Efficiently controlling the propagation of light is a most important issue in the optics. The traditional optical elements manipulate light by phase accumulation through light propagation. Metasurfaces, serving as nanoscale phase shift, have attracted the interest because they possess the ability offering fascinating possibilities to realize unprecedented photonic phenomena while interact with light over the scale of the wavelength. Although kinds of novel functionalities are reported, monolayer metasurfaces and hybrid metasurfaces are limited by their less geometric structure parameters. Since the hybrid multilayer metasurfaces have more adjustable parameters, expanding the capacity to control the light beam, we use the hybrid multilayer metasurfaces to realize polarization-insensitive anomalous reflection and polarization-sensitive focusing. The gradient metasurface exhibits high efficiency anomalous reflection for both x-polarized and y-polarized light. The metalens has opposite focus for right-handed circularly polarized and left-handed circularly polarized incident light. The results may offer some help to find various potential applications in nanophotonics.

The earlier developed molecular dynamics approach is applied to the investigation of porosity and surface structure of thin films obtained under different deposition conditions. The empirical Monte-Carlo simulation procedure is developed and applied for the search of pores in silicon dioxide thin films. The pores distribution depending on the thickness of growing films and porosity dependence on substrate temperature and deposition energy are studied. It is revealed that the dimensions of pores increase with the decrease of deposition energy. The growth of substrate temperature from 300 K to 500 K results in the increase of porosity in the case of high-energy deposition and in the decrease of porosity in the case of low-energy deposition. It is found that in the case of high-energy deposition film structural properties vary insignificantly with the variation of energy distribution of deposited atoms providing that the average energy of deposited atoms is constant.

Optical thin films are essential for many laser applications in industry and science. The increasing demand for highest quality laser optics, requires the enhancement of existing coating technology as for example Ion Beam Sputtering (IBS). By facing new challenges like the large area deposition for line beam optics with up to two-meter edge length, LASEROPTIK is already pushing the limits of coating technology. This contribution describes an approach to combine Glancing Angle Deposition (GLAD) with IBS utilizing the MAXIMA deposition machine. To analyse the dependence of the refractive index, the ultra violet absorption edge, the mechanical stress and the laser damage resistance on the mean deposition angle to the substrate surface, single layers as well as multilayer coatings are realized at five different mean deposition angles between 30° and 90°. By coating one substrate at each of the five different mean deposition angles in the same batch the influence of run to run process variations is minimized. Besides fundamental research regarding this coating technology the results of this experiment will gain further insight into the deposition of thin films on strongly curved surfaces applying curvature dependent velocity profiles.

The goal achieved by this work has been to produce stable, durable, low-absorbing, low-scattering magnesium fluoride (MgF₂) films without additional heat or fluorine. This was done with IAD in a chamber that could do production on a commercial basis. Stability with respect to humidity and temperature shifts and durability with respect to abrasion resistance depend on the density of the films. Absorption depends on the stoichiometry of the films. Scattering partially depends on stress cracking due to mismatch of the coefficients of thermal expansions of the substrates and the coatings. In recent decades, MgF₂ has become a preferred material in the DUV to wavelengths as short as 180 nm. It has been shown that MgF₂ often suffers from a fluorine deficiency when deposited by energetic processes. It has been demonstrated that much of the resulting absorption can be eliminated by ultraviolet annealing which provides enough energy to give mobility to fluorine atoms to reunite with nearby magnesium atoms. This implies that the fluorine deficiency is due to dislocations of the fluorine atoms, but that they are not all lost from the matrix of the film and pumped away by the vacuum process. It is believed that energetic ions from sputtering or IAD sources cause the dissociation of the F atoms from the Mg if their energy level exceeds some threshold. Present results provided "fully" dense films for hardness, low temperature/humidity shifts, and low absorption and scattering by using IAD at 160 eV or less and no added fluorine.

Complex interference multilayer systems typically implemented in high-performance optics consists of several layers of low and high refractive index materials. Low mechanical stress of the coatings is desired to avoid cracking and delamination of the film or a deformation of the substrate. It is known that the ion energies in plasma-assisted deposition can be employed to control material properties and thereby mechanical stress. In this study, we evaluate the influence of substrate biasing on mechanical stress and optical properties of alumina (Al₂O₃) coatings deposited by plasma enhanced atomic layer deposition (PEALD). Substrate biasing up to -300 V was applied during O2 plasma exposure in the second step of a two-step PEALD process. To distinguish the physical effect of ion bombardment from the physico-chemical effect, a substrate bias of -100 V was applied separately and only during Ar plasma exposure that constituted the third step of a three-step PEALD process. Al₂O₃ films were characterized using spectroscopic ellipsometry, spectrophotometry, xray photoelectron spectroscopy (XPS), x-ray diffractometry (XRD), x-ray reflectometry (XRR), Fourier transform infrared spectroscopy (FT-IR), wafer-curvature measurement and atomic force microscopy (AFM).

The production of large area coatings in the vacuum chamber with the dimensions of 100×100×100 inches is considered. The chamber has the planetary rotation system with three planets. The original monitoring system with two broad band optical monitors combines the advantages of direct and indirect optical monitoring. The results of production of large area coatings are presented to illustrate the capabilities of the combined direct-indirect monitoring system.

