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This paper summarizes our results and findings made throughout the past years on the way towards a one millimeter thin, flexible, and scalable foil camera. The sensor part of the camera consists of multiple thin-film luminescent concentrator (LC) layers, each of which is sensitive to a different band of the light spectrum. A special optical micro-structure cut into the edges of the LC layers multiplexes the transported light signal into a variant of the Radon transform of the image focused on the LC surface. For increasing the camera’s depth of field beyond the sensor surface, various thin-film imaging layers, such as optical Söller collimators realized by means of X-ray lithography on a PMMA wafer, have been investigated. The flexibility and scalability of our thin-film camera has the potential to lead to new human–computer interfaces that are unconstrained in shape and sensing-distance. Applications such as contact-less sensing, smart skin sensors for autonomous robots and industrial machines, and environment sensing for vehicles are imaginable.

We demonstrate a concept and fabrication of lithography-free layered metal-SiO2 thin-film structures which have reduced reflectivity (black appearance), to as low as 0.9%, with 4.9% broadband reflectance (8.9% for soda lime) in the 500&ndash, 1400 nm range. The multi-layered (four layers) thin-film metamaterial is designed so that optical impedance matching produces minimal reflectance and transmittance within the visible and infra-red (IR) spectral region for a range of incident angles. The structure has enhanced absorbance and is easily tuned for reduced minimal transmission and reflection. This approach should allow for novel anti-reflection surfaces by impedance matching to be realized.

Thin film optics, based on light interference characteristics, are attracting increasing interest because of their ability to enable a functional color coating for various applications in optical, electronic, and solar industries. Here, we report on the dependence of coloring characteristics on single-layer TiO2 thicknesses and alternating TiO2/Al2O3 multilayer structures prepared by atomic layer deposition (ALD) at a low growth temperature. The ALD TiO2 and Al2O3 thin films were studied at a low growth temperature of 80°C. Then, the coloring features in the single-layer TiO2 and alternating TiO2/Al2O3 multilayers using both the ALD processes were experimentally examined on a TiN/cut stainless steel sheet. The Essential Macleod software was used to estimate and compare the color coating results. The simulation results revealed that five different colors of the single TiO2 layers were shown experimentally, depending on the film thickness. For the purpose of highly uniform pink color coating, the film structures of TiO2/Al2O3 multilayers were designed in advance. It was experimentally demonstrated that the evaluated colors corresponded well with the simulated color spectrum results, exhibiting a uniform pink color with wide incident angles ranging from 0° to 75°. This article advances practical applications requiring highly uniform color coatings of surfaces in a variety of optical coating areas with complex topographical structures.

To date, there is no ideal anti-reflection (AR) coating available on solar glass which can effectively transmit the incident light within the visible wavelength range. However, there is a need to develop multifunctional coating with superior anti-reflection properties and self-cleaning ability meant to be used for solar glass panels. In spite of self-cleaning ability of materials like TiO2 and ZnO, these coatings on glass substrate have tendency to reduce light transmission due to their high refractive indices than glass. Thus, to infuse the anti-reflective property, a low refractive index, SiO2 layer needs to be used in conjunction with TiO2 and ZnO layers. In such case, the optimization of individual layer thickness is crucial to achieve maximum transmittance of the visible light. In the present study, we propose an omni-directional anti-reflection coating design for the visible spectral wavelength range of 400–700 nm, where the maximum intensity of light is converted into electrical energy. Herein, we employ the quarter wavelength criteria using SiO2, TiO2 and ZnO to design the coating composed of single, double and triple layers. The thickness of individual layers was optimized for maximum light transmittance using essential Mcleod simulation software to produce destructive interference between reflected waves and constructive interference between transmitted waves.

