bluuebunny/crossref_metadata_2025 huggingface dataset:
Specifications for Low Scatter Optics
Authors: Stover John C.
Published: February 2023

The 1970’s and 80’s generated considerable concern over scatter in optical systems. Although it was often recognized in advance that low scatter optics were required for a given application, the specifications were usually either non-existent (a best effort requirement) or inappropriate. The easiest, most available and cheapest scatter measurement was the Total Integrated Scatter (TIS) measurement. Until the mid-1980’s most of the specifications written to handle scatter concerns were either TIS (often given without angle limits) or rms roughness found from some sort of profile data (and given without the corresponding spatial frequency limits).
Detection of Discrete Surface and Subsurface Defects
Authors: Stover John C. , McGary Douglas E.
Published: February 2023

Smooth surface topography (finish) has been related, almost exactly, to the corresponding reflected scatter pattern under the condition that the sample is a smooth, clean, front surface reflector [1-3]. However, another extremely useful application of light scatter metrology is the detection and mapping of component defects that do not meet the smooth, clean, reflective conditions of many mirror surfaces. Examples of such defects are surface contaminants, deep scratches and digs, coating globs and residues, and subsurface defects. When detecting the presence of these defects by scatter measurement, the surface topography scatter is a limiting source of noise. Although smooth non-topographic defects often scatter more light than the surrounding surface topography, they may sometimes scatter considerably less light because they have a small cross-sectional area or because they are buried just beneath a reflective surface. In such cases, a low signal to noise ratio results. If it can be established that non-topographic defects scatter light differently than surface topography, then these differences can be exploited to improve signal to noise and map the defects using various raster techniques described in the literature. This paper discusses polarization differences in topographic and defect scatter and outlines techniques that have been used to enhance defect detection.
Evaluation of Highly Corrected Optics by Measurement of the Strehl Ratio
Authors: Bobroff Norman , Rosenbluth Alan E.
Published: February 2023

Lord Rayleigh demonstrated that the normalized central irradiance in the image of an infinitesimal object is a sensitive measure of aberration. He utilized this criteria in the study of symmetric and asymmetric aberrations in spectroscopes 1. Rayleigh's technique was applied by Strehl to the analysis of atmosphere induced wavefront distortions on telescope images 2. The normalized central irradiance of the point spread function (PSF) has become known as the Strehl Ratio (SR). SR is now widely used as a figure of merit in optical design. SR is often determined indirectly from interferometric measurements by applying Marechai's relation 3 to the measured wavefront aberration.
Absolute Testing of Flats Using Four Data Sets
Authors: Shao Lianzhen , Parks Robert E. , Ai Chiayu
Published: February 2023

Recent interest in using optical systems at shorter and shorter wavelengths for applications like UV photolithography and synchrotron focussing mirrors has put increasing pressure on optical metrologists to improve absolute methods of testing. Because optical metrologist do not have the luxury of possessing measuring instruments that are many times more accurate than what they want to measure, they are forced to make differential measurements between "reference" surfaces and the surface under test. However, even the (often) flat reference surface figure is not known to the accuracy now required by these new applications. This need for a more accurate knowledge of the reference surfaces has created a wide interest in the absolute calibration of flats.
Stressed-lap Polishing of Large, Highly Aspheric Primary Mirrors
Authors: Martin H. M. , Anderson D. S. , Burge J. H. , West S. C.
Published: February 2023

Stressed-lap polishing has been used to complete three fast borosilicate honeycomb-sandwich mirrors. The 1.8-m f/1 primary mirror for the Lennon Telescope being built by the Vatican Observatory and the University of Arizona has been figured to an accuracy of 17 nm rms surface error, the 3.5-m f/1.5 primary mirror for the Starfire Optical Range of the U. S. Air Force Phillips Laboratory to 21 nm rms, and the 3.5-m f/1.75 primary mirror for the Astrophysical Research Consortium to 19 nm rms. The 3.5-m mirrors were figured in a new polishing facility, using a computer-controlled polishing machine and vibration-isolated test tower both sized for 8-m mirrors.
International Optical Drawing and Coating Standards
Authors: Parks Robert E.
Published: February 2023

This paper describes the recently written international standards on how to draw and indicate features on optical element and system layout drawings, and how to specify optical thin film coatings. Both of these standards represent significant changes from US standard practice (or, in most cases, non-practice) for making lens element drawings and specifying coatings. The drawing layout per se is not particularly new or different, but the methods of indicating features and the number of feature parameters available is totally new. The same is true for specifying coatings but here the logic is more easily understood.
Flatness Intercomparison Measurements Made on an Optical Flat
Authors: Slomba Albert F. , Hull-Allen C. Gregory , Takacs Peter Z. , Evans Christopher J. , Bennett Jean M.
Published: February 2023

