Universal antireflection coatings for substrates for the visible spectral region

It is possible to design normal-incidence antireflection coatings that reduce the reflectance of any substrate with a refractive index that lies in the range of 1.48 to 1.75. The performance of such coatings depends on the width of the spectral region over which the reflectance is to be suppressed, on the coating materials used for their construction, and on the overall optical thickness of the layer system. For example, the calculated average spectral reflectance of a set of six different substrates with refractive indices 1.48, 1.55, 1.60, 1.65, 1.70, and 1.75, when coated with a 0.56-μm-thick, eight-layer antireflection coating designed for the 0.40-0.80-μm spectral region, was 0.34%. This is higher than the average reflectance that is attainable with a conventional antireflection coating of similar optical thicknesses designed for a particular refractive index. However, it is an acceptable value for most applications. With the universal type of antireflection coating described, it is thus possible to coat a number of different refractive-index substrates in one deposition run, and this can result in considerable cost and time savings.     

Infrared filters and coatings for the High Resolution Dynamics Limb Sounder (6-18 microm)

We describe the spectral design and manufacture of the narrow-bandpass filters and 6-18-mum broadband antireflection coatings for the 21-channel High Resolution Dynamics Limb Sounder. A method of combining the measured spectral characteristics of each filter and antireflection coating, together with the spectral response of the other optical elements in the instrument, to obtain a predicted system throughput response is presented. The design methods that are used to define the filter and coating spectral requirements, choice of filter materials, multilayer designs, and deposition techniques are discussed.     

Millimeter-wave antireflection coating for cryogenic silicon lenses

We have developed and tested an antireflection (AR) coating method for silicon lenses used at cryogenic temperatures and millimeter wavelengths. Our particular application is a measurement of the cosmic microwave background. The coating consists of machined pieces of Cirlex glued to the silicon. The measured reflection from an AR-coated flat piece is less than 1.5% at the design wavelength. The coating has been applied to flats and lenses and has survived multiple thermal cycles from 300 to 4 K. We present the manufacturing method, the material properties, the tests performed, and estimates of the loss that can be achieved in practical lenses.     

Expanded viewpoint for broadband antireflection coating designs

Examining spectral regions outside of the band where an antireflection coating is specified can aid in finding optimal design solutions. The reflectance versus wavenumber plots at low frequencies indicate the overall thickness of the design. These plots also point to whether the design will provide the minimum possible average reflectance in the specified band. It has been discovered that these patterns are nearly replicated by the plot of a quarter-wave stack at peak frequency. It is also found that optimal solutions exist only at quantized intervals.     

钼酸铅晶体表面红外增透膜的研究

本文讨论了用于钼酸铅晶体表面的宽带红外增透膜的设计以及其在真空环境中的制备。膜系设计中 ,运用反射率图解法以获得满意的光学性能 ;与传统的热蒸发镀膜工艺相比 ,在真空沉积过程中采用了离子辅助沉积技术 ,从而大大提高了膜层的光学特性及膜层品质。试验表明所镀膜层性能优异 ,在光纤通信领域具有广阔的应用前景     

Antireflection coatings for UV radiation obtained by molecular-beam deposition

We have developed fluoride antireflection (AR) coatings on MgF(2) substrates for a wavelength of 248 nm by molecular-beam deposition. Transmission and laser-induced damage threshold of the samples were measured and atomic force microscope (AFM) investigations were carried out. We compare a 14-layer design for AR coatings with sublayer thicknesses of 12 nm with a conventional two-layer design with quarter-wavelength thicknesses. The laser-induced damage threshold of the 14-layer coating is slightly higher than that of the two-layer coating. The AFM surface images show that the 14-layer coating has a smoother surface than the two-layer coating.     

Multilayer optical thin films for use at terahertz frequencies: method of fabrication

A new method of fabricating multilayer optical coatings used at terahertz frequencies has been developed. Using plasma-enhanced chemical-vapor deposition, a multilayer antireflection coating for germanium optics at terahertz frequencies was fabricated. The coating consists of amorphous silicon and silicon-oxide layers. The transmittance and structure of the coating were experimentally investigated. The transmittance spectrum of the coating on the Ge substrate shows a wideband antireflection behavior in the 40-120 cm(-1) region.     

Optical coatings for deuterium fluoride chemical laser systems

The high-power laser system has brought an interesting challenge to the development of optical coatings. A wide variety of coating specifications that are often contradictory have to be fulfilled. The choices of deposition process as well as coating materials are critical to coating loss, damage threshold, long-term stability, and other optical properties. A number of optical coatings being newly applied to deuterium fluoride laser systems are presented. The 3.8-mum laser reflection coatings with high damage threshold, multichromatic beam splitters, antireflection coatings with widely separated dual-wavelength bands, and 0.55-14-mum wide-band reflective coatings have been developed on substrates such as Si, Mo, fused silica, chemical vapor deposition ZnSe. Superior results have been obtained with ion-assisted deposition and electron-beam evaporation. Approaches to coating design and practical aspects of coating development are also discussed.     

Optical and durability properties of infrared transmitting thin films

Refractive indices and extinction coefficients have been calculated for 14 oxide and fluoride thin films over a wavelength range of 0.6-12 mum. Results from adhesion, abrasion, and humidity testing have been included to characterize the durability of each film. The data allow selection of the best oxide and fluoride materials for IR antireflection coatings, and detailed optical constants are provided for the coating design.     

Development of optical coatings for 157-nm lithography. II. Reflectance,absorption, and scatter measurement

The total loss that can be suffered by an antireflection (AR) coating consists of reflectance loss, absorption loss, and scatter loss. To separate these losses we developed a calorimetric absorption measurement apparatus and an ellipsoidal Coblentz hemisphere based scatterometer for 157-nm optics. Reflectance, absorption, and scatter of AR coatings were measured with these apparatuses. The AR coating samples were supplied by Japanese vendors. Each AR coating as supplied was coated with the vendor's coating design by that vendor's coating process. Our measurement apparatuses, methods, and results for these AR coatings are presented here.     

