Morris Braunstein

Refractive indices of ir materials: 10.6-μm ellipsometer measurements

10.6-microm ellipsometric measurements, using a modulated light ellipsometer, are reported for the refractive imdies of KCL, CdTe, and ZnSe crystals and for ZnSe and ThF(4) films.

Optical Coatings for High Energy ZnSe Laser Windows

The development of surface finishing and coating technology at 10.6 microm for polycrystalline ZnSe laser windows is presented. Optical evaluation of the coated windows shows that the 10.6-microm absorption and reflection can be held to less than 0.1% per surface. Surface finishing procedures, theoretical coating designs, and recent experimental results for antireflection coatings for ZnSe are presented.

Infrared characterization of surfaces and coatings by internal-reflection spectroscopy

Some problems which arise in the characterization of surfaces and coatings by internal reflection spectroscopy are described. The ir spectra of bare CaF(2) trapezoids and of ThF(4)- and ZnSe-coated trapezoids exhibit absorption bands in the same spectral region as those of H(2)O and hydrocarbon impurities. In accord with previous investigations, it is observed that the absorptance due to water is much greater in the ThF(4) films than in the ZnSe films or on the CaF(2) surfaces. These results suggest that the water is distributed throughout the ThF(4) films, whereas for ZnSe it resides primarily on the surface. In addition, a number of interesting observations on the desorption and adsorption of water and hydrocarbons to these materials are made. The experimentally observed absorptances are analyzed on the basis of the reflectance for a threelayer system. The analysis enables reasonably quantitative values for the absorption coefficient to be determined for these thin-film coatings.

Measuring the infrared absorption in thin film coatings.

Traditionally, the optical absorption in thin dielectric films has been obtained by comparing the absorption in coated and uncoated substrates. A new technique has been developed in which the absorption of the film is obtained directly without resorting to comparison or difference methods. This method relies on the separation of surface and bulk heat that results from laser calorimetric measurements on long, bar-shaped samples. Single layer films of As(2)S(3), CaF(2), ThF(4), and PbF(2) were deposited on a KCl bar, and the absorption coefficient of each film was extracted from the slopes of the temperature-time curves.

Ultraviolet–visible absorption in highly transparent solids by laser calorimetry and wavelength modulation spectroscopy

The requirements for low-loss optical materials for use on excimer lasers have stimulated the investigation of optical absorption in a variety of highly transparent materials at visible and uv wavelengths. To provide information over a wide spectral range at low absorption levels ( approximately 10(-5) cm(-1)), laser calorimetric and wavelength modulation spectroscopic techniques were used. Blending these two methods provided, for the first time, spectral information well below the usual levels of absorption measured in studies of the Urbach tail.

Thin-film 2.8-μm and 3.8-μm absorption in single-layer films

A systematic study was made of thin-film absorption at 2.8microm and 3.8 microm for a wide variety of transparent coating materials. The extinction and absorption coefficients were measured using HF/DF chemical laser calorimetry in single-layer films of PbF(2), LiF, YbF(3), NaF, ThF(4), As(2),S(3), As(2),Se(3), Si, MgO, ZnSe, and Al(2),O(3), on CaF(2), substrates. The lowest absorbing film materials were the As glasses, ZnSe, and some fluorides. In these cases, high-purity starting material led to the lowest loss films.

Infrared Coatings For High Energy Laser Reflectors And Windows

This paper reviews infrared coating materials for reflectors and windows for use in high energy laser systems operating in the 2 μm to 10.6 μm spectral regions. The work discussed is the result of research performed at our laboratories during the last several years. The primary emphasis in the discussion is on coatings that have low optical absorption. A long-term objective of our work has been to reduce optical absorption in infrared coatings to less than 0.1%.

High-performance dichroic beam splitters for deuterium fluoride chemical lasers

The optical performance of dichroic beam splitters developed for deuterium fluoride (DF) laser applications as shared-aperture components is presented. These components simultaneously provide high reflectance/transmittance in the 3.8-microm DF laser output band and high transmittance/reflectance in the long-wave-length 8-14--m band. Optical evaluation of the reflecting dichroic yields absorption and transmission losses of <0.2 and 0.1%, respectively, at DF laser wavelengths and average transmittance 80% in the 8-14-microm band. The 3.8-microm transmitting dichroic yields absorptance losses of <0.4% in the DF laser band and average reflectance of >50% in the 8-14-microm region.

Low-loss antireflection coatings for DF chemical lasers

The optical performance of antireflection coatings on alkaline earth fluoride window materials at DF chemical laser wavelengths is presented. Reported coating absorption losses are less than 0.01% per surface. Those material properties that are important for this application are discussed, and theoretical coating designs are compared with experimental results.

Strain induced anisotropy in As 2 S 3 , As 2 Se 3 , and ZnSe films on KCl substrates via 10.6-μm and 0.6328-μm ellipsometer measurements and 0.6328-μm reflector measurements

Ellipsometric measurements at 10.6 microm using a modulated light ellipsometer and ellipsometer and reflectometer measurements at 0.6328 microm are reported for the refractive indices of As(2)S(3), As(2)Se(3), and ZnS films deposited on KCl substrates. The observation of strain-induced anisotropy is reported, and an analysis of the effects of anisotropy in thin film ellipsometry is presented.