This PDF file contains the front matter associated with SPIE Proceedings Volume 9627 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

Antireflective (AR) coatings for lenses with extreme curvature must be designed for use in the visible and the near-infrared ranges to ensure sufficient AR performance in the visible range on the inclined surfaces of such lenses. In this work, multiple inorganic and nanostructured organic layers are considered for use in AR coatings with alternating high-index and low-index layers and in arrangements with effective indices that decrease from the substrate side to the surrounding medium. An AR coating effective in the spectral range from 400 nm to 1400 nm was realized by combining a multilayer interference system with a plasma-etched organic layer. Step-down index systems or gradient layers with sufficient thickness are especially promising for lenses.

The modern state-of-the-art in general purpose design technique is discussed. An importance of taking into account additional practical demands in the course of designing is demonstrated. Special purpose design techniques capable to take into account specific practical demands are considered. Possible types of the pre-production error analysis are discussed in connection with the types of monitoring techniques used for coating production.

We discuss the production of antireflection coating with low reflection zones in the spectral regions around the wavelengths of 546nm, 1060 nm and 11000 nm and additional demands for the reflectance maxima in the visible spectral region. For the coating production we use ZnSe as a substrate material and ZnS/YbF₃ as layer materials. Their optical parameters are accurately determined in a wide spectral region using modern characterization and reverse engineering software tools. For the coating production we apply broad band monitoring in the spectral region from 1200 to 2300 nm that does not overlap with the regions where target requirements are specified. In order to select the most practical design that can be reliably manufactured we apply a combination of various modern design approaches and computational manufacturing experiments simulating production runs. Application of the most up-to-date software tools allows us to obtain excellent manufacturing results even from the first production run.

Simulation and modeling find more and more their way into thin film technology. Beside theoretical models for layer design, pre-production design analysis, and real time process control, atomistic simulation techniques gain of importance. Here, especially classical procedures such as Direct Simulation and Particle-in-Cell Monte Carlo (DSMC/PIC-MC), kinetic Monte Carlo (kMC) and Molecular Dynamics (MD) as well as quantum mechanical techniques based on Density Functional Theory (DFT) have to be mentioned. These methods are applied in order to investigate the material transport inside the coating facilities, the thin film growth in dependence of characteristic process conditions, and the optical and electronic thin film properties. By combination of these atomistic techniques in a suitable manner, a multiple scale simulation model can be realized for investigating the influence of specific process conditions on the resulting layer properties. The further extension of this “virtual coater” concept with respect to rate equation models enables the possibility to investigate also the interaction of laser irradiation with the modeled thin film structures.

A new method for supercomputer atomistic modeling of the ion beam sputtering process is presented allowing atomistic modeling of the systems consisting of 10⁶ – 10⁸ atoms. Deposition process is organized as a sequence of molecular dynamic cycles in which deposited atoms interact with the substrate with earlier deposited atoms and form new chemical bonds. The method is applied to the modeling of SiO₂ thin optical films. For interatomic potential energy calculation the original DESIL force field with high computational efficiency has been developed. Atomistic modeling of the deposition processes with different Si atom energies is performed for the films with thicknesses up to 30 nm (about one million deposited atoms). Dependence of thin film density on film thickness is investigated. It is found that film densities depend on the energy of sputtered atoms and exceed the density of fused silica substrate by 0.1-0.2 g/cm³. In all experiments interface layers with the thicknesses of about 1-2 nm between thin film and substrate are observed.

Oxide coatings have been prepared by PIAD by means of a Leybold Syrus pro 1100 deposition system. Focus was placed on tantalum pentoxide, hafnium oxide, and zirconium oxide films. Coating characterization pursued the determination of the refractive index in the VIS/UV spectral regions, as well as the geometrical film thickness. In situ spectrophotometry was used to obtain information about the shift of the coatings. Measurements of the coating stress as well as EDX characterization have further been performed to complete the picture.

Results are presented which provide information about the correlation between deposition parameters (Assistance, choice of working gas) and the optical properties of the films. Correlations between optical and non-optical (stress, EDXresults) properties are further presented and discussed in terms of classical models. Reproducibility issues are discussed, too.

For the most demanding infrared applications, fine knowledge of system performance under operational temperature is required. Management of thin film spectral and mechanical behaviour at cryogenic temperature is a key factor to improve infrared system performances.

Reosc recently investigated models and methods to anticipate measure and control effects of low temperature on coated optical components. Solutions have been developed in order to maximize highest performances under operational conditions. Effects of temperature on spectral transmission and flatness have been studied.

This work has been applied to narrow band pass filters and dichroic coatings working in the range 55K to 90K. Measurements show satisfying correspondence with model. On the basis of model prediction, process and design have then been adapted to improve performances at operational temperature. It has been applied to manufacturing of optics for MTG satellites and IASI NG instrument.

Multilayer coatings in the far UV (FUV) are required for various fields of application, such as space instrumentation for astrophysics, solar physics and atmosphere physics, as well as free electron lasers, plasma diagnostics, synchrotron radiation, spectroscopy, etc. In order to design the desired multilayer, accurate optical constants of the materials are required. Several fluorides are among the materials in nature that keep their transparency down to the short FUV, which makes them almost the only choice for multilayer coatings tuned in the ~100-150-nm wavelength range.

