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.

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.

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.

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.