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In the paper, we review our work on heterogeneous III-V-on-silicon photonic components and circuits for applications in optical communication and sensing. We elaborate on the integration strategy and describe a broad range of devices realized on this platform covering a wavelength range from 850 nm to 3.85 μm.

This paper presents a technology of hybrid integration vertical cavity surface emitting lasers (VCSELs) directly on silicon photonics chip. By controlling the reflow of the solder balls used for electrical and mechanical bonding, the VCSELs were bonded at 10 degree to achieve the optimum angle-of-incidence to the planar grating coupler through vision based flip-chip techniques. The 1 dB discrepancy between optical loss values of flip-chip passive assembly and active alignment confirmed that the general purpose of the flip-chip design concept is achieved. This hybrid approach of integrating a miniaturized light source on chip opens the possibly of highly compact sensor system, which enable future portable and wearable diagnostics devices.

For the first time, III-V opto-electronic components are coupled to silicon waveguide circuits using transfer-printing. Efficient III-V material usage is enabled in silicon photonics by providing III-V only where needed. We present transfer-printed single-spatial-mode LEDs coupling to silicon-on-insulator waveguides as first examples of this technology.

Powders of yttrium disilicate (Y2Si2O7) doped with Er3+ have been prepared by the sol-gel method. The structure of the obtained powders has been determined. Room temperature emission spectra have been recorded and excited state decay profiles have been analyzed. Differences between the spectroscopic properties of Er3+ in monoclinic alpha-Y2Si2O7 (space group P-1) and beta-Y2Si2O7 (space group C2/m) polymorphs have been investigated and shown. The significant broadening of the emission spectra recorded for the alpha phase compared to the one for the beta phase was discussed in terms of higher number of Y3+ sites (4) present in the alpha phase with respect to only one Y3+ site in the case of beta phase. The higher value of the luminescence decay time of beta phase (11.2 ms) compared to the alpha phase (8.5 ms) is associated with the higher site symmetry of beta-Y2Si2O7. Moreover it was found that Er3+ concentration affects the shape of the I-4(13/2) -> I-4(15/2) emission band. It results in changes of the relative emission intensities of peaks localized at 1527 nm and 1532 nm; this indicates changes of the Y3+ sites occupation on increasing the Er3+ concentration. The luminescence lifetime was observed to decrease with the increase of Er3+ concentration. The spectroscopic results have been compared with the ones relative to thin films of Y2Si2O7:Er3+ with a similar composition. The lower value of the luminescence decay time observed for thin films compared to the powder of alpha phase was explained with the changes of the particles packing resulting in the change of the effective refractive index. (C) 2015 Elsevier B.V. All rights reserved.

Silicon is now firmly established as a high performance photonic material. Its only weakness is the lack of a native electrically driven light emitter that operates CW at room temperature, exhibits a narrow linewidth in the technologically important 1300- 1600 nm wavelength window, is small and operates with low power consumption. Here, an electrically pumped all-silicon nano light source around 1300-1600 nm range is demonstrated at room temperature. Using hydrogen plasma treatment, nano-scale optically active defects are introduced into silicon, which then feed the photonic crystal nanocavity to enahnce the electrically driven emission in a device via Purcell effect. A narrow ({\Delta}{\lambda} = 0.5 nm) emission line at 1515 nm wavelength with a power density of 0.4 mW/cm2 is observed, which represents the highest spectral power density ever reported from any silicon emitter. A number of possible improvements are also discussed, that make this scheme a very promising light source for optical interconnects and other important silicon photonics applications.

This article presents the flip-chip bonding of vertical-cavity surface-emitting lasers (VCSELs) to silicon grating couplers (GCs) via SU8 prisms. The SU8 prisms are defined on top of the GCs using non-uniform laser ablation process. The prisms enable perfectly vertical coupling from the bonded VCSELs to the GCs. The VCSELs are flip-chip bonded on top of the silicon GCs employing the laser-induced forward transfer (LIFT)-assisted thermocompression technique. An excess loss of < 1 dB at 1.55 µm measured from the bonded assemblies is reported in this paper. The results of high speed transmission experiments performed on the bonded assemblies with clear eye openings up to 20 Gb/s are also presented.

We successfully demonstrate for the first time, VCSEL-to-silicon grating coupler flip-chip assembly using SU8 prism fabricated by non-uniform laser ablation. Excess loss of < 1 dB and data transmission up to 20 Gb/s @ 1550 nm was achieved.