We prepare photonic crystal (PC) films both on rigid silicon (Si) and flexible plastic substrates by a vacuum coating method. The PC films are designed for far-infrared and laser-compatible camouflage, and we calculate their reflectance spectra by means of the characteristic matrix method using thin film optics theory. The reflectance of the 8–12 μm band and the defect locations are affected slightly, but the far-infrared and laser-compatible camouflage are still excellent. Also we prepare the PC films on polystyrene and polyethylene terephthalates (PET), which exhibit outstanding flexibility and remarkable optical properties with a reflectance of >0.95 in the far-infrared and ∼0.08 at the defect wavelength. These results provide new materials to fabricate PC films for far-infrared and laser-band applications with high flexibility and excellent camouflage compatibility.

Holography can offer unique solutions to the specific problems faced by automotive optical systems. Frequently, when possibilities have been exhausted using refractive and refractive designs, diffraction can come to the rescue by opening a new dimension to explore. Holographic optical elements (HOEs), for example, are thin film optics that can advantageously replace lenses, prisms, or mirrors. Head up display (HUD) and LIDAR for autonomous vehicles are two of the systems where our group have used HOEs to provide original answers to the limitations of classical optic. With HUD, HOEs address the problems of the limited field of view, and small eye box usually found in projection systems. Our approach is to recycle the light multiple times inside a waveguide so the combiner can be as large as the entire windshield. In this system, a hologram is used to inject a small image at one end of a waveguide, and another hologram is used to extract the image several times, providing an expanded eye box. In the case of LIDAR systems, non-mechanical beam scanning based on diffractive spatial light modulator (SLM), are only able to achieve an angular range of few degrees. We used multiplexed volume holograms (VH) to amplify the initial diffraction angle from the SLM to achieve up to 4π steradian coverage in a compact form factor.

With the increment of awareness of health, people now pay more and more attention to the safety of sunscreen products. Inorganic sunscreen agents, such as nano- TiO 2 , nano- SiO 2 , nano- ZnO , and nano- Al 2 O 3 are very popular among consumers for their advantages, such as the nontoxic, the odorless, not easy to decompose, not easy to undergo metamorphism, and a good ability of resisting. Based on the theory of thin film optics, two kinds of nano-films are researched and designed on the basis of the structure of photonic crystal in this paper. We conduct the simulation calculation to the transmittance of the films in the ultraviolet region with the finite-difference time-domain (FDTD) method and theoretically validate that these films can keep the ultraviolet radiation off well. Besides, the superposition of two film stacks effectively expands the width of the forbidden band against ultraviolet light. This provides a theoretical basis for the inorganic sunscreen agents applied to umbrellas coating, sunscreen coating, and anti-UV fabric and so on.

This thesis is about the multicolored gradients seen when using certain dichroic color lters with artificial light. As of now, this phenomenon lacks a unambiguous descriptor, and “Goniochromatic Gradient” is proposed. With help of optical physics, the science of color vision and information about dichroic products, principles for the relationship between goniochromatic gradients and dichroic filters are formulated for anyone interested in exploring this visual phenomenon.

Localized rapid heating process utilizing carbide-bonded graphene-coated silicon molds is a high-efficiency and energy-saving technique for high-volume fabrication of polymer optics. The graphene coating is used as a rapid heating element because of its high thermal conductivity and low electrical resistivity. However, the optical property of molded polymer and its dependence on process conditions such as heat transfer have not been thoroughly investigated. In this research, finite element method (FEM) simulation was utilized to interpret temperature changes of the graphene coating and heat transfer between graphene and polymethylmethacrylate (PMMA) in localized rapid heating. Experiments were then carried out under different voltages to validate the numerical model. In addition, refractive index variation of the PMMA lens resulting from nonuniform thermal history in molding was demonstrated by simulation modeling as well. Finally, wavefront variation of a PMMA lens molded by localized rapid heating was first studied using an FEM model and then verified by optical measurements with a Shack–Hartmann wavefront sensor (SHWFS). The wavefront variation in a PMMA lens molded by conventional method was also measured. Compared with conventional molding process, localized rapid heating is shown to be a possible alternative for better optical performance with a much shorter cycle time.

