Although coating design software is now quite powerful there are still certain filter designs that benefit from having good starting configurations. This is particularly true when more that two materials are used in the design or when filters function at several angles of incidence. We show in this paper that it is often possible to supply sufficiently good starting designs for the optimization by applying some general principles and having the computer supply the details. This pre-optimization step is accomplished through software specifically designed for particular classes of applications. An example is given for the design of a short wave pass filter that eliminates a harmonic and a dispersion-induced half wave hole in the pass region. Another example uses this design approach for an edge filter operating over a wide angular range.

An exact design method for multilayer dielectric thin film filters of uniform optical thickness based on a frequency transformation and classical lossless filter synthesis is introduced. The proposed method consists of finding the optimal realizable inverse transmittance function (power loss ratio) which fulfills additional constraints such as number of layers and the calculation of the refractive indices of the individual layers. The proposed algorithm can easily be implemented because it only requires determining the roots of a polynomial. In contrast to known methods the proposed method is not limited to symmetrical multilayers or filters with geometric symmetry and allows for both reflective and transmissive characteristics of the optical filter. Several designs based on the new algorithm will be presented to demonstrate the usefulness of the exact synthesis procedure. The resulting filters can be transformed into filters with readily available indices using a known transform algorithm.

We have studied biaxial, birefringent, one-dimensional multilayer structures and found a wavelength region where the phase of one specific polarizatin component of the transmitted field increases with wavelength, giving rise to unusual polarization dependent dispersive effects of the input beam. We have analysed the delay obtained with birefringent one-dimensional multilayer structures and the effect of the dispersion in the materials to generate anomalous phase in the spectrum.

Gravitational waves are a prediction of Einstein's General Theory of Relativity. Astrophysical events like supernova and binary neutron star inspirals are predicted to create potentially detectable waves. The Laser Interferometer Gravitational-wave Observatory (LIGO) is an experiment to detect these waves using Michelson interferometers with 4 km long arms. The effect of gravitational waves, even on an interferometer with such a long baseline, is extremely, with mirror displacements around 10^-18m. Reducing noise is thus a primary design criterion. For the next generation interferometers now being designed, thermal noise from the optical coatings of the interferometer mirrors could prove a problematic limiting noise source. Reducing the mechanical loss of these coatings to improve thermal noise, while preserving the sub-ppm optical absorption, low scatter, and high reflectivity needed in the interferometer is an important area of research.

In the present paper we are dealing with the thermal fields for laser-metallic thin film interaction. We propose a simplified model which takes into account just one global heat equation instead of two couple heat equations. For the parameters which are the same order of magnitude we take into account just the thermal coefficients of the substrate. The idea of our model is to consider an absorption coefficient as close as possible to reality. We solve the heat equation using the integral transform technique. We plot the thermal field at the interface for different situations. Our results indicate that: (i) the thermal field depends strongly on the absorption coefficient of the thin film and (ii) the length of the interface, at least in the domain 0.1-10 μm does not play an important role in the thermal fields. Specific results are presented for a laser beam operating in the mode TEM₀₁.

Ion-assist applications of broad-beam ion sources are reviewed for ion energies up to about 1 keV. These applications are organized by ion energy and cover a wide range of thin-film technologies. Optimum ion-assist doses are described when available. Except for applications that benefit from specific ion energies, the majority of ion-assist applications are probably done best in the low-energy range that extends from about 25 eV to 100 eV.

Energetic process development in the production of optical coatings has progressed significantly over the last two decades, permitting the practitioner of thin film coating depositions a wide choice of deposition parameters. Primarily, a series of important advances has occurred in the nearly ubiquitous use of Ion Assisted Deposition (IAD) for the production of high performance optical coatings. Progressing from the rudimentary use of ionized gas technology for pre-cleaning substrates, to the advanced IAD produced telecom filters (DWDM), energetic processes now play a vital role in most optical coating production. The advances in IAD technology culminate in the development of stable and durable thin films for a wide variety of stringent spectral specifications from the UV to the Far IR. The technical progression from IAD use in either sputtered or physical vapor deposition (PVD) processes to the development of Ion-Assisted Filtered Cathodic Arc Deposition (IFCAD) technology for applications from temperature-sensitive optics to future space coatings will be discussed.

