Purple membrane (PM) from Halobacterium halobium consists of a two-dimensional crystal of the photochromic retinal protein bacteriorhodopsin (BR). Purple membrane embedded in inert polymer matrices can be used as reversible recording medium in holography. The thermal and photochemical stability (at least 100.000 recording cycles at room temperature), the high quantum yield (70%), the high resolution (~ 5000 lines/mm) and the wide spectral range (400-680 nm) of these films are promising features for any possible technical application. The variability of this material was restricted to chemical modifications of the chromophoric group for a long time. new class of BR based recording media is introduced by the availability of variants of BR with a modified amino acid sequence. After generation of a mutant strain PM variants can be easily produced by the same cultivation and purification procedures as the PM of the wildtype and therefore are available in virtually unlimited amounts, too. As an example the properties of PM-films containing the variant BR-326, which differs from the wildtype by a single amino acid, are reported here. The improved diffraction efficiency (~ 2-fold) and increased sensitivity (~ 50%) of films containing BR-326 give an impression of the new possibilities for optimizing reversible recording media by biochemical and gentechnological methods as an alternative or an addition to conventional chemical methods.

Thin films of a diacetylene derivative with carbazol substituents have been prepared under vacuum by epitaxial growth on an organic single crystal. We have been able to obtain these films on large crystals with an area of about 10 cm2. The thermal topochemical polymerization in the solid state has been performed on the film laying on the substrate. The resulting polycrystalline film (pDCH) is uniaxially oriented along a privileged direction of the single crystal substrate as shown by electron microscopy. The sizes of the crystals are in the range of 0.1 to 0.3 μm and some particularly long and well oriented needle crystals can be seen on the surface. Optical studies such as UV-Vis spectroscopy or third harmonic generation (THG) have been performed on these mono-oriented films. The single orientation of the polymer chains and crystals on the organic substrate is perfectly confirmed by the angular dependence of the THG intensity which follows the theoretical law.

Thermally induced optical bistability (OB) in II-VI single crystals has already been studied in various publications. Thermal evaporated films have the advantage of easy production compared with single crystal growth. In this paper we report our most recent results about room temperature OB of evaporated layers. Optical modulation characteristics and (bistable) switching times were also measured at reduced temperatures.

Thin films of Sn1-xZrx02 with x ranging from 0 to 0.33 were prepared by d.c. magnetron sputtering on room temperature substrates. From the measured transmission and reflection data the optical constants were calculated. The energy gap was analysed by McLean's method. The shift of the absorption edge towards high energies with increasing Zr amount was observed. Energy gaps were found in the range from 3.8 eV for SnO2 to 4.5 eV for Sn1-xZrx02 with x=0.33. Electrical conductivity was measured in the temperature range from 20 °C to 500 °C under vacuum conditions. It turned out that at low Zr concentrations (a few per cent) the prepared oxide layers show a remarkable electrical conductivity and simultaneously higher optical transmission as pure SnO2 layers prepared under similar conditions.

ZnO films deposited onto InP substrates by using sputtering has been studied. Several sputtering parameters including RF power, substrate temperature and oxygen content have been investigated to get a better ZnO thin films. The suitable ratio of oxygen and argon makes an important role in getting high guality films. 20% oxygen content is the best one for sputtered ZnO films. From SEM measurements and the etching patterns, a fine dense grain structure with a smooth interface and fine growth pattern can be obtained.

Dielectric zinc oxide films were prepared by reactive r.f. sputtering on amorphous and crystalline substrates. The optical, morphological and structural properties were studied as a function of the deposition parameters. Scanning electron microscopy, X-ray diffraction and reflection high energy electron diffraction were used to characterize film morphological and structural properties. The optical properties were studied in the 0.5-3.1 eV spectral range by transmittance data. Taking account of the quality of the films described in the present paper, planar light waveguide were prepared on both substrate kinds. Optical loss of about 5 dB/cm were measured on 5cm length waveguides.

The next generation of fusion lasers requires mirrors with laser damage thresholds of at least 40 J/cm for 10 ns laser pulses. Up to now, no deposition technique ha been developed to produce such mirrors. Best values realized today are around 30 J/cm for e-beam evaporated mirrors. R&D on conventional e-beam coating processes over the last 10 years has come up with marginal improvements in laser damage thresholds only. This aspect was the motive to investigate novel (unusual) deposition techniques which may provide the laser damage thresholds necessary.

The optical and semiconductor properties of lead telluride coatings are dependent on various factors contributing to its performance. In this paper, we will present the temperature dependent effects of single layer lead telluride coatings on the dispersion and absorption characteristics, absorption edge, and carrier concentration from 15 K to 436 K using both experimental and theoretical analysis.

The absorption in Ion Beam Sputtered laser mirrors was examined. It is known that impurities influences the absorption of optical films. Therefore the impurity content of the sputtered films has been investigated using total reflection X-ray fluorescence analysis (TRFA). Impurity analysis revealed stainless steel components (iron, chromium, nickel) to be an important part of the impurities, but also material from the preceding sputter run was detected. The absorption measurement showed that besides the stainless steel components the cosputtered material leads to an enlarged absorption. These absorptions are causing mirrors deformations in a high power argon laser.

