Characterization of solid state array cameras for the mid-IR

We present a characterization of some processes affecting the performance of solid state array cameras designed for ground based astronomical imaging in the 8–13m atmospheric window. Our discussion includes a novel model for electron-hole generationrecombination noise based on the probable pathlength of an electron in a photoconductor. We use the Berkeley mid-IR Array Camera as an example. For this camera, the results show that the total optical system composed of the camera, a 3m telescope, and the atmosphere has an efficiency of about 3%, a 1 noise equivalent flux density of 25 mJy min^–1/2arcsec^–2 measured over a /=10% band width, and a noise equivalent expressed as the ambient temperature thermal black body noise of 23%.     

Au–Cu nanoparticles produced by laser ablation of mixtures of Au and Cu microparticles

In this study we investigate the possibility of producing alloy nanoparticles (NP) from mixtures of elemental microparticle (MP) powders using the laser ablation of microparticle (LAM) process. Mixtures of Au and Cu particles with a diameter of 1.5–2.0 m were fed in aerosol form into a laser ablation cell and ablated using a pulsed laser. The resulting NP were collected electrostatically and characterized using TEM. The NP were spherical and crystalline with a size that depended on the collection location but ranged from 2 to 15 nm. Using TEM/SAD, it was determined that the NP had a face-centered cubic (fcc) crystal structure and, with EDS, it was found that individual NP consisted of both Au and Cu. These experimental results confirm previous numerical models that suggested that it might be possible to form alloy NP from mixtures of elemental MP using the LAM process.     

Direct absorption of gas-phase atomic hydrogen by si(100): A narrow temperature window

We discuss the thermal conductivity of a chain of coupled rotators, showing that it is the first example of a 1D nonlinear lattice exhibiting normal transport properties in the absence of an on-site potential. Numerical estimates obtained by simulating a chain in contact with two thermal baths at different temperatures are found to be consistent with those based on linear response theory. The dynamics of the Fourier modes provides direct evidence of energy diffusion. The finiteness of the conductivity is traced back to the occurrence of phase jumps. Our conclusions are confirmed by the analysis of two variants of this model.     

Resonant frequency-domain interferometry via third-harmonic generation

A method for measuring resonances using a combination of third-harmonic generation and frequency-domain interferometry is described and demonstrated in an index-matched dielectric material. The phase of the third-harmonic spectrum of a pulse generated from a resonant NdAlO(3) thin film and a temporally displaced sapphire substrate pulse was measured by analyzing the spectral interference pattern. The appropriate combination of substrate and film signals was obtained by translating the sample through the laser focus while observing the third-harmonic intensity.