Preservation of photon indistinguishability after transmission through surface-plasmon-polariton waveguide

We experimentally demonstrated preservation of indistinguishability between two photons via mode conversions, namely, photon-to-plasmon and plasmon-to-photon conversions. A two-photon interference experiment was carried out using a broadband photon pair generated through a spontaneous parametric downconversion process. We observed the so-called Hong-Ou-Mandel dip with an interferometer including a 1-mm-long surface-plasmon-polariton (SPP) waveguide. The photon indistinguishability of 92.4% was retained after propagation in the SPP waveguide.     

Packing density of conventional waveguides and photonic crystal waveguides

We compare coupling between parallel waveguides within one-dimensional photonic crystals and coupling between conventional waveguides. We consider the situation in which coupling between the waveguides is minimized, so that light in the waveguides propagates essentially independently. Subject to this condition, we compare the minimum mutual distance between conventional planar waveguides and waveguides in one-dimensional photonic crystals. We find that the packing densities of the conventional and periodic structures are comparable.     

Bragg reflection waveguides

The possibility of using Bragg reflection to obtain lossless confined propagation in slabs with a lower dielectric constant than that of the surrounding media is proposed and analyzed.     

Multimode nematicon waveguides

We report on the first (to our knowledge) experimental observation of higher-order modes guided by soliton-induced waveguides in nematic liquid crystals. We find that the nematicon waveguides operate in a bounded power region specific to each guided mode. Below this region, the guided beams diffract; above this region, the mode mixing and coupling give rise to an unstable output.     

细菌形成光波导

当激光束通过含有海洋细菌的水时,它把这些微生物拖入光束之内,从而使光束发生了聚焦。     

Low-loss silica-on-silicon waveguides

Waveguiding structures are one of the fundamental components of integrated photonic circuitry. Devices with low loss and a linear response across a wide wavelength range are especially desirable. In the present Letter, we have successfully developed and characterized low-loss silica waveguides integrated on a silicon substrate with a novel suspended cylinder geometry. The unique design creates a device that is effectively air clad, resulting in a large refractive index contrast for improved optical field confinement. The measured loss is constant from 658 to 1550 nm, and it is independent of the polarization of the input light and the input power.     

Asymmetric biaxial waveguides

The expressions for the propagation constant in the three types of cylindrical asymmetric biaxial waveguides, in which the axes of two media are displaced one from the other, are derived. Taking the wave indexm=0 for an asymmetric wave we reobtain the known result in coaxial waveguides. Withm0 the field intensities increase with increasing the asymmetry. By increasing the size of outer surface the attenuation will be decreased.I would like to express my sincere thanks to Dr. D. Fraitová for her help and to Prof. Hoang Phuong for initially suggesting this problem.     

Focusing diffused waveguides

Focusing optical fibre and thin film guide can be made to have nearly the same group velocity for every mode if the optimum distribution of refractive index or thickness of the film is realized. A focusing optical fibre is manufactured from a multilayer glass rod by solid state diffusion. A thin film waveguide is prepared from nitrocellulose by controlling the airflow distribution. Undulation of light propagating in the film is observed, and it is confirmed that the focusing property is determined by the distribution of the film thickness. The field distributions of the TE modes have been analysed for an optical waveguide fabricated by solid state diffusion. Glass waveguide has been manufactured with the appropriate concentration of lead ions to give the maximum propagation constant. A low loss waveguide is fabricated by the diffusion of lead or thallium ion into glass followed by selective etching.     

Morphological effects on surface-plasmon-polariton waves at the planar interface of a metal and a columnar thin film

A theoretical study predicts that surface-plasmon-polariton (SPP) waves may propagate along the interface of a columnar thin film (CTF) and a metal over a range of propagation directions relative to the morphology of the CTF. The range of propagation directions depends on the tilt of the columns in the CTF. The phase speed of the SPP wave varies mainly as a function of the tilt of the CTF columns. Both the confinement of the SPP wave to the interface and the decay of the SPP wave along the direction of propagation depend strongly on the direction of propagation relative to the morphologically significant plane of the CTF. The greater the columnar tilt in relation to the interface, the shorter is the range of propagation. Because of CTF porosity and the ability to engineer this biaxial dielectric material, the CTF–metal interface may be more attractive for sensor applications than the traditional dielectric–metal interface used for SPP-wave-based sensors.     

