In this letter, using mult-half-wave structure and some chosen films optimized method, the long-wave infrared (LWIR) narrow-band pass filter is investigated, meanwhile the opposite of the substrate coated with long-wavelength pass film. The transmittance of design spectrum is more than 80% at wavelength region of 8.05–8.35 \mu m, and the average transmittance is less than 0.5% at wavelength region of less than 7.95 and 8.45–14 \mu m. The filter is prepared by thermal evaporation method, and plasma-assisted deposition technology. The experiment result shows that the average transmittance is about 75% in the transmission wavelength range, and the average transmittance of cut-off band is about 0.3%. The results show that multi-half-wave structure and some chosen films optimized method for the preparation LWIR narrow-band pass filter are feasible. The film system is simplified and is convenient to prepare the film.

Aiming at the crosstalk problem caused by small spectral intervals between fluorescent reagents in fourplex fluorescence quantitative polymerase chain reaction (PCR) detection analysis system, we calculate and analyse the effect of cut-off steepness, central wavelength positioning, and bandwidth of filters on crosstalk. Design and prepare four sets of fluorescence excitation and emission filters with proper shape cut-off steepness (optical density (OD) from OD 0.3 to OD 6 is less than 8 nm) and bandwidth (9–11 nm). In fourplex PCR instrument, crosstalk coefficient in all four channels are less than 0.3%.

The preparation and characterization of in-plane polarized lead zirconate titanate (PZT) piezoelectric diaphragms for sensors and actuators applications are demonstrated in this letter. The single phase PZT films can be obtained on SiO2-passivated silicon substrates via sol-gel technique, in which PbTiO3 (PT) films are used as seed layers. Al reflective layer is deposited and patterned into concentric interdigitated top electrode by lithographic process, subsequently. The diaphragms are released using orientation-dependent wet etching (ODE) method. The size of the diaphragms is 5 mm in diameter and the outer interdigitated (IDT) electrode diameter (4.25 mm) is fixed at 85% of the diaphragm diameter. The three-dimensional (3D) profiles results indicate that the measured maximum central deflection at 15 V is approximately 9 \mu m. Sensing measurements show that the capacitance continually decreases with an increase of applied force, while the case of induced charge exhibits a reverse tendency.

A fiber-optic relative-humidity (RH) sensor composed of multilayer of porous dielectric films is proposed. The transducer deposited on fiber end-face is multilayer coating consisting of nano-porous TiO2 and SiO2 films, which forms a low-fineness Fabry-Perot (F-P) filter with one of minimum reflections at about 1 350-nm wavelength. The dielectric thin films realized by e-beam evaporation without ion-source assistance have columnar and porous structures, which exhibit sensitivity to RH change of environments. When the sensor is exposed to an environment of RH change from 10.9% to 92.8%, experimental results demonstrate 77.9-nm shift of characteristic wavelength.

For high precise laser systems like laser gyro, gravitational waves interferometers, the optical components which lie in the cavity or laser path need to control the total loss, scattering, reflection, absorption, and so on. Low loss high-reflection (HR) and antireflection (AR) coating mirrors are their key components and their aging optical properties are the most important performance parameters for long operating lifetime. Low loss AR coatings on quartz substrates for He-Ne laser are designed and manufactured by ion beam sputtering (IBS) technology. Ta2O5 and SiO2 are used as high and low refractive index materials and the obtained total optical loss of AR coating is less than 50 ppm. Aging optical properties of AR coatings are investigated as a function of time placed in the air. When the placed time exceeds 40 days, optical properties tend to be stabilization. The obtained results indicate that the prepared low loss AR coatings have good stability of optical properties and can be applied for high precise laser systems.

Design and preparation of multilayer optical coatings are investigated on laser crystal Nd:YVO4, YVO4, and frequency doubling crystal KTP substrate. Multilayer optical coatings are deposited on one surface of the crystals using the ion beam sputtering technique, and the other surface is coated with a single SiO2 as protective layer. For the YVO4 crystal after coating, the reflectivity at 1 064 and 532 nm are greater than 99.9% and 99.8%, respectively, and the transmissivity at 808 nm is greater than 91.5%. For the KTP crystal after coating, the reflectivity at 1 064 nm is greater than 99.95%, and the transmissivity at 532 nm is greater than 99.5%. After thermal annealing, the transmissivity can be improved. The obtained coated crystals can be used in high power solid-state lasers.

