Enhanced 1.54 μm emission in Y-Er disilicate thin films on silicon photonic crystal cavities

Spherical Bragg resonators for lasing applications: a theoretical approach

This work considers a perfect 3D omnidirectional photonic crystal; Spherical Bragg Resonators (SBR), for lasing applications. We use the recursive transfer matrix method to study scattering in an Er³⁺ doped SBR. We find the threshold gain factor for lasing by scanning poles and zeros of the S-matrix in the complex frequency plane. For a six Si/SiO₂ bilayer SBR, the threshold gain factor corresponds to a dopant density of Er³⁺ of 5.63 × 10²⁰ions/cm³. We believe, our work is the first theoretical demonstration of the ability to engineer optical amplification and threshold gain for lasing in SBRs.

Efficient Sensitized Photoluminescence from Erbium Chloride Silicate via Interparticle Energy Transfer

In this study, we prepare Erbium compound nanocrystals and Si nanocrystal (Si NC) co-embedded silica film by the sol-gel method. Dual phases of Si and Er chloride silicate (ECS) nanocrystals were coprecipitated within amorphous silica. Effective sensitized emission of Er chloride silicate nanocrystals was realized via interparticle energy transfer between silicon nanocrystal and Er chloride silicate nanocrystals. The influence of density and the distribution of sensitizers and Er compounds on interparticle energy transfer efficiency was discussed. The interparticle energy transfer between the semiconductor and erbium compound nanocrystals offers some important insights into the realization of efficient light emission for silicon-based integrated photonics.

Enhanced photoluminescence from ring resonators in hydrogenated amorphous silicon thin films at telecommunications wavelengths

We report enhanced photoluminescence in the telecommunications wavelength range in ring resonators patterned in hydrogenated amorphous silicon thin films deposited via low-temperature plasma enhanced chemical vapor deposition. The thin films exhibit broadband photoluminescence that is enhanced by up to 5 dB by the resonant modes of the ring resonators due to the Purcell effect. Ellipsometry measurements of the thin films show a refractive index comparable to crystalline silicon and an extinction coefficient on the order of 0.001 from 1300 nm to 1600 nm wavelengths. The results are promising for chip-scale integrated optical light sources.

A novel violet/blue light-emitting device based on Ce2Si2O7

Rare-earth silicates are highly efficient materials for silicon-based light sources. Here we report a novel light-emitting device based on Ce2Si2O7. Intense violet/blue electroluminescence was observed, with a turn-on voltage of about 13 V. The violet/blue emission is attributed to 4f-5d transitions of the Ce(3+) ions in Ce2Si2O7, which are formed by interfacial reaction of CeO2 and Si. Electroluminescence and photoluminescence mechanisms of the Ce2Si2O7 light-emitting device are also discussed.

Effect of structure and composition on optical properties of Er-Sc silicates prepared from multi-nanolayer films

Polycrystalline Er-Sc silicates (Er(x)Sc(2-x)SiO₅ and Er(x)Sc(2-x)Si₂O₇) were fabricated using multilayer nanostructured films of Er₂O₃/SiO₂/Sc₂O₃ deposited on SiO₂/Si substrates by RF- sputtering and thermal annealing at high temperature. RBS, TEM, GIXD, and PL results show the presence of Er(x)Sc(2-x)SiO₅ with an emission peak at 1528 nm for annealing from 900 to 1100 °C, and Er(x)Sc(2-x)Si₂O₇ with an emission peak at 1537 nm for higher annealing temperature. The PL intensity of the Er(x)Sc(2-x)Si₂O₇ phase is five times stronger than that of the Er(x)Sc(2-x)SiO₅ phase at 1250 °C. From PLE and PL spectra of Er(x)Sc(2-x)Si₂O₇ thin film, we schematically illustrate the Er³⁺ Stark energy levels of ⁴I(13/2) to ⁴I(15/2) manifolds due to the crystal field strength effect of Sc³⁺. Temperature-dependent PL of the Er(x)Sc(2-x)Si₂O₇ phase exhibits a variation of the full-width at half-maximum (FWHM) from 1.1 to 2.3 nm. The narrow FWHM is due to the small ionic radii of Sc³⁺, which enhance the crystal field strength affecting the optical properties of Er³⁺ ions located at the well-defined lattice sites of Sc silicate. A large excitation cross-section (σ(ex)) is equal to 3.0x10⁻²⁰ cm² at λ(ex) = 1527.6 nm.

Scandium effect on the luminescence of Er-Sc silicates prepared from multi-nanolayer films

Polycrystalline Er-Sc silicates (Er x Sc2-x Si2O7 and Er x Sc2-x SiO5) were fabricated using multilayer nanostructured films of Er2O3/SiO2/Sc2O3 deposited on SiO2/Si substrates by RF sputtering and thermal annealing at high temperature. The films were characterized by synchrotron radiation grazing incidence X-ray diffraction, cross-sectional transmission electron microscopy, energy-dispersive X-ray spectroscopy, and micro-photoluminescence measurements. The Er-Sc silicate phase Er x Sc2-x Si2O7 is the dominant film, and Er and Sc are homogeneously distributed after thermal treatment because of the excess of oxygen from SiO2 interlayers. The Er concentration of 6.7 × 10(21) atoms/cm(3) was achieved due to the presence of Sc that dilutes the Er concentration and generates concentration quenching. During silicate formation, the erbium diffusion coefficient in the silicate phase is estimated to be 1 × 10(-15) cm(2)/s at 1,250°C. The dominant Er x Sc2 - x Si2O7 layer shows a room-temperature photoluminescence peak at 1,537 nm with the full width at half maximum (FWHM) of 1.6 nm. The peak emission shift compared to that of the Y-Er silicate (where Y and Er have almost the same ionic radii) and the narrow FWHM are due to the small ionic radii of Sc(3+) which enhance the crystal field strength affecting the optical properties of Er(3+) ions located at the well-defined lattice sites of the Sc silicate. The Er-Sc silicate with narrow FWHM opens a promising way to prepare photonic crystal light-emitting devices.

Silicon nanostructures for photonics and photovoltaics

Silicon has long been established as the material of choice for the microelectronics industry. This is not yet true in photonics, where the limited degrees of freedom in material design combined with the indirect bandgap are a major constraint. Recent developments, especially those enabled by nanoscale engineering of the electronic and photonic properties, are starting to change the picture, and some silicon nanostructures now approach or even exceed the performance of equivalent direct-bandgap materials. Focusing on two application areas, namely communications and photovoltaics, we review recent progress in silicon nanocrystals, nanowires and photonic crystals as key examples of functional nanostructures. We assess the state of the art in each field and highlight the challenges that need to be overcome to make silicon a truly high-performing photonic material.