A 4 inch (100 mm) diameter 0.75 inch (19 mm) thick fused silica optical flat is being used as the master to calibrate the 50 mm long slideways of the China Lake Nanostep Surface Profiler. The average of profiles taken along the 50 mm center sections of two mutually perpendicular diameters has been used for the calibration of the slideways. It is hoped that the Nanostep instrument will be capable of measuring absolute flatness. Until recently, the flat had been defined as being "perfectly flat" in order to obtain a slideways correction. Now actual measurements of the flatness have been undertaken at three laboratories, all using interferometric measurements but of different types. The persons who have taken the measurements and their laboratories are the first three groups of authors listed above. At the Optics and Applied Technology Laboratory, the optical flat was mounted vertically in a nonrestricting ring mount and comparisons were made with the flat being made part of a cavity in a Fizeau-type interferometer and the same cavity but without the optical flat. At Brookhaven National Laboratory, the flat was placed on its back and measurements were made with a pencil beam interferometer1,2 which measures surface slopes and then integrates them to obtain a surface profile. At the National Institute of Standards and Technology, a classical three flat interferometric intercomparison was made with the flat mounted vertically in a V-block. One profile from these last measurements is shown in Fig. 1 for the flatness along the full 100 mm diameter of one of the marked diameters. The measurements are an average of six independent determinations with a standard deviation of 0.52 nm. The dashed line is a polynomial fit through the data. Note that, according to these measurements, the flatness over the central 50 mm is very good indeed, with a peak-to-valley deviation of less than 2 nm.
Aberration Measurement Using Axial Intensity
Authors: Gong Qian , Hsu Smiley
Published: February 2023

Lateral (or transverse) information at either the exit pupil or the focal plane has been used in optical testing for quite some time[1]; however, aberrations can also be measured by using longitudinal intensity information. Geary and Peterson [2] showed that for an unobscured system, spherical aberration can be determined by taking an intensity scan along the optic axis near paraxial focus. In this paper, we describe how the same technique can be applied to systems containing a central obscuration and how the technique can be used to determine the location of paraxial focus. We also investigate the effects of coma and astigmatism. Experimental results demonstrate good agreement with theoretical predictions.
Scale-Up Of LLNL Fused Silica Polishing Process
Authors: Tesar A. , Fuchs B. , Gowac E. , Waite S.
Published: February 2023

The scale-up experiment described in this paper demonstrates the feasibility of using a LLNL fused silica polishing process on a 1.2 meter commercial planetary continuous polishing (CP) machine. The experiment was the first time these particular operating conditions had been attempted. Thus it was not possible to optimize all conditions (such as lap smoothness and slurry flow rate) for this machine in this experiment. The process used was developed and documented on a small, 40cm machine [1,2]. However, the experiment illustrates the benefits of this process which include higher efficiency and improved surface quality. This permits the use of only one lap with constant polishing conditions. The purpose of this development is to encourage production of the highest quality surfaces possible without increasing cost. The polished surface character of optical components has a tremendous impact on performance in many areas of optical technology. The work described below is an example that significant improvements in "mature" technologies can be made if processes are carefully studied and an understanding of the process is developed.
An Ion Beam Figuring System for Medium-Sized Optics
Authors: Schindler A. , Hänsel T. , Nickel A. , Thomas H.-J. , Bigl F.
Published: February 2023

Ion beam etching becomes more and more established in the development of high precision surface and thin film processing. Both the transfer of resist patterns with lateral micrometer and nanometer dimensions and the figuring of large surface areas with nanometer accuracy in depth scale can be realized by this method.
Improved optical performance of silicon backplane spatial light modulators using chemical-mechanical polishing
Authors: O’Hara A. , Vass D. G. , Underwood I.
Published: February 2023

The optical performance of current electrically addressed spatial light modulators is impaired because of the low optical quality of the metal mirrors. The distortion in the metal film is accounted for by hillock formation during the sintering phase of the metallization stage [1]. There have been several techniques developed to reduce or eliminate hillock formation [2,3,4] all of which increase the complexity of the processing sequence. From an electrical point of view the hillocks are only problematic in multi-level metallization schemes where they can cause shorts between levels, therefore, the added work to eliminate hillock formation is only applied to lower level metal. The top level metal which is always used to provide the mirrors has no hillock reduction applied since electrically this is not necessary which results in low quality mirrors. Silicon fabrication foundries will not alter the fabrication sequence to suit one application which leaves only one way to improve the mirrors and that is by post-processing completed wafers and adding another level of metal.
Fabrication of Spherical Quartz Rotors for Gravity Probe-B Gyroscopes
Authors: Graham Victor A
Published: February 2023

Gravity Probe-B (GP-B) is the Stanford/NASA experiment being developed to check Einstein's general theory of relativity using orbiting gyroscopes. The gyroscopes, contained in an Earth satellite and placed in polar orbit, are used to detect the extremely small relativistic motions predicted by the theory. Each gyroscope, essentially, consists of a solid sphere of fused quartz (gyro rotor), coated with a very thin uniform layer of superconducting niobium, and electrically suspended in a vacuum(1). So tiny are the motions to be measured, the gyro rotor must be virtually drift free. Newtonian drift is to be less than 10-11 degrees/hour; any imbalance in the spinning rotor that may overwhelm the relativistic motions has to be eliminated.
Precision Ellipsometric Investigation of Polished Optical Glasses
Authors: Linder Michael
Published: February 2023

Surface modification layers on optical glasses are investigated by means of MAI-MWL (multiple angle of incidence, multiple wavelength) ellipsometry. These modifications in the near-surface region are caused by polishing and cleaning processes.

