Simulations of the effect of waveguide cross-section on quantum dot–plasmon coupling (original) (raw)
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In this paper we image the highly confined long range plasmons of a nanoscale metal stripe waveguide using quantum emitters. Plasmons were excited using a highly focused 633 nm laser beam and a specially designed grating structure to provide stronger incoupling to the desired mode. A homogeneous thin layer of quantum dots was used to image the near field intensity of the propagating plasmons on the waveguide. We observed that the photoluminescence is quenched when the QD to metal surface distance is less than 10 nm. The optimised spacer layer thickness for the stripe waveguides was found to be around 20 nm. Authors believe that the findings of this paper prove beneficial for the development of plasmonic devices utilising stripe waveguides.
Colloidal Quantum Dot Integrated Light Sources for Plasmon Mediated Photonic Waveguide Excitation
ACS Photonics, 2016
We operate micron-sized CdSe/CdS core− shell quantum dot (QD) clusters deposited onto gold patches as integrated light sources for the excitation of photonic waveguides. The surface plasmon mode launched by the QD fluorescence at the top interface of the gold patches are efficiently coupled to photonic modes sustained by titanium dioxide ridge waveguides. We show that, despite a large effective index difference, the plasmonic and the photonic modes can couple with a very high efficiency provided the vertical offset between the two kinds of waveguides is carefully controlled. Based on the effective index contrast of the plasmonic and the photonic modes, we engineer in-plane integrated hybrid lenses. The hybrid lenses are obtained by shaping the contact interface between the plasmonic and the photonic waveguides. We demonstrate a 2-fold enhancement of the coupling efficiency for tapers equipped with a hybrid lens. Our results are expected to be useful for the development of low-cost, integrated light sources deployed in photonic circuits. F ully integrated photonic devices are typically comprised of passive photonic components and active elements, including sources and detectors. The integration of solid-state light sources in photonic integrated circuits is most often an expensive and technologically challenging procedure whatever the waveguiding material platform. 1 On the other hand, colloidal quantum dots (QDs) have been identified as a costeffective and efficient solution for the development of light emitting diodes. 2,3 Hence, whenever an incoherent, low bandwidth, broad spectrum light source is needed, colloidal QDs offer a strategic alternative to complex heterostructures. It was suggested recently that colloidal QDs could be operated as surface plasmon sources when arranged in a controlled way at the micron scale 4 or the nanoscale. 5 The interaction of colloidal QDs with waveguide modes is also reported in the literature, 6−8 but so far only little is done in the direction of hybrid plasmophotonic coupling configurations of colloidal integrated light sources. In this work, we investigate configurations comprised of gold thin film patches optically connected to titanium dioxide (TiO 2 ) ridge waveguides. The QD clusters are deposited onto the metal patches and the surface plasmon modes launched by the QD fluorescence are coupled to the photonic modes of the TiO 2 waveguides. The interest of an hybrid approach for the QD fluorescence excitation of the photonic waveguides is 2-fold. First, a plasmon-assisted excitation is efficient at selecting a well controlled polarization state impinging the entrance of the photonic waveguide. Second, a hybrid configuration offers the opportunity to develop in-plane integrated micro-optics for improved light injection. Indeed, by taking advantage of the high effective index contrast between the plasmonic and the photonic modes, we show that in-plane integrated optical elements such as lenses can be implemented by a careful design of the transition surface between the metal patches and the photonic waveguides. Such configurations are of practical interest down to the single-QD level for the development of plasmon assisted integrated colloidal single-photon sources. 9 Although the hybrid plasmophotonic configurations demonstrated in this work rely on TiO 2 waveguides, our approach is not restricted to visible spectral domain and may be extended to other waveguiding platform such as silicon-on-insulator and emitting materials (PbS QDs, for example).
Plasmonic Quantum Dot Nanolaser: Effect of “Waveguide Fermi Energy”
Plasmonics, 2019
This study models quantum dot (QD) plasmonic nanolaser. A metal/semiconductor/metal (MSM) structure was considered to attain plasmonic nanocavity. The active region (semiconductor layers) contains the following: QD, wetting layer (WL), and barrier layers. Band alignment between layers was used to predict their parameters. Momentum matrix element for transverse magnetic (TM) mode in QD structure was formulated. Waveguide Fermi energy was introduced and formulated, for the first time, in this work to cover the waveguide contribution (Ag metal layer) in addition to the active region. The high net modal gain was obtained when the waveguide Fermi energy was considered which meant that the increment comes from the material gain, not from the confinement factor. The obtained results were reasoned the high gain due to the change in waveguide Fermi energy in the valence band, where the valence band QD states are fully occupied that are referring to an efficient hole contribution.
arXiv (Cornell University), 2015
By using the real-space method, switching of a single plasmon interacting with a hybrid nanosystem composed of a semiconductor quantum dot (SQD) and a metallic nanoparticle (MNP) coupled to one-dimensional surface plasmonic waveguide is investigated theoretically. We discussed that the dipole coupling between an exciton and a localized surface plasmon results in the formation of a hybrid exciton and the transmission and reflection of the propagating single plasmon could be controlled by changing the interparticle distance between the SQD and the MNP and the size of the nanoparticles. The controllable transport of the propagating single surface plasmon by such a nanosystem discussed here could find the significant potential in the design of next-generation quantum devices such as plasmonic switch, single photon transistor and nanolaser and quantum information.