Particle contamination is a limiting factor for the quality of multilayer thin films, and to evaluate this effect, coated optics are typically subjected to an ex situ inspection. However, to identify the generation mechanisms of particles during the deposition process, it is necessary to record data in situ. In this work we report on a camera based detection method for time resolved particle measurements during plasma deposition processes. We analyze silicon substrates in the vacuum coating chamber by means of dark field illumination to reach high sensitivity to small defects on the substrate surface. We show camera images of the substrate, which document the evolution of particle contamination during the deposition process, and compare the results to microscopy. By providing a cost-efficient monitoring strategy, we take the steps towards an identification of particle sources in the vacuum chamber.

Time durability and environmental stability of silver-coated glass mirrors improve if silver layer is protected by a transparent thin film coating. The choice of the protecting layer material and of the methods for mirror manufacturing influences the mirror optical and mechanical properties. This work reports on a systematic study of silver mirrors overcoated by silicon oxide, nitride and oxy-nitrides. Variable angle spectroscopic ellipsometry was implemented to get an insight on metal-dielectric interface of the coatings. The results have been analyzed considering the coating deposition conditions and physical-chemical properties of the dielectric materials used as protective layers.

Silicon thin films were prepared on silica substrates by ion beam sputtering, electron beam evaporation and ion assisted deposition. The transmittance spectrum, the reflectance spectrum and the ellipsometric spectrum were obtained in the wavelength region from 300nm and 2000nm, where Lambda 900 spectroscopy and VASE ellipsometer were applied. The optical constants were calculated by multiple spectrum analysis with WVASE32 which is the analysis software for ellipsometry of J.A.Woollam company. There were about ten nanometers of silicon dioxide layers on the surface of the silicon films. The near infrared extinction coefficient of the silicon thin film prepared by ion beam sputtering was the largest, followed by ion assisted deposition, the extinction coefficient of the electron beam evaporated silicon film was the smallest, and the refractive index of the electron beam evaporated silicon thin film was the lowest. The heat treatment experiments of 300°C and 400°C showed that the refractive index of the 600nm-200nm band of the ion beam sputtering silicon film decreased obviously, while the refractive index of the electron beam evaporation and the ion assisted deposition silicon thin film had little change, and the heat treatment at 300°C could significantly reduce the extinction coefficient of the near infrared band of the three silicon thin films. In the further heat treatment at 400°C, the extinction coefficient of the ion beam sputtering silicon film and the ion assisted deposition silicon film continued to decrease, while the extinction coefficient of the electron beam evaporated silicon film increased.

With the development of grazing incidence telescopes, X-ray astronomy has experienced a rapid development in the last decades. Effective area plays an important role in telescopes performance. Except for increasing the geometric area, improving the reflectivity of coating mirror is a good way to increase effective area. Generally, the reflective coating is a smooth single layer of a heavy metal, such as gold, platinum, or iridium. We used a structure of bi-layer thin films with high reflectivity. The thin films were deposited on D263 glass substrate and the hard X-ray reflectance was measured. We compared the reflectivity of two samples, which coated with bare platinum and bi-layer structure, respectively. The fabricated structure is characterized and the estimated theoretical results of the reflectivity is calculated, reflectivity reached 95% and 91% in the energy region of 2 and 2.5 keV at the grazing incidence angle of 0.5°.

Mirrors based on Al protected with a MgF₂ film provide high reflectance over a broad spectral range down to the wavelength of 120 nm in the Far UV (FUV). After more than 50 years since the development of this technology, a significant FUV reflectance enhancement has been obtained in the last years. Such enhancement originates mostly in the higher transparency of the MgF₂ protective layer deposited on a hot Al-coated substrate. Research has been conducted at GOLD to measure the dependence of the FUV reflectance enhancement with MgF₂ deposition temperature. A reflectance enhancement was found for freshly-prepared samples; moreover, the reflectance degradation over time of Al films protected with hot-deposited MgF₂ was also smaller than for the coatings deposited at room temperature. A reflectance as high as 90% was measured at 121.6 nm (hydrogen Lyman α line) for aged samples. A FUV reflectance enhancement was also obtained on samples fully deposited at room temperature and later annealed in vacuum. The reflectance of Al mirrors as a function of MgF₂ deposition temperature, as well as of post-deposition annealed mirrors, and their stability over time is presented. Structural data on film roughness, density, and main crystal orientations for mirrors with a MgF₂ film deposited both at room temperature and at 250°C are also presented.

Aperiodic multilayer interference coatings are of particular interest for a variety of hard x-ray applications, including target diagnostics, astrophysics, high energy physics and free-electron lasers. Such applications require large field of view along with the highest achievable photon efficiency for their optical components, pushing reflective multilayer coatings to their limits. This work investigates the design, experimental performance, modeling and optimization of high-reflectance aperiodic multilayers. Multilayer design starts with the implementation of an analytical method developed in the literature, which calculates the most efficient coating, featuring the highest achievable reflectivity with the least number of layers. A numerical optimization step is added for smoothing of high-frequency "ripples" or to comply with any specific requirement in terms of spectral or angular response. The design process also includes material-dependent specificities (e.g. typical roughness, interlayer formation) which are often crucial for accurate prediction of actual coating performance. We applied this method to develop novel high-reflectance broadband multilayers at 17.4 keV (Mo K_α emission line), working at angles of grazing incidence up to 0.6 degrees. The design methods employed in this work are presented, as well as the results obtained for a few multilayer systems, including Mo/Si, W/Si and W/SiC.

