651 research outputs found
Bond orbital description of the strain induced second order optical susceptibility in silicon
We develop a theoretical model, relying on the well established sp3
bond-orbital theory, to describe the strain-induced in
tetrahedrally coordinated centrosymmetric covalent crystals, like silicon. With
this approach we are able to describe every component of the
tensor in terms of a linear combination of strain gradients and only two
parameters and which can be estimated theoretically. The
resulting formula can be applied to the simulation of the strain distribution
of a practical strained silicon device, providing an extraordinary tool for
optimization of its optical nonlinear effects. By doing that, we were able not
only to confirm the main valid claims known about in strained
silicon, but also estimate the order of magnitude of the generated
in that device
Enhanced light emission from Carbon Nanotubes integrated in silicon micro-resonator
Single-wall carbon nanotube are considered a fascinating nanomaterial for
photonic applications and are especially promising for efficient light emitter
in the telecommunication wavelength range. Furthermore, their hybrid
integration with silicon photonic structures makes them an ideal platform to
explore the carbon nanotube instrinsic properties. Here we report on the strong
photoluminescence enhancement from carbon nanotubes integrated in silicon ring
resonator circuit under two pumping configurations: surface-illuminated pumping
at 735 nm and collinear pumping at 1.26 {\mu}m. Extremely efficient rejection
of the non-resonant photoluminescence was obtained. In the collinear approach,
an emission efficiency enhancement by a factor of 26 has been demonstrated in
comparison with classical pumping scheme. This demonstration pave the way for
the development of integrated light source in silicon based on carbon
nanotubes
Light Emission in Silicon from Carbon Nanotubes
The use of optics in microelectronic circuits to overcome the limitation of
metallic interconnects is more and more considered as a viable solution. Among
future silicon compatible materials, carbon nanotubes are promising candidates
thanks to their ability to emit, modulate and detect light in the wavelength
range of silicon transparency. We report the first integration of carbon
nanotubes with silicon waveguides, successfully coupling their emission and
absorption properties. A complete study of this coupling between carbon
nanotubes and silicon waveguides was carried out, which led to the
demonstration of the temperature-independent emission from carbon nanotubes in
silicon at a wavelength of 1.3 {\mu}m. This represents the first milestone in
the development of photonics based on carbon nanotubes on silicon
Optical Gain in Carbon Nanotubes
Semiconducting single-wall carbon nanotubes (s-SWNTs) have proved to be
promising material for nanophotonics and optoelectronics. Due to the
possibility of tuning their direct band gap and controlling excitonic
recombinations in the near-infrared wavelength range, s-SWNT can be used as
efficient light emitters. We report the first experimental demonstration of
room temperature intrinsic optical gain as high as 190 cm-1 at a wavelength of
1.3 {\mu}m in a thin film doped with s-SWNT. These results constitute a
significant milestone toward the development of laser sources based on carbon
nanotubes for future high performance integrated circuits.Comment: 4 figure
Optical pump-rejection filter based on silicon sub-wavelength engineered photonic structures
The high index contrast of the silicon-on-insulator (SOI) platform allows the
realization of ultra-compact photonic circuits. However, this high contrast
hinders the implementation of narrow-band Bragg filters. These typically
require corrugations widths of a few nanometers or double-etch geometries,
hampering device fabrication. Here we report, for the first time, on the
realization of SOI Bragg filters based on sub-wavelength index engineering in a
differential corrugation width configuration. The proposed double periodicity
structure allows narrow-band rejection with a single etch step and relaxed
width constraints. Based on this concept, we experimentally demonstrate a
single-etch, thick, Si Bragg filter featuring a corrugation
width of , a rejection bandwidth of and an
extinction ratio exceeding . This represents a ten-fold width
increase compared to conventional single-periodicity, single-etch counterparts
with similar bandwidths
Ensemble forecast of solar radiation using TIGGE weather forecasts and HelioClim database
International audienceMedium-range forecasts (one day to two weeks) of solar radiation are commonly assessed with a single forecast at a given location. In this paper, we forecast maps of surface solar irradiance, using ensembles of forecasts from the THORPEX Interactive Grand Global Ensemble (TIGGE) with a 6-h timestep. We compare our forecasts with observations derived from MeteoSat Second Generation (MSG) and provided by the HelioClim-3 database as gridded observations over metropolitan France. First, we study the ensembles from six meteorological centers. Second, we use sequential aggregation to linearly combine all the forecasts with weights that vary in space and time. Sequential aggregation updates the weights before any forecast, using available observations. We use the global numerical weather prediction from the European Center for Medium-range Weather Forecasts (ECMWF) as a reference forecast. The issue of spatial resolution is discussed because the low resolution forecasts from TIGGE are compared to high resolution irradiance estimated from MSG data. We found that the TIGGE ensembles are under-dispersed but rather different from one to another. Aggregation decreases the forecast error by 20%, and produces a more realistic spatial pattern of predicted irradiance
- …