Silicon and Silicon Nitride photonics arc on their way to open the route towards integrated on-chip spectropholometers, Cost, miniaturization, miniaturization, hut also performance advantages ace at the origin of their potential We will discuss several integrated on-chip spectropholometers that are on the eve of commercial lake up.

A novel design geometry for an optically pumped LED by integrating thin III-V membranes on SOI is proposed. Simulation results predict power efficiency and fabrication tolerance. We present a first proof-of-concept demonstration of the LED.

Light emission in crystalline silicon (c-Si) has been a subject of intense research over the past two decades. Many different strategies have been explored to make silicon an efficient infrared emitter at strategic telecom wavelengths, including doping with rare-earth atoms, or exploiting optically active structural defects.

This work was supported by Era-NET NanoSci LECSIN project coordinated by F. Priolo, by the Italian Ministry of University and Research, FIRB contract No. RBAP06L4S5 and by the EPSRC UKSp project. Partial financial support by the Norwegian Research Council is also acknowledged. We demonstrate intense room temperature photoluminescence (PL) from optically active hydrogen- related defects incorporated into crystalline silicon. Hydrogen was incorporated into the device layer of a silicon on insulator (SOI) wafer by two methods: hydrogen plasma treatment and ion implantation. The room temperature PL spectra show two broad PL bands centered at 1300 and 1500 nm wavelengths: the first one relates to implanted defects while the other band mainly relates to the plasma treatment. Structural characterization reveals the presence of nanometric platelets and bubbles and we attribute different features of the emission spectrum to the presence of these different kind of defects. The emission is further enhanced by introducing defects into photonic crystal (PhC) nanocavities. Transmission electron microscopy analyses revealed that the isotropicity of plasma treatment causes the formation of a higher defects density around the whole cavity compared to the ion implantation technique, while ion implantation creates a lower density of defects embedded in the Si layer, resulting in a higher PL enhancement. These results further increase the understanding of the nature of optically active hydrogen defects and their relation with the observed photoluminescence, which will ultimately lead to the development of intense and tunable crystalline silicon light sources at room temperature. Publisher PDF

We demonstrate electrically pumped silicon nano-light source at room temperature, having very narrow emission line (

Highly Er-doped Yb-Y disilicates thin films grown on c-Si will be presented. The approach has permitted to vary independently the concentrations of both active rare earths, Er and Yb, and to effectively control the Er sensitization from Yb ions. We will demonstrate that these films are stable, having a uniform distribution of the chemical components throughout their thickness and a favored crystallization of the alpha-phase, which is the most optically efficient. We verified that this crystallization can be ascribed to a densification of the material and to the mobility locally introduced by ion implantation. Finally we will show a strong PL emission at 1.54 mu m, associated to the Yb-Er energy transfer mechanism, without any deleterious energy back-transfer. These properties make this new class of thin films a valuable and promising approach for the realization of efficient planar amplifiers. (C) 2012 Optical Society of America

We present the different approaches we recently followed to achieve intense room temperature photoluminescence (PL) from Si-based materials. On one side we obtained sub-bandgap PL from H-related defects induced by the H-2 plasma treatment of Si photonic crystal (PhC) nanocavities. We demonstrated that a strong and narrow PL emission can be obtained in the PhC nanocavities due to the formation of a damaged layer mainly consisting of nanometric platelets and bubbles. An overall 40000-fold enhancement of the PL signal, with respect to pure crystalline Si, has been achieved and moreover the signal can be tuned in a wide range by only changing the PhC parameters. On the other side, we focused our attention on the properties of SiO2 and SiOC host matrices doped with Eu ions. C addition produces a strong enhancement of the Eu PL with respect to pure SiO2 films. The chemical and structural characterization of these materials reveals an extensive Eu clustering in SiO2-based films, while C addition induces a significant reduction of this phenomenon, enhancing the fraction of optically active Eu ions. These results can be applied for the realization of efficient Si-based light sources.

We investigate the optical properties of Er-Yb-Y disilicate thin films in which Er and Yb contents are varied independently. From time-resolved measurements of Yb decay in absence and in presence of Er, we analyzed and modeled the energy transfer mechanism identifying all the de-excitation channels and measuring a coupling constant CYb-Er = 3.0 x 10(-39) cm(6)/s. Finally, we calculated the efficiency of Yb-Er energy transfer process and we correlated it with Er photoluminescence, demonstrating that it is controlled by the energy transfer mechanism. The maximum efficiency is found for 1.5 x 10(21) Er/cm(3) and 1.5 x 10(22) Yb/cm(3), by making this material very promising for optical amplifiers.

