Laser & Photonics Reviews

Cover image for Vol. 8 Issue 4

Editor: Katja Paff

Impact Factor: 7.976

ISI Journal Citation Reports © Ranking: 2012: 2/80 (Optics); 8/128 (Physics Applied); 9/68 (Physics Condensed Matter)

Online ISSN: 1863-8899

Associated Title(s): Advanced Optical Materials, Journal of Biophotonics

News

RSS feeds: news | news + recent journal content.

May 30, 2014

Combed radio frequencies

Combed radio frequencies

Optical frequency comb technology for ultra-broadband radio-frequency photonics.

Gothenburg (Sweden) – The outstanding phase-noise performance of optical frequency combs has led to a revolution in optical synthesis and metrology. The broad impact of this tool was recognized with half of the 2005 Nobel Prize in Physics awarded to T. W. Hänsch and J. L. Hall. Since its demonstration in 2000, the applications are expanding, going from molecular spectroscopy and optical clocks to optical and radio-frequency arbitrary waveform generation. However, the ideal characteristics of an optical frequency comb are application dependent. High-repetition-rate optical frequency combs with a relatively broad optical bandwidth, compactness, and low noise level offer a huge new avenue of possibilities in radio-frequency photonics.
In a review article, Victor Torres-Company from Chalmers University of Technology, Gothenburg, Sweden and Andrew M. Weiner from Purdue University, West Lafayette, USA present the available technologies for the generation and processing of high repetition-rate (>10 GHz) optical frequency combs and highlight their unique characteristics for emerging applications in radiofrequency photonics. These include high-performance filtering of microwave signals, ultra-broadband coherent wireless/optical communications, and high-fidelity synthesis of ultra-broadband waveforms.
The authors assume that, in the future, it is likely that optical frequency comb generators and pulse shapers will be developed in a compact platform to reduce their size, cost, weight, and power consumption, helping to enable applications outside the laboratory. In this direction, the use of photonics devices engineered at the nanoscale is considered as crucial for the next generation of optical communications as well as photonic microwave signal processing systems.
They expect to see in the future high-performance frequency comb generators and programmable devices with more subsystems all embedded on a single chip. Efforts towards hybrid integration constitute a reasonable yet challenging direction.
(Text contributed by K. Maedefessel-Herrmann)

See the original publication: Victor Torres-Company and Andrew M. Weiner, Optical frequency comb technology for ultra-broadband radio-frequency photonics, Laser Photonics Rev., 8:3, 368-396 (2014)

March 27, 2014

As black as can be

As black as can beA novel ultra-black broadband absorber concept based on a needle-like silicon nanostructure has been developed: ultra-black silicon (ub-Si) exhibits an absorptance of more than 99.5% between 350 nm and 2000 nm and about 99.8% between 1000 nm and 1250 nm.

Jena (Germany) – From solar thermal energy conversion over optical spectroscopy to photothermal light detection – these and many more applications need highly efficient light absorbers. Materials with broadband absorptance as high as possible are high on the wish list/highly desirable. From that point of view, there are three interesting materials with broadband absorptance of more than 99%: gold-black coatings, large area carbon nanotube arrays (CNT) and the so-called ultra-black nickel-phosphorus (ub-NiP). Although CNT exhibit the highest absorptance of more than 99.9% around 550 nm, the mostly used material is ub-NiP because of its well established, simple fabrication and its absorptance of up to ∼99.8%. Martin Steglich and his colleagues from Friedrich Schiller University Jena (Germany) now add an attractive absorber concept based on needle-like silicon nanostructure called Black Silicon.
The novel absorber material consists of a 1.6 μm deep Black Silicon nanostructure established on a highly doped silicon substrate by inductively coupled plasma reactive ion etching (ICP-RIE) and an additional dielectric coating (Al2O3) prepared by atomic layer deposition. The fabrication procedure is free of lithography and only consists of a dry etching and an oxide deposition step. The etching relies on a randomly distributed formation of silicon oxyfluoride particles (SiOxFy) on the silicon surface. The new method is reliable, well-repeatable, up-scalable and does not require lithography or any sample pre-treatment. Fabrication of the absorbers is consistent with CMOS standards.
The absorber concept with Black Silicon yields an absorptance beyond 99% in a broad wavelength range between 350 nm and 2250 nm. Particularly and in contrast to other publications, the high absorptance in the wavelength region beyond the silicon bandgap (λ > 1100 nm) is accomplished by applying highly doped, degenerate silicon substrates which exhibit a finite coefficient of light absorption in this range. To stay consistent with the term ultra-black NiP, the concept is similarly referred to as ultra-black silicon (ub-Si).
Improved absorbers also incorporate an additional oxide capping layer on the nanostructures and reach an absorptance of A > 99.5% in the range of 350 to 2000 nm and A ∼ 99.8% between 1000 and 1250 nm.
(Text contributed by K. Maedefessel-Herrmann)

See the original publication: M. Steglich, D. Lehr, S. Ratzsch, T. Käsebier, F. Schrempel, E.-B. Kley, and A. Tünnermann, An ultra-black silicon absorber. Laser Photonics Rev., 8:2. L13-L17 (2014); http://dx.doi.org/10.1002/lpor.201300142
Contact: laser@wiley.com

May 30, 2014
Combed radio frequencies

March 27, 2014
As black as can be

SEARCH

SEARCH BY CITATION