Kiseok Suh

Er3+ luminescence and cooperative upconversion in ErxY2−xSiO5 nanocrystal aggregates fabricated using Si nanowires

Er3+ luminescence and cooperative upconversion in ErxY2−xSiO5 nanocrystal aggregates fabricated using Si nanowires is investigated. X-ray diffraction and photoluminescence spectroscopy indicate that the composition of the final nanocrystals can be varied continuously from pure Y2SiO5 to pure Er2SiO5 while keeping the crystal structure the same. Analysis of concentration and pump-power dependence of the Er3+ photoluminescence intensity and decay time shows that while cooperative upconversion occurs at high Er concentrations, the cooperative upconversion coefficient is only (2.2±1.1)×10−18cm3∕s at a Er concentration of 1.2×1021cm−3. This is nearly ten times lower at more than ten times higher Er concentration than that reported from Er-doped silica and demonstrates the viability of using such silicates for compact, high-gain Si-based optical material for Si photonics.

Large-scale fabrication of single-phase Er2SiO5 nanocrystal aggregates using Si nanowires

Single-phase Er2SiO5 nanocrystal aggregates were produced on a large scale using Si nanowire (Si-NW) arrays as templates. A dense array of Si-NWs was grown by vapor-liquid-solid mechanism using Au catalyst on Si (111) substrate. Afterwards, ErCl3∙6H2O dissolved ethanol solution was spin coated and annealed first at 900°C for 4min in a flowing N2∕O2 environment and then at 1200°C in a flowing Ar environment for 3min. X-ray diffraction, scanning electron microscope, and high-resolution transmission electron microscope measurements indicate that due to the use of Si-NWs, such a short annealing procedure is sufficient to completely transform the Er-coated Si-NWs into a thick, large-area aggregate of pure, single-phase to Er2SiO5 oxyorthosilicate nanocrystals. The crystalline nature of Er2SiO5 film and the loose nature of the aggregate result in an atomlike Er3+ spectrum with a very narrow luminescence linewidth at 1.53μm, which together with a complete lack of temperature quenching of Er3+ luminescence and a ...

Cooperative upconversion and optical gain in ion-beam sputter-deposited Er x Y 2-x SiO 5 waveguides

Single-phase, polycrystalline Er(x)Y(2-x)SiO(5) thin films were deposited by reactive ion-beam sputter deposition and rapid thermal annealing. Due to the crystalline nature, the silicate thin films provide peak Er(3+) emission cross-section of 0.9 +/- 0.02 x 10(-20) cm(2) that is higher than that in silica. Optical gain, with near 60% inversion, is achieved via optical pumping of a single-mode, ridge-type waveguide with the silicate core with an Er concentration of 1.7 x 10(20) cm(-3). Analysis of pump-power dependence of the optical gain and spontaneous emission intensity of Er(3+) indicate that the gain is limited by cooperative upconversion process, whose coefficient is determined to be (8 +/- 3) x 10(-17) cm(3)/sec.

Optical activation of Si nanowires using Er-doped sol-gel derived silica

Optical activation of Si nanowires (Si-NWs) using sol-gel derived Er-doped silica is investigated. Si-NWs of about 100 nm diameter were grown on Si substrates by the vapor–liquid–solid method using Au catalysts and H2 diluted SiCl4. Afterwards, Er-doped silica sol-gel solution was spin-coated, and annealed at 950 °C in flowing N2/O2 environment. Such Er-doped silica/Si-NWs nanocomposite is found to combine the advantages of crystalline Si and silica to simultaneously achieve both high carrier-mediated excitation efficiency and high Er3+ luminescence efficiency while at the same time providing high areal density of Er3+ and easy current injection, indicating the possibility of developing sol-gel activated Si-NWs as a material platform for Si-based photonics.

Development and Application of Er-Doped Silicon-Rich Silicon Nitrides and Er Silicates for On-Chip Light Sources

On-chip light sources are a critical part for an integrated Si photonic technology, yet they lag other photonic components in their level of development. In this chapter, Er used as an optical dopant and utilizing its intra-4f transition at 1.54µm will be introduced as a viable means for on-chip light generation that has the advantage of being compatible with long-distance telecom as well. First, a general introduction to the topic of developing a Si-based/compatible light source will be presented, with emphasis on the need for a novel high-index material for Er-doping that can provide both a higher Er content and refractive index than has been reported so far. Second, Er-doped silicon-rich silicon nitride (SRSN) and Er silicates will be introduced as a promising host material for compact on-chip light sources. Finally, results of fabricating basic photonic components using Er-doped SRSN and Er-silicates will be presented.

Materials and devices for compact optical amplification in Si photonics

Materials and devices.for compact optical amplification in Si photonics is reviewed. In particular, as the requirement for high gain per length together with high refractive index renders traditional oxide-based approach problematic, Er-doping of silicon-rich silicon nitride and erbium silicate nanocrystals are proposed and shown to be promising alternatives. Using such new materials, microdisk resonators and slot waveguides that concentrate the light in a compact volume for high functionality are fabricated and characterized.

Er x Y 2−x SiO 5 thin film waveguide for high optical gain per length at 1.53 μm

Ridge-type Er_xY_2-xSiO₅ waveguides were fabricated. Amorphous Er_xY_2-xSiO₅ was deposited using reactive ion beam sputter deposition, and crystallized by high-temperature annealing. The inversion level achieved was 0.4, limited by grain-boundary scattering and multimodedness of waveguide.

ErxY2-xSiO5 nanocrystal and thin film for high gain per length material

We report on fabricating ErxY2-xSiO5 nanocrystals using ErCl3•6H2O and YCl3•6H2O solutions and Si nanowires grown by VSL method. Use of crystalline host allows incorporation of up to 25 at % Er without clustering and loss of optical activity, and use of Y enables continuous mixing of Er and Y for controlling cooperative upconversion. We obtain a cooperative upconversion coefficients of (2.2±1.1)×10-18 cm3/s and (5.4±2.7)×10-18 cm3/s at an Er concentration of 1.2×1021 cm-3 and 2.0×1021 cm-3, respectively. These values are up to 10 times lower at 10 times higher Er concentration than those reported for Er-doped silica, and shows that up to 69 dB/cm gain could be achieved for ultra-compact optical amplification. Also, we report on the deposition of ErxY2-xSiO5 thin film on Si substrate using ion beam sputter deposition. Rapid thermal annealing at 1100°C is enough to form crystal phase the film and activate most of Er3+ ions.

Optically activated Si nanowires and nanoribbons as a platform for Si-based photonics

This paper reports on optical activation of Si nanowires and Si nanoribbons by coupling Er. Single crystalline Si nanowires with diameters 100 nm and with length exceeding mum, and Si nanoribbons with thickness of 5-10 nm and with length of a few hundred of mum were grown by vapor-liquid-solid (VLS) growth mechanism using metal catalysts. Such Er-activated Si nanowires display strong Er3+ luminescence, excited via carriers in Si nanowires, yet comparable to pure silica in luminescence efficiency, showing promise of becoming a new material platform for Si-based photonics.

Surface functionalization of silicon micropillars spin-coated with Er-doped YSO silicate nanoparticles

Optically active and electrically excitable silicon pillar structure is fabricated by electrochemical etching method. Silicon pillars structure is made by etching porous silicon layers in hydrofluoric acid-based solution. Afterwards, silicon pillars that are spin-coated with Er silicate show strong Er-related 1.53 mum photo luminescence.