bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of silicon nitride by sequential magnetron sputtering of silicon and nitrogen ion bombardment
Authors: Netterfield R P , Martin P J , Bendavid A , Kinder T J
Published: February 2023

There are difficulties associated with DC magnetron sputtering of insulating compounds such as nitrides and oxides at high rate. Such films are usually deposited from an elemental target in a reactive gas environment. It is difficult to maintain constant deposition conditions to produce stoichiometric films without progressively poisoning the cathode. Very recently there has been considerable interest in the synthesis of such films by cycling between elemental deposition by magnetron sputtering and subsequent compound synthesis by ion irradiation from an ion gun using the relevent reactive gas. Sequencing is usually on the scale of about one monolayer and the substrate is transported between the different deposition zones [1]. A somewhat similar deposition technique of alternating ion-plating was pioneered earlier by Schiller et al [2]. We report on the synthesis of silicon nitride films prepared in a similar manner but where the substrate is stationary and sequencing of the different deposition parameters is controlled by a computer. The technique will be referred to in the rest of this paper as MAGIC deposition (MAGnetron sputtering and Ion Conversion). The growth dynamics and film stress have been monitored in-situ by ellipsometry and interferometry, and the optical properties and stress are compared to those of silicon nitride films prepared by IAD and conventional magnetron sputtering.
Optical Multilayer Coatings Produced with Automatic Deposition Error Compensation
Authors: Sullivan Brian T. , Dobrowolski J. A.
Published: February 2023

Complex optical multilayer (non-quarterwave) coatings can be difficult to manufacture on a routine basis because of problems with the control of the layer thicknesses or the optical constants of materials. The challenge is to achieve very accurate control over a large number of layers in order to realize the desired optical performance. The solution lies in detecting and then compensating for any errors in a layer thickness or in the expected optical constants.1
Plasma Impulse Chemical Vapour Deposition - A Novel Technique for Optical Coatings
Authors: Heming M. , Hochhaus J. , Otto J. , Segner J.
Published: February 2023

Plasma assisted CVD techniques are increasingly important in semiconductor and wear resistant tool fabrication. Although the CVD process has the potential of low fabrication costs, applications in the optical coating field, however, are still rare up to now. The reason is mainly the limited layer thickness uniformity. This situation has changed now. In this paper we present a plasma impulse CVD (PICVD) process, which is capable of producing high quality optical layers at moderate costs.
In-situ characterization by spectroscopic ellipsometry and photoemission of CaF2 films grown by molecular beam deposition in ultra-high vacuum
Authors: Rivory J. , Fisson S. , Van Nguyen V. , Vuye G. , Wang Y. , Abeles F. , Yu-Zhang K.
Published: February 2023

As previously mentionned [1], ultra high vacuum conditions and molecular beam deposition bring significant improvements in the stability of optical thin films and allow to benefit of in situ surface analysis techniques.
UV Laser Coatings at 193 nm - 355 nm
Authors: Wang Xiu Fen , Zhang Hong , Qian Weizhen
Published: February 2023

Interest in UV optical coating has increased in recent years, due to applications in excimer lasers and lithography. Aluminium mirrors coved MgF coatings are tranditional UV reflection optics. The mirrors with reflectance of 80-85% have been used in many applications.
Optical Coatings for the Omega Upgrade Laser
Authors: Smith Douglas J. , Schmid Ansgar W. , Chrzan Z. Roman , Papernov Semyon
Published: February 2023

The OMEGA Laser has been successfully used for implosion experiments of inertial fusion for the past decade. The number of useful direct-drive experiments are now limited due to the energy and uniformity of illumination at the target. The OMEGA laser in its current configuration has a 2.4-KJ maximum output at 0.7 ns in 24 beams with a 18-cm aperture. An upgrade will be made to the current laser that will increase the energy and beam number respectively to 30 KJ and 60 KJ. Each beam will increase in aperture to 30 cm, while the pulse will actually be composed of a 5-ns pulse followed by a 0.7-ns pulse. The two pulses will co-propagate down the same beamline with the long (foot) pulse in the central region while the short (main) pulse will propagate in an annulus surrounding the foot pulse.1 As in the OMEGA laser, the radiation at 1054 nm will be frequency tripled to 351 nm with a pair of KDP crystals. A decision was made during the preliminary design process to place the frequency-conversion crystals in the laser bay (rather than directly on the target chamber). This placed stringent damage fluence requirements on the blue transport mirrors, which prompted development of 351-nm-high reflectors. A summary of the requirements for some of the 2000 optical elements which will be required by the OMEGA Upgrade, is given in Table 1.
Gradient Index Bandpass Filters
Authors: Hall Randolph L.
Published: February 2023

The performance of filters having sinusoidal refractive index profiles have been published by various authors1. In general, these filters have a strong reflection at the design wavelength and offer the promise of no harmonics at any wavelength2. Further, these refractive index profiles may be superimposed with each other creating multiple stopbands. Fig. 1 shows the refractive index profile and predicted performance of this type of filter, commonly referred to as a rugate (from the Latin for wrinkled) filter. Presented in this paper is an approach for the design of narrow bandpass filters based on this type of refractive index profile. These filters are suitable for applications which require very narrow passbands.
Recent Progress of Optical Thin Films in Automobile Industry
Authors: Taga Yasunori
Published: February 2023