In this paper we excite bound long range stripe plasmon modes with a highly focused laser beam. We demonstrate highly confined plasmons propagating along a 50 µm long silver stripe 750 nm wide and 30 nm thick. Two excitation techniques were studied: focusing the laser spot onto the waveguide end and focusing the laser spot onto a silver grating. By comparing the intensity of the out-coupling photons at the end of the stripe for both grating and end excitation we are able to show that gratings provide an increase of a factor of two in the output intensity and thus out-coupling of plasmons excited by this technique are easier to detect. Authors expect that the outcome of this paper will prove beneficial for the development of passive nano-optical devices based on stripe waveguides, by providing insight into the different excitation techniques available and the advantages of each technique.
Indian Journal of Physics, 2023
We have theoretically investigated practically controllable routing properties of a surface plasmon by GaAs/ AlGaAs quantum dot (QD) embedded in the silver nanowire with a side branch on the basis of the real space approach. Our results showed that the routing properties such as transmission, reflection and transfer rate of traveling surface plasmons in such a hybrid nanosystem could be modulated by adjusting the classic control field, the frequency of the input field, detunings, and coupling strengths between the QD and silver nanowires. In particular, the influence of the classic control field makes us possible to divert the travel direction of a surface plasmon from the input branch to the side one. Such a proposed scheme could have a great potential in the achievement of integrated plasmonic devices based on a surface plasmon switch, a nano-plasmonic beam splitter, and a directional coupler for applications in quantum information processing.
Nanotechnology, 2016
The transport properties of a single plasmon interacting with a hybrid system composed of a semiconductor quantum dot (SQD) and a metal nanoparticle (MNP) coupled to a one-dimensional surface plasmonic waveguide are investigated theoretically via the real-space approach. We considered that the MNP-SQD interaction leads to the formation of a hybrid exciton and the transmission and reflection of a single incident plasmon could be controlled by adjusting the frequency of the classical control field applied to the MNP-SQD hybrid nanosystem, the kinds of MNPs and the background media. The transport properties of a single plasmon interacting with such a hybrid nanosystem discussed here could find applications in the design of next-generation quantum devices, such as single-photon switching and nanomirrors, and in quantum information processing.
Plasmonics, 2019
We proposed an experimentally feasible scheme of nano-plamonic switch and quantum router via the single self-assembled InGaAs/GaAs semiconductor quantum dot (SQD) with a V type three-level energy structure located between two silver metallic wa veguides. We studied theoretically transmission and transfer rates of single plasmons in s uch a multi-ports system via the real-space approach, where our results showed that singl e plasmons from the input port could be switchable and redirected by controlling parame ters, such as the intensity of the classical field, the detunings, and the interaction between the SQD and the waveguides. Our proposed scheme could be used not only in the design of quantum routers and quantum switches for the construction of quantum network, but al so in quantum photonic integrated circuits.
Controlling quantum-dot light absorption and emission by a surface-plasmon field
Optics Express, 2014
The possibility for controlling both the probe-field optical gain and absorption, as well as photon conversion by a surface-plasmonpolariton near field is explored for a quantum dot located above a metal surface. In contrast to the linear response in the weak-coupling regime, the calculated spectra show an induced optical gain and a triply-split spontaneous emission peak resulting from the interference between the surface-plasmon field and the probe or self-emitted light field in such a strongly-coupled nonlinear system. Our result on the control of the mediated photon-photon interaction, very similar to the 'gate' control in an optical transistor, may be experimentally observable and applied to ultra-fast intrachip/interchip optical interconnects, improvement in the performance of fiber-optic communication networks, and developments of optical digital computers and quantum communications.
A Plasmonic quantum dot nanolaser: effect of “waveguide Fermi energy” on material gain
Mağallaẗ al-Kūfaẗ li-l-fiziyā’, 2019
This work studies the gain from plasmonic quantum dot (QD) nanolaser. A metal/semiconductor/metal (MSM) structure was considered to attain plasmonic nanocavity with active region contains: QD, wetting layer (WL) and barrier layers. Band alignment between layers was used to predict their parameters. Momentum matrix element for transverse magnetic (TM) mode in QD structure was formulated. Waveguide Fermi energy was introduced and formulated, for the first time, in this work to cover the waveguide contribution (Ag metal layer) in addition to the active region. High net modal gain was obtained when the waveguide Fermi energy was taken into account which means that the increment comes from the material gain not from the confinement factor. The change in waveguide Fermi energy in the valence band explained the high gain, where the valence band QD states are fully occupied referring to an efficient hole contribution.