The optical constants of thin films of MgF₂, LaF₃, and CeF₃ have been determined in the spectral range of 30-950 nm. Among them, MgF₂ is a low refractive index material whereas LaF3 and CeF3 have a relatively high refractive index at short wavelengths; this contrast is adequate to make multilayer coatings. Fluoride thin films were deposited by evaporation onto substrates at 523 K. Optical constants were calculated using sets of transmittance, reflectance, and ellipsometry measurements. The measured optical constants were extended to a broader range with literature data and extrapolations in order to obtain self-consistent sets of data using the Kramers-Krönig analysis. The optical constant data here presented extend the available literature data both shortwards and longwards, particularly for CeF3 where few data had been reported.

The obtained optical constants of MgF₂ and LaF₃ were used to design narrowband reflective multilayer coatings for the short FUV. Multilayer coatings centered at 121 and at 130 nm with remarkable reflectance were prepared. The coatings kept a valuable reflectance after ageing in a desiccator for 12 months.

Mid infrared optical coatings are commonly designed & manufactured using typically electron beam evaporated films of Silicon and Silicon oxide. However the transparency of these coatings is limited by optical absorption in the films when producing coatings for wavelengths beyond 4um approximately. This work reports improvements in mid infrared (3 to 6um) filter transparency achieved by exploiting recent advances in microwave plasma assisted pulsed DC magnetron sputtering technology. Sputtered silicon compound films have been used to demonstrate efficient room temperature deposited optical coatings for gas sensing applications at wavelengths between 3 to 6um. This process technology allows a new selection of film materials to be used in design of mid infrared filters, with transmission and thermal drift characteristics enhanced compared with conventional electron beam evaporated coatings. The spectral location of the optical coatings is controlled by a non-optical method, which avoids the complex optical monitoring configurations normally required. Durable filters are obtained at room temperature, which would otherwise be required in conventional evaporation processes. Importance of water partial pressure control during deposition for mid infrared is emphasised.

Composite organic-inorganic coatings are realized by ion beam sputtering (IBS) from a zone target consisting of PTFE and Al₂O₃. The composition of the sputtered coatings is measured by Energy-Dispersive X-ray spectroscopy and the molecular structure is analyzed by Fourier Transform Infrared spectroscopy. The variation of the refractive index and the optical quality in dependence of the carbon-fluorine content for different material compositions is investigated. Furthermore, the intrinsic stress of the coatings is analyzed and a change from compressive to tensile stress in dependence of the composition is observed. The production of ion beam sputtered composite coatings with low refractive index and tensile stress is demonstrated.

Diamond Like Carbon (DLC) is the preferred material for the termination layer in optical interference coatings using infrared (IR) materials since it enhances the environmental stability of the otherwise typically soft substrate and coating materials used in IR. In the state of the art processes, the coating with the infrared materials is deposited in a box coater, then the substrates are transferred and loaded into a separate deposition machine where the DLC layer is then deposited. In the novel box coater presented in this article, the DLC and IR (or dielectric) processes can be run consecutively in the same machine. We will discuss the implementation of the DLC process, then we show how the DLC process was optimized using in-situ stress and broadband optical measurements as well as ex-situ characterization of the adhesion, hardness and abrasion. The resulting single layer DLC films have perfect adhesion to silicon, germanium, glass and antireflection coatings. Furthermore, they are hard and scratch resistant, pass the wiper test and are virtually absorption-free in the 3-5μm and 8-12μm wavelength ranges. We will show the results for adhesion, abrasion and spectral performance of a wideband antireflection coating for 3-5μm including a DLC termination layer.

The lamination process is a common method to generate polymer multilayer foils. However, the substrate materials used need to be miscible to give a stable connection. A typical set of incompatible polymers that is often used in optical applications is cyclic olefin copolymer (COC) and polymethylmethacrylate (PMMA). In this paper, we report about the development of a “Reactive Lamination Process” that is capable of forming a stable optical polymer multilayer of PMMA and COC. This paper focuses on the development of a spray coating process and the further processing with photoreactive PMMA copolymer systems that act as an unspecific primer to obtain optical polymer multilayer devices.

During the last years, optical low loss components gained more and more industrial interest and led to novel approaches for the production in optical coating technology. The application of filtered deposition technologies promises a significant reduction of particle contamination. Usually, filtered techniques are applied in combination with processes which produce a high level of undesired particles, like the cathodic arc deposition. In the present contribution, a magnetic field filter is applied in combination with a high quality ion beam sputtering process. The focus of the investigation constitutes the modulation of the guiding process with respect to the guiding efficiency. Numerical investigations reveal the trajectories of the ions during the guiding process and allow to analyze the influence of the magnetic field and the resulting electrostatic potential. In this study, the guiding effect is observed to be dominated by the electric potential compared to the magnetic field. However according to the simulations, very high ion guiding efficiencies can be achieved using moderate magnetic fields and electrical potentials. Furthermore, it is demonstrated that the experiemental and calculated efficiencies agree well. Consequently, the simulation is the basis for a further optimization of the filtered ion beam sputtering processes.

We present hereafter the results on the manufacturing of complex optical coatings done with dual ion beam sputtering technique (DIBS). Such technology uses a first ion beam gun for sputtering a target and a second one for compacting the sputtered material. The density of the deposited layer is very close to the bulk material and enables the coatings to be nearly insensitive to environmental parameters. This technology is well adapted to severe environments as it allows the production of very dense layers and high quality coatings.