A great amount of efforts has been devoted to the constant improvements of such basic performance of automobiles as drivability, safety and environmental protection. The total combination of various technologies such as mechanics, electronics and optics results in making automobiles safer and more comfortable. Among these technologies, surface and thin film technologies are mainly concerned with various application fields. For example, optical thin films including interference coatings were applied to the control of the solar energy invading through automobile windshield, which results in low fuel consumption and also protection of the driver's skin and sheet materials from strong ultraviolet ray irradiation. Birefringent and polarizing films are also effective for the construction of display devices of interior panels for man-machine interface. From the safety driving point of view, ultrasonic mirrors combined with hydrophobic thin film coating was widely used for keeping high viewing field of mirrors in rainy days.
Degradation Studies of Silver and Nitride Based Solar Control Films
Authors: Andersson K. E. , Wahlström M. K. , Georgson M. , Ribbing C. G. , Roos A.
Published: February 2023

Solar control coatings are important in warm climates. The coating should have a high transmission of visible light, i.e. for wavelengths 0.4-0.7 µm, and reflect as much as possible of the solar radiation in the wavelength interval 0.8-2.5 µm. One concept in the design of such a film is the noble metal based multilayer1-3. where the metal film is sandwiched between antireflecting oxide layers. Although having favourable optical performance, the presence of a thin noble metal film in the multilayer limits the stability of the configuration to the extent that they can only be used in sealed windows.
The applications of optical and opto-electrical films in LCLV
Authors: Jinfa Tang , haifeng Li , Peifu Gu , Xu Liu
Published: February 2023

The photoaddressed liquid crystal light valves which are widely used in optical information process and large screen display1,2, are mainly composed of optical and opto-electrical films (shown in Fig.1). In order to improve the performance of the LCLV, all these films should be refined and made perfectly, especially the photoconductive films which determine the opto-electronic characteristic. With the high quality of CdS/CdSe photoconductive film and all other optical and opto-electrical films, the LCLV gets good contrast ratio(>100:1 white light), fast response (<15ms), high brightness (>20001m) and high resolution (>50pl/mm).
Bandpass Filters for Communications
Authors: Cushing David
Published: February 2023

There is considerable interest today for filters for fiber optics telecommunications are in the Near Infra-red spectral area. Activity is centered about 1550 nm. Components for Wavelength Division Multiplexer filters used with fiber amplifiers require very high transmission of certain selected wavelengths with very low transmission of an adjacent wavelength in the band of 1530 to 1580 nm. Lasers for this spectral area have a high degree of wavelength variability with operating environments and also with aging. The bandwidth of the filter is specified to pass the signal over a wide range of conditions. Ripple in the passband must also be controlled to meet stringent customer demands. The number of cavities in the filter is determined by the requirements for isolation of allowed wavelengths of the other channel(s).
Robust Filter Design with Evolutionary Strategies
Authors: Greiner Horst
Published: February 2023

The mathematical design of an interference filter meeting given optical specifications is a complicated global optimization problem for an appropriately defined figure of quality which in general depends in a multimodal fashion on the layer thicknesses and the assignment of the available optical materials to the layers. In the past methods of global optimization including cluster analysis, random search, simulated annealing, genetic and evolutionary algorithms have been brought to bear on this problem in the optics literature. For a review of these methods from a more mathematical point of view we recommend ref.1,2.
A New Approach to Reject Background Transmittance of Infrared Filters
Authors: Dehua Xiao , Lai Wang , Hengyi Li
Published: February 2023

The fast development of infrared technology makes infrared tracing, infrared guidance more and more applicable in the millitary arm systems. But when flying object fly against the sun, the background signal from sunlight will make it impossible to trace and detect, so it is necessary to reduce the influence of sunlight, CO2 in the atmosphere makes it impossible, becaues CO2 shows strong absorption to the sunlight of 4.184-4.454um region. If we can design an infrared filter, which transmits the light at the wavelength region, the flying object is much nearer to detect system than to the sun, which means the influence of sunlight can be neglected. To obtain sufficient sensitivity and high contrast ratio, such bandpass filter must have high transmittance (Tp) and very low background transmittance(Tb).
Extending Transmittance Bandwidth of Filters
Authors: Zheng Anmin , Whatley Alan , Bovard Bertrand G.
Published: February 2023

From time to time, IR optical systems require blocking for all wavelengths from the middle ( 8μm ) to the far IR., beyond 40pm, ( even 50μm ). In many cases, particularly at cold temperatures, the use of the absorption of coating materials and substrates to block the radiation is not enough. Therefore interference filters are required to produce such wide wideband blocking. Furthermore, these interference filters sometimes require wideband reflectance at the long wavelengths complemented with wideband transmittance at the short wavelengths.Unfortunately, such special requirement cannot be met by the normal short wave pass filters with a basic period of ( H/2LH/2 ) or ( L/2HL/2 ). Epstein and Thelen have proposed approximate theories and designed a variety of filters with extended pass bands (1), (2), (3). Markov etc. (4). actually manufactured one type of such filters by using PbTe in the IR. region. In this paper, following the previously-proposed method, explained here is a simple and general design method, and several samples are also given.
Durability Examination of Silver-Copper Films via Surface Plasmon Resonance
Authors: Bussjager R. , Macleod H. A.
Published: February 2023