This is a difficult kind of beam splitter in a cemented cube. The specification is: under angle of incidence (AOI)=55o, the reflectivity at 905 nm is no less than 85%, and in the visible range the average transmittance is 40+(-)2%, and T+R>=90%. Because the AOI is 55o, it needs to use a metal coating material to make sure the film be designed. The film has some problems on durability, and its optical performance is very hard to be controlled. We get some experiments after changing its design including coating material and evaporation technique. Final results show that the beam splitter has good properties, and passed temperature, and environmental durability.

We discuss a merit function F as judgment of photo-thermal conversion efficiency instead of two independent parameters: solar absorptance \alpha and thermal emittance \varepsilon. The merit function F is developed using Essential Macleod software to optimize the photo-thermal conversion efficiency of solar selective coating. Bruggeman and Maxwell-Garnett models are used to calculate the dielectric function of composite cermet film. Mo, W, V, and Pd are used as metallic component as well as infrared (IR) reflector materials, and SiO2, Al2O3, AlN, and TiO2 are used for dielectric component or antireflection (AR) layer materials. The layer structure can be described as substrate (Sub)/IR reflector/ high-metal-volume fraction (HMVF)/low-metal-volume fraction (LMVF)/AR. Results show that Mo-Al2O3, Mo-AlN, W-SiO2, W-Al2O3, VSiO2, and V-Al2O3 double-cermet coatings have high conversion efficiency which is greater than 86%. The best among above is Mo-SiO2 with \alpha =0.94, \varepsilon =0.05 at 450 oC, f= 89.9%. Some selective coatings with different layer thicknesses have been successfully optimized for different solar irradiations (air mass (AM0), AM1.5D, and AM1.5G spectra) and different operating temperatures (300, 450, and 600 oC), respectively. However, the optical constants for calculation are from the software, most datum are measured for bulk materials. Therefore, results are more useful to indicate the trend than the exact values.

In this letter, the application of dry etching to prepare Black Silicon nanostructures on crystalline silicon thin films on glass is described. The utilized reactive ion etching with an inductively coupled plasma (ICP-RIE) of SF6 and O2 is discussed and a remarkable increase in light absorption of about 70% is demonstrated.

In this letter, a design with both metal nanoparticles and back diffraction gratings is put forward for enhancing the efficiency of thin film silicon solar cells. The coupling mechanism between the metal nanoparticles and silicon absorber layer, and that between the incident light and the modes of the silicon absorption layer through the grating layer are both analyzed. The interaction between the front metal nanoparticles and back gratings is analyzed, which substantially increases the light trapping by 58% compared to flat solar cell.

Light scattering properties of back grating structures that composed of one-dimensional ZnO gratings and a flat 300-nm Al reflectors are investigated. Results show that grating structures cause an 8% reduction of the total reflectivity, as grating periods increasing from 620 to 1 435 nm, both the diffuse reflectivity and the haze parameter enhance drastically between 400 and 1 000 nm, whereas the diffraction angle at normal incidence reduce greatly, which agree with the values calculated from grating equation. It is concluded that rear gratings have the potential of scattering a substantial amount of incident light to specific angles and enlarging the optical path.

A comprehensive material study of different transparent conductive oxides (TCOs) is presented. The layers are deposited by pulsed direct current (DC) magnetron sputtering in an inline sputtering system. Indium tin oxide (ITO) films are studied in detail. The optimum pressure of 0.33 Pa (15Ar:2O2) produces a 300-nm thin film with a specific resistivity \rho of 2.2 \times 10-6 m and a visual transmittance of 81%. Alternatively, ZnO:Al and ZnO:Ga layers with thicknesses of 200 and 250 nm are deposited with a minimum resistivity of 5.5 \times 10-6 and 6.8 \times 10-6 m, respectively. To compare the optical properties in the ultraviolet (UV) range, the optical spectra are modeled and the band gap is determined.