Optical interference thin films designed and fabricated for use in a Cassegrain telescope were deposited by ion-beam-assisted deposition. The optical parameters of optical interference filters array and the protection layers of silver reflector were simulated and optimized by using admittance loci analysis. The patterned multispectral assembly containing blue, green, red, near infrared, and panchromatic multilayer high/low alternated dielectric band-pass filter arrays in a single chip was fabricated by photolithography process. The corresponding properties of the films were measured by in situ optical monitor and spectrometry. It was found that the average transmittances were above 90% for the multispectral assembly, with a rejection transmittance of less than 1% in the spectral range of 350–1100 nm. The average reflectance of the large area silver mirror (with three layers protective interference coating) is boosted above 99% in visible spectrum. In addition, the equivalent admittance of the three protection layer has been derived.

A simulation of room temperature spectral emissivity of an industry standard VOx-based microbolometer structure, with x equal to 1·8, is presented in this study. The simulation is based on Multi-Rad, a package that implements thin film optics in the form of matrix method of multilayers and assumes the layers to be optically smooth, parallel to each other and optically isotropic. The simulated results are shown to be in good accord with the available experimental data in the literature. The calculations show that bare VOx, that is VO2, V2O3 and V2O5, with different thicknesses, exhibits wavelength-dependent emissivity that scales almost linearly with thickness. In the wavelength range of 8–14 µm, the spectral emissivity of bare VOx, consisting of the stacked layers of the thin films of VO2, V2O3 and V2O5, of total thickness of 500 Å, behaves as a mixed system. The Si3N4 overlayer does not change the spectral emissivity of Al/Si while it decreases the spectral emissivity of the VOx/Si3N4/Air/Al/Si system. Calculations show that the Si3N4 layer provides the much-desired linear performance of the VOx-based microbolometer.

Structural effects contribute to the coloration of many animals. Whereas extremely complex structures have evolved, often coloration is due to the most simple structure, namely a thin film. Here we present a number of examples where thin film optics plays a prominent role, namely in insect wings and bird feathers. Most butterfly wing scales have a lower lamina that prominently determines the color. Damselfly wings with protrusions have reduced thin film reflections. A limited stack of multilayers features also distinct thin film properties, as is shown for feather barbules of the bird of paradise, Lawes’ parotia. A simple method to derive the thickness of the wing structures is described.

Large aperture thin film optics typically have substantial shape errors which are difficult to quantify with conventional measurement methods, such as interferometry. The interferograms are normally too complex and contain too much information to discern relevant shape information pertinent to (for example) solar energy collection. This has led to the development of the laboratory-oriented, less expensive and less complex measurement procedure presented here. The method is based on well-defined geometric relationships and provides a novel approach to measuring the shape of large optics that are known to have substantial surface distortion. Once the local reflection (surface tilt) angles are determined, the overall shape can be reconstructed and further analyzed using ray tracing software to obtain aberration coefficients if desired. This technique lends itself to being easily scalable to very large membrane structures and the measurement precision is only limited by the equipment chosen.

In search of next-generation solar cells, silicon nanowire arrays have attracted great attention since they are cost-effective and may absorb more light compared to current thin-film silicon solar cells. Theoretical studies using finite-difference time-domain and transfer matrix methods have been performed to investigate the optical properties of silicon nanowire (SiNW) arrays. However, these methods are computationally intensive and require periodic conditions, which may not be satisfied with most fabricated samples. In the present study, an effective medium analysis considering the anisotropic nature of vertically aligned SiNWs is performed to study their optical properties in the wavelength range from 310 nm to 1100 nm, which is of the most importance for solar photovoltaic cells. The effective dielectric functions of the SiNW layer for both ordinary and extraordinary waves are obtained from the Bruggeman approximation. Thin-film optics formulae incorporating the anisotropic wave propagation in uniaxial media are employed to calculate the reflectance and absorptance of the SiNWs on silicon substrates for different polarizations. The effect of geometric parameters such as filling ratio and wire length is investigated. In addition to modeling the directional radiative properties at various angles of incidence, the hemispherical properties are also calculated to understand the light absorption and to facilitate the optimal design of high-performance SiNW solar cells.