A surface plasmon resonance (SPR) occurs when a thin metal film on the hypotenuse of a prism is illuminated with p-polarized light beyond the critical angle under conditions that permit the coupling into a surface plasmon, a progressive wave bound to the outer metal surface. The shape and angular position of the resonance are very sensitive functions of the conditions at the metal surface and have been used by many people to measure the properties of thin over-layers or contamination, and in the characterization of chemical and biological processes1,2,3. Here we use it to probe environmentally induced changes in a silver layer that has been treated with a thin copper layer. In the probing of biomembranes by a surface plasmon resonance technique, the silver layers that support the plasmon are exposed to an aqueous phase. This exposure eventually leads to a deterioration of the silver, limiting its useful life. In the study of silver coatings for astronomical applications, Song discovered that an enhanced environmental resistance resulted from the incorporation of a copper underlayer4. Evidence supported the proposed mechanism of cathodic protection of the silver by copper that had migrated along the grain boundaries to the outer surface. This present contribution examines the effectiveness of a very thin copper layer deposited directly over the silver film in the SPR sensor.
Effects of Rough Interfaces in a Thin-Film
Authors: Garcia-Llamas R. , Regalado Luis E.
Published: February 2023

A thin film of materials that crystalize rapidly during its growth, as in the case of flourines and oxides, present shallow surface roughness. Reflectance studies of these materials show small scattering that in general is negligeable. Studies on Pyridine/Ag (1) y WO3/Au (2) have shown resonances in the reflectance spectrum associated with the excitation of Surface Plasmons.
Optical absorption of HfO2 and mixed HfO2/Al2O3 thin films in the 230-700 nm range.
Authors: Schink H. , Masetti E. , Montecchi M. , Flori D.
Published: February 2023

Film of HfO2 and mixed HfO2/Al2O3 have been deposited on silica substrates for the purpose of obtaining low absorbing film for applications in excimer laser optics. Different samples were prepared by e-beam thermal evaporation with and without assistance of Al and Xe ions in oxidizing atmosphere. In Tab.1 the preparation methods are reported. All the substrates, Suprasil type 1, were cleaned in the same way with a last rinse in Acetone and dried with Nitrogen puff. The substrate surfaces showed no detectable absorption before the deposition. Substrate preparation and film deposition were performed in clean room (class 100). To achieve a resolution in the measurement of the optical absorption better than 20 ppm, a calorimetric technique, namely the photothermal deflection spectroscopy (PDS), was employed. To enhance the instrument detectivity the PDS measurements are usually performed in CCl4, a liquid with a high temperature coefficient of the refractive index dn/dT. As the CCl4 does not show a suitable transparency in the UV, alternative deflecting liquids were tested. We found Iso-Octane and Ethylene as the best candidates. When high purity Iso-Octane was used, a residual signal due to fluid absorption (the noise level) as low as 15 ppm at 250 nm was obtained. The scheme of the experimental set up is reported in Fig. 1.
Consequences of Ti and Li ion implantations on the optical properties of single layers of Ta2O5
Authors: Flory F. , Berthier D. , Rigneault H. , Roux L.
Published: February 2023

Few materials are used to make optical coatings. Their optical properties, tightly linked to the deposition technique, are generally well defined. It could be useful to locally change them for future applications.
PACVD Deposition of Ultradurable IR Optical Coatings
Authors: Waddell E M , Gibson D R , Lewis K L
Published: February 2023

Plasma assisted chemical vapour deposition (PACVD) can be used to deposit a range of materials with exceptional mechanical properties. At Pilkington Optronics we have determined that boron phosphide (BP), gallium phosphide (GaP), germanium carbide (GeC) and diamond like carbon (DLC) to be amongst the most useful for IR applications1.
All-dielectric High-efficiency Reflection Gratings Made with Multilayer Thin-film Coatings
Authors: Li Lifeng , Hirsh Jeffrey
Published: February 2023

It is well known that a high reflectivity mirror can be made by coating multiple pairs of dielectric thin films of high refractive index contrast and quarter wave optical thickness onto an optically flat surface. The advantages of a multilayer dielectric mirror over a metallic first surface mirror include high reflectivity, low absorption, and therefore high optical damage threshold. In connection to diffraction gratings, one may naturally ask the question: can a high diffraction efficiency grating be made by coating multilayer dielectric thin-films onto a bare surface relief grating? The answer is yes. In this paper, we present the results of our theoretical and experimental investigation.
Diffractive Optics Using Artificial Index Modulation
Authors: Chen F. T. , Craighead H. G.
Published: February 2023

