Highly-sensitive chemical detection in the infrared regime using plasmonic gold nanocrosses

Abstract

Here we investigate an optical counterpart of the quantum Hanle effect. By employing the concepts of nonhermitian quantum mechanics 7,8 , we have designed an artificial plasmonic "atom" which has a pair of degenerate resonances that split by 3 broken time-reversal symmetry due to the presence of loss. This is a complete optical analogue of the atomic system where initially degenerate atomic states are split when the time-reversal symmetry is broken by the magnetic field 1 . Twodimensional (2D) arrays of these particles can form a new artificial material (metamaterial) with extremely efficient optical activity.Metamaterials provide vast opportunities to manipulate light beams in an uncommon way 11 , promising a wide range of potential applications such as cloaking 12,13 and perfect lensing 14 based on negative index of refraction. In the optical range, the properties of metamaterials rely on plasmonic effects 11 . In this work we will employ the localized surface plasmon (LSP) resonances supported by metal nanoparticles made of noble metals 15 . These resonances are solely determined by the particle's shape and surrounding environment and can be engineered and tuned to the desired frequency [16][17][18] .The basic scheme of the Hanle effect is represented in Fig. 1(a-b). Linearly polarized light, being a superposition of left and right circular polarizations, excites coherently the p-orbitals of an atom, conserving the total angular momentum. The degeneracy between p-states [ Fig. 1(a)] could be removed by an applied static magnetic field [Fig 1(b)]. The excited p-states evolve in time with slightly dissimilar time constants, adding different phases for opposite circular polarizations and, as a consequence, resulting in polarization-unpreserved light scattering. The polarization of the scattered light depends then on the strength of the magnetic field. The plasmonic "atom level" diagram of our optical analogue is shown in Fig. 1(c-d)

Integrated Collinear Refractive Index Sensor with Ge PIN Photodiodes

“…A comparison of our experimental results with experimental data from selected conventional, non-integrated plasmonic structures for refractive index sensing shows that the sensitivity in our setup is markedly higher than what can be observed for plasmonic Au nanoparticles 12 and, in particular, exceeds the sensitivities typically obtained in Al nanohole arrays 27 (see table 1). 28 700 647 Au nanocross 29 1400 500 Au nanopillar 30 1300 -1500 1000 Periodic array of Au mushrooms 31 1260 1010 Hybrid Au nanohole array 15 650 -700 670 Suspended NHA in Au film 32 795 717 Passivated Al NHA 27 700 -750 487 This work 1310 -1350 1180 When the device is incorporated into a microfluidic setup with a laser diode as the vertical illumination light source 33 , the operating wavelength λop is fixed. In this operating mode, a resonance peak shift induced by a change in nSup can be detected as a change in responsivity at λop.…”

Features of Local Electric Field Excitation in Asymmetric Nanocross Illuminated by Ultrafast Laser Pulse

“…It has been widely used in the field of chemosensing [4,5], surface enhanced Raman scattering [6,7], biomedicine [8,9], and near-field control [10,11]. In these applications, a variety of structural geometries have been used in order to achieve desired functionalities.…”

Recent advances in surface plasmon resonance imaging: detection speed, sensitivity, and portability

“…The sensitivity enhancement was found to be attributed to an increased surface reaction area and stronger coupling between analytes and the excited LSPs. Rodríguez-Fortuño et al fabricated gold nanocross arrays on silicon substrate for chemical sensing [99]. Owing to the flexibility of electron beam lithography, the parameters of the nanocross structures could be optimized for successful sensing of chemical monolayers with an ultrahigh sensitivity of 500-700 nm/RIU.…”