Joseph W. Haus

Degenerate four-wave mixing in colloidal gold as a function of particle size

The conjugate reflectivity of colloidal gold has been measured for four samples containing particles with mean sizes of 5, 10, 15, and 30 nm. The response times of the samples indicate a size dependence, but the conjugate signal strength was found to be only weakly dependent on particle size. Calculations of the local-field enhancement in the host matrix by the effective-medium theory indicate that the nonlinearity is inherent in the gold particles.

Photonic bands: simple-cubic lattice

Photonic band structures have been calculated for various structures with the periodicity of the simple-cubic lattice. Band gaps have been found, and the conditions for the appearances of such gaps are discussed. The effective long-wavelength dielectric constant is calculated and compared with the predictions of effective-medium and Maxwell–Garnett theories.

Nonlinear-optical properties of conductive spheroidal particle composites

We apply effective-medium theory, generalized for nonlinear media, to the problem of four-wave mixing in composites consisting of conducting particles embedded in a linear dielectric medium. For spheroidal conducting particles two cases are considered: (i) the particles are oriented and (ii) the particles have a random orientation. An experiment on gold particle suspensions in glass (Schott RG6) examines the frequency dependence of the conjugate signal intensity in a four-wave mixing geometry. Analysis of these results indicates that the particles with spheroidal shapes are mixed in the glass. We find that frequency and optical depth dependence of the conjugate intensity can be used to gain insight into the shape of the particles, since a large enhancement of the conjugate reflectivity is expected at the surface plasmon resonances, which are highly sensitive to small shape distortions.

Enhanced optical properties of metal‐coated nanoparticles

Metal‐coated, nanometer‐size particles are modeled with a realistic distribution of coating thicknesses. General expressions are given for the local‐field enhancement, absorption, and nonlinear optical response. In addition, heuristic arguments are used to determine the effects of a diffuse, rather than a sharp interface. The linear and nonlinear optical properties are discussed within the context of the effective medium theory for small volume fractions. An efficient method of solution is used with the flexibility to handle an arbitrary number of coatings.

A Brief Review of Theoretical Results for Photonic Band Structures

Abstract This article is a review of theoretical calculations on three-dimensional photonic band structures. The salient features of the electromagnetic dispersion spectrum are discussed and speculation on possible future research directions are offered.

A Two-Dimensional Photonic Crystal Laser

We report on observation of laser action unique to a two-dimensional (2D) photonic lattice. When dye-solution filled in air-holes of a 2D lattice was optically-pumped, laser action without external mirrors is found to occur at a specific wavelength corresponding to a flat band-dispersion in a high-symmetry direction of the 2D lattice plane; a small group-velocity is responsible for the lasing. On further increasing the pump-fluence, another laser action is also found to occur around a peak wavelength of the spontaneous emission spectrum. This lasing is interpreted of as arising from the so-called uncoupled modes possessing a high Q-value.

Optical bistability in small metallic particle composites

We predict that a composite dielectric material composed of silver particles can have an optical bistable transmission without cavity feedback. Our model includes propagation and exhibits an inhomogeneous absorption characteristic that can be useful for device applications. Results are presented for quantum‐size silver particles embedded in silica glass.

Fabrication of Two-Dimensional Photonic Band Structure with Near-Infrared Band Gap

We have succeeded in fabricating a two-dimensional photonic band structure with a near-infrared band gap for p-polarization in a two-dimensional Brillouin zone.The sample consists of circular air rods constituting a triangular lattice with a lattice constant of 1.17 µm and a background dielectric constant of 2.6. The transmission spectra were measured over a range from 1.4 to 5.0 µm for both p- and s-polarizations. The energies of complete reflection regions observed in the Γ- X direction were in good agreement with the theoretical calculation for both p- and s-polarizations. This agreement indicates that the above band gap should exist.

Synthesis and optical properties of coated nanoparticle composites

Abstract The synthesis of coated nanoparticles is a new direction in engineering, specifically in the study of physical properties of materials. We examine semiconductor coated semiconductor particles, CdS PbS , and metal coated particles, Au 2 S Au , and the theoretical basis for their unique properties. Coated self-assembled nanoparticles are also studied and recent progress is reported.

Vector soliton fiber lasers

We show by simulations that a nonlinear optical loop mirror with birefringent fiber can have intensity-dependent transmission of vector soliton pulses with a 50/50 coupler. Using this result we propose two mode-locked laser cavity designs.