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- ItemNanowire-supported plasmonic waveguide for remote excitation of surface-enhanced Raman scattering(London : Nature Publishing Group, 2014) Huang, Y.; Fang, Y.; Zhang, Z.; Zhu, L.; Sun, M.Due to its amazing ability to manipulate light at the nanoscale, plasmonics has become one of the most interesting topics in the field of light-matter interaction. As a promising application of plasmonics, surface-enhanced Raman scattering (SERS) has been widely used in scientific investigations and material analysis. The large enhanced Raman signals are mainly caused by the extremely enhanced electromagnetic field that results from localized surface plasmon polaritons. Recently, a novel SERS technology called remote SERS has been reported, combining both localized surface plasmon polaritons and propagating surface plasmon polaritons (PSPPs, or called plasmonic waveguide), which may be found in prominent applications in special circumstances compared to traditional local SERS. In this article, we review the mechanism of remote SERS and its development since it was first reported in 2009. Various remote metal systems based on plasmonic waveguides, such as nanoparticle-nanowire systems, single nanowire systems, crossed nanowire systems and nanowire dimer systems, are introduced, and recent novel applications, such as sensors, plasmon-driven surface-catalyzed reactions and Raman optical activity, are also presented. Furthermore, studies of remote SERS in dielectric and organic systems based on dielectric waveguides remind us that this useful technology has additional, tremendous application prospects that have not been realized in metal systems.
- ItemThermal tuning of a fiber-integrated Fabry-Pérot cavity(Washington, DC : Soc., 2021) Singer, Clemens; Goetz, Alexander; Prasad, Adarsh S.; Becker, Martin; Rothhardt, Manfred; Skoff, Sarah M.Here, we present the thermal tuning capability of an alignment-free, fiber-integrated Fabry-Pérot cavity. The two mirrors are made of fiber Bragg gratings that can be individually temperature stabilized and tuned. We show the temperature tuning of the resonance wavelength of the cavity without any degradation of the finesse and the tuning of the individual stop bands of the fiber Bragg gratings. This not only permits for the cavity’s finesse to be optimized post-fabrication but also makes this cavity applicable as a narrowband filter with a FWHM spectral width of 0.07 ± 0.02 pm and a suppression of more than -15 dB that can be wavelength tuned. Further, in the field of quantum optics, where strong light-matter interactions are desirable, quantum emitters can be coupled to such a cavity and the cavity effect can be reversibly omitted and re-established. This is particularly useful when working with solid-state quantum emitters where such a reference measurement is often not possible once an emitter has been permanently deposited inside a cavity.
- ItemOptical properties of silicon nanowire arrays formed by metal-assisted chemical etching: Evidences for light localization effect(New York, NY [u.a.] : Springer, 2012) Osminkina, L.A.; Gonchar, K.A.; Marshov, V.S.; Bunkov, K.V.; Petrov, D.V.; Golovan, L.A.; Talkenberg, F.; Sivakov, V.A.; Timoshenko, V.Y.We study the structure and optical properties of arrays of silicon nanowires (SiNWs) with a mean diameter of approximately 100 nm and length of about 1-25 μm formed on crystalline silicon (c-Si) substrates by using metal-assisted chemical etching in hydrofluoric acid solutions. In the middle infrared spectral region, the reflectance and transmittance of the formed SiNW arrays can be described in the framework of an effective medium with the effective refractive index of about 1.3 (porosity, approximately 75%), while a strong light scattering for wavelength of 0.3 Ă· 1 μm results in a decrease of the total reflectance of 1%-5%, which cannot be described in the effective medium approximation. The Raman scattering intensity under excitation at approximately 1 μm increases strongly in the sample with SiNWs in comparison with that in c-Si substrate. This effect is related to an increase of the light-matter interaction time due to the strong scattering of the excitation light in SiNW array. The prepared SiNWs are discussed as a kind of 'black silicon', which can be formed in a large scale and can be used for photonic applications as well as in molecular sensing.
- ItemCoherent interaction of atoms with a beam of light confined in a light cage(London : Nature Publishing Group, 2021) Davidson-Marquis, Flavie; Gargiulo, Julian; GĂ³mez-LĂ³pez, Esteban; Jang, Bumjoon; Kroh, Tim; MĂ¼ller, Chris; Ziegler, Mario; Maier, Stefan A.; KĂ¼bler, Harald; Schmidt, Markus A.; Benson, OliverControlling coherent interaction between optical fields and quantum systems in scalable, integrated platforms is essential for quantum technologies. Miniaturised, warm alkali-vapour cells integrated with on-chip photonic devices represent an attractive system, in particular for delay or storage of a single-photon quantum state. Hollow-core fibres or planar waveguides are widely used to confine light over long distances enhancing light-matter interaction in atomic-vapour cells. However, they suffer from inefficient filling times, enhanced dephasing for atoms near the surfaces, and limited light-matter overlap. We report here on the observation of modified electromagnetically induced transparency for a non-diffractive beam of light in an on-chip, laterally-accessible hollow-core light cage. Atomic layer deposition of an alumina nanofilm onto the light-cage structure was utilised to precisely tune the high-transmission spectral region of the light-cage mode to the operation wavelength of the atomic transition, while additionally protecting the polymer against the corrosive alkali vapour. The experiments show strong, coherent light-matter coupling over lengths substantially exceeding the Rayleigh range. Additionally, the stable non-degrading performance and extreme versatility of the light cage provide an excellent basis for a manifold of quantum-storage and quantum-nonlinear applications, highlighting it as a compelling candidate for all-on-chip, integrable, low-cost, vapour-based photon delay.
- ItemAll-optical supercontinuum switching(London : Springer Nature, 2020) Melchert, Oliver; BrĂ©e, Carsten; Tajalli, Ayhan; Pape, Alexander; Arkhipov, Rostislav; Willms, Stephanie; Babushkin, Ihar; Skryabin, Dmitry; Steinmeyer, GĂ¼nter; Morgner, Uwe; Demircan, AyhanEfficient all-optical switching is a challenging task as photons are bosons and cannot immediately interact with each other. Consequently, one has to resort to nonlinear optical interactions, with the Kerr gate being the classical example. However, the latter requires strong pulses to switch weaker ones. Numerous approaches have been investigated to overcome the resulting lack of fan-out capability of all-optical switches, most of which relied on types of resonant enhancement of light-matter interaction. Here we experimentally demonstrate a novel approach that utilizes switching between different portions of soliton fission induced supercontinua, exploiting an optical event horizon. This concept enables a high switching efficiency and contrast in a dissipation free setting. Our approach enables fan-out, does not require critical biasing, and is at least partially cascadable. Controlling complex soliton dynamics paves the way towards building all-optical logic gates with advanced functionalities. © 2020, The Author(s).
- ItemFocus on nonlinear terahertz studies(Bristol : IOP, 2014) Leitenstorfer, A.; Nelson, K.A.; Reimann, K.; Tanaka, K.Resulting from the availability of improved sources, research in the terahertz (THz) spectral range has increased dramatically over the last decade, leading essentially to the disappearance of the so-called 'THz gap'. While most work to date has been carried out with THz radiation of low field amplitude, a growing number of experiments are using THz radiation with large electric and magnetic fields that induce nonlinearities in the system under study. This 'focus on' collection contains a number of articles, both experimental and theoretical, in the new subfield of THz nonlinear optics and spectroscopy on various systems, among them molecular gases, superconductors, semiconductors, antiferromagnets and graphene.