Recent Advances in Optical Coatings

A special issue of Coatings (ISSN 2079-6412).

Deadline for manuscript submissions: closed (31 October 2016) | Viewed by 52171

Special Issue Editor


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Guest Editor
School of Computing, Engineering and Physical Sciences, University of the West of Scotland, Paisley PA1 2BE, UK
Interests: optical thin film and coatings, including medical device applications
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

This Special Issue is dedicated to highlighting the important advances and innovations in “Optical Coatings”. An optical coating is one or multiple thin films of material deposited on an optical component, such as a lens or mirror, altering the way in which the optical surface reflects and transmits light. The most common type of optical coating is an antireflection coating, which reduces unwanted reflections from surfaces and is used in a wide variety of applications including ophthalmic and photographic lenses. Another type is the high-reflector coating, which can be used to produce mirrors which reflect greater than 99.99% of the incident light. More complex optical coatings exhibit high reflection over some range of wavelengths, and anti-reflection over another range, allowing the production of dichroic thin film optical filters.

In such optical coatings the final characteristics and functions are critically determined by the quality of the individual film bulk and interface properties. Moreover, the design of optical coatings requires selection of materials based on knowledge of their optical, mechanical and thermal properties particularly the absorption and dispersion characteristics achieved for various deposition processes. Frequently, the selection of suitable materials results from compromises between these various properties as no single material will possess the ideal characteristics required to suit the wide variety of applications.

Application of optical coatings has provided substantial benefits into a wide variety of industries and optical systems, such as optical communications, energy control and solar coatings, photonic and sensor devices, high power lasers, displays, ophthalmics, and microscopy. Due to increasing industrial demands, optical coatings have gone through several generations of development, driving the need for lower optical loss, higher precision, increased production throughput and use over extended spectral regions. This has resulted in emerging use of novel materials and deposition technologies based on new sputter and chemical vapour deposition strategies, plasma assisted and atomic layer processes.

This Special Issue of Optical Coatings is intended to provide a forum for original research articles as well as critical reviews and perspectives on current advances and innovations in the field of optical coatings from both academia and industry. Areas of interest include, but are not limited to, novel software and/or design techniques, new deposition processes including combined methods, multifunctional coatings (combining optical with other performance requirements such as durability or electrical conductivity), real­time
process
monitoring
and
control
of optical
coating
deposition methods, challenging optical coating requirements and solutions in areas, such as lighting, photonics, sensors, optical telecommunications, deployment in space, solar cells, and life sciences.

Prof. Dr. Desmond Gibson
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Coatings is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.


 

Keywords

  • Novel
 optical
 interference
 design
 software 
and 
design
 techniques
  • Energetic 
processes
 (ion
 and
 plasma
 sources,
 densification
 and
 stress
 control)
  • Multifunctional 
coatings (optical combined with other functions)
  • Deposition, 
characterization,
 and
 applications 
of
 sculpted
 and 
textured 
films
  • New
 deposition 
processes
 for
 optical
 coatings 
and 
combination
 processing
  • New
 low
 cost 
processes
 for
 optical coatings
  • Application 
of 
real­-time
 process
 monitoring 
and
 control
 of optical
 coating 
processes
  • Novel
 coating
 materials
  • Low loss optical coatings
  • Coatings
 on
 polymers
 and 
special
 substrate
 materials
  • Metrology
 of
 optical
 films 
(new
 instrumentation,
 in-­line
 approaches and developments to
 make
 characterization 
viable)
  • Optical
 film
 characterization
  • Applications 
in 
non-­traditional 
spectral wavelength regions
  • Complex
 3­-D 
optical
 devices
  • Optical
 coatings 
for
 energy
 control
 and
 solar 
power
  • Optical 
coatings 
for 
laser 
applications; high power and/or short pulse duration control
  • Optical
 coatings
 for 
aerospace 
and
 space applications
  • Integrated
 photonic
 devices and sensors

 

Published Papers (6 papers)

