David F. Edwards

Infrared refractive index of silicon

The infrared refractive index of silicon is determined by using the channel spectrum technique.(AIP)

Infrared refractive index of diamond

The refractive index of natural Type IIa diamond is reported for the spectral region 2.5–25 μm. The data have been fitted to a Herzberger-type dispersion formula with a quality of fit of a few places in the fifth decimal place. The resultant index uncertainty is about 10−3.

Cubic Carbon (Diamond)

Publisher Summary Diamond is essentially classified into four types depending on its optical and electrical properties. Common to each type is an absorption band in the 2 to 6 μm infrared region, which is because of a multiphonon absorption. Most natural diamonds are of type Ia. The ultraviolet absorption edge of type Ia diamonds is at about 291 nm. Synthetic diamonds are type Ib and contain nitrogen as an impurity in a dispersed form. Type IIa diamonds are effectively free of nitrogen and exhibit only the intrinsic 2 to 6 μm absorption. The ultraviolet absorption edge is at about 222 nm. Therefore, type IIa diamonds exhibit the optical properties best suited for infrared optical components. Optical components with flat surfaces can be produced to specification from diamond. It is also possible to produce diamond Fresnel lenses, diffraction gratings, and other components with flat surface patterns. The index of refraction of diamond sensitively depends on the properties of the crystal. The crystal internal structure, defects, impurities, and mechanical inclusions can also alter the index.

Multiple-pass reflectometer

The multiple-pass reflectometer has been shown to be a convenient and precise instrument for measuring absolute spectral reflectance values in excess of 0.99. Given here is an extension of earlier work. We present details of the setup, operation, parameter optimization, and some limitations of the reflectometer. For a carefully aligned instrument the precision of the measurement is limited by the uncertainty in the computer fit of a straight line to the data. For the UV and visible spectral regions, typical reflectance precision is a few parts in 104. Systematic errors due to nonuniform photosurfaces and astigmatism have been minimized for the setup described here.

Multilayer dichroic mirrors for the 16-μm spectral region: their design and fabrication

The design and fabrication of multilayer mirrors for the 16-mum spectral region present special problems in materials selection and stress compensation. Details are given of the solution of these problems for two types of dichroic mirrors. Equivalent layers with nonquarterwave thicknesses were found to yield stresscompensated coatings having the desired transmittance and reflectance. Auger analyses indicate that the absorption in these coatings is probably due to deviation from stoichiometry in one of the materials rather than from an impurity.

Landau-Placzek ratio of KBr single crystals—I

Abstract The Mandelshtam-Brillouin and Gross scattering was measured for a series of purified KBr crystals. The ratio I G 2I MB , which for a pure, perfect crystal would be the Landau-Placzek ratio, was found to vary with the type of reactive gas treatment used in the final purification. With these crystals both the longitudinal and mixed mode bands were observed with θ and φ equal to 90°. The ratio I L I M was in agreement with calculated intensity ratios and the Δμ for these bands gave C11 + C12 = 41.6 GPa and C44 = 5.18 GPa.

Mechanical Stress Compensation In Multilayer Dichroic Mirrors For The 16 µm Spectral Region

Multilayer quarterwave stacks were fabricated to reflect at λ = 16 μm. Due to the substantial metric thickness of the stack, the mechanical stress caused the coating to separate from the substrate. The optical thickness of the lead fluoride was 35% thicker than the zinc selenide in the stress-compensated design. The tensive stress of the former compensated the compressive stress of the latter.