The use of an in-situ optical monitoring system in visible and near infrared range (up to 2500nm) permits to reach severe spectral specifications and to have a good agreement with the theoretical designs.

In this paper, we will focus on some complex optical functions that have been manufactured with DIBS technique: narrow band-pass filters and wide band filters including large blocking range with more than 100 layers and 25 μm total thickness, antireflection coatings which reach very low values of reflectivity in the near infrared spectral domain for wide angular ranges, and also metal-dielectric absorbing coatings.

We will also give an analysis of the cosmetics performances of the deposited layers, which shows the high quality of the coatings even with functions with large total thickness.

Many experimental results of qualification tests in temperature, humidity, thermal vacuum, radiations,… are presented and show the reliability of these multidielectric components in space or cryo-vacuum environment.

In this paper, we will present recent achievements done with our large dimension magnetron sputtering coating machine that has been implemented by CILAS company in its premises in Aubagne. Such equipment called PACA2M (PulvérisAtion CAthodique de 2M) is an inline coating system that has been designed to ensure uniform coating on large optical components, up to 2 meters by 2 meters, 40 centimeters thick and to 1.5 ton weight.

We will see how its wide variety of configurations based on seven 2.5 meters-long planar magnetrons, that may be powered in various modes (RF, MF, DC, ..) allows us producing complex optical functions such as multilayer dielectric mirrors, antireflective coatings and protected or enhanced metallic mirrors from ultraviolet to infrared applications. Moreover, an all-fibered broadband optical monitoring system developed in collaboration by Institut Fresnel is installed on this industrial machine and allows extremely accurate monitoring carried out on samples and fine characterization directly on components.

Many spectral measurements and cosmetic results will be given that show that this equipment is well adapted for producing large optical components with high quality for various applications in the fields of industry, space or astronomy. In particular, for space application, PACA2M coating machine can be used to produce in a same batch all the required models as it is possible to simultaneously coat flight models, qualification witnesses and spare models.

The stability of the performances in severe environmental conditions compatible with space environment will be illustrated with qualifications tests and characterizations.

Cylindrical targets give the opportunity to improve the process stability of magnetron sputtering processes although reactive deposition might be a challenge. Sputtering from metal doped oxide targets in connection with a plasma source unlocks the full potential: the process can be driven in well-known mid-frequency mode and the plasma source ensures fully stoichiometric films with low loss.

During the last years different developments for oxide cylindrical targets were done. The suitable composition has to be found regarding e.g. the density and an arc-free process as familiar for planar targets. In the tube geometry new manufacturing methods are required that ensure these properties.

In the present paper we show some examples of the high refractive index materials tantalum oxide: single film characterization as well as realized complex precision optical filters. The results are accompanied by performance measurements in terms of uniformity over 200 mm glass wavers as well as carrier to carrier and batch to batch. These were measured by the position of a quarter-wave stack’s edge.

A new, highly efficient impedance matching network is introduced , increasing the LION300 RF-source efficiency by approximately 20% and enabling considerably higher SiO₂ rates for the production of shift-free and low scattering interference filters. Results of single layer coatings and a UV-IR cut filter are presented.

In this study, Al₂O₃:SiO₂ composite films were grown using atomic layer deposition (ALD) with the thicknesses of Al₂O₃ and SiO₂ being between 1 Å - 20 Å. The composition of the films was varied by changing the relative number of ALD cycles from 1 to 20. The optical properties of the layers were investigated with spectroscopic ellipsometry (SE). The experimental refractive indices of the composite films with Al₂O₃ and SiO₂ ALD cycles of 1-10 were shown to be higher than the calculated values. This was attributed to the hampered growth of the SiO₂ during the first ALD cycles. On the other hand, the experimental and calculated refractive indices of the mixture 20 cycles:20 cycles agreed very well indicating a nanolaminate behavior. Selective etching of the alloys 1:1 and 2:2 resulted in a nanoporous SiO₂ films. The refractive index of the final porous SiO2 films was dependent on the thickness of the initial alloy layer.

This study focuses on the atomic layer deposition (ALD) of high quality SiO₂ thin films for optical application. One of the challenges for the application of dielectric ALD layers in optical coatings is the realization of low absorption and scattering losses. Furthermore the layers have to be prepared with a precise controlled thickness and repeatable optical properties. SiO₂ films were deposited using tris[dimethylamino]silane (3DMAS) and oxygen plasma on Si(100)substrates, quartz and BK7 glass substrates at temperatures between 100 °C and 300 °C. Film growth rate and refractive indices of SiO₂ thin films were studied as function of deposition temperature. A linear growth behavior of SiO₂ ALD films is confirmed, allowing a scalability of film thickness just by counting ALD cycles. The grown films are resistant to abrasion and possess good adhesion to glass substrates. The optical losses of the films are negligible in the investigated spectral range from 250 nm to 1100 nm. An antireflective (AR) coating was prepared by atomic layer deposition using SiO₂ as low refractive index material and HfO₂ as high refractive index material.