The paper presents investigations of the optical properties of thin high-refractive-index silicon nitride (SiN x ) and diamond-like carbon (DLC) films deposited by the radio-frequency plasma-enhanced chemical vapor deposition method for applications in tuning the functional properties of optical devices working in the infrared spectral range, e.g., optical sensors, filters or resonators. The deposition technique offers the ability to control the film's optical properties and thickness on the nanometer scale. We obtained thin, high-refractive-index films of both types at deposition temperatures below 350 °C, which is acceptable under the thermal budget of most optical devices. In the case of SiN x films, it was found that for short deposition processes (up to 5 min long) the refractive index of the film increases in parallel with its thickness (up to 50 nm), while for longer processes the refractive index becomes almost constant. For DLC films, the effect of refractive index increase was observed up to 220 nm in film thickness.

Initiated by the analysis of phase relationship and by use of the films’ characteristic matrix expression, we deduced two implicit function expressions of the spacer’ moderate refractive index as well as P-polarization and S-polarization’ central wavelengths. From this, the value of moderate refractive index and corresponding central wavelength can be quickly and accurately obtained. Simulation calculations of two concrete filter designs for single cavity and three cavities prove that the method is feasible.We also proves that the algorithm is highly accurate though the examples data analysis of difference curves with incidence angle from 0° to 30°.

We are investigating differential deposition as a way of correcting small figure errors inside full-shell grazing-incidence x-ray optics. The optics in our study are fabricated using the electroformed-nickel-replication technique, and the figure errors arise from fabrication errors in the mandrel, from which the shells are replicated, as well as errors induced during the electroforming process. Combined, these give sub-micron-scale figure deviations which limit the angular resolution of the optics to approx. 10 arcsec. Sub-micron figure errors can be corrected by selectively depositing (physical vapor deposition) material inside the shell. The requirements for this filler material are that it must not degrade the ultra-smooth surface finish necessary for efficient x-ray reflection (approx. 5 A rms), and must not be highly stressed. In addition, a technique must be found to produce well controlled and defined beams within highly constrained geometries, as some of our mirror shells are less than 3 cm in diameter.

An interferometric technique for measuring the spectral dependence of the refractive index of solid-state materials to an accuracy of 10−5 over the entire transparency region is described. The possibilities of the technique are demonstrated by the example of new phosphate glasses formulated for laser and fiber optics. It is shown that, in the presence of absorption bands in the transmission spectrum, the technique allows their associated jumps in the refractive index values to be recorded on the order of 10−4−10−5 and below. The shift in the spectral dependence of the refractive index in the region of the absorption band with intensity at 1.7 cm−1 is measured for the first time.

The present article conducts extensive numerical simulations to investigate conduction and radiation heat transfer characteristics in thin silicon layers irradiated by pulsed lasers. The two temperature model is used for estimating carrier and lattice temperatures during laser irradiation. The energy absorption in thin films is predicted by the electromagnetic theory, including wave interference effects through thin film optics. The present study predicts the carrier and lattice temperatures during laser irradiation and examines the influence of film thickness and laser pulse duration on characteristics of energy transport. It is observed that, unlike bulk materials, the variation of the film thickness causes significant changes in the reflectivity of silicon film due to wave interference effects in thin film structures. The maximum value of the reflectivity is estimated to be about seven times larger than the minimum value. For the spatial distributions of carrier and lattice temperatures, it is found that a periodic tendency appears for picosecond pulse because of the difference between the pulse duration and the time for energy diffusion. It indicates that the traditional usage of Beer’s law is not appropriate for prediction of radiation heat transfer in thin film structures.

