Optical Nanowires Research Articles

Optical fiber microwires and nanowires manufactured by modified flame brushing technique: properties and applications

The modified “flame brushing” technique has been used to manufacture microwires and nanowires from both silica and compound glasses. In this paper, the properties of the wires manufactured by this technique are presented. Applications fabricated from microwires are also discussed.

Modeling bending losses of optical nanofibers or nanowires

Bending losses of nanofibers or nanowires with circular 90 degrees bends are simulated using a three-dimensional finite-difference time-domain (3D-FDTD) method. Dependences of bending losses on wavelength and polarization of guided light are investigated, as well as the diameters, refractive indices, and bending radii of nanowires. The acceptable bending losses (approximately 1 dB/90 degrees) predicted in glass, polymer, and semiconductor nanowires with bending radii down to micrometer level may offer valuable references for assembling highly compact photonic integrated circuits or devices with optical nanowires.

Endface reflectivities of optical nanowires

Endface reflectivities (ERs) of optical nanowires are investigated using three-dimensional finite-difference time-domain simulations. Typical ERs of both free-standing and substrate-supported silica, tellurite, PMMA and semiconductor nanowires or nanofibers are obtained. Unlike in conventional waveguides such as optical fibers, ERs of nanowires are usually considerably lower when operated in single mode. Dependences of ER on the diameter and the refractive index of the nanowire, and the wavelength of the guided light are also investigated. These results are helpful for estimating and understanding ERs in optical nanowires with diameters close to or smaller than the wavelengths of the light, and may offer valuable references for practical applications such as nanowire or nanofiber-based resonators and lasers.

Compact and Tunable Slow and Fast Light Device Based on Two Coupled Dissimilar Optical Nanowires

We propose a novel and compact all-optical device for tunable slow and fast light propagation in parallel coupled structures consisting of two dissimilar optical nanowires. Advancement/delay tunability is achieved by varying the spacing between two nanowires. We develop a simplified analytical model to describe the dependence of achievable time advancement/delay and pulse broadening on the diameter of optical nanowires and it is indicated that this model agrees well with numerical results. Simulation results show that achievable maximum group-index change is about 1.4 and a 10-mm-long device can advance/delay a 2-ps pulse by 15.9 ps with pulse broadening factor equaling to 2.

An embedded optical nanowire loop resonator refractometric sensor

A novel refractometric sensor based on an embedded optical nanowire loop resonator is presented. The device sensitivity has been studied in two typical configurations and its dependence on the nanowire diameter and coating thickness determined.

Optical Nanowires for Microwave Applications

In this paper, we propose to take advantage of specific properties of nanophotonics to achieve microwave functions which are difficult to get with more conventional ways. With this goal, we developed new technologies to fabricate III-V nanowaveguides. Two ways were explored: the first one by deep etching of conventional epitaxies and the second one by embedding nanowires in polymer. We show in this paper some results on first devices mainly based on nanowires embedded in polymer.

Demonstration of III-V Semiconductor/Benzocyclobutene Optical Nanowires and Nanotapers

High index contrast waveguides in the III-V material line are demonstrated here. Created thanks to a wafer bonding technology, they are made of a GaAs nanowire embedded in a benzocyclobutene (BCB) matrix. We also report some of those waveguides properties and an example of active device considered with this technology.

Modeling of evanescent coupling between two parallel optical nanowires

Evanescent coupling between two parallel nanowires is investigated using the finite-difference time-domain method. Silica, tellurite, and silicon nanowires are used as typical materials in the simulation. Compared with weakly coupled waveguides, strongly coupled nanowires show much smaller transfer lengths without sacrificing high coupling efficiencies, suggesting possibilities for developing highly compact evanescent-coupling-based nanowire photonic devices, as well as for achieving high-efficiency interconnection between nanowires and external optical systems. Meanwhile, the polarization-dependent coupling properties, the considerably high minimum coupling efficiency, and the supermode-cutoff-like behavior are also observed. Evanescent coupling properties of strongly coupled nanowires demonstrated may provide valuable references for practical applications of optical nanowires.

Conical and biconical ultra-high-Q optical-fiber nanowire microcoil resonator

New 3D geometries of the optical nanowire microcoil resonator are suggested and investigated theoretically. The dependence of the Q factor on coupling parameters is calculated and compared for three different profiles. Results suggest that ultra-high-Q resonators can be fabricated more easily when the nanowire microcoil resonator has a biconical profile.