An artificial dielectric is an array of dielectric objects spaced so closely together that for sufficiently long wavelengths, it behaves as a homogeneous film, i.e., no diffraction or scattering occurs. By proper design, the principal indices of the artificial dielectric can be tailored to suit specific needs. For example, using vertical artificial index modulation, broadband antireflection structures are produced[1]. In this paper, we will be concerned with the fabrication of high-performance diffractive optical elements such as deflector gratings and Fresnel lenses using lateral artificial index modulation.
Capabilities and Limitations of Various Gridless Ion Sources
Authors: Willey Ron
Published: February 2023

The benefits of Ion-Assisted Deposition (IAD) have been well described in the literature for more than a decade. Energetic processes such as IAD, sputtering, and Reactive Ion Plating (RIP) have become much more widely applied to optical thin film production. The rate at which many materials can be deposited with the benefits of IAD is limited by the ion power available. If more ion density could be provided, the rates, and therefore production, could be increased. The electron volts of the ions also needs to be below the level which would damage the coatings. This value appears to be 200-300eV for TiO2 and probably other metal oxides, although materials such as SiO2 appear to tolerate higher voltages in the range of 600eV. Therefore, we might desire as high an ion current as possible at less than 300eV. Several commercially available ion sources have been tested by the author for such applications. The experiences and observations of these sources is the topic of this paper.
Ion Assisted Deposition of Apodised Quintic Rugate Filters
Authors: Allen J. , Herrington B.D. , Girow P.G. , Slim T.
Published: February 2023

Rugate filters exhibit a spectral response which is the Fourier transform of the refractive index profile. Where the index modulation is apodised and matched to the incident and exit media using a quintic polynomial profile, it is possible to generate spectral characteristics with minimal sidelobes and absence of harmonics.
Optical inhomogeneity and microstructure of ZrO2 thin films prepared by ion-beam assisted deposition
Authors: Cho H. J. , Hwangbo C. K.
Published: February 2023

Most conventionally-deposited optical thin films have columnar microstructure since they are deposited under a thermal nonequilibrium condition. The columnar microstructure evokes many undesirable optical effects, such as lower packing density and refractive index, vacuum-to-air spectral shift of optical spectrum, and anisotropy in index. Ion beam assisted deposition(IBAD) has been used widely as a technique to produce denser films than conventional films. It is known that zirconia films have negative inhomogeneity in refractive index as they grow and the optical inhomogeneity was related to the crystalline inhomogeneity[1]. It suggests that the columnar microstructure may be contracting as the thickness increases from the substrate[2]. It is reported that IBAD produces denser ZrO2 films than conventional films and induces crystallization of ZrO2 films into cubic phase at room temperature[3]. However, the relationship between inhomogeneity and microstructure of IBAD ZrO2 films has not been studied much. The purpose of this paper is to study the effects of Ar ion bombardment on the the inhomogeneity and microstructure of ZrO2 films and their optical and mechanical properties are presented in terms of normalized ion momentum.
AC Magnetron Sputtering
Authors: Glocker David A.
Published: February 2023

Sputtering has become an extremely important and widespread manufacturing process for depositing optical interference coatings. This is due to a number of factors, including the excellent control sputtering offers over deposition rates and film properties, as well as the relative ease of scaling processes to large coating systems. Today there is a very large installed manufacturing base for sputtering optical films on substrates that range in size from small individual elements to architectural glass and continuous webs of polyester. Depositing dielectric materials reproducibly and at the high rates needed for manufacturing presents interesting challenges, however.
Design and fabrication of graded reflectivity mirrors
Authors: Dinca Andreea , Trifan M. E. , Lupei V. , Dinca M. P.
Published: February 2023

The paper describes the realization of a graded reflectivity mirror destined to work like output mirror in a YAG:Nd unstable laser resonator at λo = 1.064 μm. The advantages offered by this type of mirror are well known [1-3].
Monitoring and Thickness Control of Thin Films
Authors: Sullivan Brian T.
Published: February 2023

In order to deposit complex optical multilayer coatings, accurate layer thickness control during deposition is required. Several different approaches will be reviewed including quartz crystal monitoring, single wavelength optical monitoring (most-sensitive wavelength or extremum) and wideband optical monitoring. The advantages and disadvantages of each method will be discussed and examples of multilayer coatings deposited by each method will be presented.
Combination of in-situ photo spectroscopy and most sensitive wavelength methods for the deposition of optical multilayer systems
Authors: Jan Ray , Ho F. C.
Published: February 2023

Broadband optical monitoring technique has been used recently in many optical coating laboratories (1-6). The prominent advantage to use this method in the fabrication of multilayer coatings is that one can actually see what is happening to the layer system during the deposition process. With the access to follow the spectral performance layer by layer, high yield of good quality coatings can be obtained.
The Improvement of Evaporated Dielectric Polarizer and Beamsplitter Coatings Through the use of Multiple Crystal Monitoring
Authors: Anzellotti J. F. , Smith D. J. , Chrzan Z. R.
Published: February 2023