The optics of thin film multilayers plays an important role in many modern technologies. The design and optimization of these systems requires an understanding of how light interacts with stratified structures involving sub-wavelength dimensions. Two well established methods are presented for calculating the linear, first order optical and magneto-optical effects of multilayers, given the refractive indices and magneto-optical Voigt parameters for the layers comprising the stack. The first method is a re-iterative approach and is relatively simple to implement. The second is a matrix method that has more general application.

Optical monitoring plays an important role in film deposition. In this study, an optical monitoring method which can work out the refractive index of material in real-time improves the quality of narrow-band pass filter effectively.

In optics, artificially structured nanomaterials act as effective media whose complex refractive index may be ad-hoc designed for applications in multilayer coatings. © 2016 SPIE.

The self-mixing interference in distributed feedback laser diode (DFB-LD) with multiple external cavities is analyzed. Each external cavity is considered to be an optical thin film, and the equivalent reflectivity can be got from the theory of the thin film optics, the general expressions of gain and frequency in compound laser cavity are theoretically deduced. This principle is helpful to build the fiber-coupled self-mixing interference system. Considering that different parameters have influence on self-mixing interference, we make some simulation analysis at different conditions. The output of self-mixing interference is analyzed in numerical analysis, and the amplitude variations of the output gain is discussed along with different parameters, e.g., the coupling coefficient, the linewidth enhancement factor, and the reflection coefficient of external reflector.

Ray-tracing method (RTM) based on geometric optics is a convenient tool in radiative heat transfer by tracing the intensity during light scattering, absorption, and multiple reflections. Some recent studies employed a modified RTM to trace the field amplitude and phase during light scattering from rough surfaces. Because phase is included, this method will be called PRTM hereafter. PRTM works well for multiple reflections in thin films with smooth interfaces, but its applicability for prediction of radiative properties of rough surfaces has not been established. The present study compares both PRTM and RTM with Kirchhoff’s approach (KA) for one-dimensional rough surfaces. The elements of the Mueller matrix calculated from these methods are compared for both dielectric and highly reflecting surfaces. When the characteristic lengths of roughness are much greater than the wavelength, the three methods yield essentially the same results. For small characteristic lengths, PRTM predicts certain coherent peaks resulted from wave interferences. However, the predicted peaks by PRTM are always smaller than those by KA. In addition, PRTM fails to predict coherent peaks for some elements. Therefore, PRTM cannot accurately address the wave features of rough surfaces with small characteristic lengths, due to its inherent assumption of specular reflection at surface microfacets, adopted from geometric optics.

Many infrared (IR) transmitting materials are available for windows and lenses, this chapter discusses only window materials. Geometrical optics refers to the classical refraction and specular reflection. The reflectance and transmittance of a particular material at a given wavelength can often be determined from graphs. Optical interference effects are observed when radiation from one source is separated, travels through different paths, and then comes together again. Such a situation can be set up with gratings or reflecting layers. Diffraction of light provides the necessary situation. Analysis of any optical system and prediction of spot size should include a calculation of the diffraction limit. The chapter describes the features that are most important to detector and IR system personnel: ways to describe a lens, objects, and images, as well as stops and apertures.

We present new lenses – waveplate lenses created in liquid crystal materials. Waveplate lenses allowed focusing and defocusing laser beam depending on the sign of the circularity of laser beam polarization. Using an electrically-switchable liquid-crystal half-wave retarder we realized switching between focused and defocused beams by the waveplate lens. A combination of two such lenses allowed the collimation of a laser beam as well as the change of focal length of optical system. Lenses of varied size and focal length are presented.

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.

