Temperature-dependent Sellmeier coefficients are necessary to optimize optical design parameters of the optical fiber transmission system. These coefficients are calculated for fused silica (SiO/sub 2/), aluminosilicate, and Vycor glasses for the first time to find the temperature dependence of chromatic dispersion at any wavelength from UV to 1.7 /spl mu/m. The zero dispersion wavelength /spl lambda//sub 0/ (1.273 /spl mu/m for SiO/sub 2/, 1.393 /spl mu/m for aluminosilicate, and 1.265 /spl mu/m for Vycor glasses at 26/spl deg/C) varies linearly with temperature, and d/spl lambda//sub 0//dT is 0.03 nm/K for aluminosilicate and Vycor glasses, whereas for SiO/sub 2/ it is 0.025 nm/K. This study interprets the recently observed experimental value of d/spl lambda//sub 0//dT for two dispersion shifted optical fibers; and the dominantly material origin of d/spl lambda//sub 0//dT is confirmed here as a fundamental property of the optical fiber glasses. >

https://www.slac.stanford.edu/grp/arb/tn/arbvol5/ARDB436.pdf

Temperature-dependent Sellmeier coefficients and chromatic dispersions for some optical fiber glasses

The refractive index and its variation with temperature, the thermo-optic
coefficient (dn/dT), are
analyzed with two separate physically meaningful models for more than a dozen
of some important Schott and Ohara optical glasses to find the refractive
index at any operating temperature for any wavelength throughout the
transmission region. The room-temperature catalog values of refractive indices
are fitted with a two-pole Sellmeier equation. Both the average electronic
absorption band gap and the lattice absorption frequency, lying in the vacuum
UV and IR regions, respectively, contribute to the refractive indices and
their dispersion. The estimated absorption band gaps are at 8.5–11.9 eV,
and these values agree with the measured values at 8.8–11.6 eV
satisfactorily for normal optical glasses. The higher-index glasses have
electronic absorption in the region of 5.6–6.3 eV, and the estimated band
gap of SF6 glass is 6.0 eV. The dispersion of thermo-optic coefficients is accounted for satisfactorily with
a model, based on three physical parameters, the thermal expansion coefficient and excitonic and
isentropic optical band gaps that are in the vacuum UV region. These optical constants are used to
compute refractive indices at any operating temperature and wavelength. The Abbe number and the
chromatic dispersion characteristics of these glasses are evaluated from the computed optical constants;
the values of the chromatic dispersions are evaluated particularly at the three optical windows of the
optical fiber communication systems and femtosecond technology.

Sellmeier coefficients and dispersion of thermo-optic coefficients for some optical glasses.

Using the Cryogenic, High-Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center, we have measured the absolute refractive index of five specimens taken from a very large boule of Corning 7980 fused silica from temperatures ranging from 30 to 310 K at wavelengths from 0.4 to 2.6 microns with an absolute uncertainty of plus or minus 1 x 10 (exp -5). Statistical variations in derived values of the thermo-optic coefficient (dn/dT) are at the plus or minus 2 x 10 (exp -8)/K level. Graphical and tabulated data for absolute refractive index, dispersion, and thermo-optic coefficient are presented for selected wavelengths and temperatures along with estimates of uncertainty in index. Coefficients for temperature-dependent Sellmeier fits of measured refractive index are also presented to allow accurate interpolation of index to other wavelengths and temperatures. We compare our results to those from an independent investigation (which used an interferometric technique for measuring index changes as a function of temperature) whose samples were prepared from the same slugs of material from which our prisms were prepared in support of the Kepler mission. We also compare our results with sparse cryogenic index data from measurements of this material from the literature.

/pdf/temperature-dependent-absolute-refractive-index-measurements-393bn8e160.pdf

Temperature-dependent Absolute Refractive Index Measurements of Synthetic Fused Silica

Undoped graphene is semimetallic and thus not suitable for many electronic and optoelectronic applications requiring gapped semiconductor materials. However, a periodic array of holes (antidot lattice) renders graphene semiconducting with a controllable band gap. Using atomistic modeling, we demonstrate that this artificial nanomaterial is a dipole-allowed direct-gap semiconductor with a very pronounced optical-absorption edge. Hence, optical infrared spectroscopy should be an ideal probe of the electronic structure. To address realistic experimental situations, we include effects due to disorder and the presence of a substrate in the analysis.

/pdf/optical-properties-of-graphene-antidot-lattices-3jou725klf.pdf

Optical properties of graphene antidot lattices

We present the first high-contrast images obtained at the ESO Very Large Telescope using a four-quadrant phase mask coronagraph. The two-night commissioning was carried out in 2004 January on NACO, the near-IR camera with adaptive optics at UT4. We evaluated the behavior of the coronagraph on a variety of astrophysical targets: binary stars, circumstellar disks, and active galactic nuclei. The performance of the coronagraph is in agreement with our expectations based on numerical simulations. The phase mask provides a stellar peak attenuation of a factor of about 10 on average (for long exposure), and its performance is limited only by the phase residuals (mainly low-order aberrations) that are left uncorrected by the adaptive optics system.

https://www.jstor.org/stable/10.1086/425735

The Four‐Quadrant Phase Mask Coronagraph. IV. First Light at the Very Large Telescope

The refractive index of silica glass has been measured in the UV and visible regions from −165.4 to 83.3°C. The wavelength dispersion at each temperature was fitted by the three-term Sellmeier equation. Analysis of the Sellmeier equation shows that the temperature dependence of the refractive index originates from the temperature shift of the observed shift of the exciton peak at around 10.4 eV.

T. Kitaoka

Papers

Temperature dependence of refractive index of SiO2 glass