The device used is a special ellipsometer arrangement using only absolutely necessary elements but allowing fast and very accurate measurements, especially for ultra-thin films. While the basic principle was reported in a previous paper /1/, further improvements of device and evaluation techniques are described. The latter will mainly include residual roughness, which cannot be neglected for the ultra-weak modification layers.
Applied Grinding Wheel Performance Evaluation for Optical Fabrication*
Authors: Piscotty Mark A. , Taylor John S. , Blaedel Kenneth L.
Published: February 2023

We are collaborating with the Center for Optics Manufacturing (Rochester, NY) to develop optimal designs of fine diamond grinding wheels for the spherical grinding of glass optics. To this end, we typically employ a standardized method1 for wheel performance evaluation that focuses on workpiece quality, including surface roughness, figure and subsurface damage. New elements of our work include the use of in-process acoustic emission (AE) measurements for correlating with performance and the use of 3-D surface profiles of wheel topography. This paper includes recent AE measurements taken during the evaluation of several fine diamond grinding wheels and discusses how this new information might relate to the physical performance of the wheels. An interesting observation is also reported relating to the surface topography of worn bronze wheels using an interferometric profiler.
Grating interferometer for metrology of transparent flats
Authors: de Groot Peter
Published: February 2023

Transparent flats are difficult to measure because of the reflections from the front and back surfaces of the flat. The metrology is even more difficult if the surface deformations are too large for conventional testing, as is often the case for plastic hard disk blanks, flat panel displays and silicon wafers. This paper describe an interferometer that successfully separates the front and back surface reflections while working at an equivalent wavelength of 12μm, thus solving both problems with one system.
The role of sampling errors in the specification and testing of EUV mirror surfaces
Authors: Church E. L. , Takacs P. Z.
Published: February 2023

There are two sides to the bright coin of mirror quality: One is specification -- the determination of acceptable level of errors in the shape and finish of the mirror surface -- and the second is testing -- the procedure for measuring those errors to ensure compliance with the specifications.
Liquid mirrors: A new technology for optical designers
Authors: Thibault Simon , Borra Ermanno F.
Published: February 2023

Over the past decade or two, as new technologies have shifted product emphasis toward electronic features and digital processing, optical system design has frequently been relegated to a low priority. Recently, however, there has been a revival of interest in solving optical problems with innovative optical system designs. Liquid mirrors are such new tools available to the optical designers. Rotating liquids make inexpensive and high quality large parabolic mirrors useful for solving optical problems.
Fabrication of Deep Concave Glass Micro Lens by ELID Grinding
Authors: Yamgata Yutaka , Moriyasu Sei , Morita Shin-ya , Ohmori Hitoshi , Higuchi Toshiro
Published: February 2023

Due to the progress in fiber optics, optical storage systems and portable information devices, fabrication technologies for micro optical components becomes more and more important. The fabrication process of micro optical componets especially deep concave glass micro lens is facing a number of diffculties: (1)Since the diameter of the micro optical component is very small and the depth of the surface is large, the grinding wheel must have even samller diameter. (2)In order to obtain optimum cicumference speed, the rotation speed of the grinding wheel becomes extremely high. In order to overcome those problems, inclined grinding wheel can be used to cut the deep concave surface. This method solves the first problem but still extremely high rotation speed is necessary. The authors present a new resolution to those problems using ELID (ElectroLytic In-process Drssing) grinding method. Using ELID grinding, the grinding wheel is continuously dressed during the machininig process and always kept sharpened. This results in a very high quality surface finish even under low circumference speed. Fabrication example of glass micro concave lens (radius:4.6mm) is carried out with small grinding wheel (diameter 5mm) at relatively low rotation speed of 20,000 rpm, which is equivalent to 300m/min circumference speed. Surface roughness of 40nmp-ν and profile accuracy of approximately 1μm was obtained.
The Design of Precision Mounts for Optimizing the Conversion Efficiency of KDP Crystals for the National Ignition Facility*
Authors: Hibbard Robin L. , Norton Mary A. , Wegner Paul J.
Published: February 2023