A primary source of error in the layer thicknesses of electron-beam evaporated dielectric coatings is variation in the vapor plume. Using multiple crystal monitors mounted in different positions of the substrate plane can help to detect and understand these variations. Subsequently, material preparation and electron-beam sweep procedures can be developed to minimize these variations. In addition, layer thicknesses can be adjusted during the coating run to compensate for plume variations as they occur.
Characteristics of silica deposition from a high-frequency sweep e-beam system
Authors: Chow Robert , Tassano Patricia L. , Tsujimoto Nick
Published: February 2023

Silica is the preferred low refractive index material for high laser damage threshold coatings at 1.06 μm. In order to coat large aperture optics, the thickness distribution of the evaporant plume should be as broad as possible while carve-in of the source avoided. High frequency sweep e-beam systems offer the possibility of more stable temperature profiles in the source for thickness uniformity; and programmable sweep controllers offers the possibility of more efficient erosion patterns in the source.
Low loss D.I.B.S. mirrors @ 1064 nm for the Virgo interferometer
Authors: Pinard L. , Ganau P. , Mackowski J.M. , Michel C. , Napolitano M. , Vireton E. , Boccara A.C. , Loriette V. , Piombini H.
Published: February 2023

Virgo is a franco-italian project which goal is to build a giant Michelson type interferometer to detect gravitational waves (1). As the typical signal to be detected is very small, all the optics in this interferometer must be almost perfect with extreme low total losses (Absorption and scattering in the range of 1 part per million (ppm)) and a high wavefront homogeneity on about 400 mm diameter.
The Automatic Spectrogoniometry: Integral Analysis of Optical Parameters.
Authors: Antón J.C. Martínez , Bernabeu E.
Published: February 2023

Consider a sample and a white light beam incident on it. Spectrogoniometry could be defined as the possibility of measuring at any angle of incidence and observation, and to decompose the transmitted or reflected beam spectrally, all of that automatically and independently. We have developed an instrumental equipment with such capabilities. The spectrogoniometer [1] we use is presented squematically in Fig. 1. It was made by SOPRA [2], permits the setup of additional optics such polarizers, wich give an additional value to the instrument. It can be seen as a tool capable of integral optical information extraction of a sample. Only some of the photometric possibilities of the spectrogoniometer will be presented.
Substrate Effects on Absorption of Coated Surfaces
Authors: Roche Pierre , Commandré Mireille , Escoubas Ludovic , Borgogno Jean Pierre , Albrand Gérard , Lazaridès Basile
Published: February 2023

The minimization of absorption of coated surfaces and the elimination of local defects are two important challenges in optical technology. The choice of evaporated materials, the use of adequate designs of multilayer components and the optimalization of deposition processes can reduce strongly absorption and defects on a coated surface. Furthermore polishing and cleaning of substrate play an important role in losses.
Laser Damage and Passive Loss of Multilayer Thin-Film Coatings in 1.5…1.6 μm Range
Authors: Kolodny G. Ya. , Levchuk E.A. , Novopashin V.V. , Sidoryuk O.E.
Published: February 2023

Development of multilayer reflective and antireflection coatings for spectral range of 1.5…1.6 μm is of great interest since they are used for design of a new generation of eye-safe laser rangefinders. Nevertheless, there is little information about methods of production of such coatings in literature [1], and there is no information about laser-damage thresholds at 1.5…1.6 μm [2].
The latest developments in sputtered fluoride films
Authors: Quesnel E. , Dijon J. , Dumas L. , Garrec P. , Pellé C. , Poupinet L. , Rolland B.
Published: February 2023

In the optical thin film field, the fluoride coatings have been widely used for many years, particularly for IR applications. More recently, owing to the increasing demand of optical components for UV-lasers, these materials are also the object of an intense investigation for their use, for example, in UV multilayer minors [1,2]. Among the different dielectric materials available, the fluorides exhibit, indeed, the wider optical gap. Most of the time, the deposition of fluoride films is achieved by conventionnal evaporation. Nevertheless, such a process two main limitations which are i) a mechanical instability of the film for a thickness higher than 1-2 μm, ii) a natural trend of the films to generate optical scattering, in particular in the shorter wavelengths spectral range. For two years, in the framework of the MEGAJOULE project and the achievement of 351 nm - centered UV mirrors, the LETI-CMO laboratory has been investigating a new way to deposit fluoride coatings by using the ion beam sputtering technics (IBS) [3]. This paper aims at focusing on the main characteristics of these IBS fluoride coatings and at evaluating the future prospects of this technology in relation with its extension to deep UV applications.
Questions to Consider in the Design of an AC-Sputter System
Authors: Adair Robert , Hichwa Bryant
Published: February 2023