The separation between s- and p-polarization components invariably affects thin film edge filters used for tilted incidence and is a difficult problem for many applications, especially for optical communication. This paper presents a novel design method to obtain edge filters with non-polarization at incidence angle of 45°. The polarization separation at 50% transmittance for a long-wave-pass filter and a short-wave-pass filter is 0.3 nm and 0.1 nm respectively. The design method is based on a broadband Fabry-Perot thin-film interference filter in which the higher or lower interference band at both sides of the main transmittance peak can be used for initial design of long-wave-pass filter or short-wave-pass filter and then can be refined to reduce the transmittance ripples. The spacer 2H2L2H or 2L2H2L of the filter is usually taken. Moreover, the method for expanding the bandwidth of rejection and transmission is explained. The bandwidth of 200 nm for both rejection region and transmission band is obtained at wavelength 1550 nm. In this way, the long-wave-pass and short-wave-pass edge filters with zero separation between two polarization components can easily be fabricated.

Numerous effective medium models have been proposed for the effective optical properties of nanoporous media. However, validations of these models against experimental data are often contradictory and inconclusive. This issue was numerically investigated by solving the two-dimensional Maxwell's equations in non-absorbing nanoporous thin films with various morphologies. It was found that below a certain critical film thickness, the effective index of refraction depends on the porosity and on the pore size, shape and spatial distribution. For thick enough films the effective index of refraction depends solely on porosity and on the indices of refraction of the two constitutive phases. The numerical results agree very well with a recent model obtained by applying the Volume Averaging Theory to the Maxwell's equations. However, commonly used models systematically and sometimes significantly underpredict the numerical results.

Modeling of the bidirectional reflectance of thin-film coatings on rough surfaces has been an important and challenging problem. In the past, there have been studies that use thin-film optics to take account of the coating-induced interference effects and the geometric optics approximation to model the surface roughness. In an effort to delineate the validity regime of the hybrid method, the predicted bidirectional reflectance is compared with that obtained from the rigorous electromagnetic-wave solution for one-dimensional rough surfaces, considering the effect of coating thickness and roughness parameters. Two hybrid models are implemented using the Monte Carlo ray-tracing algorithm: the surface generation method and microfacet slope method. The former relies on statistically generated surfaces according to the root-mean-square roughness and the autocorrelation length, whereas the latter uses the microfacet whose orientation is stochastically determined, when a ray hits the surface, according to the slope distribution without creating deterministic rough surfaces a priori. The validity regimes of the hybrid models are established for silicon dioxide films on silicon substrates. The advantages and disadvantages of each hybrid model are discussed. Some useful guidelines are provided for the simulation of optical scattering from coated rough surfaces.

Optical thin films used at oblique incidence exhibit inevitable polarization dependent properties. In reflective projection display systems, Philips prisms with color splitting filters are widely used. Generally, illuminating light at different polarization components passes the color splitting filters twice in such Philips prism. Color splitting filters operate as color separation for s-polarization and as color recombination for p-polarization, and thus performances of the color splitting filters for s- and p-polarization are equally important. In order to reduce stray light, it is necessary to design non-polarizing thin film edge filters for color separation and recombination system in projectors. The novel design method is based on a broad-band Fabry–Perot interference filter in which both sides of transmittance band can be used as initial designs for long-wave-pass filter or short-wave-pass filters, and through suitable refinement to reduce the transmittance ripples, it is possible to achieve zero separation between two polarization components.

We describe a simple experiment which allows unequivocal determination of optical phase change upon reflection of light at the mica-silver interface. While the physical origin of such a phase change at the dielectric-metal interface is well understood to lie in absorption of electromagnetic energy by the metal, inconsistency and ambiguity has persisted as to what its sign and magnitude should be in the field of thin film optics. Most commonly, it has been assigned to be negative for mathematical convenience or just arbitrarily. Our finding shows that with the convention exp(-iωt) for time dependence of the electromagnetic wave, the phase change at the interface between mica and the thin silver film is necessarily positive and its magnitude falls between π and 3π/2 for silver thicknesses down to nanometres. This gives a physically reasonable correspondence to an increased equivalent thickness of the dielectric material, and it clarifies the assignment of interference orders in the harmonic series in a spectrum.