A key design challenge for the National Ignition Facility (NIF), being constructed at Lawrence Livermore National Laboratory (LLNL), [Hibbard, R. L., 1998], is the frequency converter consisting of two KDP crystals and a focusing lens. Frequency conversion is a critical performance factor for NIF and the optical mount design for this plays a key role in meeting design specifications. The frequency converter, Figure 1, is a monolithic cell that mounts the optics and is the point on the beamline where the frequency conversion crystals are optimally aligned and the cell is focused on target. The lasing medium is neodymium in phosphate glass with a fundamental frequency (1ω) of 1.053 µm. Sum frequency generation in a pair of conversion crystals (KDP/KD*P) produces 1.8 MJ of the third harmonic light (3ω or λ=0.35 µm). The phase-matching scheme on NIF is type I second harmonic generation followed by type II sum-frequency-mixing of the residual fundamental and the second harmonic light. This laser unlike previous laser system designs, must achieve high conversion efficiency, 85%, which is close to the 90.8% theoretical maximum. As a result, this design is very sensitive to angular variations in beam propagation and in the crystal axes orientation. Factors that influence the phase matching angle include crystal inhomogeneity, residual and induced stress in the crystals, the crystals’ natural and mounted surface figure, mounting imperfections and gravity sag. These angular variations need to be controlled within a 40 µrad error budget. The optical mount contributions to the angular error budget are 20 µrad and are what make the frequency converter in the Final Optics Cell (FOC) such a challenging precision design.
Test results to support an automated scratch/dig inspection instrument for large laser optics
Authors: Brusasco Raymond M. , Brunfeld Andrei , Bissinger Horst , Toker Gregory
Published: February 2023

The National Ignition Facility (NIF) laser, currently under construction at the Lawrence Livermore National Laboratory (LLNL), is comprised of over 9000 large optics.1 The size of these optics range from 41 cm × 41 cm to 45 cm × 80 cm and in thickness from 1 cm to 9 cm. All of the large glass optics are either square or rectangular and are fabricated of either fused silica, BK-7 or Nd-doped laser glass. Among the optic quality tests to be performed during fabrication is the mapping of surface imperfections, i.e. scratch and dig measurements.
Partially coherent illumination in interferometers for optical testing
Authors: Schwider J.
Published: February 2023

In the last few years one can observe a renaissance of partially coherent illumination in interferometers. The reason behind is the roughening of wavefronts due to dust diffraction, inhomogeneities, and the remaining micro-roughness of all optical components within the light path. Illumination with the TEM00 mode of a laser will show these effects in the interference pattern rather clearly /1/. Because of the heterodyne advantage of interferometry small scattered light amplitudes result in rather pronounced modulations of the lateral intensity distribution of the laser beam and inevitably give rise to small lateral phase modulations on the order of 1/100 of a light wave. These small phase variations can easily be detected in a laser interferogram even if the light has carefully been filtered with the help of a pinhole in the collimation optics. The amount of phase uncertainty introduced in the measurement of surface shapes and other parameters of optical components depends on the type of interferometer as well as the amount of tilt fringes in the interferogram.
Ion-Induced Desorption of Moisture in Optical Coatings
Authors: DeSandre L. , Hodgkinson I. J. , Macleod H. A. , Messerley M. , Saxe S. , Wharton J. J.
Published: February 2023

Ion-beam milling of optical coatings and concurrent measurement of transmittance or reflectance has been shown to be a useful destructive characterization technique [1][2]. As the coating is gradually removed, an optical signal is obtained that reproduces the monitoring signal in reverse. During operation of this technique almost invariably an initial rapid change in signal level was detected, which was quite uncharacteristic of the gradual sputtering of the multilayer as a whole. This rapid change occurred even at flux levels that were established as too low to cause perceptible sputtering in a reasonable time. The effect was found to be due to rapid desorption of moisture within the coatings.
Crystalline Phase Characterization of TiO2 Optical Coatings by Raman Spectroscopy
Authors: Pawlewicz W.T. , Exarhos G.J.
Published: February 2023

Raman spectroscopy can be used to characterize the crystalline phase composition (rutile/anatase) of single-layer TiO2 optical coatings, multilayer TiO2/SiO2 coatings on reflective metals, and general all-dielectric TiO2/SiO2 structures such as high reflectors and Fabry-Perot filters. Measurements can be made in 1 second using diode array detection techniques or in a few minutes using a conventional scanning spectrometer. No special specimen preparation is required. The Raman technique contrasts markedly with conventional phase identification techniques such as x-ray and electron diffraction where extremely long counting times (about 24 hours) or difficult specimen preparation are always necessary and not always sufficient to produce the required resolution. Raman spectroscopy thus appears to be an excellent research tool for systematically understanding and optimizing optical properties, thermal stability and perhaps laser damage resistance in TiO2 coatings, which are generally two-phase mixtures of anatase and rutile.
Development of a Wavelength Scanning Laser Rate Calorimeter
Authors: Atkinson R
Published: February 2023

In order to investigate the total optical loss mechanisms in multilayer coatings it is useful to complement radiation scattering experiments with measurements of losses due to absorption. Laser calorimetry is an appropriate technique for measuring absorption in low- and high-loss coatings since it is capable of producing absolute measurements (without the need for calibration using a sample of known absorptance) and has the potential for high sensitivity.
Visual Detection of Organic Monomolecular Films by Interference Colors - optical conditions for reflecting surfaces
Authors: Sandström T. , Stenberg M. , Nygren H.
Published: February 2023