Demonstration of III-V Semiconductor/Benzocyclobutene Optical Nanowires and Nanotapers

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GaAs/polymer optical nanowires: fabrication and characterisation

The fabrication and propagation loss measurement of GaAs/polymer optical nanowires are reported. Their design consists of a 300×300 nm cross-section GaAs core buried into a polymer matrix bonded on a Si host substrate. The propagation loss at λ=1.55 µm is measured as about 5 dB/mm for both polarisations.

Dispersion shifts in optical nanowires with thin dielectric coatings

Based on exact solutions of Maxwell's equations of a 3-layer-structured cylindrical waveguide, we calculated dispersion shifts in thin-dielectric-coated optical nanowires. Typical parameters of silica and silicon nanowires are used for numerical simulations. It shows that, the dispersion of a nanowire waveguide can be made highly sensitive to the thickness and index of the coating layer, and a thin coat may lead to considerable dispersion shift of the guided light. For example, in a 300-nm-diameter silicon nanowire, a 1% decrease in diameter of the silicon core by oxidation of silicon into silica shell leads to a 34% decrease in dispersion at 1450-nm wavelength. Results presented in this work suggest the possibility of tuning waveguide dispersions of optical nanowires by coating thin dielectric layers.

Fabrication and characterization of β-Ga 2O 3 optical nanowires

Monoclinic gallium oxide (β-Ga 2O 3) nanowires with lengths of tens of micrometers and diameters ranging from 100 to 250 nm are synthesized using simple physical evaporation based on vapor–liquid–solid (VLS) mechanism. The as-synthesized straight β-Ga 2O 3 nanowires show excellent diameter uniformity and sidewall smoothness, making them suitable for optical wave-guiding. Light from a fiber taper is launched into the nanowire by means of evanescent coupling. Measured propagation loss of the nanowire at 633 nm wavelength is on the order of 10 dB/mm. Favorable mechanical strength of these nanowires for elastic bending is also observed. Our results suggest that β-Ga 2O 3 nanowires are promising building blocks for micro- and nanophotonic circuits and devices.

Compound-glass optical nanowires

A simple method to fabricate nanowires with radii as small as 90 nm from compound-glass fibres is described. Low transmission losses at 1.55 µm have been achieved in nanowires fabricated from lead-silicate and bismuth silicate optical fibres.

Modeling of silica nanowires for optical sensing

Based on evanescent-wave guiding properties of nanowire waveguides, we propose to use single-mode subwavelength-diameter silica nanowires for optical sensing. Phase shift of the guided mode caused by index change is obtained by solving Maxwell's equation, and is used as a criterion for sensitivity estimation. Nanowire sensor employing a wire-assembled Mach-Zehnder structure is modeled. The result shows that optical nanowires, especially those fabricated by taper drawing of optical fibers, are promising for developing miniaturized optical sensors with high sensitivity.

Subwavelength Nonlinear Plasmonic Nanowire

We investigate numerically, by means of the finite-difference time-domain method, the propagation characteristics of surface plasmon-polariton (SPP) modes excited in an optical nanowire consisting of a chain of Ag spheres embedded in dielectric shells made of materials with optical Kerr nonlinearity. It is demonstrated that, in the linear limit, the nanowire supports two SPP modes, a transverse and a longitudinal one, separated by Δλ = 20 nm. Furthermore, the dependence of the transmission characteristics of these SPP modes, on both the pulse peak power and Kerr coefficient of the dielectric shell, is investigated. Nonlinear optical phenomena, such as power dependence of mode frequency, switching, or optical limiting, are observed and discussed.

Linear and Nonlinear Transmission of Surface Plasmon Polaritons in an Optical Nanowire

ABSTRACTPolymer-metal composites offer the possibility of strongly enhanced nonlinear optical properties, which can be used for ultrasmall photonic devices. In this paper, we investigate numerically, by means of the finite-difference time-domain (FDTD) method, the propagation characteristics of surface plasmon polariton (SPP) modes excited in an optical nanowire consisting of a chain of either metallic cylinders or metallic spheres embedded in dielectric shells made of polymers (or other material) with optical Kerr nonlinearity. Our FDTD calculations incorporate both the nonlinear optical response of the dielectrics as well as the frequency dispersion of the metals, which is considered to obey a Drude-like model. It is demonstrated that, in the linear limit, the nanowire supports two SPP modes, a transverse and a longitudinal one, separated by Δλ = 20 nm. Furthermore, the dependence of the transmission of these SPP modes, on both the pulse peak power and Kerr coefficient of the dielectric shell, is investigated. Nonlinear optical phenomena, such as power-dependent mode frequency, switching, or optical limiting, are observed.