In this article, we present a new versatile method for calculating the interference colour of any configuration of thin, optically isotropic, dielectric films. This method is free from common weakness of previous methods, namely the poor accuracy for large angles of incidence of light. This method gives full control over the accuracy and speed of computations, and allows for adjustments of the parameters according to the physical and chemical properties of the film, in order to present the optimal results. We also present a formula to model the thickness of thin films made up of liquids, such as soap bubbles.

We exploited the insulator-to-metal phase transition of vanadium dioxide (VO2) to create tunable thin film optical components and metasurfaces in the mid-infrared spectral range. Thermally and electrically tunable modulators and thermal emitters are demonstrated.

The thermal conductivity of amorphous silicon thin films is determined by using the non-intrusive, in situ optical transmission measurement as well as by the 3ω method. The temperature dependence of the film complex refractive index is determined by spectroscopic ellipsometry. The acquired transmission signal is fitted with predictions obtained by coupling conductive heat transfer with multi-layer thin film optics in the optical transmission measurement. The results of the two independent methods are in close agreement.

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The performance of optical components is usually improved by optical coatings. Some of these optical components exhibit complex geometrical shapes and are therefore very difficult to coat in a homogeneous way. The spectral performance of the optical coatings on such substrates will vary as a function of its geometry making it very difficult to keep the spectral performance within customer specifications all over the substrate. Examples for optics with complex geometries are half sphere lenses, freeform surfaces, diffraction gratings, microlense arrays, large substrates etc. We developed a simulation tool that can calculate and optimize the spectral performance of a given multilayer stack on arbitrarily shaped optics as a function of the processing parameters of the coating plant. This tool will obviously reduce the risk and the development costs. The spectral performance of a multilayer stack is given in general by the coating design, that means by the individual layer thicknesses and the refractive indices of the different layer materials. On curved optics different coating materials exhibit different thickness and refractive index distributions. Consequently the optical layer stack will exhibit varying spectral performance at different positions on the substrate. Empirical models for thickness and refractive index distributions have been developed as a function of the most important processing parameters (e.g., deposition rate, deposition angle, ion impingement rate and temperature).

It is shown that omnidirectional reflection (ODR) is possible from quasi-periodic isotropic dielectric stacks following a Fibonacci sequence (FS). The transition from truly periodic to fully quasi-periodic structure is investigated by building periodic structures having unit cells made of FS of order j. The number of periods required to achieve ODR decreases as j increases until only a single period is required at which the structure is fully quasi-periodic. As compared to the periodic case, for the quasi-periodic structure the spectral range is wider, the thickness of the single layers is smaller and the tolerance on the layer thicknesses is smaller.

Plasma enhanced chemical vapor deposition(PECVD) is being increasingly used for the fabrication of transparent dielectric optical films and coatings. This involves single-layer, multilayer, graded index, and nanocomposite optical thin filmsystems for applications such as optical filters, antireflective coatings, optical waveguides, and others. Beside their basic optical properties (refractive index, extinction coefficient, optical loss), these systems very frequently offer other desirable “functional” characteristics. These include hardness, scratch, abrasion, and erosion resistance, improved adhesion to various technologically important substrate materials such as polymers, hydrophobicity or hydrophilicity, long-term chemical, thermal, and environmental stability, gas and vapor impermeability, and others. In the present article, we critically review the advances in the development of plasma processes and plasmasystems for the synthesis of thin film high and low index optical materials, and in the control of plasma–surface interactions leading to desired film microstructures. We particularly underline those specificities of PECVD, which distinguish it from other conventional techniques for producing optical films (mainly physical vapor deposition), such as fabrication of graded index (inhomogeneous) layers, control of interfaces, high deposition rate at low temperature, enhanced mechanical and other functional characteristics, and industrial scaleup. Advances in this field are illustrated by selected examples of PECVD of antireflective coatings, rugate filters, integrated optical devices, and others.