Thin (<10 nm) dielectric layers of biological origin are visible to the unaided eye, on a reflecting substrate, if the substrate is first covered with a dielectric film which gives a strong interference color. Simple and sensitive immunoassays can be based on such reflection phenomena. Slides previously used for this purpose consist of a metal substrate with a dielectric layer on top. Systems used are barium steareate on chromium [1,2], tantalum oxide on tantalum [3], and indium oxide on a gold-indium alloy [4]. A similarly functioning system with a semi-transparent metal layer, on top of a dielectric layer on a metal, has also been described [5]. However, there is no systematic study of the phenomenon. Likewise, there is no system proposed which promises high sensitivity together with simple production and good biochemical properties.
Accurate and Precise Reflectance Measurement of Highly Reflecting Mirrors
Authors: Wierer Peter G. , Guenther Karl H.
Published: February 2023

The reflectance R of a real surface can be separated into the specular reflectance Rs and the diffuse reflectance Rd, the latter also referred to as diffusion or Tight scattering. Rd is usually a function of the scattering angle, with its maximum intensity directed into the specularly reflected light beam. Hence, with a finite acceptance solid angle of any real detector always some fraction of experimentally determined R origins from Rd, its value depending on the detector solid angle. By this, the accuracy of different reflectance measurement methods and instruments is difficult to compare. With this work, we are aiming on an exact separation of Rs and Rd, thus enabling the accurate measurement of the specular reflectance of highly reflecting mirrors, e.g. as used in laser gyro applications.
Visible and Ultraviolet Thin Film Coating Characterization
Authors: Gallant David J. , Stewart Alan F.
Published: February 2023

Recent advances in high power lasers operating in the visible and ultraviolet, such as the free electron laser (FEL) and the high power excimer laser, have shown that optical thin film coatings require further study and improvement in order to optimize these laser systems. In addition to the problem of laser induced damage in thin films, reflective and window coatings for a visible or ultraviolet laser system must exhibit dramatic improvements in reflectivity, scatter levels, surface figure, homogeneity, and optical absorption losses. Optical materials as well as polishing and thin film coating techniques must be improved and new technologies exploited.
Reduction of Stress in Cerous Fluoride Films
Authors: Pellicori S.F.
Published: February 2023

The endless search for stable low index materials (n ~ 1.4 to 1.5) for the infrared has focussed on a temporary solution with ThF4. However, ThF4 is not ideal environmentally and, further, it presents handling problems because of its radioactivity. For some applications it can produce increased detector noise. Other fluoride compounds possess the low index value required for high efficiency AR coating applications, but are not useable in thick layers because of their large tensile stress and/or moisture vulnerability. The Group IIA fluoride compounds suffer in varying degrees from low density or excessive absorption out to 12 μm in QW layers. Substrate temperatures in excess of 250°C are required to achieve a packing density within 90% of the bulk value. These high temperatures often cause other stress problems in multilayer combinations.
Phase Shifting Thin Film Multilayers for Michelson Interferometers
Authors: Piotrowski Susan H.C. , Dobrowolski J.A. , Shephard Gordon G.
Published: February 2023

Several wide-angle Michelson Doppler imaging interferometers will be flown in the near future on the Space Shuttle and on the Upper Atmospheric Research Satellite to study the winds, temperatures and volume omission rates of the upper atmosphere. For one measurement four consecutive images will be taken with the Michelson mirror moved an eighth of a wavelength between each image.
Cuton and Cutoff Edge Slopes of All—Dielectric Cavity Filters
Authors: Kohin Margaret
Published: February 2023

Filters designed using the microwave prototype techniques described by Baumeister (ref. 1 and 2) have decreasing cuton and cutoff edge slopes with increasing numbers of cavities. If we neglect the effects of phase dispersion narrowing, the edge slopes for maximally flat designs are found to be proportional to bandwidth and depend only on the number of cavities in the design. The proportionality constants for designs having up to eight cavities have been determined and are reported. In addition, the proportionality constant is found to differ from that for the true maximally flat case in quasimaximally flat and Chebyshev type designs. In the Chebyshev case, the slope is found to decrease with decreasing passband transmittance. This variation in proportionality constant with passband transmittance has been plotted for the three—cavity case and equations are presented that can be used to design three—cavity filters with specific minimum passband transmittances.
Silver-Magnesium Fluoride Cermet Films: Preparation, Microstructure and Optical Properties
Authors: McPhedran R. C. , Gajdardziska-Josifovska M. , McKenzie D. R. , Collins R. E. , Cockayne D. J. H.
Published: February 2023

This study of the silver-magnesium fluoride composite system was undertaken in order to clarify the relationship between the microstructure of the material and its optical properties. We were interested in making a range of cermet systems, determining their structure as well as we could by direct means, observing their optical properties and correlating those properties with various theoretical models of composites.
Effect of Ion-Assisted Deposition on the Crystallinity of Samarium Fluoride Films
Authors: Lingg L. J. , Hwangbo C. K. , Bovard B. G. , Lehan J. P. , Macleod H. A.
Published: February 2023

Crystalline structure is known to be a very important factor in coating performance. This was shown most recently in fluorides by work on MgF21,2 and on LaF33,4. This paper examines the influence of ion-assisted deposition (IAD) and deposition temperature on single layer coatings of SmF3. The samarium cation is both divalent and trivalent and the trifluoride has two possible crystalline structures: hexagonal and orthorhombic. As a result, the two variations on deposition technique produce films of very different crystal structures and orientations.
Ion-Plating of Silicon Nitride Optical Thin Films
Authors: Bovard Bertrand G. , Ramm Jurgen , Hora Ralf , Hanselmann Fritz
Published: February 2023

