdTexS1−x semiconductor‐doped glass

We present experimental evidences of quantum confinement in borosilicate glasses with a new microcrystallite CdTexS1−x semiconductor. The microcrystallite sizes are controlled by the heat‐treatment time and temperature. Transmission electron microscopy measurements show the microcrystallites average diameters near 55 A for the sample treated for the longest time. We observe a red shift from 570 to 640 nm in the absorption and photoluminescence spectra as the size increases. These shifts agree with the expected quantum‐confined energies, varying from 0.80 to 0.60 eV. The absorption spectra also show a second feature which can be assigned to the second quantum‐confined transition.

Multiwavelength frequency-doubling in bulk galliumlanthanumsulphide glasses for optical fiber amplifiers at 1.3 μm

Abstract We report on the experimental investigation of efficient multiwavelength frequency-doubling in bulk undoped and Pr3+-doped Ga:La:S glasses for optical fiber amplifiers in the 1.3 μm telecommunications window. The amorphous sulphide-based glass samples were pumped by several wavelengths (1.06, 1.12, 1.16 and 1.32 μm) and unseeded frequency doubled signals at 532, 560, 580 and 660 nm, respectively, were generated instantaneously for all these pump wavelengths separetely. Second-harmonic conversion efficiencies as high as 0.02% were obtained at 1.32 μm. The results also revealed that in Pr3+-doped sulphide-based glasses the frequency-doubling mechanism is enhanced owing to the presence of the praseodymium dopant in the glass matrix.

Non-linear optical properties and femtosecond dynamics of CdTe quantum dots

The authors have grown CdTe quantum dots in glass, studied the relaxation dynamics in the femtosecond time scale, and measured the non-linear refractive index in the infrared. Their observations, of very large non-linear refractive index in the transparency region and femtosecond recovery times of the resonant non-linearity, indicate that these materials are most promising for all-optical photonic switching applications.