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...s of the last decade have thensconsisted in increasing the propagation lengths of SPPs by appending gain media in the dielectric. There havesbeen several demonstrations of net gain or ASE [190] [191] =-=[192]-=- in plasmonic structures incorporating organicsgain materials, which can be dyes in solution[191], in polymer matrices[189] or conjugated polymers[189]. Reds(or infrared) dyes are especially relevant ...

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... loss. In the optical regime, metals are highly lossy and SP is strongly affected by this loss. One possible way to overcome this problem is to compensate for the loss by using an optical gain medium =-=[4,5]-=-. Another possibility is to integrate plasmonics with other photonic technologies, for example, with silicon-on-insulator (SOI). In this approach, the low-loss SOI guides will be used to guide light o...

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...s of the last decade have thensconsisted in increasing the propagation lengths of SPPs by appending gain media in the dielectric. There havesbeen several demonstrations of net gain or ASE [190] [191] =-=[192]-=- in plasmonic structures incorporating organicsgain materials, which can be dyes in solution[191], in polymer matrices[189] or conjugated polymers[189]. Reds(or infrared) dyes are especially relevant ...

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...um can be introduced to compensate the loss of propagating SPP [57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72] or even to allow a net gain during the propagation in a gold nanostripe =-=[73]-=-. However, the gold nanostripe reported in Ref. [73] has a width of 1 μm which is not competitive enough for making a nano-width device, especially for the case of sub-wavelength dimension for visible...

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...’s function, the dispersion relation of TM SPP surface wave can be expressed as [29]: ε0√ k2P − ε0ω2/c2 + εd√ k2P − εdω2/c2 = − iσg ωε0 , (2) where kP is the wave number of the guided TM SPP wave and k0 the wave number of excitation light in free space expressed as ω/c. For an isolated graphene layer, there is ε0 = εd = 1. Eq. (2) can be simplified as [24, 27]: kp = k0 √ 1 − (2/η0σg)2, (3) where η0 ≈ 377Ω denotes the intrinsic impedance of free space. For an isolate graphene sheet, the chemical potential is determined by the carrier density [24]: ns = 2 π2V 2f ∫ ∞ 0 ξ[fd(ξ) − fd(ξ + 2μc)]dξ, (4) here Vf is the Fermi velocity and ns the sheet doping of graphene. In the analysis, μc = Vf √ πns and Vf = 106 m/s [30]. The most important advantage of graphene is the tunability of conductivity. The carrier density can be tuned by changing the thickness of the dielectric spacer underneath the graphene layer, which influences the dispersion and intraband losses of graphene. Therefore, surface carrier density ns can also be depicted as [13]: ns = ε0εdVg/he, (5) where h is the thickness of the spacer and Vg the gate voltage. Thus, according to Eqs. (4) and (5), the relationship between the th...

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...any frequency across the whole electromagnetic spectrum. 2 1. Introduction: The fields of nanophotonics and metamaterials have experienced an explosive growth in the past decade. Superlens [1], invisibility cloaking [2] and nanolasers [3] are possibly the best known examples. One general ingredient in these developments is the use of metals (e.g, gold, silver) that supports surface plasmon resonance [4]. The progress is currently limited by the intrinsic loss of metals. New strategies are constantly sought to tackle the loss issue. Examples include the use of gain medium to compensate the loss[5], and the adaption of high-index puredielectrics materials in the design [6]. This paper studies light interaction with puredielectric micro- and nanospheres, aiming to fully understand its near-field focusing properties which are important to super-resolution applications including field localization, fabrication[7, 8], characterization, sensing and imaging[9]. More than a decade ago Lu and Luk’yanchuk et al. first demonstrated that enhanced optical near-fields of a 500-nm silica sphere can be used for subwavelength structuring of silicon surface [10]. Since, there has been a strong continuin...