There are 830 transport mirrors with a combined surface area of approximately 255 m² of precision multilayer coatings deposited on 50 metric tons of BK7 glass in the high fluence transport section of the National Ignition Facility (NIF). With peak fluences over 20 J/cm² at 1053 nm, less than five percent of these mirrors are exchanged annually due to laser damage since full system operations began in 2009. Multiple technologies have been implemented to achieve these low exchange rates. The coatings are complex dichroics designed to reflect the fundamental wavelength (1053 nm) and an alignment beam (374 nm) while suppressing target backscatter wavelengths (351 nm and 400-700 nm) from backward propagation up the beamlines. Each optic is off-line laser conditioned to nominally 50% over the average fluence and nominally 90% of the peak fluence allowing the final laser conditioning to occur on-line during NIF operations. Although the transport section of NIF is sealed in a clean argon environment, air knives were installed on upward facing transport mirrors to blow off particulates that could accumulate and initiate laser damage. Beam dumps were installed in between the final optics assembly and the final transport mirrors to capture ghost reflections from the anti-reflection coated surfaces on the transmissive optics used for polarization rotation, frequency conversion, and focusing the 192 laser beams on target. Spot blockers, normally used for the final optics, are sometimes used to project a shadow over transport mirror laser damage in an effort to arrest laser damage growth and extend transport mirror lifetime. Post analysis of laser-damaged mirrors indicates that the dominant causes of laser damage are from surface particulates and the 351-nm wavelength target backscatter.

While various layer schemes have been developed to protect thin film silver mirrors from tarnish and corrosion, the mechanisms by which these protective layers improve mirror durability are not fully understood. Mixed flowing gas exposure of plasma beam sputtered silver mirrors was used to investigate how the composition of the very thin adhesion layer changes the mechanism of corrosion feature growth. Two model mirror coatings were analyzed in which the composition of the base layer below the silver and the adhesion layer above were varied. Optical measurements and microscopy, SEM, TEM, and EDS were used to characterize the compositional and chemical effects at the layer interfaces. Large circular corrosion features formed along the silver-chromium interfaces; the addition of nickel to the layers on either side of the silver limited the growth of these features, but resulted in the corrosive attack of the silver itself.

To effectively improve color neutrality of antireflection (AR) coatings, a layer with a very low refractive index (n < 1,3) must be used as the top layer. However, solid materials with such a low refractive index (n) does not exist. The deposition of low molecule weight organic materials as compact films, and a subsequent plasma etching procedure on these films, offered the possibility to produce a nanostructured layer with a very low refractive index as top layer for an antireflection coating. Strongly curved aspheric lenses were coated with such a super-broadband AR design (ARplas2) and the antireflection performance was measured at different locations on the lens. An average reflection < 0,25 % over the full visible wavelength range was measured even in the outermost region of the curvature.

In this study, single layer antireflection (AR) coatings have been realized using nanoporous SiO₂ thin films made by atomic layer deposition (ALD) and wet chemical etching. The run-to-run and etch-to-etch reproducibility of nanoporous coatings have been monitored nearly one year. Excellent reproducibility of the film thickness and refractive index, and accordingly of the optical function are demonstrated. Furthermore, the stability of the coatings in vacuum as well as at 200°C has been analyzed.

The potential application of high-power UV lasers as an illumination source has stimulated the study and the development of new materials with high refractive index as constituents for optical devices. As a wide band gap and high refractive index material, Sc₂O₃ has been explored for UV optical coating applications. The physical and optical properties of Sc₂O₃ films are strongly dependent upon the deposition method, growth conditions and some postdeposition treatment. Plasma ion assisted deposition (PIAD) is a well-known advanced deposition technique to deposit dense dielectric films with superior optical properties such as smoothness, low scatter, and environmental stability. This research work is to apply PIAD process to obtain homogenous and UV transparent Sc₂O₃ layers to be paired with SiO₂ to prepare UV 266nm antireflection coatings. Higher bandgap materials require higher photon energies when absorbed by a material and converted to electron excitation which promotes a valence electron to the conduction band. This would result in higher laser damage threshold. The coating performance and UV laser induced damage threshold of these AR coatings made with Sc₂O₃ layered with SiO₂ are compared with the coatings made with HfO₂-SiO₂ paired AR coatings. The Sc₂O₃-SiO₂ paired coatings demonstrate a comparable low reflectivity to AR coatings using HfO₂ as high index materials. Furthermore, it shows a higher UV laser damage threshold than HfO₂-SiO₂ paired AR coatings. Sc₂O₃ demonstrates its potential application through this research work as optical interference coatings for high power UV laser devices.