The transfer matrix method was used to calculate the transmission of electromagnetic waves through alternate layers of thin silver films separated by air. It was found that the plasma frequency is a clear divide between good and poor transmission. Equally the calculations show that for frequencies above the plasma frequency the transmission coefficient shows a Bragg-like behavior with oscillations that manifest coherent reflections on the entrance side of the layer at favored wavelengths.

Fabrication and characterization of a guided-mode resonance-based polarizer is presented. This polarizer is made by electron-beam patterning a single layer of amorphous silicon on a glass substrate. The fabricated device has high and low transmittance for transverse-electric and transverse-magnetic polarizations, respectively, over a ~ 40-nm wavelength range for normally incident light. Its experimental extinction ratio is ~ 97:1 at a central wavelength of 1510 nm.

A simple model to predict the effective properties of a porous, dielectric, thin-film helicoidal bianisotropic medium (TFHBM) is presented. A local permittivity dyadic is obtained, assuming that the TFHBM is made of electrically minute needles with a certain shape factor; and thus the TFHBM is locally homogenized into a nonhomogeneous continuum. The determination of the shape factor by comparison with measurements of the optical rotation spectrum is examined in detail, and relationships between structural and other variables are extracted from the predictions of the model. These preliminary results point out the need for more and careful optical experiments on TFHBM slabs to fabricate better theoretical models.

The change in the reflection (differential reflection) of light from an interference film as a result of the deposition of an ultrathin layer on it is investigated. Formulas describing the differential reflection around the reflectivity minima and maxima of the film are obtained by a perturbation method. It is shown that these formulas and the corresponding differential measurements can be used for an easy and unambiguous determination of the thickness and refractive index not only of ultrathin surface layers but also of the interference films themselves. The proposed method is especially convenient for monitoring the deposition of thin-film structures.

The radiative properties of patterned silicon wafers have a major impact on the two critical issues in rapid thermal processing (RTP), namely wafer temperature uniformity and wafer temperature measurement. The surface topography variation of the die area caused by patterning and the roughness of the wafer backside can have a significant effect on the radiative properties, but these effects are not well characterized. We report measurements of room temperature reflectance of a memory die, logic die, and various multilayered wafer backsides. The surface roughness of the die areas and wafer backsides is characterized using atomic force microscopy (AFM). These data are subsequently used to assess the effectiveness of thin film optics in providing approximations for the radiative properties of patterned wafers for RTP applications.

A general classification scheme for heterogeneous material concepts in thin film optics is proposed with respect to characteristic size of the inhomogeneity and pursued spectral range. As an example, a subwavelength structured notch filter design procedure is elaborated by combining theoretical tools from gradient index broadband antireflection coating design with resonant grating waveguide theory.

Three‐filter colorimetry has been introduced in the DIII–D tokamak to measure in situ the growth and the erosion of transparent wall coatings (a‐C/B:H) in the divertor region. Colorimetry uses the interference of light on a transparent layer to measure the film thickness. The colorimetry setup at DIII–D consists of a light source, a black and white camera, and a filter wheel equipped with three broadband color filters. A white light source illuminates the area of interest. A picture with each filter is recorded and digitized. Thus the interference color of a semitransparent layer is measured and the film thickness is computed using the formalism of thin film optics. Since color cameras are more sensitive to neutron damage, a set of three filters was chosen which best matches the responsivity of a radiation‐hardened B/W camera. In fact, one infrared filter and two visible filters are used. The three 2D camera images obtained from rotating the three filters into the line of sight of the camera are used to p...

Cascaded resonant grating filters are experimentally characterized. The levels to which cascaded resonant filters yield lowered sidebands and narrowed linewidths, as compared with individual filters, are measured. For example, four cascaded filters provide experimental sideband levels at -47 dB over a 50-nm wavelength range, a spectral linewidth of 0.43 nm, with an insertion loss of 3.7 dB.