Cross-sections of dielectrical laser mirrors are examined by Transmission Electron Microscopy (TEM). The TEM picture shows the whole layer structure which offers the possibility to observe the development of interface roughness from the substrate up to the top layer. The TEM pictures reveal the great difference between the interface roughness of evaporated and ion beam sputtered layers. Using computer image processing techniques the increasing roughness within the evaporated layer system has been measured. Furthermore the correlation lengths of the roughness has been determined in this way. The knowledge of these two parameters over the entire system enables the calculation of scatter losses for the system.

Laser resonators employing radially variable reflectance mirrors offer a number of advantages on standard laser configurations. Different devices have been proposed to produce variable reflectance and an interesting solution consists in the use of thin film coatings with variable thickness layers. The success of thin films in this field depends on the ability to design a coating with whatever reflectance profile and to control accurately radially variable thicknesses. In this paper a design approach is proposed and two techniques for profiled layer fabrication are illustrated. Some experimental mirrors with super-gaussian profiles have been produced and tested as output couplers of a Nd:YAG laser resonator.

The expanding field of solid state lasers and devices forms an interesting challenge for the development of coatings. A wide variety of different specifications, often contradictory, has to be matched. The choice of deposition process and coating material ist crucial with respect to losses, damage threshold, optical specifications and their long term stability. Especially diode pumped solid state lasers include a number of new applications for optical coatings, which are discussed in this paper. Band-pass filters, beam dividers, two-wavelength coatings etc. on bulk materials like Nd:YAG, KTP etc. have been developed. Different design approaches are compared and practical aspects of coating deyelopments are discussed. Ion based processes lead to superior results in most of the cases, but conventional evaporative coating processes give adequate results sometimes. Advantages and disadvantages have to be discussed for every approach separately.

Arsenic doped silica glass (ASG) is a material which is well known to the electronics industry, due to its use in integrated circuit manufacture as a conformal covering for circuitry. We report here, for the first time, the use of ASG as a low loss waveguiding material. The guiding films were made by a CVD process, carried out between 400 and 450 °C. Three inch silica and thermal oxide coated silicon substrates were used. The thermal oxide layer was between 2 μm and 10 μm thick. Typical films which have been investigated were 1.5-2 μm thick and had a refractive index of about 1.51 at 632.8 nm, corresponding to an As2O3 content of approximately 10 mol%. They have also been patterned using standard photolithographic techniques. The properties of planar films and ridge waveguides will he discussed. We present results of loss measurements made by prism coupling into planar films and from end-fire launching into ridge guides. The scattered light was detected using a computer controlled camera system. Typically, we have measured a loss of 0.50 dBcm-1 with ±5% error for the lowest order TE mode in a planar film at 632.8 nm. The effects of reflow of the ASG on the measured loss of the guides will he illustrated. The potential for reducing this loss and the use of ASG as a passive waveguide material in integrated optics will also he discussed.

Transient behaviour of all-optical bistable system based on a nonlinear planar wave-guide with the prism coupler has been studied both experimentally and theoretically. Switching waves with an asymmetrical spatial profile in a nonlinear planar waveguide have been realized and explained.

High reflectance low-scatter mirrors have been developed for laser-gyro applications. The mirrors were made of a multilayer system consisting of SiO2 and of a new unusual material for the high index layer. This material is a compound of titanium oxide and praseodymium oxide which is oxygen depleted (PrTiO3-x). To obtain best results superpolished substrates were fabricated. They were examined by high resolution Nomarski differential contrast microscopy and light scattering. The laser mirrors were produced in a Balzers BAK 600 plant. Both coating materials were electron-gun evaporated at different oxygen partial pressures. The fabricated mirrors were investigated in terms of reflectivity and scattering using an ultra-precise measurement equipment. Scattering was measured in an Ulbricht integrating sphere; resolution: 0.2.10-6. Reflectivity measurements were carried out in a special developed reflectometer with a resolution of 10.10-6.

The LPE growth technique was used to prepare the thick films of Bi-substituted iron garnets for optical isolators. Phase diagrams of the complex flux systems were investigated. It was shown that in systems with rare-earth oxides concentration less than 0,5 mol. % stabilization of the growth rate takes place. According to our investigations Y, Ho and Dy have more "equilibrium" cation radii for dodechahedral sublattice of garnet structure. That is why we selected (lin,B1)3(Fe,Ga)5O12 garnet film compositions with Ln = Y, Ho and Dy for the preparation of more perfect layers. The duration of LPE processes was in the range 2,5 to 12 hours. Bi content in the prepared films was 1,5-2,0 atoms per formula unit. The uncracked samples with 0,2-0,4 mm sum thickness observed the Faraday rotation of more than 45° at the wavelength range 800-1300 mm. The absorption spectra for high level of Bi substitution and different Ln were also investigated.

