Search

The coupling efficiency of grating couplers is derived for a Gaussian incident beam. Its optimum value depends on the beam waist and on the position of a light spot with respect to the coupler edge for given grating parameters. The characteristic coupling length has been experimentally determined for the grating coupler studied. Relative measurements of the coupling efficiency as a function of incident beam characteristics are in good agreement with the numerical results. Key words: Integrated optics, optical waveguides, grating couplers.

We have investigated light propagation through a single line-defect photonic crystal waveguide on a InP membrane. Modal analysis was performed using the finite-difference time-domain method. The fundamental mode has been found to be very close to the fundamental mode in a "refractive" waveguide but, in this case, it is inherently leaky. The propagation losses of this mode in the complete three-dimensional structure have been computed and measured to determine if its use could be of interest for practical applications. Propagation losses in the range of 0.1 dB/µm have been found numerically and experimentally for the fundamental mode whereas stronger out-of-plane losses have been observed for the other leaky mode within the band gap. The origins of the out-of-plane losses were then investigated and have clarified the inherent lower leakage of the fundamental mode. [ABSTRACT FROM AUTHOR]

We theoretically and experimentally demonstrate a strong and tunable optical anisotropy in epitaxially-grown VO2 thin films. Using a combination of temperature-dependent X-ray diffraction, spectroscopic ellipsometry measurements and first-principle calculations, we reveal that these VO2 thin films present an ultra-large birefringence (Δn > 0.9). Furthermore, leveraging the insulator-to-metal transition of VO2, we demonstrate a dynamic reconfiguration of optical properties from birefringent to hyperbolic, which are two distinctive regimes of anisotropy. Such a naturally birefringent and dynamically switchable platform paves the way for multi-functional devices exploiting tunable anisotropy and hyperbolic dispersion.

The light propagation through a single line-defect photon crystal wave-guide on an InP membrane is detailed. The propagation loses on the fundamental mode in the complete three dimensional structure are in the range of 0.1 dB/micron meter.

This paper highlights that combining laser interference lithography and electrochemical etching is a cost-effective, efficient method to realize periodic nanopore arrays in silicon with lattice pitch as small as 300 nm on centimeter-scale substrates. The fabrication of wide-area and high aspect ratio 2D pore arrays with 250 nm diameter and 5 μm depth is demonstrated. All the steps of the process have been optimized to achieve vertical sidewalls with 50 nm thickness, providing pore arrays with aspect ratio of 100 on n-type silicon substrates over an area of 2 x 2 cm². These results constitute a technological advance in the realization of ordered pore arrays in silicon with very small lattice parameters, with impact in biotechnology, energy harvesting, or sensors. [ABSTRACT FROM AUTHOR]

Photonics on CMOS is the integration of microelectronics technology and optics components to enable either improved functionality of the electronic circuit or miniaturization of optical functions. The integration of a photonic layer on an electronic circuit has been studied with three routes. For combined fabrication at the front end level, several building blocks using a silicon on insulator rib technology have been developed: slightly etched rib waveguide with low (0.1 dB/cm) propagation loss, a high speed and high responsivity Ge integrated photodetector and a 10 GHz Si modulators. Next, a wafer bonding of silicon rib and stripe technologies was achieved above the metallization layers of a CMOS wafer. Last, direct fabrication of a photonic layer at the back-end level was achieved using low-temperature processes with amorphous silicon waveguide (loss 5 dB/cm), followed by the molecular bonding of InP dice and by the processing in microelectronics environment of InP μsources and detector. [ABSTRACT FROM AUTHOR]

Efficient compact sources are necessary to consider on chip optical interconnections in integrated circuits. Properties of III–V microdisk light amplification by stimulated emission of radiation (LASERs) coupled to Si waveguides and fabricated on a 200-mm complementary metal–oxide–semiconductor (CMOS) pilot line are investigated. [ABSTRACT FROM PUBLISHER]

Results concerning a Bragg surface wave device based on porous silicon and intended for sensing application are reported. Existence of optical surface waves on Bragg structures is experimentally shown. Such device is expected to be very sensitive to the grafting of biological molecules. The authors demonstrate this sensing effect by grafting of amine chemical groups. The optical characterization using m-line spectroscopy shows that the increase of the coupling angle is about 20° after the amine grafting. The authors show that porosity is essential for reaching this high sensitivity. [ABSTRACT FROM AUTHOR]

Thin film solar cells may exhibit high conversion efficiencies provided their active material exhibits a high quality, like in the case of crystalline silicon, and if incident light coupling and absorption are appropriately controlled. We propose to integrate an advanced light trapping process relying on photonic crystals including a controlled pseudo-disorder. Thanks to Rigorous Coupled Wave Analysis, we determine the optimized nanophotonic structures that should be appropriately introduced in 1 µm thick crystalline silicon layers standing on a metal layer like aluminum. Thanks to a carefully controlled pseudo-disorder perturbation, absorption in these designed nanopatterns overcome that predicted in the case of fully optimized square lattice photonic crystals. Fabricated structures are analyzed in light of this numerical investigation to evidence the impact of such controlled perturbations, but also the influence of the measurement method and the technological imperfections. Thanks to the optimized perturbated photonic crystals, the integrated absorption in 1 µm thick crystalline Silicon layer increases from 37.7%, in the case of the unpatterned stack, to 70.7%. The sole effect of pseudo-disorder on the fully optimized simply periodic photonic crystals leads to an absolute increase of the integrated absorption up to 2%, as predicted by simulations, while both structures are fabricated using exactly the same process flow. [ABSTRACT FROM AUTHOR]