Fabrication of Ag or Au nanocolumns by oblique angle deposition (OAD) is now prevalent for their surface enhanced Raman scattering (SERS) property and their biosensor application. However, the size, shape, and the density of nanocolumns are not directed in a desired way. To sufficiently realize the growth process controlled by multiple physical factors like deposition angle (\alpha), substrate temperature (T), and deposition rate (F), we develop a three-dimensional (3D) kinetic Monte Carlo (KMC) model for simulating processes of Ag nanocolumnar growth by oblique angle deposition. The dependences of nanocolumnar morphologies on these factors are analyzed. The mimical results reach a reasonable agreement with the experimental morphologies generated by OAD.

During the last decade, striking improvements could be achieved for the precise control of deposition processes in optical coating technology. For example, as a consequence of enormous progresses in measurement and computer technology, direct optical monitoring in a broad spectral range can be considered as a common tool in many production environments nowadays. Besides the development of the corresponding hardware and measurement channels, advanced approaches for the evaluation of the acquired data and new multiple sensor monitoring strategies moved into the focus of modern research on the way towards deterministic deposition techniques. In this context, also innovative concepts for the simulation of deposition processes to forecast the result for a specified coating design and automatic online correction algorithms gained of importance to reduce the risk of failure in coating production. The present contribution will be dedicated to selected aspects in this field, especially addressing broad band optical monitoring systems. A short review on examples for existing hardware configurations and software tools will be presented illustrating the advantages of modern process control techniques. Novel approaches based on the modeling of thin film growth are discussed as an additional strategy to improve the predictability of coating processes.

A novel optimization procedure for optical precision sputter coaters with respect to the film homogeneity is demonstrated. For a coater concept based on dual cylindrical sputtering sources and a rotating turn-table as sample-holder, the inherent radial decay of the film thickness must be compensated by shaper elements. For that purpose, a simulation model of the particle flux within such a coater is set up and validated against experimental data. Subsequently, the shaper design is optimized according to the modeled metal flux profile. The resulting film thickness deviations are minimized down to ±0.35%.

Trimethylamine (TMA), TiCl4, and water are applied as the precursors to deposit Al2O3 and TiO2. With different substrate temperatures, the optical properties and surface morphologies of the two oxides TiO2 and SiO2 are studied, respectively. With substrate temperature of 120 oC, amorphous TiO2 can be obtained, and the surface roughness (RMS) is only 0.928 nm. Applying Al2O3 and TiO2 deposited in 120 oC as low and high refractive index materials, anti-reflection (AR) coating at single point (550 nm) is designed. Furthermore, with the calibrated growth rates, this AR coating is fabricated, and its ultimate reflectance for the AR coating at 550 nm is less than 0.2%, which can meet the requirement for most applications.

We demonstrate that ultra-thin porous alumina membrane (PAM) is suitable for controlling of both size and site of Ge nanodots on Si substrates. Ge nanodots are grown on Si substrates with PAM as a template at different temperatures with molecular beam epitaxy (MBE) method. Ordered Ge nanodot arrays with uniform size and high density are obtained at 400 and 500 oC. Spatial frequency spectrums transformed from scanning electron microscopy images through fast Fourier transform are utilized to analyze surface morphologies of Ge nanodots. The long-range well-ordered Ge nanodot arrays form a duplication of PAM at 400 oC while the hexagonal packed Ge nanodot arrays are complementary with PAM at 500 oC.

This contribution presents a magnetron sputter deposition tool with broadband optical monitor and online re-optimization capability for high volume production. The layer termination relies on a comparison of the actually measured reflection spectrum with a pre-calculated target spectrum. Spectra recorded after each deposited layer are analyzed by the re-optimization module and–in case of significant deviations–layer thicknesses and target spectra for the remaining layers are recalculated. This technique significantly improves the performance and reproducibility in case of highly demanding coating designs and is able to correct abnormal production errors in individual layers, which will lead to coating failure without reoptimization.