Plasmonic crystal waveguides

We study the properties of electromagnetic waves propagating along the waveguides with a periodic core created by alternating metal and dielectric layers, the so-called quasi-one-dimensional plasmonic crystal waveguides. Such waveguides can be symmetric or asymmetric, depending on the cladding or substrate material properties, as well as on the termination of the periodic structure. We analyze the dispersion characteristics as well as the profiles of the guided modes for several types of waveguide structure.     

Multilayer graphene waveguides

We study dispersion properties of TM-polarized electromagnetic waves guided by a multilayer graphene metamaterial. We demonstrate that both dispersion and localization of the guided modes can be efficiently controlled by changing the number of layers in the structure. Remarkably, we find that in the long wavelength limit, the dispersion of the fundamental mode of the N-layer graphene structure coincides with the dispersion of a plasmon mode supported by a single graphene layer, but with N times larger conductivity. We also compare our exact dispersion relations with the results provided by the effective media model.     

Modes of periodic waveguides

We calculate exactly the two bound Floquet modes of a periodic linear waveguide induced in a medium by a second-order soliton of the nonlinear Schr?dinger equation. The modes are degenerate at the writing frequency, having the same quasi-propagation constant, which suggests applications of our method to spectral filtering.     

Photonic bandgap plasmonic waveguides

A type of a plasmonic waveguide has been proposed featuring an "open" design that is easy to manufacture, simple to excite and offers convenient access to a plasmonic mode. Optical properties of photonic bandgap (PBG) plasmonic waveguides are investigated experimentally by leakage radiation microscopy and numerically using the finite element method confirming photonic bandgap guidance in a broad spectral range. Propagation and localization characteristics of a PBG plasmonic waveguide have been discussed as a function of the wavelength of operation, waveguide core size, and the number of ridges in the periodic reflector for fundamental and higher order plasmonic modes of the waveguide.     

High-transmission planar x-ray waveguides

We have studied the propagation of hard x rays in a planar x-ray waveguide with a sub-20 nm guiding layer. To optimize the transmission and to minimize absorption losses, a novel waveguide design based on a two-component cladding was implemented. Optimized transmission is achieved by placing an appropriate interlayer between the cladding and the guiding core. The experimental results along with simulations of field propagation show that high transmission values can be obtained in waveguide optics at parameters relevant for x-ray imaging. These are small beam diameters below 20 nm and the relatively long guiding length necessary for efficient blocking of multi-keV photon energy beams.     

Adiabatic coupling between conventional dielectric waveguides and waveguides with discrete translational symmetry

We study adiabatic transformation in optical waveguides with discrete translational symmetry. We calculate the reflection and transmission coefficient for a structure consisting of a slab waveguide that is adiabatically transformed into a photonic crystal waveguide and then back into a slab waveguide. The calculation yields high transmission over a wide frequency range of the photonic crystal waveguide band and indicates efficient coupling between the slab waveguide and the photonic crystal waveguide. Other applications of adiabatic mode transformation in photonic crystal waveguides and the coupled-resonator optical waveguides are also discussed.     

Gallium-diffused waveguides in sapphire

The fabrication and characterization of gallium-diffused planar waveguides in sapphire are reported. Waveguides were fabricated by diffusion of 60-200-nm-thick films of gallium oxide into c -cut sapphire at 1600 degrees C for times ranging from 6 to 16 h. Near-field intensity profiles of the guided modes were measured at wavelengths from 488 to 850 nm, and the surface-index elevation was estimated to be up to (0.6+/-0.02)x10(-2) . Potential applications for low-threshold Ti:sapphire waveguide lasers and for optical integrated circuits with passive and active elements in sapphire are discussed.     

Self-induced transparency in waveguides

A theory of self-induced transparency (SIT) in waveguides, covered by thin films (thickness d ? λ = 2π/cω) of a resonant substance, has been developed. The shape of a waveguiding soliton (waveguiding “2π”-pulse) has been determined, and its velocity as a function of the film thickness and other characteristics of the resonant layer has been investigated.