We present hereafter the results on the fabrication of complex optical filters within the Institut Fresnel in close collaboration with CILAS. Bandpass optical interference filters, with central wavelengths ranging in near ultraviolet or in the near infrared, were deposited on both sides of glass substrates with a very good congruence with theoretical designs. For these applications, the required functions are particularly complex as they must present a very narrow bandwidth as well as a high level of rejection over a broad spectral range. Moreover, in order to satisfy more and more critical specifications on flatness of the component treated on both faces, the stress induced by the different layers has to be taken in account in the filter design.

All these components were manufactured using Plasma Assisted Reactive Magnetron Sputtering (PARMS) technics offered by the HELIOS machine and monitored in real time with an OMS5000 in-situ optical monitoring, both developed by BUHLER Optics.

Compressive mechanical stress of 364 MPa and 55 MPa respectively for SiO₂ and Nb₂O₅ are measured, final sag of 326 nm and 13 nm, and uniformity from -0.05% to 0.10% and from -0.10% to 0.20% are obtained respectively for the two manufactured filters.

Absorption and gain are difficult to define precisely but in the sense we shall use the terms, they represent a failure of the sum of specularly reflected and transmitted light to equal that incident. A greater sum represents gain and a lesser, absorption. Although there is a variety of physical processes that can contribute to these phenomena, their quantitative expression can be achieved through a nonzero extinction coefficient k. In the normal way we encourage gain and discourage absorption, but, recently, an increasing interest in enhancing absorption has emerged. Calculations involving nonzero k are straightforward but understanding the consequences can be a little more difficult. The admittance diagram can help in this and especially in respect of lasers, amplifiers and perfect and coherent perfect absorbers. Normal thin-film calculations start from the light that enters the emergent medium through the rear surface and works backwards to find the conditions at the surface of incidence, but the normal model is capable of much more. It can readily handle a much wider range of conditions. In terms of the admittance diagram, it is simply necessary to open up the second and third quadrants of the complex plane. In those quadrants the net flow of energy is in the opposite direction and the rules for the loci are a little different from those in the more usual first and fourth quadrants.

In this paper, we show how thin film absorbing coatings can be designed with multilayers using both metallic and dielectric materials involving some thicknesses that are very low down to some nanometers. Such multilayers enable to reach a very low level of reflectance and a zero value of transmittance, which can be a solution for stray light reduction in optical systems.

After a description of the design steps, we will present the manufacturing of such multilayer stacks using magnetron sputtering technique and we will see how such coating technique is very well suited for production due to its high process reproducibility even for very thin layers required in metal-dielectric absorbers.

Monitoring of such coatings is also presented with the help of a powerful in situ optical system developed in collaboration with Institut Fresnel that allows characterization of in-situ refractive indices of deposited materials and broadband monitoring of the multilayer stack.

Many results will be given on qualification samples, such as environmental tests and spectral characterizations that show the stability of the performances in severe environmental conditions.

At last, we will focus on the spectral and angular scattering behavior of such absorbing coatings and we will present several measurements performed on glass or metallic substrates with different roughnesses.

The need for imaging systems for onboard scientific applications (e.g. for planetology) is becoming of prime interest. Today’s CCD scientific cameras do not provide spectral information of the observed scene. Multi-spectral imaging therefore requires the usage of filters wheels which allow achieving the required optical performances but are a heavy and bulky solution that make them non-adapted for space missions. The goal of this work consisted in developing pixelated filters that could be directly integrated in front of an onboard CCD camera in order to provide with the required spectral information without significantly changing the volume and the weight of the whole system. In this paper, we show the first demonstration of 2×2-array pixelated optical filters with 30 × 30 μm² pixel size. Four bandpass filters centered at 550, 700, 770 and 840 nm, about 40 nm bandwidth and rejecting in a broadband from 500 to 900 nm were designed. These filters were then fabricated by a masking technique using lift-off processes with two photoresists in order to secure sharp edges for each pixel and ion assisted deposition. Local mapping of the transmission of each pixelated filter was finally carried out with a dedicated system. Comparative measurements between witness samples and filters prototypes show that the pixelated filters have performances comparable to the witness 25 mm aperture filters. This new technology therefore paves a way to the fabrication of multispectral imagers with versatile spectral specifications.

In the present work, an innovative optical element developed for the multiterawatt few-cycle light wave synthesizer based on optical parametric amplification is demonstrated. The synthesizer currently produces sub-5-fs, 80-mJ, 18-TW pulses. The required element had to be deposited on 15 mm substrate having 75 mm in diameter; an average value of the GDD of +75 fs² and reflectance exceeding 99% in the spectral wavelength region from 570 to 1030 nm.

Mechanical stresses of the designed dispersive mirror (DM) caused the substrate bending that distorts wave front quality resulting in the distorting of the beam waveform of laser system. In order to compensate this mechanical stress, the substrate back side was covered by an antireflection coating providing the lowest possible reflection in the working spectral range, having the total physical thickness close to DM thickness and total thicknesses of Nb₂O₅/SiO₂ layers close to the corresponding total thicknesses of Nb₂O₅/SiO₂ in DM. The produced DM-AR optical element exhibits excellent spectral properties.

