Search results for "Physics::Optics"
showing 10 items of 1958 documents
Near‐field optical addressing of single molecules in coplanar geometry: a theoretical study
2001
Photonic transfer through elongated optical structures of submicrometre section microfabricated at the surface of dielectric or semiconductor samples can be enhanced by an appropriate structuring of the local refraction index. We show from computerized simulations that both the light localization and the spectroscopic properties of such structures can be used to selectively excite, in coplanar geometry, individuals molecules located in the near-field.
Second-harmonic generation in surface periodically poled lithium niobate waveguides:On the role of multiphoton absorption
2008
Second harmonic generation is investigated in lithium niobate channels realized by proton exchange and quasi-phase-matched by surface periodic-poling. The reduction in conversion efficiency at high powers is interpreted in terms of multi-photon absorption via two-color terms, yielding an estimate of the dominating three-photon process.
Ridge-enhanced optical transmission through a continuous metal film
2004
Optical transmission through a continuous (without holes) metal film with a periodic structure of metal or dielectric ridges on one or both interfaces was numerically studied. The dependencies of the transmission on the ridge width and height as well as the ridge arrangements on the opposite interfaces were investigated in weak- and strong-coupling regimes. The transmission enhancement was shown to depend on the relative position of the ridge gratings on the opposite interfaces of a film, confirming the role of resonant tunneling processes involving states of the surface polariton Bloch modes.
Frequency doubling in surface periodically poled lithium niobate waveguides: Competing effects
2007
We fabricated α-phase pro ton-exchanged (PE) lithium niobate (LN) channel waveguides quasi phase-matched (QPM) via surface periodic poling (SPP) and carried out the first experimental demonstration of second harmonic generation (SHG) in such devices.[1] Experiments were performed by employing an optical parametric amplifier/oscillator producing 25 ps pulses in the range 1.1-1.6 μm with a line-width less than 2cm−1 and a repetition rate of 10Hz. SHG measurements were performed either at a fixed wavelength by varying the fundamental frequency (FF) input power or by scanning the FF wavelength, ratioing the second harmonic (SH) output to the FF input to obtain the conversion efficiency. By repe…
Phase-bistable patterns and cavity solitons induced by spatially periodic injection into vertical-cavity surface-emitting lasers
2014
Spatial rocking is a kind of resonant forcing able to convert a self-oscillatory system into a phase-bistable, pattern forming system, whereby the phase of the spatially averaged oscillation field locks to one of two values differing by $\ensuremath{\pi}$. We propose the spatial rocking in an experimentally relevant system---the vertical-cavity surface-emitting laser (VCSEL)---and demonstrate its feasibility through analytical and numerical tools applied to a VCSEL model. We show phase bistability, spatial patterns, such as roll patterns, domain walls, and phase (dark-ring) solitons, which could be useful for optical information storage and processing purposes.
Dispersive interactions between atoms and nonplanar surfaces
2009
We calculate the dispersive force between a ground state atom and a non planar surface. We present explicit results for a corrugated surface, derived from the scattering approach at first order in the corrugation amplitude. A variety of analytical results are derived in different limiting cases, including the van der Waals and Casimir-Polder regimes. We compute numerically the exact first-order dispersive potential for arbitrary separation distances and corrugation wavelengths, for a Rubidium atom on top of a silicon or gold corrugated surface. We discuss in detail the inadequacy of the proximity force approximation, and present a simple but adequate approximation for computing the potentia…
Hollow system with fin. Transient Green function method combination for two hollow cylinders
2017
In this paper we develop mathematical model for three dimensional heat equation for the system with hollow wall and fin and construct its analytical solution for two hollow cylindrical sample. The method of solution is based on Green function method for one hollow cylinder. On the conjugation conditions between both hollow cylinders we construct solution for system wall with fin. As result we come to integral equation on the surface between both hollow cylinders. Solution is obtained in the form of second kind Fredholm integral equation. The generalizing of Green function method allows us to use Green function method for regular non-canonical domains.
Absence of mutual polariton scatterings for strongly coupled surface plasmon polaritons and dye molecules with large Stokes shift
2013
The understanding and control of the dynamics of hybrid modes consisting of strongly coupled surface plasmon polaritons and molecular excitations of dye molecules is of great timely interest, as it allows one to tailor interactions between optical signals as needed for active all-optical devices. Here we utilize dye molecules with an especially large Stokes shift to demonstrate the absence of mutual scatterings among the strongly coupled hybrid modes. We employ a quantum mechanical three-level model and show that the hybrid modes decay via dephasing and internal relaxation of the molecules to a fluorescing state of the dye, which can be used as a measure for the decay. Our results provide e…
Synthetic aperture superresolution with multiple off-axis holograms
2006
An optical setup to achieve superresolution in microscopy using holographic recording is presented. The technique is based on off-axis illumination of the object and a simple optical image processing stage after the imaging system for the interferometric recording process. The superresolution effect can be obtained either in one step by combining a spatial multiplexing process and an incoherent addition of different holograms or it can be implemented sequentially. Each hologram holds the information of each different frequency bandpass of the object spectrum. We have optically implemented the approach for a low-numerical-aperture commercial microscope objective. The system is simple and rob…
Holography and Superresolution
2013
The capability of improving the spatial resolution of imaging systems is usually known as superresolution. Some methods provide improve resolution by playing with the imaging part of the system and without modifying the optical parameters of the imaging lenses. And others act over the geometry, shape and size of sampling pixels in the detection array. The former strategy allows optical superresolution while the latter provide geometrical superresolution. In this contribution, we will review the state of the art in optical superresolution approaches understood as the possibility to overcome the limited resolving power of imaging systems beyond the bounds imposed by Abbe's diffraction theory.…