Gilles Parent

Realization of single-mode telluride rib waveguides for mid-IR applications between 10 and 20 μm.

The feasibility of all-telluride integrated optics devices based on waveguides presenting a single-mode behavior in the spectral range (10-20 μm) is demonstrated. These waveguides are constituted of a several micrometer thick Te(82)Ge(18) film deposited onto a Te(75)Ge(15)Ga(10) bulk glass substrate by thermal coevaporation and further etched by reactive ion etching under the CHF(3)/O(2)/Ar atmosphere. The obtained structures were proven to behave as channel waveguides with a good single-mode transmission over the whole spectral range. These results allowed validating our technological solution for the fabrication of integrated optics modal filters for spatial interferometry.

Fabrication and testing of all-telluride rib waveguides for nulling interferometry

The feasibility of two types of all-telluride integrated optics devices being able to single-mode guiding of light in the spectral ranges [6-11 µm] and [10-20 µm], respectively, has been demonstrated. The so-called “rib” waveguides show a several micron thick Te82Ge18 film deposited onto a Te75Ge15Ga10 bulk glass substrate by thermal co-evaporation and further etched by reactive ion etching in CHF3/O2/Ar atmosphere. The obtained structures were proved to behave as channel waveguides with a satisfactory confinement of light in the whole spectral ranges. These results allowed validation of our technological solution for the fabrication of micro-components for spatial interferometry.

All-telluride channel waveguides for mid-infrared applications

In this paper, the different steps of the fabrication of single-mode RIB waveguides for both [6-11µm] and [10-20µm] spectral bands are described and the first results in term of light guiding and modal filtering are presented.

Buried channel waveguides for nulling interferometry in 6–20 μm spectral range: Fabrication and preliminary testing

One of the technological challenges of direct observation of extra-solar planets remains to develop a modal filter operating from 6 to 20 μm. In the present paper we present one of the two candidate technologies for the fabrication of such modal filters, together with Fiber Optics: Integrated Optics. The solution based on alltelluride buried channel waveguides was considered. In the so-called waveguides, the vertical confinement of the light is achieved in a higher-index core layer consisting in a 15 μm-thick Ge17Te83 film which is deposited onto a lower-index Te75Ge15Ga10 substrate, and further covered by a lower-index superstrate consisting in a 15 μm-thick Ge24Te76 film. Concerning the horizontal confinement of the light, it is obtained by etching the core layer. As this stage, the all-telluride buried channel waveguides are proved to transmit light from 2 to 5 μm and to behave as channel waveguides with a satisfactory confinement of the light. It confirms the validity of the technology and the good quality of the input and output facets. Tests between 6 and 20 μm are being performed and will allow giving a confirmation of the potential of Te-based integrated optics components for nulling interferometry.

Waveguides based on TeGe thick films for spatial interferometry

In the present paper we focus on the fabrication of waveguides which will be able to work in the large infrared window [6-20μm], compatible with the ESA requirements in the framework of the detection of Exo-solar planets by nulling interferometry. The first step in the fabrication of such components is the realization of planar waveguides being able to guide light in this spectral range. In order to do so, telluride materials were selected: Te75Ge15Ga10 bulk glasses were chosen as substrates and TeGe films as guiding layers. The Te75Ge15Ga10 bulk glasses were purified during their synthesis which ensures an optimal transmission in the whole range from 6 to 20 μm. TeGe thick films with different compositions were deposited by thermal co-evaporation. Homogeneous films with thickness up to 15 microns could be produced. The M-lines measurement of their refractive index at λ = 10.6 μm highlighted a linear behavior versus the atomic percentage in tellurium and confirmed their compatibility for the project. First planar waveguides could be optically characterized after having prepared their input and output facets by an appropriate polishing procedure. Guidance of light was demonstrated in the whole range [6-20 μm].

Silicon Nanowire Conductance in the Ballistic Regime: Models and Simulation

This paper deals with phonon heat transport in silicon nanowires. A review of various techniques that can be used to assess thermal conductance of such nanodevices is presented and a peculiar attention is paid to the case of the Landauer Formalism that can describe extremely thin wires. Several models for normal modes of silicon nanowire determination are considered, among them elastic wave theory has been used to determine the normal mode number. Besides, transmission and reflection of phonon at the interface between two nanostructures is discussed. Calculations and comparisons of thermal conductance of a 20 nm silicon nanowire between bulk thermal reservoirs are thus discussed.Copyright

FDTD Study of the Surface Waves Detection in Apertureless Scanning Near-Field Microscopy

Recent studies have shown the importance of surface waves in heat transfer near interfaces. The scanning near field optical microscopy (SNOM) provides an experimental tool to investigate the thermal electromagnetic field near surfaces. In this work, we present a three dimensional model of SNOM devices. This model is based on the finite-difference-time domain (FDTD) method associated to a near to far field transformation. Near field and far field scattered by a silicon tetrahedral tip and by a pecfectly conducting one are presented and discussed.Copyright

Monte Carlo Simulation of Heat Pulse Propagation in Silicon Nanostructure

Heat transport in nanostructured material is a critical issue in the design of electronic devices. According to the size and the temperature, thermal properties of the considered medium can change. In order to appraise these modifications new simulation techniques based on phonon transport equation solution have been developed. In this field, the Monte Carlo method dedicated to phonon motion and collision modeling has prove to be efficient. In the present paper we propose a modified form of this method that takes into account short pulse heating in order to assess specific heat c and thermal conductivity k. The parameter assessment has been done using Laplace analysis of the Monte Carlo calculated temperature profiles at short and long times through asymptotic solutions fitting. These numerical tools have demonstrated to be efficient as c and k values obtained for bulk silicon at low and room temperatures confirmed it.Copyright