Search results for "Physics::Optics"
showing 10 items of 1958 documents
Self-assembled three-dimensional inverted photonic crystals on a photonic chip
2017
Three dimensional photonic crystals (PhCs) exhibiting a full photonic band gap have high potential in optical signal processing and detector applications. However, the challenges in the integration of the 3D PhCs into photonic circuits have so far hindered their exploitation in real devices. This article demonstrates the fabrication of 3D PhCs exploiting the capillary directed self-assembly (CDSA) of monodisperse colloidal silica spheres, their inversion to silicon shells, and integration with silicon waveguides. The measured transmission characteristics agree with numerical predictions and provide strong indication of a full photonic band gap in the inverted 3D photonic crystals at wavelen…
Z+/Z− lithium niobate optical waveguide sensitivity related to pyroelectric effect
2020
Lithium niobate crystal is widely used for the design and fabrication of integrated electro-optic modulators. As a ferroelectric material, one sees its spontaneous polarization change with temperature variations. This phenomenon, known as the pyroelectric effect, induces strong waveguide transmission variations for waveguides realized on Z -cut wafers. Waveguides made by titanium in-diffusion either on the Z + or Z − side of the crystal show a significant difference in temperature behavior. Experimental data, enlightened by numerical simulations, help to show why Z − waveguides are more immune to temperature changes than Z + ones.
Single Photon Emission from Site-Controlled InAs Quantum Dots Grown on GaAs(001) Patterned Substrates
2009
5 páginas, 5 figuras.
High-resolution mapping of the optical near-field components at a triangular nano-aperture.
2009
A triangular nano-aperture in an aluminum film was used as a probe in a scanning near-field optical microscope (SNOM) to image single fluorescent molecules with an optical resolution down to 30 nm. The differently oriented molecules were employed as point detectors to map the vectorial components of the electric field distribution at the illuminated triangular aperture. The good agreement of the experimental results with numerical simulations enabled us to determine both the field map at a triangular aperture and the exact orientations of the probing molecules.
Subwavelength imaging of field confinement in a waveguide-integrated photonic crystal cavity
2005
A photonic crystal microcavity is designed to obtain an original field distribution inside the cavity and the structure is etched inside a silicon-on-insulator waveguide. Spectral location of the photonic band gap and cavity resonance are identified by using transmittance measurements and by analyzing the light collected by a scanning near-field optical microscope probe exactly positioned on the center of the cavity. The results obtained with the two techniques are in very good agreement. Then the near-field distribution above the device is mapped and light confinement inside the cavity is evidenced. Moreover, this confined light presents some remarkable patterns which clearly correspond to…
Optically Probed Laser-Induced Field-Free Molecular Alignment
2011
Molecular alignment induced by laser fields has been investigated in research laboratories for over two decades. It led to a better understanding of the fundamental processes at play in the interaction of strong laser fields with molecules, and also provided significant contributions to the fields of high harmonic generation, laser spectroscopy, and laser filamentation. In this chapter, we discuss molecular alignment produced under field-free conditions, as resulting from the interaction of a laser pulse of duration shorter than the rotational period of the molecule. The experimental results presented will be confined to the optically probed alignment of linear as well as asymmetric top mol…
Asymmetric Dual-Grating Micro-Slit Configuration for Broadband Solid State Coherent Detection of THz Pulses
2016
We demonstrated solid-state broadband coherent Terahertz characterization based on the Terahertz Field Induced Second Harmonic effect in Silica. The THz detector consists of an asymmetric micro-slit array which can be operated at 200V applied bias.
Mechanical Coupling in Gold Nanoparticles Supermolecules Revealed by Plasmon-Enhanced Ultralow Frequency Raman Spectroscopy
2016
International audience; Acoustic vibrations of assemblies of gold nanoparticles were investigated using ultralow frequency micro-Raman scattering and finite element simulations. When exciting the assemblies resonantly with the surface plasmon resonance of electromagnetically coupled nano-particles, Raman spectra present an ultralow frequency band whose frequency lies below the lowest Raman active Lamb mode of single nanoparticles that was observed. This feature was ascribed to a Raman vibration mode of gold nanoparticle " supermolecules " , that is, nanoparticles mechanically coupled by surrounding polymer molecules. Its measured frequency is inversely proportional to the nanoparticle diame…
Supramolecular control of liquid crystals by doping with halogen-bonding dyes
2017
Introducing photochromic or polymeric dopants into nematic liquid crystals is a well-established method to create stimuli-responsive photonic materials with the ability to "control light with light". Herein, we demonstrate a new material design concept by showing that specific supramolecular interactions between the host liquid crystal and the guest dopants enhance the optical performance of the doped liquid crystals. By varying the type and strength of the dopant-host interaction, the phase-transition temperature, the order parameter of the guest molecules, and the diffraction signal in response to interference irradiation, can be accurately engineered. Our concept points out the potential…
Opaline Hydrogels: Polycrystalline Body-Centered-Cubic Bulk Material with an in Situ Variable Lattice Constant
2007
Opaline hydrogels were produced as a polycrystalline bulk material with a body-centered-cubic (bcc) structure by immobilization of self-ordered charged colloidal particles crystallized under equilibrium conditions in a poly(acrylamide) matrix. The final size of a polycrystalline sample is about 7 cm3; a single crystal is up to several millimeters in length. The crystal size is tunable by varying the amount of photoinitiator and the hydrogel volume change due to swelling. The resulting photonic crystals are of high quality, showing high-order reflections. These hydrogels show a reversible shift of the diffraction Bragg peak wavelength depending on external conditions due to swelling or shrin…