The diffraction limit is one of the main difficulties in order to achieve nano-resolution. An evolution in this domain can allow a significant advance in the field of photonic circuit fabrication. Surpassing the diffraction limit can be achieved by employing significant optical nonlinearities (nonlinear refraction and/or nonlinear absorption). In this direction we investigate the nonlinear absorption efficiency of annealed Sb2Te3 chalcogenide thin films (20 nm thickness). The studies have been performed using the Z-scan technique, employing 11 ns duration pulses at 1064 nm. The Z-scan technique has been chosen as it allows the simultaneous determination of the nonlinear refraction and the nonlinear absorption of a material, under certain conditions. Our results indicate a significant nonlinear absorption, while the nonlinear refraction is at least one order of magnitude lower. The nonlinear absorption parameter has been found to be in the order of -10^-3 m/W under infrared irradiation showing the importance of the prepared materials for laser photoinscription applications. Our values are compared with previous studies, which have been carried out in the visible part of the spectrum. The possibility to perform photonic component fabrication by local modification of the linear or the nonlinear properties of the materials is also discussed.

A broadband beam splitter coating with the reflecting range from 400 to 900 nm and the transmitting range from 920 to 2300 nm was developed. To avoid absorptive losses at low wavelengths, Ta₂O₅ was chosen as the high index material. A new setup based on a Hartmann-Shack sensor was built to measure the wavefront error and its spectral dependence. An area of 120 mm diameter was measured. While in a standard coating, large resonant-like wavefront errors occur, an optimized coating with significantly reduced spectral wavefront error was designed and produced.

Recent developments in the understanding of designing polarizing beam splitter coatings as well as improvements in the thin film technology allow us to fabricate the “perfect” polarizing beam splitter cube for broadband applications in transmission and reflection. Even though the fundamentals are well known for many decades, the interpretation of the physical properties will lead us to some significant optimization of the polarizing properties.

Beam splitters separating visible (VIS) and near-infrared (NIR) light are an important component of many optical systems such as spectrometers or telescopes. Here, one part of the spectrum is transmitted while the other is reflected. Typical goal requirements are broadband high transmittance and high reflectance without local minima combined with a steep transition zone. These requirements drive the complexity of the coating design. Beside the coating design also the deposition technology has an impact on the feasibility of the coating. In this contribution, we address manufacturing challenges for manufacturing of an ideal beam splitter and compare Ion Assisted Deposition (IAD) and Plasma Enhanced Magnetron Sputtering (PARMS) technology by presenting examples of VIS-NIR beam splitters manufactured at Optics Balzers Jena GmbH (OBJ). These examples reach from beam splitters manufactured by IAD with a total coating thickness of about 3.5 μm to the beam splitter of Sentinel 2 multi-spectral instrument with more than 100 layers a and a coating thickness of about 13 μm. An example which overcomes the limitations of the IAD process is the dichroic plate of ESAs Euclid telescope manufactured by OBJ by means of PARMS process. This dichroic plate shows a reflectance of over 99% in the VIS spectral range and a transmittance of more than 98% in the NIR spectral range. Both mentioned manufacturing technologies are discussed in terms of process stability, coating homogeneity, and straylight limitations.

Atomic layer deposition (ALD) has been widely used in Micro-electronics due to its self-terminating process. The ALD films have precise thickness and nodular-free structure, which are desirable properties for high power laser applications. ALD Al₂O₃ and HfO₂ single layers were prepared through ALD process. The layer properties relevant to high power laser industry were studied and compared with IBS Al₂O₃ and HfO₂ single layers, respectively. Anti-reflection coatings for different harmonics of Nd: YAG laser were prepared through ALD and IBS respectively. ALD single layer films show comparable refractive indices and band gap energies with IBS films. ALD films have tensile stress, in contrast to the compressive stress of IBS films. ALD single layer films have absorption as small as several ppm at fundamental wavelength of Nd: YAG laser, and higher LIDT than IBS films. The spectra of anti-reflection coatings indicate precise thickness control of ALD by counting the cycles. ALD coatings show better laser resistance than IBS anti-reflection coatings at 1ω-4ω harmonics of Nd: YAG lasers. The LIDT of both ALD and IBS coatings are limited by the HfO₂ layers. Also in ALD films, defects are the main cause for ns laser damage. The study in this text indicates the high versatility of ALD films for applications in high-power coatings.

Glancing-angle–deposited thin films are used to fabricate half-wave plates in a 1-D striped geometry, forming alternating regions of linearly polarized light on a single 100-mm-diam substrate. MgO is selected for fabricating the birefringent films for use in vacuum, based on its formation of isolated columns that avoid potential tensile-stress failure of the porous film. While large-area tests have shown high defect densities for fluences <10 J/cm² , small-spot laser-damage testing has shown resistance to fluences up to 30 J/cm² (351-nm, 5-ns pulse). An amorphous silica film is investigated to match the optical thickness in the intermediate regions in an effort to fabricate a polarizationcontrol device to reduce focal-point modulation (“beam smoothing”) in high-intensity laser systems. Ongoing efforts to improve the laser-damage threshold and minimize optical losses caused by scatter are essential to realizing a practical device. Scalability of the process to meter-scale substrates is also explored.

