Detection of deep-subwavelength dielectric layers at terahertz frequencies using semiconductor plasmonic resonators

Plasmonic bowtie antennas made of doped silicon can operate as plasmonic resonators at terahertz (THz) frequencies and provide large field enhancement close to their gap. We demonstrate both experimentally and theoretically that the field confinement close to the surface of the antenna enables the detection of ultrathin (100 nm) inorganic films, about 3750 times thinner than the free space wavelength. Based on model calculations, we conclude that the detection sensitivity and its variation with the thickness of the deposited layer are related to both the decay of the local THz field profile around the antenna and the local field enhancement in the gap of the bowtie antenna. This large field enhancement has the potential to improve the detection limits of plasmon-based biological and chemical sensors

Carrier dynamics in semiconductors studied with time-resolved terahertz spectroscopy

Copyright © 2011 American Physical SocietyTime-resolved, pulsed terahertz spectroscopy has developed into a powerful tool to study charge carrier dynamics in semiconductors and semiconductor structures over the past decades. Covering the energy range from a few to about 100 meV, terahertz radiation is sensitive to the response of charge quasiparticles, e.g., free carriers, polarons, and excitons. The distinct spectral signatures of these different quasiparticles in the THz range allow their discrimination and characterization using pulsed THz radiation. This frequency region is also well suited for the study of phonon resonances and intraband transitions in low-dimensional systems. Moreover, using a pump-probe scheme, it is possible to monitor the nonequilibrium time evolution of carriers and low-energy excitations with sub-ps time resolution. Being an all-optical technique, terahertz time-domain spectroscopy is contact-free and noninvasive and hence suited to probe the conductivity of, particularly, nanostructured materials that are difficult or impossible to access with other methods. The latest developments in the application of terahertz time-domain spectroscopy to bulk and nanostructured semiconductors are reviewed.Nederlandse organisatie voor Wetenschappelijk Onderzoek (NWO): Stichting voor Fundamenteel Onderzoek der Materie (FOM) research programmeNational Science Foundatio

Hidden Silicon-Vacancy Centers in Diamond

We characterize a high-density sample of negatively charged silicon-vacancy (SiV$^-$) centers in diamond using collinear optical multidimensional coherent spectroscopy. By comparing the results of complementary signal detection schemes, we identify a hidden population of \ce{SiV^-} centers that is not typically observed in photoluminescence, and which exhibits significant spectral inhomogeneity and extended electronic $T_2$ times. The phenomenon is likely caused by strain, indicating a potential mechanism for controlling electric coherence in color-center-based quantum devices

Excited-state lifetime of the NV- infrared transition in diamond

The negatively charged nitrogen vacancy (NV-) defect in diamond serves as a popular platform for manipulating and exploiting long-lived coherent spin dynamics at room temperature combined with optical readout. The required spin polarization of the spin triplet 3A2 electronic ground state occurs through a cycle of repetitious optical photoexcitation events to the 3E electronic excited state that is accompanied by a series of electronic transitions to a 1A1 and a 1E electronic state, and back to the 3A2 state. The timescales of these transitions are largely known, yet for the relaxation time of the 1A1→1E infrared transition, which predominantly occurs via nonradiative recombination, only an upper limit of 1 ns could be determined so far. Here, we employ ultrafast transient absorption spectroscopy to probe the dynamics of the nonradiative relaxation from the 1A1 to the 1E state after photoexcitation of the 3E state and find a relaxation time of 100 ps at a temperature of 78 K.Published versio

Detection of deep-subwavelength dielectric layers at terahertz frequencies using semiconductor plasmonic resonators

Plasmonic bowtie antennas made of doped silicon can operate as plasmonic resonators at terahertz (THz) frequencies and provide large field enhancement close to their gap. We demonstrate both experimentally and theoretically that the field confinement close to the surface of the antenna enables the detection of ultrathin (100 nm) inorganic films, about 3750 times thinner than the free space wavelength. Based on model calculations, we conclude that the detection sensitivity and its variation with the thickness of the deposited layer are related to both the decay of the local THz field profile around the antenna and the local field enhancement in the gap of the bowtie antenna. This large field enhancement has the potential to improve the detection limits of plasmon-based biological and chemical sensors. © 2012 Optical Society of America.This work was supported by the European Community's 7th Framework Programme under grant agreement no FP7-224189 (ULTRA project, http://www2.teknik.uu.se/Ultratc) and is part of the research program of the “Stichting voor Fundamenteel Onderzoek der Materie (FOM)”, which is financially supported by the “Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)”. This work was also supported by the European FP7 project “Nanoantenna” (FP7-HEALTH-F5-2009-241818-NANOANTENNA).Peer Reviewe

Utilizing the International Geo Sample Number Concept in Continental Scientific Drilling During ICDP Expedition COSC-1

The International Geo Sample Number (IGSN) is a globally unique persistent identifier (PID) for physical samples that provides discovery functionality of digital sample descriptions via the internet. In this article we describe the implementation of a registration service for IGSNs of the Helmholtz Centre Potsdam – GFZ German Research Centre for Geosciences. This includes the adaption of the metadata schema developed within the context of the System for Earth Sample Registration (SESAR1) to better describe the complex sample hierarchy of drilling cores, core sections and samples of scientific drilling projects. Our case study is the COSC-1 expedition2 (Collisional Orogeny in the Scandinavian Caledonides) supported by the International Continental Scientific Drilling Program3 (ICDP). COSC-1 prompted for the first time in ICDP’s history to assign and register IGSNs during an on-going drilling campaign preserving the original parent-child relationship of the sample objects. IGSN-associated data and metadata are distributed and shared with the world wide community through novel web portals, one of which is currently evolving as part of ICDP’s collaborative efforts within the GFZ Potsdam and researchers from ICDP’s COSC clientele. Thus, COSC-1 can be considered as a ‘Prime-Example’ for ICDP projects to further improve the quality of scientific research output through a transparent process of producing and managing large quantities of data as they are normally acquired during a typical scientific drilling operation. The IGSN is an important new player in the general publication landscape that can be cited in scholarly literature and also cross-referenced in DOI-bearing scholarly and data publications