The demands of the optical communications industry have resulted in a dramatic increase in the performance requirements for thin film optical filters. Complex coatings are now manufactured with a level of control that was almost unthinkable a decade ago. In the area of anti-reflection coatings for optical fibers and laser diodes, not only has there been a push towards much lower reflectance requirements, the measurement methods and terminology are different. AR coatings are expected to have optical return losses (ORLs) of -40dB to -50dB, corresponding to reflectance values of 0.01% to 0.001%. By comparison, an element in a typical precision optics system might have an AR requirement of < 0.1% (-30dB). From a manufacturing standpoint, these requirements pose two problems: how to make such coatings, and how to measure them. In this work we review the progress towards routine manufacture of such ultra low reflectance coatings. We examine both the process control issues and the obstacles that must be overcome in the reflection measurement.

In this work we report on the damage threshold of ion beam deposited oxide films designed for high peak power short pulse laser systems. Single layers of ZrO₂, SiO₂, Al₂O₃, TiO₂, and Ta₂O₅ and multilayers of Al₂O ₃/TiO₂, SiO₂/Ta₂O₅, and SiO₂/ZrO₂ were grown on polished borosilicate glass substrates using ion beam sputter deposition. Deposition conditions were optimized to yield fully oxidized films as determined from x-ray photoelectron spectroscopy (XPS). Damage threshold testing was performed using an amplified Ti:Sapphire laser producing a train of 120 picosecond pulses at a wavelength of 800 nm. The laser output was focused with a lens to generate fluences ranging from 0.1 to 24 J/cm². The highest damage threshold of 15.4 J/cm² was measured for a single layer film of SiO₂. The damage threshold of high reflectance and anti-reflection multilayer coatings fabricated for 800 nm applications was evaluated using the same procedure as for the single layer films. Highest damage thresholds of 2.5 and 3.5 J/cm² were measured for a 6-pair ZrO₂/SiO₂ high reflectance coating and a 5 layer anti-reflection coating of the same materials.

A new film thickness sensor material, single crystal gallium orthophosphate (GaPO₄), has been investigated for use as a high temperature piezoelectric microbalance suitable for monitoring chemical vapor deposition (CVD) thin film processes. Our initial work has shown that gallium phosphate can operate at temperatures up to 930°C, and a reusable sensor housing can be constructed to hold the crystal for repeated runs. A significant shortcoming is that commercial film thickness monitors are not capable of accurately controlling GaPO₄ above 600°C due to the limitations of the oscillator electronics used in such monitors.

Thin film coatings of polypyrrole have been extensively used as gas sensors in chemiresistors where the films are deposited on insulating substrates. These polypyrrole films have also been used as coatings to glass optical fiber as a chemo-chromic transducer for gas sensing. For long term mechanical durability of these sensing films, their adhesion to the substrate is very important. Adhesion between polypyrrole films and glass slide substrates is investigated for solution deposited polypyrrole films. The substrate surface is investigated in terms of addition of silane coupling agents and substrate surface roughness, for enhancement of the film substrate adhesion. The adhesion test is performed by the standard ASTM D - 4541 Pull-off Test Method. The films deposited on as-received slides are characterized for their electrical conductivity and optical transmission for their use in both chemiresistor and optical fiber sensor applications for nerve agent DMMP (di-methylmethylphosphonate) sensing.