Order sorting filters had to be coated for the CRyogenic InfaRed Echelle Spectrograph upgrade (CRIRES+)-instrument, a high-resolution IR spectrograph to be set up at ESO’s Very Large Telescope in Chile. Therefore SiO₂ was chosen as material with low refractive index. Si and Ge have been investigated as materials with high refractive index, whereby Si has been chosen for the application of the coating. Three types of high-pass filters were deposited with transmission bands starting at 0.96μm, 1.47μm and 2.9μm. These filters need to block effectively all wavelengths between 0.5 μm and the respective band. Therefore, in the blocking range, an optical density above four, or above three for the filter starting at 2.9 μm respectively, had to be achieved. The filter-coatings also needed to survive thermal cycling down to 65K while only introducing a small wave front error. The lower total thickness, compared to coatings consisting of other materials, and the low film-stress are favorable properties for coatings deposited onto prisms and other more complex optical components.

Optimal solution for the multilayers AR coating of 4J solar cell including design and fabrication was investigated. The real layer structure of 4J solar cell was determined first through reverse fitting, then the multilayers AR coating could be designed on the complete 4J solar cell to find the global optimization. After clarifying that the performance of multilayers AR coating is affected by oxidation of AlInP, the oxide layer was characterized and compensated to improve the spectrum. Through transmission electron microscopy (TEM), the oxidation depth was determined to be 5nm. Finally, the multilayers AR coating was re-optimized by considering oxidation layer into 4J solar cell. Using ion assisted deposition, the multilayers AR coating was fabricated with a slightly increased weight average reflectance of only 0.5%.

HgCdTe crystals are very important semiconductors for the realization of infrared (IR) detectors, and as a rule an optimal response range is usually expected by controlling the exact balance of the ternary compound. Two approaches are available for the synthesis of HgCdTe semiconductors. The first is the well-known alloy process, in which the bandgap is tailored by varying the mole fraction x of CdTe in an Hg_1-xCd_xTe alloy. The second is a superlattice structure, in which the bandgap is determined by the relative thicknesses of alternating HgTe and CdTe layers in a composite semiconductor. This Overview concerns colloidal synthesis, which is used as a new technology for obtaining new plasmon materials - transparent self-assembled conductive Ag₂O, Ag, graphene oxides in the production of plasmon material based on HgCdTe (MCT). In general, the results will be used to create multi-range HgCdTe detectors based on the plasmon resonance effect.

Typical excitations in metal nanostructures are localized surface plasmon resonances (LSPR) and propagating surface plasmon polaritons (SPPs) at metal-dielectric interfaces. If the metal film is prepared with holes or periodic corrugation, then diffracted light can be coupled to both LSPR and SPPs. Controlled engineering of the geometric parameters like height and periodicity of corrugation affect the strength and spectral position of LSPR, changing the metal film thickness changes the height of the extraordinary transmission (EOT) peak, and light-SPP coupling can be changed by altering the dimensionality and refractive index contrast in the attached photonic layer. In this study, we report for plasmonic interference coupling (PIC) where the plasmonic electromagnetic (EM) enhancement is critically dependent to the optical interference in the metal-insulator-metal (MIM) structure. The basic structure consists of the top metal with nanopores as a plasmonic layer and the bottom metal as an optical mirror. By controlling the thickness of the dielectric insulator at the middle, the optical interference patterns (i.e. constructive or deconstructive interference) were alternated at the top nanopore layer, thus resulting in great effects on surface-enhanced Raman scattering (SERS) responses. Therefore, we could clearly understand that such a MIM structure should be well designed by considering PIC characteristics to effectively utilize a plasmonic EM enhancement. We used nonporous anodic aluminum oxide (AAO) and titanium dioxide templates for accomplishing such a PIC structure. Furthermore, low-cost aluminum was applied to create non-uniform nanopore AAO and compared their optical properties with those of uniform AAO-based PIC structures (i.e. high-cost template). Finally, we could confirm scalable cost-effective PIC structures. Our results might provide the suitable design way for the applications of enhanced EM on plasmonic-integrated devices.

In imaging detection of Lyman-a line of solar spectrum, in order to maintain spectral purity, a narrowband 121.6 nm minus filter is in urgent demand. Here, first-, second-, third-order narrowband 121.6 nm minus filters are designed, fabricated, and test. We just give our initial results, and due to complexity in characterization of optical constants in 115-130 nm, there are still significant deviations between design and experimental results.

Highly transparent and conductive thin films were assembled as a potential indium tin oxide (ITO) replacement using layer-by-layer (LbL) assembly with carbon nanotubes (CNTs), sodium deoxycholate (DOC) as a stabilizer and poly(diallyldimethyl ammonium chloride) [PDDA] as polycations. This LbL adsorption of both species has linear increase independent on number of bilayers deposited. The self-assembly of DOC-stabilized CNTs and PDDA was shown to realize the thinner and smoother films with transparency (<84% T) and electrical conductivity (~300 Ω/sq) with a 23.5 nm thickness. Moreover, nitric acid doping was also treated for higher conductivity (~104 Ω/sq) due to the removal of insulating materials and the charge transfer doping. The optoelectronic performance of 5 BL DWNT LbL film here is much better than most other CNT thin films and capable of the ITO replacement. Then, the CNT LbL thin films were applied to fabricate liquid crystal (LC) cells as transparent electrodes. Voltage-transmittance performance exhibited the availability of a CNT LbL electrode to LC display. Additionally, the bending stability could suggest that these films potentially be used in a variety of electronic applications. Also, the ability to tailor thin film resistance can be potentially useful for anti-static films and EMI shielding.

