Antireflection coatings for UV radiation obtained by molecular-beam deposition

Abstract

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.

Biomimetic Synthesis of Antireflective Silica/Polymer Composite Coatings Comprising Vesicular Nanostructures

“…Their refractive indices can be tuned by adjusting the film dimensions and porosity, which can be realized by varying the polymer composition and number of deposition layers. An excellent AR film can be achieved by a single index coating onto a bare substrate with the refractive index n c = ( n 1 n 2 ) 0.5 and thickness d c = λ 0 /4 n c . − The refractive indices of air and substrate such as glass are 1.0 and 1.515, respectively. For the glass substrate, the refractive index of an AR coating should be about 1.23, and the optimal thickness should be about 81 and 122 nm for the visible wavelengths of 400 and 600 nm, respectively.…”

“…The synthesis of nano- and mesoporous thin films for antireflective (AR) coatings has gained considerable interest because they have been widely applied on many devices such as eyeware, solar cells, and lasers. − Substrates with higher light transmittance can be prepared by depositing AR coatings, which would exhibit the destructive interference between light reflected from the coating/substrate and air/coating interfaces. , A good AR coating exhibited low refractive index and coating thickness of one-quarter of the visible wavelength, which is about 80–160 nm. − Nano- and mesoporous films for AR coatings can be fabricated through a number of approaches including sol–gel process, chemical/plasma etching, chemical vapor deposition, and layer-by-layer (LbL) assembly. ,,− The sol–gel process, which involves hydrolyzation and condensation of inorganic salts or metal alkoxides to form oxide materials, is one of the most prevalent technologies to fabricate AR coatings via mainly the dip or spin coating process. ,, Creating subwavelength structures on surface by using chemical/plasma etching or chemical vapor deposition can suppress the surface reflection and consequently results in the substrate exhibiting excellent AR performance. ,,,, LbL assembly technique is a simple, inexpensive, and environmentally benign approach to fabricate AR coatings as compared with other approaches. It is a versatile approach to fabricate uniform, conformal coatings with tunable composition, thickness, and structure by varying coating materials and solution conditions. ,,, …”

Hollow Silica Nanoparticles in UV−Visible Antireflection Coatings for Poly(methyl methacrylate) Substrates

“…Reflections from lenses in an optical system are undesirable because they contribute to a significant loss of transmitted light, which decreases the quality of the final image. − Any coating that is designed to reduce these reflections must also minimize extra scattering losses from the film, a requirement that is more difficult to achieve at lower wavelengths. − Hence, scattering of light within the coating can play an important role in AR films designed to operate in the near UV region, and it remains a challenge to maximize transmission in this region of the spectrum. To overcome this difficulty, a relatively smooth coating with small feature sizes (less than 1/10th of the target wavelength) is required.…”

Superhydrophobic self-cleaning antireflective coatings on Fresnel lenses by integrating hydrophilic solid and hydrophobic hollow silica nanoparticles

“…In addition to the wettability, optical properties also rely heavily on the surface morphology and structure. It is known from previous works [44][45][46][47] that excellent antireective property can be achieved by a single-layer coating of refractive index n c ¼ (n a  n s ) 1/2 , where n a is the refractive index of air (n a ¼ 1.00) and n s is the refractive index of substrate (here the substrate is PMMA Fresnel lens, n s ¼ 1.49). Thus, the refractive index of coating should be 1.22 to achieve excellent antireective property.…”