Improving the optical and mechanical properties of optical thin films deposited by thermal evaporation is a great subject of interest and research. Ion-assisted deposition [1] has proven to be a very successfull technique to achieve high packing densities, relief of tensile stress, and elimination of water absortion bands provided films are grown stoichiometrically. Ion-plating, another ion assisted process, has been successful in growing dense oxide layers such as TiO2, SiO2, Al2O3, ZrO2, and Ta2O5 onto unheated substrates [2].
Antireflective coatings on very large substrates by the dip coating process
Authors: Hussmann Eckart K. , Arfsten Nanning J. , Heusler Hans-Ulrich , Roehlen Peter H. , Piehlke Hermann J.
Published: February 2023

The inherent properties of the dip coating process were used to produce uniform antireflective layer systems on both sides of large substrates.
Deposition of Optical Thin Films by Pulsed Laser-Assisted Evaporation
Authors: Sankur H. , Gunning W.
Published: February 2023

Stringent requirements of novel optical coating designs and conditions of usage necessitate high quality material properties in thin films. Several novel physical vapor deposition techniques have recently been investigated to obtain films with high packing density and structural order and with stable optical properties. Most of these new techniques utilize energetic vapor species to achieve the above desired properties.
Large Area Coatings with Uniform Thickness Fabricated in a Small Vacuum Chamber
Authors: Hayden C. J. , Spiller E.
Published: February 2023

Coatings of uniform thickness distribution are required for many applications of thin films. Deposition from a point evaporation source onto a flat substrate will produce a nonuniform film because of distance and angle variations between the source and various points on the substrate. Several methods are commonly used to improve the thickness uniformity of thin film coatings. Examples are:1 (a) an off axis position of evaporation source to a rotating substrate, (b) large area evaporation sources, (c) planetary rotation of the substrate, (d) simultaneous rotation and wobble of a substrate, and (e) rotating a tilted substrate. All methods except the last require vacuum chambers with a diameter considerably larger that that of the substrate and all require a deposition angle far from normal incidence. A non-normal deposition angle often produces film interfaces which are rougher than those obtained for near normal incidence. This roughness can drastically reduce the performance of a multilayer coating at short wavelengths.
Characterization Of Thin-Film Surfaces By Differential Scattering Measurements And Digital Analysis Of Replicas' Micrographs*
Authors: zhong-Liang Lu , Jin-Fa Tang
Published: February 2023

Characterization of thin-film surface has been the subject of numerous accounts. The good quality optical surface can be characterized with various methods. However, it is defficult to compare the statistical parameters of surfaces measured by different techniques. The measured value depends on the bandwidth of surface spatial frequency limit of the instrument used. In this study we have used the differential scattering (DS) as well as the digital analysis of micrographs of surface replicas (DAM) for characterizing the smooth surfaces of Ag and Al films. The experimental results showed that the combination of these two techniques could measure the statistical properties of optical surfaces over an extended bandwidth of surface spatial wavelength limit from 35 Å to 60 μm.
Characterization of Vanadium Oxide Optical Thin Films by X-Ray Diffractometry
Authors: Chain E.E.
Published: February 2023

Thin-film x-ray diffractometry with Seemann-Bohlin focusing provides enhanced sensitivity to the microstructures of optical thin films. Results on vanadium oxide films are presented.
A Wideband Monitoring and Measuring System for Optical Coatings
Authors: Yen Yi-hsun , Li Li
Published: February 2023

Today, non-quaterwave optical coatings are commonly used in production, especially due to the rapid development of CAD technique. The wideband monitoring method, proposed by B. Vidal, A. Fornier and E. Pelletier [1] in 1978, is very effective to solve the monitoring problem of this kind of coatings. A practical wideband monitoring system has been established in our laboratory.
Reflectace diagram-aided technique for optical coating design and monitoring
Authors: Zheng S.Y. , Ping G. , Yen C.N. , Ma X.
Published: February 2023

This paper describes mainly applications of amplitude reflectance diagram-aided technique in the design of both induced reflection and transmission filters with narrow bandwidth, as well as in the monitoring of all-dielectric multilayers with symmertric structure. Some experimental results are also reported.
Rugate filters by laser flash evaporation
Authors: Bartholomew C.S. , Morrow M.D. , Wild W.J. , Betz H.T. , Murarka N.P.
Published: February 2023

A deposition system for laser flash evaporation was assembled and used to deposit two notch ZnSxSey rugate filters with optical densities of 2 or more and bandwidths as low as 7%.
Research on Thin Film Anticounterfeiting Coatings at the NRCC
Authors: Dobrowolski J.A. , Ho F.C. , Waldorf A.
Published: February 2023