High sophisticated optical monitoring systems like the OMS 5000 from Leyboldoptics are commonly used in vacuum coating system to improve the capabilities and reliability of production processes concerning optical performance and repeatability optics. This letter describes a method to perform high end optical filters with additional backside blocking over a wide spectral range. The direct monitoring with intermittent measurement on a large area rotating substrate holder is used to facilitate a narrow band pass filter of 2-nm half bandwidth at 532 nm and high transmittance together with a complex blocking filter to retard disturbing radiation from the ultraviolet (UV) range to the near infrared range. The machine is an ARES 1 350 coating system with basically standard configuration.

This letter describes a method for modelling film thickness variation across the deposition area within plasma enhanced chemical vapour deposition (PECVD) processes. The model enables identification and optimization of film thickness uniformity. Comparison between theory and experiment is provided for PECVD of diamond-like-carbon (DLC) deposition onto flat and curved substrate geometries. Results show DLC uniformity of 0.30% over a 200-mm flat zone diameter within overall electrode diameter of 300 mm. Use of the modelling method for PECVD using metal-organic chemical vapour deposition (MOCVD) feedstock is demonstrated, specifically for deposition of silica films using metal-organic tetraethoxy-silane.

Liquid metals-such as lead (Pb) or lead-bismuth (PbBi) are used as reactor core coolants for accelerator driven systems (ADS) proposed for high-level radioactive waste transmutation. Compatibility of steels with liquid PbBi is a key problem because steels are attacked by dissolution of the components in PbBi, so it has to form a stable coating on steel surface. There are many methods to prepare anti-corrosion coatings on steel, such as hot dipping, pack cementation, plasma spaying, and physical vapor deposition (PVD). Compared with other methods, the PVD method is easy to control the thickness of the coating and the obtained coatings are dense which is crucial to the anti-corrosion ability of the coatings. In this letter, PVD aluminum coatings are developed on the surface of T91 steel and different heat-treatment atmosphere is used to adjust the microstructure, aluminum content, and the phase of the coatings. It is found that the coatings have good adherence ability with steel. The aluminum content and the phase of the coating can be adjusted by the heat-treatment atmosphere. Corrosion tests are performed in oxygen-saturated liquid PbBi at 550 oC for 1 000 h, the phase and composition of the coating do not change drastically. All the results indicate that the PVD is a useful method to prepare coatings on the surface of steel used in liquid PbBi.

A sol-gel method for the preparation of silica coating that varied in refractive index is developed. Silicon dioxide sol is obtained by hydrolysis and co-condensation reactions occurred in acid-catalyzed system. Surface morphology, refractive index, and transmission spectrum of the samples are studied. The results of transmission spectra of single-sided coatings show that the average transmittance of the samples increases about 4% compared with the uncoated one in the spectra range from 400 to 1 200 nm in the case of vertical incidence. For the double-sided coating the maximum transmittance is 99% at the wavelength of 840 nm.

While infrared (IR) hard protective film of ZnS optical window is used in high temperature environment, its optical and mechanical stabilities are the premise of the IR optical system. IR hard protective film is deposited on ZnS optical windows by chemical vapor deposition (CVD), and ablation experiments are done to the maximum temperature the film can endure. The effects of ablation temperature on the optical and mechanical properties of the protective films are investigated by surface profiler, Fourier-transform infrared (FTIR) spectrometry, IR ellipsometer, and Metallographic microscope. It is shown that the optical and mechanical properties of ZnS hard protective film change little before 500 oC, and film refractive index and optical thickness reduce while ablation temperature surpassing 500 oC, forming crater-like ablation structure, which leads to the reduction of film combination significantly.

We report the simulation results on the thickness uniformity of optical coatings deposited on spherical substrates by optimizing the geometric configuration parameters, such as tilting angle of the substrate holder and position of the evaporation source in a 1 000-mm-diameter planetary rotation stage (PRS). We reveal that good film uniformity on convex spherical surfaces or flat substrates, as well as concave surfaces with weak to moderate curvatures can be obtained through appropriate tilting of the substrate holder. For 300-mm-diameter substrates with clear aperture to radius of curvature (CA/RoC) between -0.3 and 0.7, the achievable film uniformity is above 99%. The source position is optimized to achieve good film uniformity.