Manufacturing all dielectric mirror coating with reflectivity values of more than 99.99 % is still a challenge to achieve. Losses caused either be transmittance, absorption or scattering have to be maintained well below 100ppm. Increasing the layer number for minimizing the transmittance losses usually increases the scattering by the growth of the roughness. High energy processes are required to minimize or avoid this behavior, but which are a challenge for avoiding unwanted contamination and interface absorption due to unwanted sputtering. As high energy process we used for the preparation of high reflecting dielectric mirrors plasma assisted reactive magnetron sputtering with a Helios 800 system. The machine was equipped with 3 cathode position for low and high index materials. We used metallic tantalum and hafnium targets for the preparation of the high index, silicon and silica targets for the low index. Metallic targets were powered with mid frequency, whereas the quartz target was sputtered by RF. As substrate we used either super polished fused silica or standard silicon wafer. The optical properties of the substrates we characterized by CRD, Laser calorimetry and spectrophotometric measurements. All combination allowed us to reach reflectivity values above 99.99%, with total deficit levels as low as 36ppm.

Scattering in thin-film filters is mainly driven by the substrate roughness and the deposition technology but also by the coating design as well as by the filter orientation. A high-energy, low-loss coating technology (plasma-assisted reactive magnetron sputtering, PARMS) was used to deposit an advanced thin-film filter design on substrates with low micro roughness. This approach resulted in a significantly reduced level of scattered light as well as an excellent spectral performance of the produced filters. Compared to coatings deposited by ion-assisted evaporation (IAD), the level of out-of-band scattering could be reduced by more than 2 orders of magnitude to about 0.001%.

A newly developed wideband optical monitoring system is based on a fast triggered spectrometer with a high dynamic array detector with low signal noise. It is useful for fast in-situ transmittance measurements on the rotating substrate holder during the deposition. The spectra can be stored and used for reverse engineering analysis. Layer thickness control with monochromatic monitoring strategies can be applied by using a selected single wavelength from the array detector. The high dynamic detector supports the classical turning point monitoring as well as trigger-point cut-offs with online corrected end points. The basic system design and functionalities are described. The results of multilayer systems demonstrate the performance of the new developed monitoring system.

Ion Beam Sputtering (IBS) offers a deposition process yielding optical thin films with stable optical parameters, near bulk density, and ppm level optical loss. Recently higher throughput systems with higher deposition rate and larger substrate fixtures have been developed. The higher deposition rates make accurate layer control essential. This is most readily achieved by using an optical monitoring system (OMS).

Multiple optical bandpass, edge filters and notch filters have been deposited in a high throughput IBS system with four 333mm diameter planetary using both a single wavelength (SWLOMS) as well as a broadband OMS (BBOMS). A wavelength repeatability of less than 0.1% for five subsequent short wave pass filters is demonstrated. Results for a multi notch filter coated using the BBOMS are also presented. A control strategy utilizing a mix of a broadband and a single wavelength model was used successfully in the deposition.

Spectral performance of multiple bandpass filters using turning point control is presented. A 2D mapping of a 15nm FWHM bandpass filter centered at 830nm shows a +/-0.05% variation in the center wavelength across the central 180mm diameter and a +/-0.35nm variation in the FWHM to the edge of the wafer. A variation of the standard turning point monitoring that enables control of filters with narrower bandwidth than the spectral resolution of the OMS system has been developed. A 0.8nm FWHM bandpass filter centered at 532nm controlled using a BBOMS with a ~1.5nm FWHM spectral resolution of the spectrometer is demonstrated.

Advanced optical thin film design is the key to increase laser durability significantly: either by optimizing the electric field distribution within the coating, or by multi-index or rugate designs. Both ways may be even combined.

The electric field distribution within a thin film stack was optimized to avoid peak intensities in critical layers using refractive index engineering and/or layer thickness grading. Femtosecond laser mirrors and dichroics for 780 nm and 390 nm were designed, realized and characterized. Here we present LIDT measurements of electric field optimized mirrors and dichroics, which are almost a factor of three higher compared to standard coating designs. At 780 nm a LIDT of 1.49 J/cm² has been achieved and at 390 nm 0.58 J/cm². With the exception of Al₂O₃, all investigated coating materials show a proportional dependence of the LIDT with electric field maximum, as expected by theory. For Al₂O₃ based systems the electrical field penetrates deep into the layer stack, a high number of interfaces are involved and interface effects probably limit the achievable LIDT. A similar effect was observed for rugate designs. To exclude such interface effects from the LIDT measurement, a special AR design was developed, which is practically equal for all high index materials. Here a LIDT above substrate damage threshold of 1.7 J/cm² was achieved.

We report on the sub-picosecond laser-induced damage of optical thin films of different thickness made by Magnetron sputtering, Ion assisted deposition and Ion plating, and submitted to single irradiation of the first and the third harmonics of an Ytterbium laser (1030 and 343nm). Using a single rate equation approach for free electron excitation coupled with calculation of the spatial and temporal distribution of the electric field, we investigate numerically the spatial density distribution of the absorbed energy and evaluate its capacity to describe damage phenomena especially damage threshold and morphologies (damage diameter, ablation deepness). Laser-induced damage thresholds are compared for different film thicknesses and different irradiation conditions.