Planarization of nodular defects was investigated in order to improve the laser-induced damage threshold (LIDT) of high-reflection coatings. Monodisperse SiO₂ microspheres were first deposited on the substrate surface by a spin coating process. Using a dual ion beam sputtering system, these engineered seeds were used to create artificial nodules in 1064nm HfO₂/SiO₂ high-reflection coatings and Ta₂O₅/SiO₂ high-reflection coatings. These SiO₂ microspheres were then smoothed by a single thick SiO₂ planarization layer, where the relationship between the thickness of the planarization layer and the size of the microspheres was investigated. When the planarization layer (etching layer) thickness is slightly larger than the diameter of the seeds, the seeds could be completely planarized to obtain smooth thin films. In addition, the LIDT of the high-reflection coatings with different coating materials and different planarization layer thicknesses were tested. The results showed that the nodular defects planarization could noticeably improve the damage resistance of high- reflection coatings. In addition, the surface roughness of Ta₂O₅/SiO₂ high-reflection coatings was shown to decrease after the planarization, while the surface roughness of the 1064nm HfO2/SiO2 high-reflection coatings was shown to increase.

Modern infrared antireflection coatings can effectively increase transmission of windows and lenses. Such coatings materials include commonly chalcogenides, fluorides, silicon, germanium and oxides. It is known that chalcogenides and fluorides are characterized by relatively low mechanical strength and stability against enhanced humidity. Oxide films typically have high absorption in the MWIR and LWIR. Silicon and germanium have high refractive index and are rarely used as an upper layer. Some authors offer using diamond-like carbon (DLC) film as a protective layer for multilayer coatings (MLC). DLC thin films are characterized by high infrared transparency, high mechanical hardness, low friction coefficient and chemical inertia. In this paper we show that high performance broadband and durable infrared antireflection coatings on Ge substrates can be designed and fabricated. The initial design of an antireflective coating is a gradient-index system. Then the layers are replaced with three-layer equivalent periods. The thickness of the upper DLC layer is limited by required mechanical properties of the coating and from our experiments should be not less than 100 nm. DLC film deposited using an End-Hall ion beam deposition technique. The remaining layers were deposited using an electron beam evaporator with ion bombardments. The average transmission of the samples with MLC + DLC surface is 93% in the wavelength range between 3 and 12 μm. On the opposite surface, a broad-band antireflection coating was deposited. The peak transmission is about 97%. The coatings are passed mechanical (adhesion, abrasion) and environmental (temperature cycle, humidity) durability tests. The result is improved significantly in comparison with conventional infrared windows.

The radiation wavelength of the carbon dioxide is 4.3μm. It is a kind of background noise that affect the image contrast in infrared imaging system seriously. Mirror is an important optical element in infrared optical system. This paper intends to design a 4.3μm wavelength filter base on the mirror. So, it is called reflective filter. It can replace the original mirror in the infrared optical system in order to filter out the radiation wavelength of the carbon dioxide and enhance the image quality. The reflective filter consists of metal and dielectric films. The absorption of the Al film which is the underlayer has been induced by the outer side dielectric multilayer films at 4.3μm. And it will keep high reflectivity in other wavelength at the same time. The design result as follow was obtained after optimization design. The average reflectivity is about 98% in the range of 3.7-4.2μm and 4.4-4.8μm (reflection bands) and the reflectivity is less than 10% at 4.3μm (absorption band) when the incident angle is 45°. The reflection phase of the metal-dielectric films was analyzed. The electric field distribution of reflection bands and absorption band was shown respectively. At last, in order to filter out the peak as much as possible, the design method and result of absorption band widening of the reflective filter was shown. Compare the all dielectric transmission minus filter, the layer number of the reflective filter is fewer and the total thickness of the coating is lower. Therefore, the manufacturing process became easier. The reliability became higher. More important, a better parameter of filter was obtained.

We have designed and experimentally demonstrated a periodic multilayer structure of SiO₂ and Cr thin interlayers to achieve an ultra-broadband perfect absorber based on optical admittance matching method. The successive Nano-Cr-film make significant contribution to improving the absorption intensity of the structure. Measurements reveal high absorption over 85%, when averaged over the range 0.4–7.2 μm. Remarkably, it is the most broadband planar absorber film without involving lithography in fabrication. Incident angle and polarization dependence of the absorption spectra are also considered. The manufactured absorber also has potential applications for thermal shielding, detecting, imaging, photovoltaics (PVs), sensing, etc.

Metamaterials are artificial structures consisting of periodic sub-wavelength elements, they produce a particular electromagnetic response which often cannot be obtained from conventional media. One class of metamaterials called hyperbolic metamaterials (HMM) is widely studied nowadays due to their various applications such as subwavelength imaging and local density of states engineering.¹ In this work, HMM consisting of alternating gold, copper, and niobium pentoxide layers was designed and fabricated with plasma assisted electron beam deposition technique. For the accurate description of this material opto-geometrical parameters of thin layers composing it were determined separately using reflection and transmission measurements. Afterward, the produced material was structured using focused ion beam milling and its influence on the Alexa Fluor 647 biomolecules spontaneous emission was studied experimentally with fluorescence correlation spectroscopy and time-correlated single photon counting techniques. Combining these techniques enable the measurement of the fluorescence lifetime reduction together with the brightness enhancement per molecule. The same measurements were previously done for the structured gold films³ which let us compare the results. HMM has shown significant emission enhancement compatible with the one produced by a single gold aperture which is known for its good plasmonic properties.