The service life of the large primary mirror with aluminum coating can be effectively prolonged by a protective layer. The SiOx (1<x<2) protective material which is thermally evaporated from up to bottom is studied. Environmental adaptability experiment, spectral measurement and micro-morphology analysis are executed on bare SiOx coatings within different oxygen concentrations, and the repeatability verification is implemented by testing the SiOx protected aluminum coatings. The results show that the SiOx coatings can meet the protective qualification within oxygen flow of 50 sccm (p=5.6 \times 10-3 Pa). The fine compactness of the coating has excellent moisture resistance with the average molecular spacing of 0.335 nm. In addition, the average reflectivity of the SiOx protected aluminum coating is 90.47% in the band 400 -2 500 nm and the coating is confirmed to have good environmental performance.

YbF3 is proposed as a substitute for ThF4 in anti-reflection or reflection coatings in the infrared (IR) range. In this letter, we study on the properties of the YbF3 thin film deposited with different deposition parameters, and find the deposition rate of YbF3 has a large effect on the substrate particles deposition both on number and area. Moreover, we find the deposition temperature is a main factor of element content. In the end, we produce an anti-reflection coating on Ge substrate, and its average transmission reaches 99.5%, which can satisfy the practical requirement.

Although they are common in nature and must certainly have been observed by early man, we have to wait till Newton for the first truly scientific study of what we now understand as interference effects in thin films. Young, Fresnel, and Maxwell all contributed and the theory was well established by the beginning of the 20th century. Coatings depending on interference, at this stage, were in their infancy and antireflection and decorative coatings, and color photography were the primary applications. By the middle of the 20th century, the situation had changed completely. Today almost the entire field of optics depends on interference optical coatings. This paper will start with a rapid account of the history and end with a survey of the range of interference coatings that are employed today with a fleeting glimpse of what might be in the future.

TiO2 chiral sculptured thin films (CSTFs) prepared using glancing angle deposition (GLAD) method based on electron beam evaporation are studied. The relationship between structural parameters and circular Bragg phenomenon (CBP) is investigated. Results demonstrate that, the central wavelength of Bragg regime red-shifts with the increasing pitch of helix, and peak value of selective transmittance will increase after adding more turns to the helix. After annealing, the central wavelength blue-shifts and the peak value rises. Tuning CBP by modulating the deposition parameters and annealing can optimize the performance of circularly polarized devices fabricated from CSTFs.

In this letter, we investigate the structural, optical, and electrical properties of Al-doped ZnO (AZO) thin film coating prepared by direct current (DC) facing-target sputtering method at room temperature, of which the average optical transmittance is 81% between 400 and 700 nm while the sheet resistance is about 10 \Omega/. Then, based on this AZO coating, in order to enhance the transmittance, interfacial adhesion strength and weathering resistance, two kinds of antireflective coatings are designed for different application purposes. For the two kinds, the highest transmittances in the visible region (400–700 nm) can reach 86.9% and 81.8%, respectively. The design is performed using Macleod Optical Design software.

The infrared emissivity of low emissivity coating can be significantly reduced by adding high content concentrations of parallel distributed metallic flake pigment. However, the infrared emissivity is very difficult to calculate by the existing theory models, such as the light scattering theory and traditional Kubelka-Munk radiative transfer model, because of shape and distribution anisotropy of flake pigments. Thus, the low emissivity coating is assumed to be the superposition structure of homogeneous layers and metallic flakes are approximately uniform and parallel arrangement in each layer. Based on geometric optics theory and Kubelka's layer model, considering multiple reflection, transmission and absorption of infrared radiation among different layers, the theoretical model is established to calculate the coating emissivity. The facts of binder, pigment concentration and thickness are also systematic discussed. The result shows that the law of influence on infrared emissivity can be correctly simulated by this theoretical model. Transparent binder, high volume concentration of thin flake pigment can facilitate to reduce infrared emissivity. Moreover, this model offers the possibility of predicting the infrared optical properties of coatings by their optical constants.