The peak power handling capability of ultra-short pulse lasers is main concern for new facilities, like those for the French Apollon 10P, and European Extreme Light Infrastructure (ELI) projects. Indeed, these last generation lasers require complex, large (Ø1m) and resistant optical components with optimized thin-film coatings. Using on one hand the recent development of high laser resistant broadband high reflective coatings through a joint project with the Laboratoire d’Optique Appliquée and Fresnel Institute, and on the other hand its long time experience with polishing and measuring large and complex optical components, Reosc decided to demonstrate the feasibility of a Ø500mm aperture, 90° deviation, F/2.5 high output NA Off-Axis Parabola (OAP) dedicated to focus fs ultra-intense laser beams. The prototype of the 90° OAP has a concave surface with 20mm of aspherisation for focal length of F1250mm. The OAP is coated with a hybrid Metal/Multi-Layer-Dielectric coating. It provides a reflectivity up to 98%, an absolute Group Delay Dispersion (GDD) below 100fs² and a Laser-Induced Damage Threshold (LIDT) up to 0.5J/cm², at 15fs and under vacuum. These performances are achieved on the whole surface and on the 200nm spectral range required by the sub 20fs PW-systems. In this paper, Reosc report the developments required for the polishing, the coating and the measurements of the OAP and we will show the performances achieved on the prototype.

This paper is devoted to the presentation of a new spectrophotometric system that allows us for the accurate measurement of the transmission of thin-film filters over an ultra-wide optical density range (from 0 to 11) between 400 nm and 1000 nm. After a detailed description of its structure, we define the transmission range reachable to this set-up and we quantify the influence of the spectral profile of the source on this critical feature. A qualification of this bench, including a determination of its noise floor, is performed on a dedicated band- pass filter manufactured by Institut Fresnel, and we conclude by the presentation of results of ultra-wide range transmission measurements achieved on commercially available filters (long-pass, short-pass, and notch).

Due to market demand and technical progresses, a new generation of optical components requires much more sophisticated structures with a great number of layers. These complex structures enable to achieve severe optical performances but, at the same time, enhance light scattering processes.

For these reasons, it is essential to develop a metrological tool which provides an accurate quantification of the spectral and angular scattering losses behavior with sufficient angular and spectral resolutions.

In order to face this issue, new investigations were performed by our group at Institut Fresnel and led to the development of the new scatterometer SALSA (Spectral and Angular Light Scattering characterization Apparatus). The use of both a broad-band light source and a tunable filter allows to accurately select the illumination wavelength and the spectral bandwidth on the whole spectral range of CCD detectivity. In this paper we will present the performances of the setup and some experimental results.

Multilayer interference optical mirror coatings are traditionally fluence-limited by nodular inclusions. Planarization of these defects modifies the geometrically and interference-induced light intensification to increase the laser resistance of mirror coatings. Previous studies using engineered defects on the substrate or buried in the middle of the coating stack have focused only on understanding the improvement in laser resistance. However, real coating defects are distributed throughout the coating. To better understand differences between the critical fluence-limiting defects of both planarized and non-planarized mirror coatings, laser damage pit depths were determined as a function of laser fluence.

Metamaterials, and complex materials having plasmonic properties in general, interact with external electromagnetic radiation in a particular way compared to traditional solid thin films. The reason lays in the physics of such artificial media. Such peculiarity of metamaterials defines the choice of suitable measurement techniques used for their characterization as well as adequate methodology for measurement data interpretation, specific for the case. Here we overview main issues on the physical properties of complex plasmonic materials and methods for their modelling. The approach to modeling of their optical parameters is considered as well. The emphasis on the optical thin film applications is made.

Raman spectroscopy is an important technique that has evolved into many advanced methods, used in a wide range of fields, ranging from artwork analysis to security. In this study, we have found through template-assisted glancing angle deposition, highly ordered silver nanostructures could be fabricated across a nano-imprinted polymer to produce surface enhanced Raman scattering substrates. Various nominal film thicknesses at 85° incident angle and then deposition angles were used to fabricate the substrates, which were then characterised by scanning electron microscopy and their Raman performance was assessed using trans-1, 2-bis (4-pyridyl) ethylene as the Raman probe. Observations show that the best thickness for glancing angle deposition at 85° to be 400 nm (relative to the quartz crystal microbalance) produced the best Raman signal enhancement. The nanostructures consisted of nanorods with 851 – 1360 nm average length. Scanning electron microscopy images reveal samples had good uniformity and consistency in all films grown by this method, as the surface features provide regularly spaced nucleation sties. These findings lead show that highly sensitive surface enhanced Raman scattering substrates can be reproduced consistently cheaply.

Recording of binary volumetric diffractive optical elements within a 13 μm thick photosensitive chalcogenide layer using an innovative exposure set-up based on digital micro-mirrors devices is demonstrated. Different examples of beam transformations are shown such as the conversion of Gaussian beam into higher order modes or top-hat beam shapers.

In this study, we present high efficiency embedded gratings produced by atomic layer deposition (ALD). The chosen embedding material is a nanolaminate, which consists of alternating arranged titanium dioxide (TiO₂) and alumina (Al₂O₃) layers, where the TiO₂ layers are by a factor of 25 thicker than the Al₂O₃ layers. Consequently, the refractive index nearly equal to the refractive index of pure TiO₂ layers. Titanium dioxide has one of the highest refractive index among dielectrics and no absorption at the operating wavelength.

A pinhole free embedding of the grating is essential, since even tiny air pockets will reduce the efficiency of the diffraction optic. This has been successfully realized. However, the ALD coating produces indentations on the surface of the embedded grating. The method to remove the indentations in the excess layer on the embedded grating is discussed. The planarization is done by ion beam etching and the oxygen depletion of the top TiO₂ component is fixed by thermal treatment in O₂ atmosphere.