Further guidance for broadband antireflection coating design

Recent investigations have added to and refined the understanding of the behavior of broadband antireflection coating designs and provided further guidance for achieving more nearly optimal designs. The ability to optimize designs wherein the overall optical thickness of the design is constrained to a specific value has allowed this investigation. A broader bandwidth than previously reported has been studied and statistically fit more precisely by a polynomial equation, and also two linear equations for routine approximations have been derived. It has also been found that the optimal number of layers in the design can be predicted as a function of the bandwidth.     

Toward perfect antireflection coatings. 3. Experimental results obtained with the use of Reststrahlen materials

The equipment and methods used to produce wide-angle antireflection coatings based on Reststrahlen materials are described. The optical constants of the coating materials used in the construction of the multilayers were determined by spectrophotometric ellipsometry and are compared with the literature values. The measured performance of an experimentally produced antireflection coating is compared with the expected calculated performance. The reflectance is low over a wide range of angles, but only in the narrow-wavelength region at which the refractive index of the Reststrahlen material is close to unity.     

Antireflection properties of erbium oxide films

We have studied the optical transmission spectrum of a surface film of erbium oxide and evaluated the effect of clarification for the surface of a silicon-based photovoltaic converter with an antireflection coating of this material. It is established that erbium oxide films are highly transparent in a broad wavelength range from 250 to 1050 nm and ensure a decrease in the coefficient of reflection of a silicon surface down to 1–4.5%. The antireflection coating of erbium oxide increases the short-circuit photocurrent of the silicon-based photovoltaic converter by more than 38%.     

Optimal single-band normal-incidence antireflection coatings

Mathematical and computational evidence that strongly suggests that optimal solutions exist to single-band, normal-incidence antireflection coating problems is presented. It is shown that efficient synthesis and refinement techniques can quickly and accurately find such solutions. Several visible and infrared antireflection coating examples are presented to support this claim. Graphs that show the expected optimal performance for different representative substrates, refractive-index ratios, wavelength ranges, and overall optical thickness combinations are given. Typical designs exhibit a pronounced semiperiodic clustering of layers, which has also been observed in the past. Explanations of this phenomenon are proposed.     

Polarization filters with an autocloned symmetric structure

The process of fabricating photonic crystals comprised of alternately stacked high- and low-index dielectric materials on periodic substrates to form zigzag films is called the autocloning technique. In this study, we have fabricated TiO2/SiO2 two-dimensional polarization filters by using electron beam gun evaporation with ion-beam-assisted deposition. The shape of the zigzag structure is preserved, and the total thickness is 8?μm. The symmetric structural design can be utilized as an antireflection coating applied to reduce ripples and achieve a 200?nm working wavelength range.     

Improving thin-film manufacturing yield with robust optimization

A novel robust optimization algorithm is demonstrated that is largely deterministic, and yet it attempts to account for statistical variations in coating. Through Monte Carlo simulations of manufacturing, we compare the performance of a proof-of-concept antireflection (AR) coating designed with our robust optimization to that of a conventionally optimized AR coating. We find that the robust algorithm produces an AR coating with a significantly improved yield.     

Effect and suppression of secondary fringes in FATWindII

By considering the instrument as a complex operator on the incident electric field, a model to calculate secondary fringes of the Field-widened, Achromatic, Temperature-compensated Wind Imaging Interferometer (FATWindII) has been built. The distribution of secondary fringes on a charge coupled device detector has been plotted. The effects of secondary fringes on inversion errors of temperature and wind velocity have been presented. The results show that antireflection coating on the air/glass interface cannot meet the accuracy requirement of FATWindII. A theoretical method for calculating the optimal wedge angles of compensating glasses is derived to suppress the secondary fringes while preserving the primary ones. By adopting both methods, coating with antireflection film and shaping wedge compensating glasses, the relative intensity of secondary fringes is reduced to below 2.5% and the inversion errors of temperature and wind velocity introduced by the effects of secondary fringes can be minimized to about 0.05 K and 0.045 ms(-1), respectively.     

Fourier transform technique with frequency filtering for optical thin-film design

A Fourier analysis of existing and potentially complex refractive index profiles is often useful in the resolution of thin-film design problems. Applications of a frequency-filtering technique, which consists of the suppression of undesired spatial frequencies from the refractive index profiles, are described. A new, extremely simple antireflection coating synthesis method based on this concept is proposed.     

Optical interference coatings design contest 2004

A manufacturable, broadband, broad-angle antireflection (AR) coating for the visible (13 designs submitted) and a minimum-shift immersed short-pass filter (12 designs submitted) were the subjects of the design contest held in conjunction with the 2004 Optical Interference Coatings topical meeting of the Optical Society of America. Under the specified constraints, the broadband, broad-angle AR coating could be made more than 65 nm wide. The statistical stability of manufacturing simulations is discussed. The short-pass filter could operate up to a +/- 5.5 degree angular range. The submitted designs are described and evaluated.     

Design, production, and reverse engineering of two-octave antireflection coatings

We deal with design and production of optimal two-component antireflection (AR) coatings for an ultra broadband spectral range from 450 nm to 1800 nm. We demonstrate the whole design-production chain including design selection, choosing monitoring technique, coating production, and reverse engineering of the deposited coatings. At each step of this chain we provide thorough analysis on the basis of theoretical results and adequate computational manufacturing experiments. In order to produce the designed AR coatings we use magnetron sputtering deposition technique and accurate time monitoring.