We engineer numerically a negative index material (NIM) based on a square ring pairs (SRP) array and a thin wire net pairs (WNP). This metamaterial exhibits polarization-independence and low loss that is characterized by a figure of merit (FOM) up to 8.2 in mid-infrared spectrum.

Device to read/write data from optical storage units have polarization insensitive character at two separated wavelength. Based on a key four-layer structure and some matching layers, an initial thin film stack system is constructed. After optimized alternately by simplex and conjugate graduate algorithm, a double-wavelength polarization insensitive beam splitter with splitting ratio of R : T=50:50 at 650-nm wavelength and T > 93% at 780-nm wavelength is gained. The design result shows that the difference between reflectivity of P and S light around wavelength range of 630–670 and 760–800 nm with incident angle of 40o–50o is all very little. That indicates our design controls the polarization deviation well at two separate wavelengths with a reasonable range for both wavelength and incident angle.

We use complementary analysis techniques to determine the structure of nanometric periodic multilayers and particularly their interfaces. We focus on Co-based multilayer which can be used as efficient optical component in the extreme ultraviolet (EUV) range. The samples are characterized using reflectivity measurements in order to determine the thickness and roughness of the various layers, X-ray emission and nuclear magnetic resonance (NMR) spectroscopies to identify the chemical state of the atoms present within the stack and know if they interdiffuse. Results are validated through the use of destructive techniques such as transmission electron microscopy or secondary ion mass spectrometry.

It is well known that the optical property of an optical thin film can be influenced by even small inhomogeneity of refractive index (RI). In order to investigate the RI inhomogeneity of LaF3 single layer in deep ultraviolet (DUV) range, single-layer LaF3 samples deposited on fused silica and CaF2 substrates are prepared by resistive heating evaporation at different deposition temperatures. The reflectance and transmittance spectra of LaF3 film samples are measured with a spectrophotometer, and used to calculate the RI inhomogeneity. The experimental results show that no RI inhomogeneity of LaF3 film is observed when deposited on CaF2 substrate, while negative RI inhomogeneity is presented when deposited on fused silica substrate. The level of inhomogeneity is affected by the substrate temperature, which decreases with the increasing substrate temperature from 250 to 400 oC.

We report on the optical performance, structure and thermal stability of periodic multilayer films containing Zr and Al(1wt.-%Si) or Al(pure) layers designed for the use as extreme ultraviolet (EUV) high reflective mirrors in the range of 17–19 nm. The comparison of Al/Zr (Al(1wt.-%Si)/Zr and Al(pure)/Zr) multilayers fabricated by direct–current magnetron sputtering shows that the optical and structural performances of two systems have much difference because of Si doped in Al. From the results of grazing incidence X-ray reflection (GIXR), X-ray diffraction (XRD), and EUV, the Si can disfavor the crystallization of Al and smooth the interface, consequently increase the reflectance of EUV in the Al(1wt.-%Si)/Zr systems. For the thermal stability of two systems, the first significant structural changes appear at 250 oC. The interlayers are transformed from symmetrical to asymmetrical, where the Zr-on-Al interlayers are thicker than Al-on-Zr interlayers. At 295 oC for Al(pure)/Zr and 298 oC for Al(1wt.-%Si)/Zr, the interfaces consist of amorphous Al-Zr alloy transform to polycrystalline Al-Zr alloy which can decrease the surface roughness and smooth the interfaces. Above 300 oC, the interdiffusion becomes larger, which can enlarge the differences between Zr-on-Al and Al-on-Zr interlayers. Based on the analyses, the Si doped in Al cannot only influence the optical and structural performances of Al/Zr systems, but also impact the reaction temperatures in the annealing process.

We use interface engineering technology to obtain high interface quality of extreme ultraviolet (EUV) multilayer. By inserting ultrathin (<0.5 nm) B4C layer between Mo and Si layers in Mo/Si multilayer, the interdiffusion in the multilayer is decreased obviously and the reflectivity can be estimated to increase by 2%. By inserting a new inert material barrer between Mo and Si layers, the thermal stability of new forming Mo/X/Si/X multilayer is increased significantly. The multilayer is annealed at 500 oC for 100 h with the fluctuation of period thickness smaller than 0.1 nm, and the high resolution transmission electron microscopy image also shows that the mirostructure of the multilayer is not changed obviously.