In the past several years there has been a renewed effort among optical thin film researchers to improve reactive sputtering with either AC or pulsed-DC technology. These related technologies allow one to deposit insulating materials such as SiO2 and Al2O3 in a sputter process that uses metal targets with planar magnetrons. This ability to sputter insulating materials at high rates without arcing represents a breakthrough in technology. Since the invention of the DC magnetron in 1973, arcing has always been one of the limiting factors in reactive sputter deposition. In a 1988 paper, Este and Westwood1 demonstrated an arc reduction technique in which they applied an alternating square wave voltage to a pair of rectangular sputter targets at a frequency in the 100kHz range. Since then a number of researchers have reported on similar arc reduction techniques which allow the deposition of defect free films at DC sputter rates. The results of their work are evident in the number of papers and symposium presentations on AC sputtering and the number of systems currently being set up to sputter oxide coatings reactively. As part of this presentation we will review the current state of the art.
New high-rate automated deposition system for the manufacture of complex multilayer coatings - II. Process control
Authors: Clarke G. , Sullivan B. T. , Akiyama T. , Osborne N. , Ranger M. , Dobrowolski J. A. , Howe L. , Matsumoto A. , Song Y. , Kikuchi K.
Published: February 2023

In a companion paper, a new fully automated, high rate, deposition system for the fabrication of complex optical coatings was described. In order for this system to accurately deposit complex filters, several conditions have to be met. First, it is important that the deposited films exhibit low absorption and low scatter and have bulk-like reproducible refractive indices. Second, for the accurate optical monitoring of the layer thicknesses, it is critical that the deposited films are homogeneous, have well-defined interfaces and that the refractive indices of the thin film materials are accurately known. In this paper, we will discuss various process control techniques that are necessary to ensure the deposition of high quality SiO2 and Nb2O5 films so that complex filters based on these materials can be accurately fabricated.
Online Monitoring of Ion Beam Sputter Processes by Plasma Analysis
Authors: Arens W. , Ristau D.
Published: February 2023

During the last decade, the rapid development and implementation of new concepts in precision laser metrology generated an increased demand for high quality optical component. A special requirement in this field is the production of coatings with lowest losses which is mainly achieved by adapted ion beam sputter processes in the present state of optical thin film technology. For the optimization of an existing ion beam sputter process, a new method of online process monitoring has been installed: In general, ion beam sputter processes are based on high energetic (about 1000eV) inert gas ions which sputter the desired coating material from a high purity target. For the deposition of oxide materials, the target can alternatively consist of the oxide or the corresponding metal, which is oxidized during the process in the residual oxygen atmosphere of the recipient. In the actual process, emission of plasma radiation in front of the metal target can be observed. This radiation is investigated by an online spectrometer for different process parameters in respect to the optical properties of the produced coatings. Silicon, aluminum and tantalum were chosen as target materials and sputtered under different operating conditions of the ion source and selected oxygen flow values. In the present setup, the plasma radiation at the target surface is collected and coupled into a fiber by a convex lens (fig.1). The optical fiber is conducting the light out of the high vacuum chamber into one of two existing monochromators covering the spectral region from 200nm up to 800nm. The power of the light spectrally resolved by the monochromator is measured by a photomultiplier tube, and the corresponding signal is recorded by a standard PC which is also employed for the wavelength control.
Enhanced Absorption with Coated Rough Black Surfaces
Authors: Giovannini H. , Amra C.
Published: February 2023

Scattering from optical thin films has been studied for many years. With optical surfaces, most of the energy is carried by specular (reflected and transmitted) beams, the amount of absorbed and scattered light being negligible. In another range of applications involving design of light traps, solar collectors, telescope vanes and detectors, industrial paints[1]… multilayered rough surfaces must be considered. In these cases specular fluxes are practically reduced to zero. The aim of this paper is to briefly describe a theoretical tool that permit one to compute scattering from this kind of structures and to show the method used to design highly absorbing components. The results obtained experimentally show that it is possible to strongly increase the performances of standard quality light absorbers, by coating the bare rough black surfaces with a well-designed layer.
Scatter prediction and measurement at 325 nm for HR coatings composed of columnar structured films
Authors: Jakobs Stefan , Duparré Angela , Hehl Karl , Schumann Uwe
Published: February 2023

Recently [1] we have shown that the scattering of HR coatings composed of relatively smooth oxide layers can be predicted with high accuracy from atomic force microscopy (AFM) measurements. In this case, replication of substrate roughness was found to play a decisive role for the microtopography of all interfaces. Now we present a study for a HR coating of fluoride materials, which are useful in the UV spectral region. It is known from TEM measurements that these films have a pronounced columnar microstructure [2].
A very thin coating technology for the production of broad-band absorbers
Authors: Quesnel E. , Chaton P. , Lartigue O. , Baume F.
Published: February 2023

In the field of imaging optical systems, anti-reflective (AR) coatings are widely used in order to reduce unwanted reflections. The LETI-CMO laboratory is involved in the development of an advanced spectral separator for earth observation [1] which uses absorbing diaphragms for the separation of the different optical paths. The optical specifications of such a sytem are drastic since a reflection lower than 2% and a transmission lower than 10-3 are required on a spectral range as wide as 450 to 950 nm. In order to meet such specifications, we have chosen to develop an absorbing AR coating based on a new multilayer structure which uses thin metallic absorbing layers. As we will see, such structures exhibit particularly efficient absorbing properties.
Coupled plasmon-waveguide resonator for biochemical sensors
Authors: Salamon Zdzislaw , Tollin Gordon , Macleod Angus , Stevenson Ian C
Published: February 2023