Front surface metal mirrors need protection of the inherently fragile metal film normally deposited by evaporation in high vacuum. Dielectric thin films, also deposited by thermal or electron beam evaporation in high vacuum, provide limited protection because of their less than dense packing. These films usually have a columnar structure with voids between the columns. The voids give access to the metal film for humidity and corrosive gases or liquids. Sainty et al. [Appl. Opt. 23, 1116 (1984)] made some progress in developing better protective coatings with ion assisted deposition. We manufactured protected front surface aluminum mirrors using reactive ion plating deposition. When immersed in 0.2M NaOH, our best mirror survived for 20 hours while only degrading to a transmission of 10%, exceeding the results of Sainty et al. by a factor of 5 under the same test conditions. Electron beam evaporated dielectric coatings provided protection for about 1.5 to 2 hours in the same solution. We will discuss the reason for the significant improvement brought about by low voltage reactive ion plating deposition, and its advantage for large scale production.

Dielectric multilayer thin film stacks deposited on glass plates or prisms can work as polarizing beam splitters when used at an oblique angle of light incidence. Coatings deposited in vacuum by conventional electron beam or reactive thermal evaporation have an inherently large internal surface area, because of the columnar micro-structure, and have packing densities less than unity. Exposed to ambient humid air, their spectral response and polarization characteristics change. The cause is adsorption or desorption of water vapor on their inner surfaces upon changes in humidity and temperature. The novel deposition technique of low voltage reactive ion plating produces thin films with a packing density of unity or higher. This prevents them from any uptake of humidity at all. We demonstrate the fabrication of stable polarizing beamsplitters for the HeNe wavelength of 632.8 nm by this technique.

Determination of thin film thickness is ultimate important in many technology area, particularly those of optics and microelectronics. There are numerous ways to measure thin film thickness, many of them need after measurement numerical calculations, namely, some physical constants of the film: refractive index, absorption coefficient, or electrical conductivity, etc., need to be known beforehand in order to- carry out the calculation which. relates a certain measured physical quantity of the film: transmission spectrum, electrical resistance etc., to these constants and film thickness. The accuracy of these constants is crucial to the accuracy of the film thickness deduced from the calculation. Unfortunately, physical constants of thin films are always different significantly from those of bulk materials. The use of bulk value in the calculation inavoidably lead to inaccurate film thickness determination. There are some methods which directly measure the film thickness without numerical process and knowledge of other physical constants of the film. Among those methods, surface profile determination by stylus mechanically or by interferometry optically are frequently used. A film edge has to be created, the edge height measured directly by stylus profile or interference pattern is equal to the film thickness. There are some disadvantages for these methods, stylus may scratches the film and substrate which are soft, the range of film thickness which can be determined is limited by the optical wavelength in the interference method.

Stylus profilometry plays an important part in characterising topography of substrates and films for x-ray optics, through such commercial instruments as the Rank Taylor Hobson Talystep and Form Talysurf. The Talystep, further developed as the Nanosurf by Lindsey and co-workers at the NPL, has 50pm vertical resolution and is well suited to the measurement of large flat substrates; however, its vertical range of 10 microns limits use on curved substrates. The Form Talysurf avoids this range limitation by use of an interferometric transducer but its vertical resolution of l0nm is inadequate for measurement of x-ray optical surfaces. We report an experimental investigation of the factors limiting the resolution of the Form Talysurf. It is shown that the limit can be reduced without modification to the interferometric transducer, and limits to accuracy from differential non-linearity of the transducer and the performance of the cantilever stylus arm are considered.

The reflection matrix of plumbum arachidate Langmuir films on silicon was measured by means of the generalized ellipsometric technique. The lateral anisotropy of the films was shown. The problem of light reflection from uniaxial film on isotropic substrate with arbitrary axis orientation was solved and used for the measurment interpretation. A simple generalized ellipsometric technique for measuring the nondiagonal reflection matrix of weak anisotropic medium is described. Film refraction indices, monolayer thickness and the angle between the optical axis of the film and the normal to the surface were determined. Models of molecular packing with lateral anisotropy are discussed. Difference in wetting angle of odd and even monolayers is supposed to be the origin of the noncentrosymmetric structure of bilayer resulting in lateral anisotropy of the film.

Many types of electro-optical thin films are under investigation. Among them PLZT thin film is an attractive material due to its large electro-optical effects. Oriented PLZT thin films have been prepared on sapphire and glass substrate by R.F. magnetron sputtering using a powder target. Some properties have been studied and preliminary results are promising for applications in a variety of optical processing and computing systems. In addition PLZT thin film has also been prepared for the first time by the metallo-organic decomposition method. This method can offer lower firing temperature to form PLZT phase.

We applied our microcleavage technique to observe various thin films deposited on silicon substrate by evaporation and sputtering. To be observed by TEM, small particles are usually deposited on thin films such as amorphous carbon films. We present the unique possibilities of our technique to observe them when a thick brittle substrate is used. As we already did it in multilayer characterization, the substrate is used as an in-situ scale.