Random thickness error is an important factor which effects the calibration accuracies of deposition rates for extreme ultraviolet (EUV) multilayer coatings fabricated by sputter deposition techniques. A least square fitting method is proposed to determine deposition rates and extract random thickness errors accurately. The validity of this method is shown by evaluating two deposition systems with control abilities of ~0.1 nm and better than 0.01 nm respectively.

The multilayer (ML) mirror with high-reflectivity (HR) at a specific emission line of 19.5 nm (Fe line) and low-reflectivity (LR) at 30.4 nm (He line) is needed to be designed and fabricated for observing the image of sun. Based on a variety of optimizations utilized different structures, the design is performed and the final results demonstrate that the reflectivity at 30.4 nm does not achieve minimum value when the reflectivity at 19.5 nm reaches the maximum value. The tradeoff should be done between the HR at 19.5 nm and LR at 30.4 nm. One optimized mirror is fabricated by direct current magnetron sputtering and characterized by grazing-incident X-ray diffraction (XRD) and synchrotron radiation (SR). The experimental results demonstrate that the ML achieves the reflectivity of 33.3% at 19.5 nm and of 9.6 \times 10-4 at 30.4 nm at the incident angle of 13.

An approach for determining the optical constants of the weakly absorbing substrate is developed and applied to obtain the parameters of CaF2 and fused silica substrates in deep ultraviolet (DUV) and vacuum ultraviolet (VUV) range. A method for extracting the optical constants of thin films deposited on strongly absorbing substrate, which is based on the reflectance spectra measured at different angles of incidence, is also presented. The optical constants are determined by fitting the measured spectra to the theoretical models. The proposed method is applied to determine the refractive index and extinction coefficient (n, k) of MgF2 film deposited on silicon substrate by electron beam evaporation with substrate temperature 300 oC and deposition rate 0.2 nm/s. The determined n, k values at 193 nm are 1.433 and 9.1 \times 10-4, respectively.

Residual stress, which can be inevitably introduced during the optical films deposition process, must be controlled in many applications since the surface deformation is caused. The residual stress is traditionally controlled by adjusting the process parameters. However, the process parameters are determined by other more desired properties in many fields. In these cases, layer structure is the only variable to change the residual stress status of the components. Ta2O5/SiO2 is most commonly used material pair in visible/near infrared (VIS/NIR) region. In this letter, stress behaviors of Ta2O5 and SiO2 single layers deposited by ion-assisted deposition (IAD) are studied. Stress-thickness linear correlation curves of the two materials are obtained, which agree with the commonly reported linear results. Based on these features, a kind of antireflection (AR) coating acted as back side coating is designed to control the residual stress of components by the layer structure designing. A series of AR coatings at 1 319 nm are designed, according to residual stress status desired to introduce.

Laser induced damage threshold (LIDT) testing is the effective methods to research the lifetime of optical elements. According to ISO 11254 standards, a LIDT testing system of ArF excimer laser is established. The laser beam size on the sample surface can be varied from 0.3 to 0.6 mm in diameter. The maximum laser energy density is larger than 4.5 J/cm2. Besides the Nomarski microscope, He-Ne scattering is used and demonstrated as an effective and reliable method for the on-line monitoring of laser damage. The uncertainty of LIDT results and the main effecting factors are analyzed. The laser induced damage of fused silica substrates with different absorptions and CaF2 substrates with different absorptions are investigated in 1-on-1 mode, respectively. The roles of absorption on the LIDT results of the two kind substrates are discussed.

