Active planar optical waveguide made from luminescent silicon nanocrystals

We show experimentally that a layer of silicon nanocrystals, prepared by the Si-ion implantation (with the energy of 400 keV) into a synthetic silica slab and exhibiting room-temperature red photoluminescence, can serve simultaneously as a single-mode planar optical waveguide. The waveguide is shown to self-select guided transverse electric and transverse magnetic modes from the broad photoluminescence emission of the nanocrystals resulting in a substantially narrower emission spectrum for these modes. We further report on an investigation of optical gain in a sample implanted to a dose of 4×1017 cm−2. Despite the occurrence of strong waveguiding, results of the variable stripe length method turned out not to be able to give unambiguous evidence for optical gai

Micrometer and sub micrometer-size structures fabricated by direct writing using femtosecond light pulses

In this report we present the results of the sub micrometer-size hillocks and bits recording on the surface and in the volume of dielectric materials using a direct femtosecond laser writing (DFLW) method. Lateral and axial dimensions of fabricated defects were measured (170 ±50) and (440 ±100) nm, respectively. 2D and 3D matrixes with the corresponding densities of 1 Gbit/cm2 and 6 Tbit/cm3 as well as waveguides were recorded using DFLW method

Ultrafast decay of femtosecond laser-induced grating in silicon-quantum-dot-based optical waveguides

Femtosecond transient laser-induced grating (LIG) experiments were performed in planar optical waveguides made of luminescent silicon quantum dots. The LIG was created by interference of two pulses from the frequency-doubled output of a Ti-sapphire lase

Characterization of as-grown and heavily irradiated GaN epitaxial structures by photoconductivity and photoluminescence

The influence of radiation defects on photoconductivity transients and photoluminescence (PL) spectra have been examined in semi-insulating GaN epitaxial layers grown on bulk n-GaN/sapphire substrates. Defects induced by 10-keV X-ray irradiation with a dose of 600 Mrad and 100-keV neutrons with fluences of 5×1014 and 1016 cm−2 have been revealed through contact photoconductivity and microwave absorption transients. The amplitude of the initial photoconductivity decay is significantly reduced by the radiation defect density. A simultaneous decrease with radiation-induced defect density is also observed in the steady-state PL intensity of yellow, blue and ultraviolet bands peaked at 2.18, 2.85, and 3.42 eV, respectively. The decrease of the PL intensity is accompanied by an increase of asymptotic decay lifetime, which is due to excess carrier multi-trapping. The decay can be described by the stretched exponential approximation exp[-(t/τ)α] with different values of α in as-grown material (α≈0.7) and irradiated samples (α≈0.3). The value of the fracton dimension ds of the disordered structure, evaluated as ds=2α/(1-α), changes from 4.7 to 0.86 for as-grown and irradiated material, respectively, implying percolative carrier motion on an infinite cluster of dislocations net in the as-grown material and cluster fragmentation into finite fractons after irradiation

Fabrication and replication of micro-optical structures for growth of GaN-based light emitting diodes

Abstract not reproduced here by request of the publisher. The text is available from: http://dx.doi.org/10.1117/12.203370