The thin film optical constants are key parameters to carry out optical simulation or optimization of multilayer mirrors with high efficiency. However, for most materials, different sets of optical constants can be found in the literature especially in the EUV range, as these parameters are not as well-known in the EUV as in the visible or wavelength range. In this work, we have used several reflectance and transmittance measurements in the wavelength range from 10 nm to 60 nm. Different optical constant files have been tested and compared with the IMD simulation software. We will present some experimental spectra and theoretical simulations to highlight the existing problem on the reliability of optical constants sets and to discuss potential solutions. We focus our research on a few materials of particular interest in the EUV range such as aluminum, aluminum oxide, molybdenum, zirconium, magnesium, silicon carbide, and boron carbide. These analyses lead us to select the most reliable and accurate optical constants set, or to create the best one from the concatenation of existing data for each material of interest.

Standard high reflectivity mirrors consist of layers with high and low refractive indexes. Typically, optical resistivity of such elements is limited by the threshold value of material with high index. Combination of two deposition methods, namely ion-beam sputtering and glancing angle deposition, was used to form high reflectivity mirrors for the wavelength of 355 nm. Variation of the design for standard coating and the number of top layers, deposited at oblique angle have been investigated. Laser induced damage thresholds, surface roughness, spectral performance etc. were tested for all the experimental samples. Analysis indicate that combination of both deposition methods allows to enhance the optical resistivity of typical high reflictivity mirrors. Fully sculptured thin film based mirrors also exhibit spectral instability and optical losses. Introducing standard method allows to stabilize the spectra and reduce the losses of total optical component.

Several studies have reported on the detrimental effects of inadequate cleaning on the performance of optical components exposed to laser radiation. The remaining particulates, contaminants or residue located in the coating or on the substrate surface can absorb laser energy and consequently induce damage. To minimize these contaminants, investigations of various cleaning processes have been performed in both the research and industry communities. Transparent published results and comparisons of the different cleaning processes considered, however, are limited due to proprietary considerations. In addition to this, the manufacturing environment, deposition processes, substrate- and deposition materials all have an influence on the effectiveness of a cleaning process. The purpose of this study was to investigate different cleaning procedures and their influence on the laser resistance of ion-beam sputtered antireflective coatings. For this purpose, a SiO₂ / Ta₂O₅ multilayer antireflective coating for a normal angle of incidence at 1064 nm was deposited onto fused silica substrates. Prior to deposition, the substrates were cleaned with a variety of cleaning solutions and procedures and their roughness and surface quality inspected. All samples were characterized in terms of their laser damage threshold using a 1064 nm ns-pulsed test bench and subsequently visually inspected in order to understand the cause of the damage. In this work, the details of the cleaning steps and the corresponding laser damage performance for the different cleaning processes are presented and compared.

Ultra-thin metal films possess big possibilities in design and manufacture of multilayer structures with sophisticated spectral performances over wide wavelength ranges. Continuous ultra-thin metal film has a smaller depolarizing effect than dielectric film, due to this reason the amount of total coating thickness and layers number in non-polarizing coatings can significant reduced. Nevertheless, depending on the substrate temperature, the deposition rate, the thickness, ultra-thin metals films can form continuous or discontinuous nano island structures. When optical components are used at oblique angles of incidence, the reflectance and transmittance of thin film exhibit strong polarization effects. However, for many applications, the polarization effects are undesirable and should be reduced. Non-polarizing coatings are widely used for a variety of photonic applications ranging from interferometry and holography. Their aim is to divide incident light into transmitted and reflected beams in a certain ratio for both s- and p-polarized light. In present work, different combinations of deposition parameters were investigated for silver thermal evaporation. Various dependencies on silver thin metal film formation are shown. The dependence on metal thickness showed different regime of film formation. Microstructure and optical properties were investigated by using of atomic force microscope, ellipsometry and spectrometer measurement A novel plate metal–dielectric three-layer, broadband nonpolarizing beam splitter (nPBS) with an ultra-thin silver film was designed.

We manufactured and investigated narrow spectral selection filter with a defect layer. Design of the filter was performed based on results of modeling. The main idea of that filter is sandwich structure of 5 layers with high aspect ratio between refractive indices of two different layers and phase diffractive optical element in the central layer. The structure was manufactured for operation at wavelength of 532 nm. The ZnO (n=2.03) and TiO₂ (n=2.67) thin films were chosen as materials for the designed sandwich structure. The thin films were deposited by the magnetron sputtering system “Caroline D12A”. The thickness of each ZnO layer is 50 nm, the thickness of each TiO₂ layer is 65 nm. The central defective layer was fabricated with the help of a plasma-chemical etching system through a hard mask of chromium. The chromium hard mask was manufactured by direct laser writing. The central TiO₂ layer was etched in a SF6 gas. Then the mask was removed by liquid chemical etching. The influence of the multilayer structure properties and parameters of defective layer on the spectral characteristics of the optical filter was investigated. This filter shows very narrow spectrum selection and high efficiency. The possibility of the use of such filters for selecting a narrow range of wavelengths that can find various applications in the field of information transfer and medical devices was shown.