The outer surface of a high-performance metal can support a propagating surface wave that decays exponentially into both the metal and the surrounding medium. P-polarized light can be coupled into such a surface wave under conditions involving a narrow range of angles of incidence beyond the critical angle and a correct thickness of metal film, readily achieved by depositing the metal film on the base of a dielectric prism. Illumination of the prism base from within achieves coupling with a surface wave on the outer surface of the metal, characterized by a deep, narrow dip in p-polarized reflectance known as a surface plasmon resonance. Because the resonance depends critically on the conditions at the outer surface of the metal, it is very sensitive to any changes there. In particular, when a very small amount of additional material is added to the metal surface, the resonance responds by moving to a greater angle of incidence and changing its shape. Measurement of these changes can then be interpreted in terms of the properties of the additional layer. Three principal parameters characterize the resonance, width, depth and angular position, and these can be related to the thickness and optical properties of the added layer. This contrasts with ellipsometric measurements that have essentially two parameters and possesses the additional advantage over these and other techniques that the measurement is completely confined to the side of the metal film remote from the film under measurement. The technique has been used in many applications but especially in biochemical investigations of membrane protein processes [1, 2].
Development of optical coatings for CMT’s
Authors: van der Voort André
Published: February 2023

Today all Colour Monitor Tubes (CMT) are provided with an optical coating. Most of these coatings reduce specular reflection by diffuse light reflection, but also conductive interference coatings are introduced to reduce specular reflection and to discharge the tube surface.
Optical Filter to Enhance the Lifespan of Colored Gels
Authors: Kruschwitz Jennifer D. T.
Published: February 2023

In the field of stage and studio lighting many stage lighting designers use colored gels with spot or flood lights to set the mood or ambiance of a theater stage. The gels are versatile and cost effective. Spot and flood lights that incorporate cold mirror reflectors or hot minor filters have increased the lifespan of these low melting point gels. However, in the industry, gels that are of a highly saturated color of blue or green have a limited lifespan when used with a high intensity spot light. The gels have a tendency to bleach and bum after short periods of time. This paper will show how the use of a visible wavelength filter incorporated into existing spot lighting systems increases the lifespan of a saturated green or blue colored gel while not affecting their perceived color.
Optically isotropic polymer / liquid crystal hybrid filters
Authors: Blacker Richard S. , Lewis K.L. , Sage I. , Mason I. , Webb K.
Published: February 2023

Commercially available polymer dispersed liquid crystal (PDLC) systems act as scatter mode devices in which discrete liquid crystal droplets (whose dimensions are greater than λ/10) scatter incident light when the liquid crystal units are randomly aligned, but when aligned by an applied electric field become transmissive1. The reduced scattering is due to two non-competitive effects: a reduction in refractive index to match that of the host polymer, and an alignment of the liquid crystal units. The current work has developed a system where the initial size of the discrete liquid crystal droplets is below the visible light scattering limit. This hybrid PDLC system remains optically isotropic irrespective of the applied electric field strength. This novel nanocomposite has been incorporated into etalon cavities where it is utilised as an electrooptic spacer layer, thus enabling a frequency tuneable filter to be realised.
Near-surface refractive index of optical coatings
Authors: Horowitz F.
Published: February 2023

Detailed knowledge of refractive indices is usually required for precise coating applications, such as in optical systems, optoelectronic devices or integrated optics. In all-optical waveguide switches, for example, it was shown that small index inhomogeneities can lead to relevant degradation of device performance.[1] In addition, proximity to an interface may significantly modify the refractive index of a coating,[2] including the appearance of a second-order nonlinear component in centrosymmetric materials.[3]
Vacuum deposition of biaxial films with surface-aligned principal axes and large birefringence Δn
Authors: Hodgkinson Ian , Wi Qi hong , Brett Michael , Robbie Kevin
Published: February 2023

Birefringent thin films enable the construction of polarizing elements for use with light at normal incidence. Vacuum deposition at angle θ
v
on to a stationary substrate leads to the growth of a biaxial film with a columnar nanostructure tilted at angle ψ with respect to the substrate normal.1, axis-1 is in the deposition plane parallel to the columns and axis-2 is also in the deposition plane but perpendicular to the columns. Axis-3 is perpendicular to the deposition plane, and hence parallel to the surface. Typical values of the column angle and the birefringence, for zirconium oxide deposited at θ
v
= 60°, are ψ ≈ 30°, n1 − n2 ≈ 0.31, n1 – n3 ≈ 0.17 and n3 − n2 ≈ 0.14. However, for light incident normally on such a film, the difference between the refractive indices associated with the p-polarization (parallel to the deposition plane) and the s-polarization (perpendicular to the deposition plane) is Δn = n
s
− n
p
~ 0.07. Thus, only a fraction of the maximum available birefringence of a tilted-columnar film is accessed by light incident normally on the coating. Another disadvantage is that oblique deposition on to a stationary substrate leads to a film with uneven thickness.
Optical characterisation of thin metal film using surface plasmons resonance
Authors: Yunus W. Mahmood Mat , Mokhtar Rosmiza , Moksin Mohd Maarof , Talib Zainal Abidin , Hassan Zainul Abidin
Published: February 2023