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Research

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2319 KiB  
Article
Development of Mirror Coatings for Gravitational Wave Detectors
by Stuart Reid and Iain W. Martin
Coatings 2016, 6(4), 61; https://doi.org/10.3390/coatings6040061 - 16 Nov 2016
Cited by 30 | Viewed by 8528
Abstract
The first detections of gravitational waves, GW150914 and GW151226, were associated with the coalescence of stellar mass black holes, heralding the opening of an entirely new way to observe the Universe. Many decades of development were invested to achieve the sensitivities required to [...] Read more.
The first detections of gravitational waves, GW150914 and GW151226, were associated with the coalescence of stellar mass black holes, heralding the opening of an entirely new way to observe the Universe. Many decades of development were invested to achieve the sensitivities required to observe gravitational waves, with peak strains associated with GW150914 at the level of 10−21. Gravitational wave detectors currently operate as modified Michelson interferometers, where thermal noise associated with the highly reflective mirror coatings sets a critical limit to the sensitivity of current and future instruments. This article presents an overview of the mirror coating development relevant to gravitational wave detection and the prospective for future developments in the field. Full article
(This article belongs to the Special Issue Recent Advances in Optical Coatings)
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3632 KiB  
Article
Comparison of Single-Layer and Double-Layer Anti-Reflection Coatings Using Laser-Induced Damage Threshold and Photothermal Common-Path Interferometry
by Caspar Clark, Riccardo Bassiri, Iain W. Martin, Ashot Markosyan, Peter G. Murray, Des Gibson, Sheila Rowan and Martin M. Fejer
Coatings 2016, 6(2), 20; https://doi.org/10.3390/coatings6020020 - 10 May 2016
Cited by 8 | Viewed by 7431
Abstract
The dielectric thin-film coating on high-power optical components is often the weakest region and will fail at elevated optical fluences. A comparison of single-layer coatings of ZrO2, LiF, Ta2O5, SiN, and SiO2 along with anti-reflection (AR) coatings optimized at 1064 nm comprised of [...] Read more.
The dielectric thin-film coating on high-power optical components is often the weakest region and will fail at elevated optical fluences. A comparison of single-layer coatings of ZrO2, LiF, Ta2O5, SiN, and SiO2 along with anti-reflection (AR) coatings optimized at 1064 nm comprised of ZrO2 and Ta2O5 was made, and the results of photothermal common-path interferometry (PCI) and a laser-induced damage threshold (LIDT) are presented here. The coatings were grown by radio frequency (RF) sputtering, pulsed direct-current (DC) sputtering, ion-assisted electron beam evaporation (IAD), and thermal evaporation. Test regimes for LIDT used pulse durations of 9.6 ns at 100 Hz for 1000-on-1 and 1-on-1 regimes at 1064 nm for single-layer and AR coatings, and 20 ns at 20 Hz for a 200-on-1 regime to compare the //ZrO2/SiO2 AR coating. Full article
(This article belongs to the Special Issue Recent Advances in Optical Coatings)
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2889 KiB  
Article
Influence of Material Composition on Structural and Optical Properties of HfO2-TiO2 Mixed Oxide Coatings
by Michal Mazur, Danuta Kaczmarek, Jaroslaw Domaradzki, Damian Wojcieszak and Agata Poniedzialek
Coatings 2016, 6(1), 13; https://doi.org/10.3390/coatings6010013 - 22 Mar 2016
Cited by 12 | Viewed by 6264
Abstract
In this paper the influence of material composition on the structural, surface and optical properties of HfO2-TiO2 mixed oxide coatings was investigated and discussed. Five sets of thin films were deposited using reactive magnetron sputtering: HfO2, TiO2 [...] Read more.
In this paper the influence of material composition on the structural, surface and optical properties of HfO2-TiO2 mixed oxide coatings was investigated and discussed. Five sets of thin films were deposited using reactive magnetron sputtering: HfO2, TiO2 and three sets of mixed HfO2-TiO2 coatings with various titanium content. The change in the material composition had a significant influence on the structural, surface and optical properties. All of the deposited coatings, except for (Hf0.55Ti0.45)Ox, were nanocrystalline with crystallites ranging from 6.7 nm to 10.8 nm in size. Scanning electron microscopy measurements revealed that surface of nanocrystalline thin films consisted of grains with different shapes and sizes. Based on optical transmission measurements, it was shown that thin films with higher titanium content were characterized by a higher cut-off wavelength, refractive index and lower optical band gap energy. The porosity and packing density were also determined. Full article
(This article belongs to the Special Issue Recent Advances in Optical Coatings)
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4290 KiB  
Article
Low Group Delay Dispersion Optical Coating for Broad Bandwidth High Reflection at 45° Incidence, P Polarization of Femtosecond Pulses with 900 nm Center Wavelength
by John C. Bellum, Ella S. Field, Trevor B. Winstone and Damon E. Kletecka
Coatings 2016, 6(1), 11; https://doi.org/10.3390/coatings6010011 - 09 Mar 2016
Cited by 13 | Viewed by 7781
Abstract
We describe an optical coating design suitable for broad bandwidth high reflection (BBHR) at 45° angle of incidence (AOI), P polarization (Ppol) of femtosecond (fs) laser pulses whose wavelengths range from 800 to 1000 nm. Our design process is guided by quarter-wave HR [...] Read more.
We describe an optical coating design suitable for broad bandwidth high reflection (BBHR) at 45° angle of incidence (AOI), P polarization (Ppol) of femtosecond (fs) laser pulses whose wavelengths range from 800 to 1000 nm. Our design process is guided by quarter-wave HR coating properties. The design must afford low group delay dispersion (GDD) for reflected light over the broad, 200 nm bandwidth in order to minimize temporal broadening of the fs pulses due to dispersive alteration of relative phases between their frequency components. The design should also be favorable to high laser-induced damage threshold (LIDT). We base the coating on TiO2/SiO2 layer pairs produced by means of e-beam evaporation with ion-assisted deposition, and use OptiLayer Thin Film Software to explore designs starting with TiO2/SiO2 layers having thicknesses in a reverse chirped arrangement. This approach led to a design with R > 99% from 800 to 1000 nm and GDD < 20 fs2 from 843 to 949 nm (45° AOI, Ppol). The design’s GDD behaves in a smooth way, suitable for GDD compensation techniques, and its electric field intensities show promise for high LIDTs. Reflectivity and GDD measurements for the initial test coating indicate good performance of the BBHR design. Subsequent coating runs with improved process calibration produced two coatings whose HR bands satisfactorily meet the design goals. For the sake of completeness, we summarize our previously reported transmission spectra and LIDT test results with 800 ps, 8 ps and 675 fs pulses for these two coatings, and present a table of the LIDT results we have for all of our TiO2/SiO2 BBHR coatings, showing the trends with test laser pulse duration from the ns to sub-ps regimes. Full article
(This article belongs to the Special Issue Recent Advances in Optical Coatings)
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Review