In present work, oblique angle deposition technique was employed to form nano-structured anisotropic layers evaporating amorphous materials. The combination of birefringent nano-structured and isotropic layers allows to form highly transparent (T ~ 99 %) wave-plates. Furthermore, such combination can be used to form two spectrally separated Bragg reflection zones for perpendicular polarizations. This feature allows to form polarizers for zero angle applications. Both elements can be manufactured using only one material by changing only its structural morphology what leads to superior LIDT value. In this work, the possibility to evaporate waveplates and polarizers for zero angle applications was shown.

We present a novel method of forming the phase diffractive optical elements (DOEs) by direct laser writing in thin films of aluminum with the help of the circular laser writing system "CLWS-200S". The quality of the aluminum films were investigated depending on the parameters of magnetron sputtering process. Circular phase diffraction gratings of Al₂O₃ on the quartz substrate with a period of 4 μm and 50% duty cycle were fabricated for the desired wavelength of 532 nm. In the visible wavelength spectrum, Al₂O₃ has a refractive index of 1.8 which is higher than the refractive index of quartz 1.5 that provides a significant refractive index contrast. As a result, this fact reduces the requirement of high aspect ratio of the diffractive element structures in the Al₂O₃ film as compared to the structures in quartz by 20%. This method of phase diffraction optical elements forming substantially reduces the time, fabrication steps, costs of production and significantly improves the quality of the elements in comparison with traditional process.

High surface quality of the optical elements is one of the key factors enabling their effective application in high power laser systems. In our work, commercially polished undoped YAG crystals were etched using low energy oxygen plasma. Surface roughness and optical properties were investigated using two different etching depths. Obtained results demonstrate smoothing of initial crystal surface and 1-4 % decrease of transmittance within UV-VIS spectral range.

In this communication, we show preliminary results on transmissive TiO₂ wire-grid polarizers (WGP) operating in the deep ultraviolet (DUV) range. WGP are devices based on strips of materials with large values of the modulus of the dielectric constant along with high absorption in the operational range. The merit function Π is introduced as a new tool to find the optimum material for WGPs in a given spectral range. The experimental dielectric constant of TiO₂ thin films deposited by pulsed laser deposition are obtained through spectroscopic ellipsometry, and the Π function indicates that TiO₂ is the best candidate for WGP in the DUV range when it is compared with other oxides. Once the material selection for WGP is done, we present and compare two different design approaches for WGP: one using an effective medium theory for the periodic structure, and the second using finite-difference time-domain (FDTD) analysis. A prototype of WGP is fabricated by electron beam (e-beam) lithography followed by lift-off process; the topography of the sample is analyzed by AFM, and we found noticeable deviations in the grating from the designed values. In preliminary characterization work the effective dielectric constant in two perpendicular orientations is obtained by ellipsometry and the contrast is compared with the design.

Higher laser powers are pushing the limits of common coating materials in various applications, from frequency conversion processes to space based LIDAR systems. Towards further ultraviolet material optimizations, luminescence spectroscopy may be employed to identify responsible energy levels as possible precursors for laser induced damage. Hafnium dioxide and aluminum oxide deposited by reactive ion beam sputtering are considered in the present study as a basis. Selected characterization methods are employed to determine the optical properties of the single layers of about four quarter wave optical thicknesses at 1064 nm. The luminescence induced by 193 nm excimer irradiation with about 2 mJ pulsed energy at 200 Hz repetition rate was evaluated by fiber coupled spectrophotometry. Detected aluminum oxide emission bands describe band gap intermediate states representing structural imperfections. Hafnium dioxide exhibits luminescence around 2.8 eV of photon energy that can be attributed to atomic and molecular interstitial defects and oxygen vacancies. Process variations like the supply of oxygen by the primary source keep the luminescence characteristics of hafnium dioxide unaffected. Luminescence transformations resulted from simultaneous ion bombardment of the growing layers associated to increased degrees of micro crystallinity. Luminescence spectroscopy can be considered as a process optimization tool for dual ion beam sputtering towards for example enhanced laser induced damage thresholds.

In the current study triblock copolymers (Pluronics) consisting of central poly(propylene oxide) (PPO) block flanked by two poly(ethylene oxide) (PEO) chains are used as organic templates for generating mesoporosity in thin Nb₂O₅ films. In order to optimize the polymer framework within the Nb₂O₅ films, two copolymers with different chemical compositions and properties are used, namely Pluronic PE 6200 and PE 9400. The copolymers’ micelle formation is studied by Dynamic Light Scattering (DLS) measurements of the copolymer aqueous solutions at different temperatures and concentrations and by Transmission Electron Microscopy (TEM). Thin films of mesoporous Nb2O5 films are deposited by sol-gel and spin-coating methods and characterized by TEM, UV-VIS reflectance spectroscopy and non-linear fitting for optical properties determination. The porosity of the films is calculated using effective medium approach on the basis of dispersion curves of the calculated refractive indices. The development of porosity in the films is studied as a function of the duration of the annealing. Besides, the sensing properties of mesostructured films are tested with vapors of acetone as a probe molecule of VOC’s (Volatile Organic Compounds) by reflectance measurements prior to and after exposure to vapors. The films optical response is demonstrated and possible application as optical indicator for VOC’s is discussed.