Finally, we developed an embedded grating with transmission efficiency higher than 97.0 % at 1030 nm wavelength. The experimentally measured efficiency is in excellent agreement with the theoretical value obtained by rigorous coupled wave analysis. In contrast, a conventional, binary grating with the same period reaches only a maximum theoretical efficiency of 92.3 % at the same wavelength in Littrow-configuration.

After a recall of some basic concepts in close relationship with the definition of the refractive index of a material, we will perform a sweep of the specific properties of some important classes of metamaterials, such as NIM, ENZ or ZIM. These fundamentals will allow us to examine the possible benefits induced by the use of one or more NIM layers into the formula of standard filtering functions, like Bragg quarter-wavelength mirror, Fabry-Perot band-pass filter or antireflective coatings. As a conclusion, we will deal some practical issues showing possible implementation ways for these new and attractive concepts.

Fishnet metamaterials (MM) conceived for optical coating applications have been simulated for metal-dielectric-metal structures based on silver and oxides. Preliminary experimental results on large-scale fabrication are presented here for alumina-silver based structures. Millimeter-size MM layers have been realized by combination of r.f. sputtering and focused-ion-beam writing.

2D photonic-crystal structures of Papilio blumei butterfly were constructed and the corresponding reflectance spectra were simulated by finite-difference time-domain (FDTD) method. The structural color of butterfly depends on the thickness of film and the size of air hole. Hence, we can obtain any color by manipulating the parameters of FDTD simulation model.

The high resolution extreme ultraviolet spectroscopy mission based on the normal-incidence multilayered diffraction grating technology, which provides high effective area and spectral resolution, can carry out a survey of local Galactic stellar and white dwarf targets. Compared to grazing-incidence systems, this approach allows previous observatory-class science to be delivered in a low-cost package. The instrument has already been proven in two sub-orbital space flights. However, the multilayer used before is periodic one and the working band-pass is limited. In this paper, the spectroscopic properties of a normal-incidence multilayered diffraction grating were simulated with three kinds multilayers for the wavelength range between 17.5nm and 25.0nm, which includes lines of Fe VIII to XIII that will be strongest in the cooler (solar like) coronae, plus some weaker lines of O, Si, S and Ar. The highest efficiency at central wavelength of band-pass can be obtained if the periodic multilayer is adopted. The most flat response efficiency can be achieved if we utilized a non-periodic multilayer. The simulation results demonstrated that the choice of the multilayer is dependent on the requirement to the spectroscopy mission and should be considered carefully.

A multiple scale model approach is presented in order to investigate Al₂O₃ thin film growth in the framework of an existing Ion Beam Sputtering (IBS) coating process. Therefore, several simulation techniques are combined via optimized interfaces for realizing the concept of a virtual coater. Characteristic coating process parameters of the IBS coating plant are applied as input parameters to model the material transport in the chamber, the energy and angular distribution of the coating material at the substrate, the formation of structural thin film properties, and the optical as well as the electronic layer properties. The resulting thin film properties are validated to the data of an experimental IBS Al₂O₃ single layer prepared applying the underlying coating facility. The comparison accounts for a good agreement between the modeled layer properties using the virtual coater concept and the experimental characterization data.

In the present study the preparation and characterization of Al₂O₃/AlF₃ material mixture coatings is described. The main focus is on the correlation between the optical properties (refractive index, extinction coefficient), elemental composition and mechanical properties, depending on deposition conditions. The thin mixture films prepared with E-Beam gun evaporation with and without plasma ion assistance show a continuous change in the refractive index between the basic materials extrema (n=1.4 - 1.75), depending on the constituents volume filling factors. At the same time, extinction coefficients vary between less than 1x10^-4 and 2x10^-3. In addition, it can be shown that in dependency of the applied plasma ion assistance, the residual stress inside the mixture layers is tunable. Finally, several multilayer coatings has been prepared and investigated.

Optical coatings are essential for many applications of excimer or solid state lasers in industry and science. An increasing demand for larger optics of highest quality, mainly generated by the display industry processing active matrix organic light emitting diode (AMOLED) backplanes, is posing new challenges for substrate and coating suppliers. For the deposition process development principally the coating uniformity, but also the handling and the cleaning steps of optics with one edge length (L) above 1 meter and several kilograms of weight have to be considered. To provide coatings for optics up to 2 meter edge length, a new ion beam sputtering (IBS) machine was developed and built at LASEROPTIK. This contribution describes an approach to adapt the IBS technology with its advanced coating quality for small optics (L≤50mm) to the field of large area deposition (L≥1m). Applying a customized linear drive, the MAXIMA deposition machine is able to coat optics of up to 100kg weight sequentially. Experimental results on the uniformity, the spectral characteristics and the laser damage resistance of dielectric single- and multilayer coatings are presented and compared with the performance of standard IBS thin films. Furthermore, the deposition of thin films on convex curved surfaces applying curvature dependent movement profiles is discussed. Finally the run to run stability is evaluated on the basis of concrete coating examples.