After a brief description of the threats which face the issuers of documents and valuable papers, the concept of thin film anticounterfeiting coatings proposed by the NRCC will be explained1. The colorimetric considerations which govern the design of such devices will be reviewed. Typical coating designs suitable for use in transmission and in reflection will be discussed. Reflection coatings can be constructed with and without an integral black absorber coating. The need for geometric patterns in the anticounterfeiting coatings will be explained. Various methods for producing such logos will be proposed. Mention will be made of the various numerical tools developed for the design and investigation of single films and multilayers, their desensitization to construction errors and for the investigation of different process control strategies. During the duration of the project experiments were performed on the optical constants and non-optical properties of a number of metal and dielectric films considered for use in the anticounterfeiting coatings. These, and some of the processes and equipment investigated during the development of a prototype production facility, will be reviewed. Finally, some security and economic aspects of the devices will be considered.
Method of Determining Optical Constants of Thin Films Using an Infrared Ellipsometer
Authors: Yen Y. , Zhang K. Q.
Published: February 2023

In infrared region, some high refractive index materials for optical coatings, such as PbTe and Ge, are generally weakly absorbed. Their extinction coefficient k varies from 0.001 to 0.02 with different deposition condition. To determine optical constants of weakly absorbed thin films the most often used method is R,T method [1],[2], but it is not adequate for very thin films, for example, in such a case that optical thickness is less than half of the wavelength. To determine the optical constants of these coatings one of the methods is ellipsometry, but it is usually used for strong absorbed thin films [1], [3]. In this paper, the measurement method and results of weakly absorbed thin films using ellipsometer combined with spectrophotometer and alpha-step profilometer are described and presented. It should be pointed out that some of our methods are not new, however using these methods, the optical constants of weakly absorbed thin films have been effectively measured and some useful results have been obtained.
Determination of The Extinction Coefficient of Dielectric Thin Films from Spectrophotometric Measurements
Authors: Borgogno J.P. , Pelletier E.
Published: February 2023

Data obtained from reflectance and transmittance measurements are used to determine the extinction coefficient. We show that accuracy is limited by the substrate quality and by interface roughnesses of the layer.
A Surface Study of An Infrared Bandpass Filter Exposed to Cryo-Vacuum Freon/Ice Exposure
Authors: Garcia Marie F.
Published: February 2023

Three discrete features were observed on an infrared filter after freon/ice testing at 83°K under vacuum. These features are areas of: nodule cluster removal, dendritic growth, and dark discoloration.
Crystal Gazing - A Look Towards Optical Coatings in the Future
Authors: Lewis Keith L
Published: February 2023

Thin film optical devices are expected to play an increasingly more important role in the evolution of optical and optoelectronic technologies during the next decade. New applications are expected to emphasise a significant stretching of the performance levels currently achievable in coating production, while the continual search for cost reduction will drive the need for more efficient material deposition processes, as well as the exploitation of more effective optical designs. The scale of such devices will range from the sub-micron domain of the optoelectronic device to the metre-plus scale of the aircraft canopy or the architectural "designer" window. In many cases, there will also be spin-off into or from other areas, particularly those involving wear-resistant coatings for machine tool or decorative applications. Lastly, requirements for optical signal processing, displays and "smart" windows will drive increasing emphasis towards the incoporation of active materials into multilayer designs, forming the cornerstone of a wide range of new products.
Design a Quarter Wave Retardation Mirror with Optical Thin Film Coating
Authors: Wang Ran-Hong Raymond
Published: February 2023

A computer aided design of a thin film retardation quarter wave mirror at 632.8nm is presented. The Simplex optimization process was used in the design. The designed quarter wave mirror was manufactured and examined. The retardation of the mirror was measured. The results indicated that a retardation mirror can be successfully designed and produced.
Optimizing interference coating in adaptive microwave modulators and filters
Authors: Sysakyan I.N. , Tikhonravov A.V. , Shvartsburg A.B. , Shepelev A.V. , Yakushkina V. G.
Published: February 2023

New type of high speed tunable devices, based on heating of semiconductor free carries by electric field is elaborated for control of radiation flows in millimeter and submillimeter wave ranges [1-2]. High fast-acting and possibility of amplitude-phase tuning stipulate this technique application for decision of actual tasks in optics and laser physics in far IR-range.
Optical waveguide characterization of thick dielectric films deposited by reactive low voltage ion plating
Authors: Kimble Thomas C. , Himel Marc D. , Guenther Karl H.
Published: February 2023

Titanium dioxide (TiO2) is a material often used for thin films in optical interference coatings because of its high index of refraction. However, conventional physical vapor deposition (PVD) results commonly in thin films with pronounced columnar microstructure. This causes light scattering to an extent that PVD thin films of a thickness suitable to guide one or more modes become too lossy to guide lightwaves at all. Reactive low voltage ion plating (RLVIP) produces very dense, amorphous (i.e. vitreous) thin films1 with surfaces significantly smoother than those of conventional PVD thin films.2 Thus, RLVIP thin films appear to be potentially useful as high-index optical waveguides, similar to those produced from organometallic solutions (sol-gel coatings).3 Vice versa, we show that waveguide characterization of the refractive index and optical losses is a useful aid for optimizing the RLVIP process toward low-loss optical coatings, for example for laser applications.4 In addition, the waveguide measurements of a few select samples were compared to variable angle spectroscopic ellipsometer (VASE)5 measurements.
Laser induced damage resistance of film polarizers prepared by Ion-assisted deposition
Authors: Gu P.F. , Tang J.F.
Published: February 2023

