Wavelength multiplexing and tuning in nano-Ag/dielectric multilayers

Multicolored optical active planes have been fabricated with magnetron sputter method coupled with selective masking technique. The plane is multilayer structured with Ag nanoparticles and TiO2 thin layer as the building blocks. It was found that the formed multilayer can be readily wavelength multiplexed by simply overlapping several nano-Ag/TiO2 layered structures, each of which may have different surface plasmon resonance wavelength. Unlike high order multiple resonances of large particles each of the multiplexing wavelengths in such a system is separately tunable. Importantly, it reveals that modification of the TiO2 layer thickness generates a fine tuning of the resonance wavelength.

Wavelength multiplexing and tuning in nano-Ag/dielectric multilayers

Multicolored optical active planes have been fabricated with magnetron sputter method coupled with selective masking technique. The plane is multilayer structured with Ag nanoparticles and TiO2 thin layer as the building blocks. It was found that the formed multilayer can be readily wavelength multiplexed by simply overlapping several nano-Ag/TiO2 layered structures, each of which may have different surface plasmon resonance wavelength. Unlike high order multiple resonances of large particles each of the multiplexing wavelengths in such a system is separately tunable. Importantly, it reveals that modification of the TiO2 layer thickness generates a fine tuning of the resonance wavelength.

Influence of dielectric properties of a substrate upon plasmon resonance spectrum of supported Ag nanoparticles

Plasmon resonance spectra of supported Ag nanoparticles are studied by depositing the particles on different substrates. It was found that the dielectric properties of the substrates have significant effects on the spectral line shape, except the resonance frequency. Beyond the plasmon resonance band, the spectral shape is mainly governed by the dielectric function, particularly its imaginary part, of the substrate. The plasmon resonance band, on the other hand, may be severely distorted if the substrate is absorbing strongly.

Giant Goos-Hanchen displacement enhanced by dielectric film in frustrated total internal reflection configuration

It is predicted that the Goos-Hanchen displacement in the usual frustrated total internal reflection configuration can be resonantly enhanced greatly by coating a dielectric thin film onto the surface of the first prism when the angle of incidence is larger than the critical angle for total reflection at the prism-vacuum interface and is smaller than but close to the critical angle for total reflection at the prism-film interface. Theoretical analysis shows that the displacement of transmitted beam is about half the displacement of reflected beam in the thick limit of the vacuum gap between the two prisms. This is to be compared with the relation in the usual symmetric double-prism configuration that the displacement of transmitted beam is equal to the displacement of reflected beam. Numerical simulations for a Gaussian incident beam of waist width of 100 wavelengths reveal that when the dielectric thin film is of the order of wavelength in thickness, both the reflected and transmitted beams maintain well the shape of the incident beam in the thick limit of the vacuum gap. So largely enhanced displacements would lead to applications in optical devices and integrated optics. (c) 2007 American Institute of Physics.

Experimental observation of negative lateral displacements of microwave beams transmitting through dielectric slabs

It was theoretically predicted that when a beam of light travels through a thin slab of optically denser medium in the air, the emerging beam from the slab will suffer a lateral displacement that is different from the prediction of geometrical optics, that is, the Snell's law of refraction and can be zero and negative as well as positive. These phenomena have been directly observed in microwave experiments in which large angles of incidence are chosen for the purpose of obtaining negative lateral displacements. (C) 2005 Elsevier B.V. All rights reserved.

Negative lateral shift of a light beam transmitted through a dielectric slab and interaction of boundary effects

It is found that when a light beam travels through a slab of optically denser dielectric medium in air, the lateral shift of the transmitted beam can be negative. This is a novel phenomenon that is reversed in comparison with the geometrical optic prediction according to Snell's law of refraction. A Gaussian-shaped beam is analyzed in the paraxial approximation, and a comparison with numerical simulations is made. Finally, an explanation for the negativity of the lateral shift is suggested, in terms of the interaction of boundary effects of the slab's two interfaces with air.

Large positive and negative lateral displacements from total internal reflection configuration with a weakly absorbing dielectric film

It is theoretically shown that the simultaneously large positive and negative lateral displacements will appear when the resonant condition is satisfied for a TE-polarized light beam reflected from the total internal reflection configuration with a weakly absorbing dielectric film. Appearance of the enhanced negative lateral displacement is relative to the incidence angle, absorption of the thin Elm and its thickness. If we select an appropriate weakly absorbing dielectric film and its thickness, the simultaneously enhanced positive and negative lateral displacements will appear at different resonant angles. These phenomena may lead to convenient measurements and interesting applications in optical devices.

Large and negative lateral displacement in an active dielectric slab configuration

We investigate the large negative lateral displacements of TE polarized light beams reflected from or transmitted through an active slab surrounded by transparent medium. The large negative displacements can be achieved when the incidence angle of the beam is less than but close to the critical angle for total reflection. It is also shown that both the reflectivity and transmissivity of the beam that correspond to the large negative displacements can be enhanced by active medium. These phenomena may lead to convenient measurements and interesting applications in optical devices. (c) 2006 Elsevier B.V. All rights reserved.

Grey screening-photovoltaic soliton-induced waveguides

This paper shows that waveguides induced by grey screening-photovoltaic solitons are always single mode for all intensity ratios, which are the ratio between the peak intensity of the soliton and the dark irradiance. It finds that the confined energy near the centre of the grey soliton and the propagation constant of the guided mode increase monotonically with increasing intensity ratio. On the other hand, when the soliton greyness increases, the confined energy near the centre of the grey soliton and the propagation constant of the guided mode reduce monotonically. When the bulk photovoltaic effect is neglected for short circuits, these waveguides become waveguides induced by grey screening solitons. When the external bias field is absent, these waveguides become waveguides induced by grey photovoltaic solitons.

Soliton-induced waveguides in photorefractive photovoltaic materials

Waveguides induced by one-dimensional spatial photovoltaic solitons are investigated in both self-defocusing-type and self-focusing-type photorefractive photovoltaic materials. The number of possible guided modes in a waveguide induced by a bright photovoltaic soliton is obtained using numerical techniques. This number of guided modes increases monotonically with increasing intensity ratio, which is the ratio between the peak intensity of the soliton and the sum of the background illumination and the dark irradiance. On the other hand, waveguides induced by dark photovoltaic solitons are always single mode for all intensity ratios, and the higher the intensity ratio, the more confined is the optical energy near the centre of the dark photovoltaic soliton. Relevant examples are provided where photorefractive photovoltaic materials are of self-defocusing and self-focusing types. The properties of soliton-induced waveguides in both self-defocusing-type and self-focusing-type materials are also discussed.

Waveguides induced by screening-photovoltaic solitons in biased photorefractive-photovoltaic crystals

We investigate theoretically waveguides induced by screening-photovoltaic solitons in biased photorefractive-photovoltaic crystals. We show that the number of guided modes in a waveguide induced by a bright screening-photovoltaic soliton increases monotonically with the increasing intensity ratio of the soliton, which is the ratio between the peak intensity of the soliton and the dark irradiance. On the other hand, waveguides induced by dark screening-photovoltaic solitons are always single mode for all intensity ratios and the confined energy near the centre of a dark screening-photovoltaic soliton increases monotonically with the increasing intensity ratio. When the bulk photovoltaic effect is neglectable, these waveguides are those induced by screening solitons. When the external field is absent, these waveguides predict those induced by photovoltaic solitons.