The possible role of metal clusters and electronic defects in the near-ultraviolet, nanosecond-pulse–laser damage in HfO2/SiO2-pair-based coatings is analyzed using experimental results on absorption and damage in HfO2 monolayers with and without artificially introduced Hf nanoscale absorbers. These studies reveal a damage mechanism specific to HfO2/SiO2 pair combination comprised of a high-melting-point material (HfO2), where absorption starts, and a lower-melting-point material (SiO2), where absorption can be initiated upon reaching the critical temperature. Based on this analysis we discuss possible modifications to coating designs and desirable properties of high- and low-index materials that might lead to improve nanosecond, near-ultraviolet laser-damage performance.

Thin films used for optical components require improvements in their mechanical properties and long-term stability. We examine the influence of substrate weathering on optical thin films. The light scattering of TiO2 thin films increased as the substrate is weathered. The light scattering of the TiO2 thin film formed by ion-assisted deposition (IAD) is smaller than that of the TiO2 thin film formed by electron beam deposition (EBD).

A scanning white-light interferometer is built for precisely measuring phase properties of dispersive multilayer thin film structure with the aid of the commercial spectrometer. Combining seeking optimal function for interferogram maximas with wavelet denoising algorithm, a novel time-domain algorithm is presented which enables the direct extraction of group delay and thus obtains a remarkable decrease of noise level in group delay and group delay dispersion. The apparatus shows reasonable potential for multilayer measurement, material characterization, displacement measurement as well as profilometry.

Optical thin films are used in many optical elements; however, light scattering can be problematic. We investigate the effect of substrate surface roughness on the light scattering of optical thin films. The substrates are classified according to their surface roughness, from fine to very rough, and coated with a single TiO2 layer or a SiO2/TiO2 multilayer. The light scattering intensity increases as the substrate roughness increases. Scanning electron microscopy reveals that the number of nodules formed in the optical thin films increases with the substrate roughness, which affects the light scattering properties.

The metal aluminum (Al) is widely used because it has high reflectivity from the ultraviolet to the infrared band. But the new deposited Al films is exposed to the atmosphere, it forms transparent Al2O3 films on its surface at once. In this letter, the Al films is deposited on the quartz substrate by electron beam evaporation. The effect of Al films oxidation on refractive index and extinction coefficient is investigated by spectroscopic ellipsometry (SE). The optical constants of Al films change with the increase of oxidation time. The two parameters become stable when these films are exposed in air more than 2 days.

SiO2 films are deposited on Si substrates by an ion beam sputtering technique and continuously annealed in a quartz culture dish in air at various annealing temperature ranging from 20 to 750 oC with a step of 100 oC for a fixed time of 24 h. The effects of thermal treatment on optical anisotropy properties of SiO2 films are investigated by spectroscopic ellipsometry. When the annealing temperature is 550 oC, the optical anisotropy properties of SiO2 film is minimum. The obtained results indicate that the optical anisotropy properties of SiO2 films can be improved by a proper thermal annealing process.

Based on the photothermal detuning technique, the three linear relations among reflectance (or transmittance), temperature rise, and pump beam power are studied to achieve the absolute measurement of absorption loss. The relation between temperature and reflectance and the calculation accuracy of temperature rise on sample surface have great impacts on the measured result. The influences of parameters involved in the method and the relation between temperature and reflectance and the temperature model of sample surface are also studied. The results show that the absolute absorption loss of optical coatings can be achieved by the proposed method. The measurement accuracy depends on the temperature model and the relation between temperature and reflectance. The linear relation between reflectance and temperature rise has largest slope when probe beam wavelength is 632.8 nm and incident angle is 28o. The linear relation slope between temperature rise and pump beam power decreases with the growing of beam size and modulation frequency. The results provide theoretical and experimental supports for the perfection and further application of the photothermal detuning technique.

Germanium (Ge) films are prepared on BK7 glass and multispectral zinc sulfide (m-ZnS) substrates by ion beam assisted deposition (IBAD). The effects of substrate temperature, deposition rate, and ion energy on the microstructure and optical properties of the films are investigated. It can be concluded that Ge film deposited with higher rate or ion energy has more optical absorption, while ion energy below 150 eV helps to reduce film absorption. Film refractive index increases with film deposition rate and bombardment ion energy while it is below 300 eV. And higher growth rate or bombardment ion energy can weaken film diffraction intensity.