Boron or boron carbide based multilayers are widely used due to the boron-K absorption edge format λ=6.7nm. Pd/B₄C has a relatively high theoretical reflectivity from 7.5nm to 11nm, compared to other candidates like Mo/B₄C and La/B₄C. It can also be easily fabricated by direct current magnetron sputtering technique. In this paper, different process parameters, including base pressure and sputtering pressure, are optimized to develop the Pd/B₄C multilayer mirror. A reflectance of 36.2% were obtained at 9.41nm with 80 bilayers Pd/B₄C. Reactive sputtering with nitrogen was also explored to improve the structure and reduce the stress of the Pd/B₄C multilayers. The results showed that the EUV reflectance was not improved after the introduction of nitrogen while the stress was actually reduced.

In order to manufacture mirrors metal based coatings (Al, Au and Ag) are applied, as they enable a high reflectivity and at the same time a broad spectral bandwidth. Of all metals, Ag provides the highest reflectivity from VIS to IR.

Silver is a noble metal. However, corrosion activators (e.g. S and Cl) can lead to corrosion. Thus, a protective layer is required to prevent the corrosion and sustain the high reflectivity of the mirror. However, damage of the Ag-coating can occur, even in the case of protected-Ag. Inhomogeneous film growth of the protective layer can lead to a permeation of corrosion activators and thus to a damage of the Ag. But also the deposition of impervious protective layers is not sufficient for long-term environmental stability. Hygroscopic air borne particles can weaken the protection and therefore subsequently lead to a permeation of corrosion activators and thus to a damage of the Ag.

These damage mechanisms lead to criteria for a durable and efficient protection. AlOxNy and nanolaminates have been tested with respect to these criteria. In particular the protection based on nanolaminates shows a great potential for the protection of Ag. In addition, also the optical performance can be improved by UV-enhancement based on different nanolaminates.

In the presented work a fast frequency domain measurement system to determine group delay (GD) and group delay dispersion (GDD) of optical coatings is proposed. The measurements are performed in situ directly on moving substrates during the thin film coating process. The method is based on a Michelson interferometer, which is equipped with a high power broad band light source and a fast spectrometer. Especially for the production of chirped mirrors it is advantageous to obtain group delay and group delay dispersion data of the last layers. This additional information allows for online corrections of coating errors to enhance the precision of complex interference filters for short pulse applications.

The present contribution is concentrated on an improved method to manufacture dielectric dispersion compensating mirrors in the ultra violet (UV) range by applying a novel online phase monitoring device. This newly developed measurement tool monitors the group delay (GD) and group delay dispersion (GDD) of the electromagnetic field in situ during the deposition of the layer system. Broad band monitoring of the phase enhances the accuracy in the near infrared spectral range (NIR), significantly. In this study, the correlation of the GDD in the NIR and in the UV spectral range is investigated. A design synthesis is introduced to achieve optimum reflection and GDD target values in the UV and NIR. This requires a similar behavior of both bands according to deposition errors, to guarantee switching off the UV GDD target band proper, while monitoring the GDD in the NIR spectral range. The synthesis results in a design, characterized by a GDD of -100fs²±20fs² between 330nm and 360nm in the UV and by -450fs²±10fs² within 820nm to 870nm in the NIR. The fabricated sample, applying an ion beam sputtering process, consists of a 9μm layer stack of Hafnium oxide and Silicon dioxide. The first layers of the stack are switched and controlled by a conventional in situ spectrometric broad band monitoring in conjunction with a forward re-optimization algorithm, which also manipulates the layers remaining for deposition at each switching event. To accomplish the demanded GDD-spectra, the last layers are controlled by the novel in situ GDD monitor.

In order to enhance the final performances of complex optical systems it is required to limit the overall wasted reflected light coming from all the different surfaces involved. Ultra-low-reflectance coating becomes even a crucial point for high sensitivity experiments such as gravitational wave detectors where surfaces must have a reflectance lower than 100 ppm. Some tenths of percent is a common value for Anti-Reflective (AR) coating but reflectance below 100 ppm is trickier to achieve. The coating design sensitivity with respect to thickness errors or refractive index error can lead quickly to noncompliant reflectance.

When an AR coating has failed it is very difficult to recover the low reflectance. In theory adding one or two layers could correct the reflectance but it requires knowing exactly the actual coated stack. For large optics (diameter up to 500 mm), we developed a new technique based on reflectance measurements with different polarizations and incidence angles at one wavelength. The measurements were performed in s-polarized and p-polarized light to discriminate between several solutions. Then a correction based on one or two layers is computed in order to decrease the reflectance. The efficiency of this method is demonstrated in the case of a four-layer AR coating designed for zero reflectance at 1064nm and coated onto a 350mm diameter and 200mm thick substrate. The reflectance has decreased from 500ppm to 26ppm thanks to a correcting bilayer.

High end applications in infrared may benefit from infrared colorimetry. Actual systems are designed using filter wheel, gratings or dichroic components. Those systems are bulky, do not allow real-time acquisition and are sensitive to stray light.

Sagem & Reosc recently developed technologies to pixelate infrared coating filters at detector level. It allows designing very compact systems, easy to cool down and to significantly reduce ghost images. Optical systems are simplified and can achieve fast acquisition of multi-spectral video.

Numerical simulations have been performed in order to quantify the pattern shape influence on the optical performances at the microscopic scale. The etching processes of multilayer stacks have been developed. Finally, prototypes have been manufactured and tested.

This technology opens up new perspectives in the field of infrared filtering.