R. Dorsinville

Optical properties of gold nanocluster composites formed by deep ion implantation in silica

Planar layers of Au clusters with diameters between 5 and 30 nm were synthesized by implanting 2.75‐MeV Au+ ions in fused silica. The metal‐glass composite layer was 0.85 μm below the surface and had a width of 0.5 μm. Thermal annealing enhanced the optical absorption of the annealed samples near 2.4 eV. The third‐order nonlinear optical response time is ≤35 ps; the magnitude of the effective nonlinear susceptibility is 200 times that of similar clusters embedded in ruby‐gold melt glass.

Nonlinear optical properties of metal-quantum-dot composites synthesized by ion implantation

Abstract Over a decade ago, it was demonstrated that composites comprising metal clusters embedded in dielectric hosts could be synthesized by ion implantation. The optical properties of these metal-cluster composites are dominated by two phenomena which alter the susceptibilities from those of bulk metals: One is a classical field enhancement effect, dielectric confinement, which leads to the characteristic surface plasmon resonance of the metal clusters seen in absorption spectra. The other effect is quantum confinement of the conduction-band electrons which enhances the nonlinear susceptibility of the metal clusters for diameters smaller than about 10 nm and makes them behave as quantum dots with electronic properties which approximate those of independent electrons confined in a spherical potential well. This paper reviews our studies of the nonlinear optical behavior of quantum-dot composites synthesized by ion implantation. We also consider the potential of these quantum-dot composites as materials for nonlinear waveguide devices.

Bimolecular reactions of singlet excitons in tris(8‐hydroxyquinoline) aluminum

We have studied singlet excited state dynamics in thin films of tris(8‐hydroxyquinoline) aluminum (Alq3), a well known emitter for organic electroluminescent devices. Our experimental results show that bimolecular recombination dominates the singlet exciton decay in pristine films at high intensities, thus decreasing the photoluminescence quantum efficiency and the singlet lifetime. Because of the relatively low carrier concentration at which light emitting diodes operate the electroluminescence efficiency is not affected. The measured rate constant of singlet–singlet annihilation in Alq3 films is γss=(3.5±2.5)×10−11 cm3 s−1. The diffusion coefficient and the diffusion length of singlet excitons estimated from γss are Ds=(1.2±0.8)×10−5 cm2 s−1 and L=98±40 A, respectively.

Excited-state nonlinearity in polythiophene thin films investigated by the Z-scan technique

Measurements of the third-order optical nonlinear susceptibility χ(3) have shown that nonlinearity around the single-photon absorption region is dominated by the saturation absorption in polythiophene thin films. The sign and the size of the real and the imaginary part of χ(3) have been measured at 532 nm to be −6.1 × 10−9 and −1.9 × 10−9 esu, respectively, by the Z-scan method.

On the Vision of Complete Fixed-Mobile Convergence

This paper reviews and outlines the key features of the emerging next-generation fixed passive optical network (NG-PON)-based and fourth-generation (4G) mobile broadband access technologies and how to leverage the advantages of both of these access technologies to build a next-generation hybrid fiber-wireless (FiWi) network. Specifically, this paper presents an overview of the most recent research activities on these hybrid FiWi architectures, aiming to clarify the basic differences and distinguish between two FiWi networking architectural models, namely, the overlay or independent model and the truly integrated model. We then explore and present a new direction to the design and implementation of a simple and cost-effective all-packet-based converged fixed-mobile access networking solution that enables the true integration of NG-PON and 4G mobile broadband access technologies into the envisioned fixed-mobile platform. We briefly outline the general and technical requirements to support a unified NG-PON long-term evolution (LTE) radio access network (RAN) architecture that conforms to both the typically centralized fixed PON and the emerging distributed 4G mobile LTE access standards. The implementation methodology on how to efficiently and cost-effectively integrate these two access technologies along with the main advantages gained from such an integrated architecture are outlined and presented.

Size dependence of the third-order susceptibility of copper nanoclusters investigated by four-wave mixing

We report on the observation of the forward degenerate four-wave mixing in four composite samples with Cu nanoclusters embedded in fused silica. The mean diameters of the copper particles in the four samples were 5, 7, 10, and 13 nm. The independent tensor elements of optical Kerr susceptibility were measured with different wave-mixing polarizations by use of 35-ps laser pulses from a mode-locked, frequency-doubled Nd:YAG laser. The measured third-order susceptibilities were on the order of 10−9–10−8 esu; the response time of the nonlinearity is faster than the laser pulse duration. The experimental results are consistent with a d−3 size dependence predicted for quantum-confined conduction band electrons in Cu nanoclusters.

Photoluminescence and electroluminescence of new lanthanide-(methyoxybenzoyl)benzoate complexes

New luminescent thermally stable lanthanide-organic complexes, namely europium tris(4-methoxy benzoylbenzoate), Eu(MeOBB)3, and terbium tris(4-methoxy benzoylbenzoate), Tb(MeOBB)3, were synthesized and characterized. The UV absorption bands in these compounds are attributed to the ligand while the emission originates from the lanthanide ions’ electronic transitions. The quantum efficiency of photoluminescence, Φ, measured in 5×10−4 M methylene chloride solutions is relatively large in both compounds: Φ=0.27 for Tb(MeOBB)3 and Φ=0.16 for Eu(MeOBB)3. The narrow-band electroluminescence from these complexes is studied by fabricating and characterizing single- and multi-layer organic light emitting diodes. Energy transfer between the organic components of these devices is also discussed.

Nonlinear-optical response in polythiophene films using four-wave mixing techniques

We report measurement of X(3) in polythiophene and a homologous series of polycondensed thiophene-based polymers above and below the absorption edge using the folded-boxcar four-wave mixing technique. Above gap the nonlinear coefficient X(3) was found to be one of the largest and fastest in a polymer.

Ultrafast time response of optical nonlinearity in polysilane polymers

Ultrafast relaxation kinetics of third‐order nonlinear susceptibility χ(3) of polysilane polymers was measured using both the picosecond Kerr gate and forward degenerated four‐wave mixing. The relative contributions from various nonlinear decay mechanisms were estimated from the time response. The third‐order nonlinear response was measured to be faster than 3 ps arising from electronic mechanism. A slower component is assigned to the refractive index grating due to light pressure.

Synthesis and characterization of electroluminescent organo-lanthanide(iii) complexes

New luminescent thermally stable lanthanide-(benzoyl)benzoate complexes are synthesized and characterized. The photoluminescence in these complexes originates from the radiative transitions of the lanthanide ions which are excited via intersystem crossing from the initially excited ligands. The electroluminescent properties of the terbium-(benzoyl)benzoates were studied by fabricating and characterizing single layer light emitting diodes containing poly(N-vinylcarbazole) doped with the lanthanide complexes and butyl-PBD. The energy transfer between the organic components of the single layer devices is also discussed.