The concept of surface plasmons originates from the application of Maxwell's to plasma whereby, the free electrons of a metal are treated as an electron fluid of high density (plasma). The density fluctuations occurring on the surface of such a fluid are called surface plasmons. Optical excitation of plasmons is not possible by direct impact of light on a metallic surface, so a prism coupling arrangement is needed. One possibility is to use a Kretschmann configuration [1] in which a p-polarized, collimated light beam passing through a glass prism undergoes total internal reflection (TIR) at glass-thin-metal film-dielectric interface. In this set-up plasmons are excited by (TIR) associated an evanescent wave after penetrating up to the metal-dielectric boundary. The surface plasmon resonance condition is given as,
Electrical and optical properties of indium tin oxide thin films deposited with plasma ion-assistance
Authors: Laux S. , Kaiser N. , Zöller A. , Götzelmann R. , Lauth H. , Bernitzki H.
Published: February 2023

Transparent conductive materials such as tin doped indium oxide (ITO) are of special interest for several applications. Due to the wide band gap of around 4 eV, ITO is transparent in the visible spectral range even though it is a n-type semiconductor with free electrons in the conduction band resulting in high electrical conductivity and high reflectivity for infrared radiation [1].
Polarizing dichroic filters used in TFT-LCD projectors
Authors: Zhang Y.G. , Gu P.F. , Liu X. , Tang J.F.
Published: February 2023

The use of LCD in the projection display has made great progress in the recent years. It is expected that projectors based on active-matrix liquid crystal displays for both professional and consumer applications will produce a net manufacture revenue equal to or even greater than that of CRT-based consumer projection TV in years coming.
Optical coating computer simulation of narrow bandpass filters for dense wavelength division multiplexing
Authors: Zhou F. Q. , Zhou M. , Pan J. J.
Published: February 2023

For potential applications in dense wavelength division multiplexing networks, great efforts have been made to improve the specifications of narrow bandpass filter coatings. Besides environmental stability requirements, which have been met by utilizing ion- or plasma-assisted deposition techniques and appropriate substrate selection [1,2], the spectrum shape requirements of the narrow bandpass filters are especially critical for WDM applications. Multi-cavity design and layer optimization have been adopted to achieve better theoretical results. On the practical side, layer thickness and index monitoring is key to achieving high quality narrow bandpass filters. For multi-cavity Fabry-Perot filters, previous studies [3,4] showed that transmission turning point monitoring is the best monitoring approach due to its error compensation mechanism. However, total compensation is only achievable when the monitoring light is monochromatic. In a practical coating situation, monitoring light always has a finite bandwidth. The bandwidth of the optical monitoring light comes from three sources as depicted in Figure 1. These are the bandwidth of the monochromator, the effective bandwidth caused by non-uniformity thickness inside the monitoring light spot on the filter, and the effective bandwidth caused by the incident angle span of the monitoring light on the filter. For error compensation, smaller bandwidth is preferable. However, monitoring light intensity decreases proportionally with bandwidth (except for a laser light source, whose long coherent length is problematic). Thus, the turning point error increases. A trade-off must be taken to optimize the coating process. Due to analytical complexity, a numerical method approach was taken here.
An optical network unit (ONU) chip based on stacked planar optics
Authors: Mizuno Rogerio Jun , Kato Toshio , Aoki Yasuhiko , Iga Kenichi
Published: February 2023

In order to provide new services to the subscriber, some sophisticated system configurations based on a full fiber-optic access network such as Fiber-to-the-Home (FTTH)1) are required. In such systems, an optical network unit (ONU) working as a wavelength division multiplexing (WDM) transmitter/receiver module will become one of the key elements. To make the FTTH economically feasible, a low cost WDM module suitably designed for mass production has to be developed. Although several researches have been carried out in effort to achieve such cost-effective modules2,3), further investigations and new concepts are necessary to completely establish the optical subscriber network technology. This goal might be achieved with modules that properly combine different technologies. We introduce two of them: 1) dielectric multilayered filters, and 2) stacked planar optics4). With advances in thin-film technology, thin-film multilayered filters have been attracting significant interest for application to optical communication systems due to their high design flexibility and excellent optical performance. These filters can play a very important role in WDM modules. The stacked planar optics has been proposed to overcome the problem with alignment providing a passive alignment and simplification of both fabrication and assembly processes of optical devices. With this technology, it is also possible to realize very compact microoptics devices. Thus, low cost ONU modules suitable for mass production are expected.
Laser damage in ultraviolet phase-unifying mirrors
Authors: Piegari A. , Scaglione S. , De Nunzio G. , Perrone M.R.
Published: February 2023

Phase-unifying mirrors are optical components used as output couplers in laser resonators to improve the quality of the output laser beam (1,2). These components exhibit a high reflectance on a central area and a very low reflectance on an external area of the sample surface, with a sharp edge between the two zones. Their peculiarity is that the laser beam transmitted through the two areas does not suffer of phase distortions that means the jump, in the phase shift, is reduced to a minimum value.