Spectroscopic ellipsometry is commonly used for the optical characterization of solid state thin films and bulk substrates. In recent years, it has also gained widespread use in characterizing organic films . The discovery of carbon nano-tubes has increased the utility of organic films by allowing the engineer to alter the electrical and mechanical properties of the material by doping the film with these graphite structures. Proper understanding through PMSE characterization of the structure is necessary to control desired optical and electrical properties. In this work we present mothodes of PMSE as an advantageous, non-destructive optical tool for the study of C70 doped PS-PHMA thin film on a c-Si(100) wafer. For the samples measured, concentration of C70 is reported along with dispersion relations for PS-PHMA films in the UV-Vis spectrum for untreated, heated and shear aligned films. There is also evidence that the C70 may also align within the micro-domain of the PS-PHMA producing an anisotropic film.

Over recent years the demand for optical data storage devices with high speed has become increasingly more evident. Phase change optical storage is based on the rapid crystalline to amorphous (and vice versa) transition in a thin phase change layer enabled by laser induced heating. Among some of the potential candidates, AgSbTe alloy appears to be one of the latest promising materials that have drawn worldwide attention. Using this material as the active layer has other advantages such as the problem of material flow is reduced to a great extent. Moreover the marks written in AgSbTe based media have a well defined shape with sharp edges, leading to intrinsically lower jitter values than observed for GeSbTe based media. In the present work Ag _x-Sb _{2 (1-x)}-Te _{3 (1-x)} alloys and films are developed for different composition. The present work describes the systematic study of thermal, structural and optical properties of amorphous Ag-Sb-Te system

The time evolution of the optical properties of nanostructured silicon nitride (ns-SiN_x:H) thin films was studied by FTIR phase-modulated ellipsometry. The samples were produced by RF-PECVD and ellipsometric measurements were performed after the deposition and at different time intervals in the spectral range between 950 and 3500 cm^-1. The experimental data show an evolution from an initial not-oxidized state to a final oxidized state. The oxidation process of ns-SiN_x:H films is modeled with two different approaches: i) assuming that the oxidation starts at the film surface and diffuses towards the substrate and ii) assuming a homogeneous oxidization through the entire volume of the film. The final best fitting of the data suggests that the oxidization occurs homogeneously in all the thickness of the film.

In this paper the quantitative dependence of the mechanical stress inside diamond-like carbon films containing Si and O atoms on a flow rate ratio of methane CH₄ and hexamethyldisiloxane C₆H₁₈Si₂O in the deposition mixture is determined. For this purpose the modified Stoney's formula is employed. The important quantities taking place in this formula, i.e. the radius of curvature of the spherical surface of a deformed silicon substrate because of the film stress and the film thickness, are determined using the combined optical method based on two-beam interferometry, variable angle spectroscopic ellipsometry and near-normal spectroscopic reflectometry. It is shown that the influence of the flow rate ratio on the values of the mechanical stresses taking place inside these films is negligible within the experimental accuracy achieved for determining these stresses if the total flow rate of gases used to be constant in the deposition mixture. A discussion of this fact is also performed. The film studied were prepared using the plasma enhanced chemical vapor deposition.

A reflection-type film-substrate retarder is an optical device that changes the relative phase but not the relative amplitude of light upon reflection from a film-substrate system. While there are several such device designs based on the common negative film-substrate system, very little has been done with the other two categories of systems; zero and positive. The system category is determined by the relationship between the refractive indices of the ambient (N₀), film (N₁), and substrate (N₂). If N₁<√N₀N₂, the system is negative; if N₁=√N₀N₂, the system is zero; and if N₁>√N₀N₂, the system is positive . This paper discusses the design procedure and characteristics of zero-system reflection-retarders. The polarization and ellipsometric properties of the positive system preclude the existence of a reflection-retarder. First, a brief characterization of the zero and positive systems using constant-angle-of-incidence contours (CAICs) and Constant-thickness contours (CTCs) of the ellipsometric function is presented and discussed. Then, an algorithm outlining the design procedures is presented, and the characteristics of the obtained designs are optimized, analyzed and discussed.