The design of polarizers is similar to a band-passed filter with deturned spacers which are advantages to extending the band of polarization seperation and to reducing transmission ripple for the p-po1arisation component in the polarized band [1]. The real optical thicknesses of high and low index layers are integral number of quaterwaves of a specific wavelength, easing the production of polarizers. Topical film design is as follows: where n and m refer to the number of quarterwaves of the low index layer. The experimental transmittance of the polarizers for p-po1arized radiation has reached 97-98% and for s-polarized radiation 0.1-0.5%.
Photothermal measurements of absorption and thermal conductivity of thin films
Authors: Wu Z. L. , Reichling M. , Hu X.-Q. , Balasubramanian K. , Guenther K. H.
Published: February 2023

Thin films in optical coatings used for laser applications need to have low optical absorption to assure high laser damage threshold.1 Heat generated by even very low but finite absorption (A ≤ 10–6) of laser pulse energy needs to be dumped rather quickly and efficiently to avoid thin film damage by local overheating (melting, evaporation). Thus, the thermal conductivity of the films toward the substrate needs to be as high as possible. In comparison, lateral thermal conductivity is rather unimportant, as heat is generated over the full area of the spot size (which can be several hundred micrometers or even several millimeters) so that the distance of an individual point-like heat source within the spot to the cooler non-irradiated film is large compared to the distance to the substrate, which is an efficient heat sink. Despite this rather important influence of absorption and thermal conductivity, few reliable data is available. Early measurements on evaporated thin films showed that their thermal conductivity was one to two orders of magnitude lower than that of the same bulk material.2,3,4
Measurement of Ultralow Losses in Dielectric Mirrors
Authors: Lalezari R. , Rempe G. , Thompson R.J. , Kimble H.J.
Published: February 2023

Characterization of low loss mirrors by measurements of cavity decay time and of cavity finesse are reported around 850 nm. The lowest observed loss is 1.6 ppm (transmission and absorption and scatter), corresponding to a reflectivity of 0.9999984.
Single mode couplers through end-coatings on optical fibers
Authors: Richier R. , Pelletier E.
Published: February 2023

For some years, the society "Alliance Technique Industrielle" and the "Laboratoire d'Optique des Surfaces et des Couches Minces" have developed jointly passive components for optoelectronics. It mainly concerns multi-demultiplexers and couplers. The original feature and the interest of the developed systems result from the fact that: - the coatings used to obtain selective optical properties (transmission versus wavelength) are deposited directly on the ends of the fibers. - after coating, the fibers are directly fitted together without any additional optical part.
Optical Properties of Tantalum Oxide Films Produced by Electron Beam Evaporation, Starting from Metal Tantalum Mixed Tantalum Oxide
Authors: Aoki Tomonori , Ogura Shigetaro
Published: February 2023

Ta2O5 is a suitable high-index material for thermal resistive thin film applications, such as a component of reflector mirrors for projectors. Melting of Ta2O5 tablets by electron beam gun shows often the dissociation of starting Ta2O5 materials and gives rise of O2 level during its melting. It is, therefore, necessary to continue a long time premelting process to get sufficient low oxygen level or stable vacuum pressure before starting appropriate deposition of Ta2O5 films. It requires not only disadvantageous long process time, but also it starts again endless oxygen outlet from the insufficiently melt parts of Ta2O5 when electric power applied to electron beam gun increases towards higher level for deposition. This results inevitably unstable deposition process and hence unstable refractive indices of Ta2O5 films obtained up to now.
Effects of Compressive Stress in Thin Films
Authors: McKenzie D R
Published: February 2023

The development of compressive biaxial stress in a film as the result of energetic impact during growth has been demonstrated in a number of experimental studies. In a study of sputtered metal films, Hoffman and Thornton showed that there is a tendency towards compressive stress as the pressure of the Ar sputtering gas is reduced[1]. Because the effect of collisions is to thermalise the sputtered vapour to a temperature approaching that of the background gas, low pressure sputtering generally produces a higher flux of energetic atoms onto the growing film. In some cases, the data show a maximum in compressive stress as pressure is reduced, showing that even though the average energy of the sputtered atoms is increased by further reduction of pressure, the compressive stress is actually reduced. For Pd films subjected to Kr ion bombardment during growth, Ziemann and Kay[2] showed the presence of a maximum in the compressive stress for an impact energy of 80eV per Pd atom. In the case of sputtering in which the substrate is biased with respect to the plasma so that the energy of impact of ions onto the film may be varied, a maximum compressive stress in several metal films has been observed for bias voltages of approximately - 50V[3]. The situation in non-metallic films is similar. For TiN, the compressive stress also shows a maximum in the impact energy range less than 200eV[4].