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23236 KiB  
Review
Surface Enhanced Raman Scattering Substrates Made by Oblique Angle Deposition: Methods and Applications
by Hin On Chu, Shigeng Song, Cheng Li and Des Gibson
Coatings 2017, 7(2), 26; https://doi.org/10.3390/coatings7020026 - 15 Feb 2017
Cited by 26 | Viewed by 9100
Abstract
Surface Enhanced Raman Spectroscopy presents a rapid, non-destructive method to identify chemical and biological samples with up to single molecule sensitivity. Since its discovery in 1974, the technique has become an intense field of interdisciplinary research, typically generating >2000 publications per year since [...] Read more.
Surface Enhanced Raman Spectroscopy presents a rapid, non-destructive method to identify chemical and biological samples with up to single molecule sensitivity. Since its discovery in 1974, the technique has become an intense field of interdisciplinary research, typically generating >2000 publications per year since 2011. The technique relies on the localised surface plasmon resonance phenomenon, where incident light can couple with plasmons at the interface that result in the generation of an intense electric field. This field can propagate from the surface from the metal-dielectric interface, so molecules within proximity will experience more intense Raman scattering. Localised surface plasmon resonance wavelength is determined by a number of factors, such as size, geometry and material. Due to the requirements of the surface optical response, Ag and Au are typical metals used for surface enhanced Raman applications. These metals then need to have nano features that improve the localised surface plasmon resonance, several variants of these substrates exist; surfaces can range from nanoparticles in a suspension, electrochemically roughened electrodes to metal nanostructures on a substrate. The latter will be the focus of this review, particularly reviewing substrates made by oblique angle deposition. Oblique angle deposition is the technique of growing thin films so that the material flux is not normal to the surface. Films grown in this fashion will possess nanostructures, due to the atomic self-shadowing effect, that are dependent mainly on the deposition angle. Recent developments, applications and highlights of surface enhanced Raman scattering substrates made by oblique angle deposition will be reviewed. Full article
(This article belongs to the Special Issue Recent Advances in Optical Coatings)
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3355 KiB  
Review
Techniques and Challenges for Characterizing Metal Thin Films with Applications in Photonics
by Paul J.D. Whiteside, Jeffrey A. Chininis and Heather K. Hunt
Coatings 2016, 6(3), 35; https://doi.org/10.3390/coatings6030035 - 17 Aug 2016
Cited by 47 | Viewed by 12008
Abstract
The proliferation of laser technologies has profoundly increased the demand for high-quality optical thin films whose physical properties are tunable and well defined. Such films are frequently deposited in thicknesses much shorter than the wavelengths of visible light and consequently present challenges for [...] Read more.
The proliferation of laser technologies has profoundly increased the demand for high-quality optical thin films whose physical properties are tunable and well defined. Such films are frequently deposited in thicknesses much shorter than the wavelengths of visible light and consequently present challenges for characterization by traditional microscopy. Metal films in particular exemplify these challenges, due to their broad range of refractive indices, optical absorption and often near-complete reflectivity in the visible spectrum. However, due to their relatively consistent crystalline structure, the bulk optical properties of metal thin films are chiefly dependent on their thickness. This review therefore presents a compendium of viable alternative characterization techniques to highlight their respective utilities, limitations and resolutions, specifically with regard to the characterization of the thickness of metal films. Furthermore, this review explicitly addresses the operating theories, methods and analyses relating to the five most predominantly utilized techniques: X-ray Reflectivity (XRR), Spectroscopic Ellipsometry (SE), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS). This work is intended as an introductory guide to thin film characterization modalities and their applicability for metal and optically-absorptive films, while also identifying AFM and SEM/EDS as being amongst the more reliable of the techniques. Full article
(This article belongs to the Special Issue Recent Advances in Optical Coatings)
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