Penghui Ma

Toward perfect antireflection coatings: numerical investigation

A perfect antireflection (AR) coating would remove completely the reflection from an interface between two media for all wavelengths, polarizations, and angles of incidence. The degree to which this can be achieved is investigated numerically. It is shown that wideband solutions can be found provided that layers can be deposited with refractive indices that are close to that of the low-index medium. Thus realistic solutions exist for interfaces between two solid media. Narrow-band high-angle AR solutions are also possible for polarized light and for unpolarized light in the vicinity of certain reststrahlen bands.

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.

Design and manufacture of metal/dielectric long-wavelength cutoff filters

Thin films of high reflecting metal, such as Ag, have a high reflectance in the long-wavelength region. When they are combined with dielectric layers, it is possible, through thin film interference effects, to induce transmission in certain shorter wavelength regions. Thus, they are useful components for the design of long-wavelength cutoff filters with a broad rejection region. In this paper, metal/dielectric multilayer designs based on this principle are numerically investigated. Three designs with different cutoff wavelengths and with very broad transmission regions in the visible or near-IR spectral ranges are presented. An excellent rejection on the long-wavelength side extends beyond 20 μm. Experimental results for one of the designs produced in our magnetron sputtering system are given.

Long-wavelength polarizing cutoff filters for the 275–550-nm spectral region

The design and manufacture of a multiple-reflection-type multilayer element is described that efficiently removes all wavelengths higher than 550 nm from the incident radiation and that at the same time acts as a polarizer in the 275-550-nm spectral transmission region.

Metal-Dielectric Waveguide Facet Coatings

We present the application of metal-dielectric coatings on the facet of waveguides for the control of the modal reflectance with narrowband and wideband mirrors.

Fifty Years of Optical Interference Coatings at the National Research Council of Canada

For the past 50 years, the Thin Films Group of the National Research Council (NRC) in Canada has successfully developed optical interference coatings that have changed the fabric of our lives. The coatings have been used for everything from protecting paper currency against counterfeiting, to increasing the contrast and efficiency of organic LEDs, to forming components of artificial vision systems used in space shuttles. This article reflects on NRCs past successes, current challenges and future directions.

Wide-angle antireflection coatings based on the use of Reststrahlen materials

The measured performance of the experimentally produced antireflection coatings will be presented. The optical constants of the thin films used in the construction were determined by spectrophotometric ellipsometry and will be compared to literature values.

Polarizing cut-off filter for the 275–550 nm spectral region

The design and manufacture of a multiple reflection-type multilayer element is described which efficiently removes all wavelengths higher than 550 nm from the incident radiation and which at the same time acts as a polarizer.