François Ladouceur

Self-induced optical fibers: spatial solitary waves

To be self-guided, a beam must exactly equal the mode of the linear-optical fiber that it induces. From this elementary consistency condition we can borrow solutions and their associated physics directly from the familiar literature of linear-optical waveguides. By considering a nonlinear medium characterized by ideal saturation, we present what is to our knowledge the first exact analytical solution of a two-dimensional self-guided beam. This beam is the familiar fundamental mode of a step-profile fiber. The stability of the beam is also determined.

Diamond waveguides fabricated by reactive ion etching

We demonstrate for the first time the feasibility of all-diamond integrated optic devices over large areas using a combination of photolithography, reactive ion etching (RIE) and focused ion beam (FIB) techniques. We confirm the viability of this scalable process by demonstrating guidance in a two-moded ridge waveguide in type 1b single crystal diamond. This opens the door to the fabrication of a diamond-based optical chip integrating functional elements such as X-crossings, Y-junctions, evanescent couplers, Bragg reflectors/couplers and various interferometers.

A new general approach to optical waveguide path design

This paper introduces a new general approach to waveguide path design. We propose an alternative approach to the usual concatenation of offset line segments and arc of circles that is geometrically less constrictive and more versatile. We also propose an adapted pure bend loss reduction mechanism that relies on a continuous widening of the waveguide together with the reduction of transition loss through curvature adaptation. The numerical results presented here show that this method can improve the loss figures and ease the burden of waveguide path design. Moreover, because of its continuous nature, the proposed approach is intrinsically less dependent on wavelength than the usual concatenation technique. >

Fourier decomposition method applied to mapped infinite domains: scalar analysis of dielectric waveguides down to modal cutoff

By transforming the infinite x-y plane onto a unit square and using two-dimensional Fourier series expansions, the modal fields and propagation constants of dielectric waveguides are accurately determined within the scalar (weak-guidance) regime. The new method is reliable down to modal cutoff and gives cutoff V-values directly. Numerical cutoff values for the LP/sub 11/ modes of square- and rectangular-core waveguides are determined as a function of core aspect ratio, and are found to agree with those obtained by the finite element method to within 0.1%. >

Roughness, inhomogeneity, and integrated optics

Surface roughness (and more generally) inhomogeneity is a constraining factor on optoelectronics devices. Its more conspicuous effect is to scatter light thus leading to power attenuation. This effect partly explains the five orders of magnitude difference in attenuation between fibers and integrated waveguides. Less well known is the effect of roughness on back-coupling and mode coupling in devices such as couplers and gratings. I present here an overview of these effect analyzed from a heuristic approach based upon the length scales of the dominant physical mechanism present in such devices.

Quantum dot and silica nanoparticle doped polymer optical fibers.

A novel and highly versatile doping method has been developed to allow active dopants, including materials incompatible with the polymer matrix, to be incorporated into microstructured polymer optical fibers through the use of nanoparticles. The incorporation of quantum dots and silica nanoparticles containing Rhodamine isothiocyanate is demonstrated.

Diamond-based structures to collect and guide light

We examine some promising photonic structures for collecting and guiding light in bulk diamond. The aim of this work is to optimize single photon sources and single spin read-out from diamond color centers, specifically NV centers. We review the modeling and fabrication (by focused ion beam and reactive ion etching) of solid immersion lenses, waveguides and photonic crystal cavities in monolithic diamond.

Slot-waveguide cavities for optical quantum information applications

To take existing quantum optical experiments and devices into a more practical regimes requires the construction of robust, solid-state implementations. In particular, to observe the strong-coupling regime of tom-photon interactions requires very small cavities and large quality factors. Here we show that the slot-waveguide geometry recently introduced for photonic applications is also promising for quantum optical applications in the visible regime. We study diamond- and GaP-based slot-waveguide cavities (SWCs) compatible with diamond colour centres e.g. nitrogen-vacancy (NV) defect. We show that one can achieve increased single-photon Rabi frequencies of order O(10(11)) rad s(-1) in ultra-small cavity modal volumes, nearly 2 orders of magnitude smaller than previously studied diamond-based photonic crystal cavities.

Hybrid functional study of Si and O donors in wurtzite AlN

The properties of Si and O donors in wurtzite AlN have been studied by means of hybrid functional calculations, finding that both impurities form DX centres. In the case of Si, the stable DX centre is close in energy to the substitutional donor state and to a second metastable DX centre, thus explaining both the persistent effects and the broad range of activation energies observed experimentally. Ionisation energies have been computed for both Si and O donor states.

Surface roughness and backscattering

Surface roughness is normally considered to be the main cause of attenuation in intergrated-optics glass waveguides. Previous analyses have concentrated on scattering of light into the radiation field; in fact, depending on the roughness length scale, scattering can be predominantly in the backward direction, raising the question of how important the coupling with the backward-directed bound mode is. We investigate this effect and show that it can be neglected in most circumstances.