2017-7-29, Mayerhöfer, Thomas G., Popp, Jürgen

At the beginning of the 1980s, the first reports of surface-enhanced infrared spectroscopy (SEIRS) surfaced. Probably due to signal-enhancement factors of only 101 to 103, which are modest compared to those of surface-enhanced Raman spectroscopy (SERS), SEIRS did not reach the same significance up to date. However, taking the compared to Raman scattering much larger cross-sections of infrared absorptions and the enhancement factors together, SEIRS reaches about the same sensitivity for molecular species on a surface in terms of the cross-sections as SERS and, due to the complementary nature of both techniques, can valuably augment information gained by SERS. For the first 20 years since its discovery, SEIRS relied completely on metal island films, fabricated by either vapor or electrochemical deposition. The resulting films showed a strong variance concerning their structure, which was essentially random. Therefore, the increase in the corresponding signal-enhancement factors of these structures stagnated in the last years. In the very same years, however, the development of periodic array-based substrates helped SEIRS to gather momentum. This development was supported by technological progress concerning electromagnetic field solvers, which help to understand plasmonic properties and allow targeted design. In addition, the strong progress concerning modern fabrication methods allowed to implement these designs into practice. The aim of this contribution is to critically review the development of these engineered surfaces for SEIRS, to compare the different approaches with regard to their performance where possible, and report further gain of knowledge around and in relation to these structures.

2018, Tuniz, Alessandro, Schmidt, Markus A.

The concentration of light to deep-subwavelength dimensions plays a key role in nanophotonics and has the potential to bring major breakthroughs in fields demanding to understand and initiate interaction on nanoscale dimensions, including molecular disease diagnostics, DNA sequencing, single nanoparticle manipulation and characterization, and semiconductor inspection. Although planar metallic nanostructures provide a pathway to nanoconcentration of electromagnetic fields, the delivery/collection of light to/from such plasmonic nanostructures is often inefficient, narrow-band, and requires complicated excitations schemes, limiting widespread applications. Moreover, planar photonic devices reveal a reduced flexibility in terms of bringing the probe light to the sample. An ideal photonic-plasmonic device should combine (i) a high spatial resolution at the nanometre level beyond to what is state-of-the-art in near-field microscopy with (ii) flexible optical fibers to promote a straightforward integration into current near-field scanning microscopes. Here, we review the recent development and main achievements of nanoconcentrators interfacing optical fibers at their end-faces that reach entirely monolithic designs, including campanile probes, gold-coated fiber-taper nanotips, and fiber-integrated gold nanowires.

2021, Grimm, Philipp, Razinskas, Gary, Huang, Jer-Shing, Hecht, Bert

Coherent perfect absorption (CPA) describes the absence of all outgoing modes from a lossy resonator, driven by lossless incoming modes. Here, we show that for nanoresonators that also exhibit radiative losses, e.g., plasmonic nanoantennas, a generalized version of CPA (gCPA) can be applied. In gCPA outgoing modes are suppressed only for a subset of (guided plasmonic) modes while other (radiative) modes are treated as additional loss channels - a situation typically referred to as perfect impedance matching. Here we make use of gCPA to show how to achieve perfect impedance matching between a single nanowire plasmonic waveguide and a plasmonic nanoantenna. Antennas with both radiant and subradiant characteristics are considered. We further demonstrate potential applications in background-free sensing.

2020, Rajil, Navid, Sokolov, Alexei, Yi, Zhenhuan, Adams, Garry, Agarwal, Girish, Belousov, Vsevolod, Brick, Robert, Chapin, Kimberly, Cirillo, Jeffrey, Deckert, Volker, Delfan, Sahar, Esmaeili, Shahriar, Fernández-González, Alma, Fry, Edward, Han, Zehua, Hemmer, Philip, Kattawar, George, Kim, Moochan, Lee, Ming-Che, Lu, Chao-Yang, Mogford, Jon, Neuman, Benjamin, Pan, Jian-Wei, Peng, Tao, Poor, Vincent, Scully, Steven, Shih, Yanhua, Suckewer, Szymon, Svidzinsky, Anatoly, Verhoef, Aart, Wang, Dawei, Wang, Kai, Yan, Lan, Zheltikov, Aleksei, Zhu, Shiyao, Zubairy, Suhail, Scully, Marlan

Dr. Deborah Birx, the White House Coronavirus Task Force coordinator, told NBC News on "Meet the Press"that "[T]he U.S. needs a 'breakthrough' in coronavirus testing to help screen Americans and get a more accurate picture of the virus' spread."We have been involved with biopathogen detection since the 2001 anthrax attacks and were the first to detect anthrax in real-time. A variation on the laser spectroscopic techniques we developed for the rapid detection of anthrax can be applied to detect the Severe Acute Respiratory Syndrome-Corona Virus-2 (SARS-CoV-2 virus). In addition to detecting a single virus, this technique allows us to read its surface protein structure. In particular, we have been conducting research based on a variety of quantum optical approaches aimed at improving our ability to detect Corona Virus Disease-2019 (COVID-19) viral infection. Indeed, the detection of a small concentration of antibodies, after an infection has passed, is a challenging problem. Likewise, the early detection of disease, even before a detectible antibody population has been established, is very important. Our team is researching both aspects of this problem. The paper is written to stimulate the interest of both physical and biological scientists in this important problem. It is thus written as a combination of tutorial (review) and future work (preview). We join Prof. Federico Capasso and Editor Dennis Couwenberg in expressing our appreciation to all those working so heroically on all aspects of the COVID-19 problem. And we thank Drs. Capasso and Couwenberg for their invitation to write this paper. © 2020 Navid Rajil et al., published by De Gruyter, Berlin/Boston 2020.

2020, Jiang, Shiqi, Förster, Ronny, Plidschun, Malte, Kobelke, Jens, Ando, Ron Fatobene, Schmidt, Markus A.

Three-dimensional (3D) tracking of nano-objects represents a novel pathway for understanding dynamic nanoscale processes within bioanalytics and life science. Here we demonstrate 3D tracking of diffusing 100 nm gold nanosphere within a water-filled optofluidic fiber via elastic light scattering-based position retrieval. Specifically, the correlation between intensity and position inside a region of a fiber-integrated microchannel has been used to decode the axial position from the scattered intensity, while image processing-based tracking was used in the image plane. The 3D trajectory of a diffusing gold nanosphere has been experimentally determined, while the determined diameter analysis matches expectations. Beside key advantages such as homogenous light-line illumination, low-background scattering, long observation time, large number of frames, high temporal and spatial resolution and compatibility with standard microscope, the particular properties of operating with water defines a new bioanalytical platform that is highly relevant for medical and life science applications. © 2020 Shiqi Jiang et al., published by De Gruyter. 2020.