We investigate the electrical properties of Silicon-on-Insulator photonic crystals as a function of doping level and air filling factor. A very interesting trade-off between conductivity and optical losses in L3 cavities is also found.

α-(Yb1-xErx)2Si2O7 thin films on Si substrates were synthesized by magnetron co-sputtering. The optical emission from Er3+ ions has been extensively investigated, evidencing the very efficient role of Yb-Er coupling. The energy-transfer coefficient was evaluated for an extended range of Er content (between 0.2 and 16.5 at.%) reaching a maximum value of 2 × 10⁻¹⁶ cm⁻³s⁻¹. The highest photoluminescence emission at 1535 nm is obtained as a result of the best compromise between the number of Yb donors (16.4 at.%) and Er acceptors (1.6 at.%), for which a high population of the first excited state is reached. These results are very promising for the realization of 1.54 μm optical amplifiers on a Si platform.

We investigate the electrical properties of silicon-on-insulator (SOI) photonic crystals as a function of both doping level and air filling factor. The resistance trends can be clearly explained by the presence of a depletion region around the sidewalls of the holes that is caused by band pinning at the surface. To understand the trade-off between the carrier transport and the optical losses due to free electrons in the doped SOI, we also measured the resonant modes of L3 photonic crystal nanocavities and found that surprisingly high doping levels, up to 10(18)/cm(3), are acceptable for practical devices with Q factors as high as 4 x 10(4).

Structural and optical properties of Y 2−x Er x Si 2 O 7 thin films have been studied. For higher Er content mechanisms related to Er-Er interactions increase optical efficiency. Moreover the influence of up-conversion has been estimated.

We introduce an Y-Er disilicate thin film deposited on top of a silicon photonic crystal cavity as a gain medium for active silicon photonic devices. Using photoluminescence analysis, we demonstrate that Er luminescence at 1.54 mu m is enhanced by coupling with the cavity modes, and that the directionality of the Er optical emission can be controlled through far-field optimization of the cavity. We determine the maximum excitation power that can be coupled into the cavity to be 12 mW, which is limited by free carrier absorption and thermal heating. At maximum excitation, we observe that nearly 30% of the Er population is in the excited state, as estimated from the direct measurement of the emitted power. Finally, using time-resolved photoluminescence measurements, we determine a value of 2.3 for the Purcell factor of the system at room temperature. These results indicate that overcoating a silicon photonic nanostructure with an Er-rich dielectric layer is a promising method for achieving light emission at 1.54 mu m wavelength on a silicon platform. Publisher PDF

In this paper we have investigated the role of the Er-O interaction on the photoluminescence properties of Er-doped crystalline silicon. We demonstrate that the strong Er-O interaction leads to an O redistribution after thermal treatment. In particular, in the absence of Er, O out-diffuses from the Si surface and a depletion of O in the first micron below the surface is observed. In the presence of Er, the rare earth acts as a getter for O and therefore there is an O redistribution as a result of the balance between O out-diffusion and O trapping by the Er. This implies that the O concentration that remains in the Si crystal changes after thermal annealing and it is largely determined by the amount of Er present in the sample. These data will be presented and the implication on the Er optical activity discussed.

Y2−xErxO3 thin films, with x varying between 0 and 0.72, have been successfully grown on crystalline silicon (c-Si) substrates by radio-frequency magnetron cosputtering of Y2O3 and Er2O3 targets. As-deposited films are polycrystalline, showing the body-centered cubic structure of Y2O3, and show only a slight lattice parameter contraction when x is increased, owing to the insertion of Er ions. All the films exhibit intense Er-related optical emission at room temperature both in the visible and infrared regions. By studying the optical properties for different excitation conditions and for different Er contents, all the mechanisms (i.e., cross relaxations, up-conversions, and energy transfers to impurities) responsible for the photoluminescence (PL) emission have been identified, and the existence of two different well-defined Er concentration regimes has been demonstrated. In the low concentration regime (x up to 0.05, Er-doped regime), the visible PL emission reaches its highest intensity, owing to the in...

We show that far-field optimized PhC nanocavities can greatly enhance linear and nonlinear optical effects in silicon, thus providing a unique platform for the realization of nanoscale devices with advanced optical functionalities at room temperature.