| 1. |
- Pozina, Galia, et al.
(författare)
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Emission Properties of GaN Planar Hexagonal Microcavities
- 2020
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Ingår i: Physica Status Solidi (a) applications and materials science. - : WILEY-V C H VERLAG GMBH. - 1862-6300 .- 1862-6319. ; 217:14
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Tidskriftsartikel (refereegranskat)abstract
- Fabrication of microcavities based on III-nitrides is challenging due to difficulties with the coherent growth of heterostructures having a large number of periods, at the same time keeping a good precision in terms of thickness and composition of the alloy. A planar design for GaN microresonators supporting whispering gallery modes is suggested. GaN hexagonal microstructures are fabricated by selective-area metalorganic vapor phase epitaxy using focused ion beam for mask patterning. Low-temperature cathodoluminescence spectra measured with a high spatial resolution demonstrate two dominant emission lines in the near bandgap region. These lines merge at room temperature into a broad emission band peaking at approximate to 3.3 eV, which is shifted toward lower energies compared with the reference excitonic spectrum measured for the GaN layer. A numerical analysis of exciton-polariton modes shows that some strongly localized cavity modes can have high Purcell coefficients and can strongly interact with the GaN exciton.
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| 2. |
- Belonovski, Alexey V, et al.
(författare)
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Quantum analysis of luminescence of an exciton in a meso-cavity
- 2021
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Ingår i: Optics Express. - : Optical Society of America. - 1094-4087. ; 29:13, s. 20724-20734
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Tidskriftsartikel (refereegranskat)abstract
- Interaction of cavity modes with an exciton in a meso-cavity (the structure supporting several cavity modes separated by an energy interval comparable to Rabi-splitting of an exciton and cavity modes) has been analyzed using a quantum-mechanical approach. Simultaneous interaction of an exciton and several cavity modes results in few novel effects such as ladder-like increase of the exciton population in the system, quantum beating and non-monotonic dependence of the ground polariton state in the system on the pumping. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License.
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| 3. |
- Girshova, Elizaveta I, et al.
(författare)
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Proposal for a photoacoustic ultrasonic generator based on Tamm plasmon structures
- 2020
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Ingår i: Optics Express. - : OPTICAL SOC AMER. - 1094-4087. ; 28:18, s. 26161-26169
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Tidskriftsartikel (refereegranskat)abstract
- The scheme of a generation of ultrasound waves based on optically excited Tamm plasmon structures is proposed. It is shown that Tamm plasmon structures can provide total absorption of a laser pulse with arbitrary wavelength in a metallic layer providing the possibility of the use of an infrared semiconductor laser for the excitation of ultrasound waves. Laser pulse absorption, heat transfer and dynamical properties of the structure are modeled, and the optimal design of the structure is found. It is demonstrated that the Tamm plasmon-based photoacoustic generator can emit ultrasound waves in the frequency band up to 100 MHz with predefined frequency spectrum. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
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| 4. |
- Ivanov, Konstantin A., et al.
(författare)
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Control of the surface plasmon dispersion and Purcell effect at the metamaterial-dielectric interface
- 2020
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Ingår i: Scientific Reports. - : NATURE RESEARCH. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- The use of metamaterial as a way to mitigate the negative effects of absorption in metals on the Purcell effect in metal-dielectric structures is investigated. A layered metal-dielectric structure is considered as an anisotropic medium in the long-wavelength limit. The dispersion of the surface plasmon appearing at the boundary between such a structure and a different dielectric material, as well as the position of the peak in the local density of states are studied for various combinations of materials and filling factors of the periodic structure. The calculated frequency dependence of the Purcell factor demonstrates an increase in peak value compared to the conventional plasmonic structure. The results obtained using effective media approach are compared to the results of numerical modelling.
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| 5. |
- Morozov, Konstantin M., et al.
(författare)
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Efficient UV Luminescence from Organic-Based Tamm Plasmon Structures Emitting in the Strong-Coupling Regime
- 2020
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Ingår i: The Journal of Physical Chemistry C. - : AMER CHEMICAL SOC. - 1932-7447 .- 1932-7455. ; 124:39, s. 21656-21663
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Tidskriftsartikel (refereegranskat)abstract
- Excitons in organic semiconductors possessing a large oscillator strength demonstrate strong coupling with cavity modes at room temperature. A large Stokes shift in some organic semiconductors enriches and complicates the picture of the emission in strongly coupled systems of organic excitons and light. Here, we demonstrate strong coupling of excitons in 4,4-bis(N-carbazolyl)-1,1-biphenyl (CBP) and Tamm plasmons in the ultraviolet (UV) band, accompanied by a bright emission from the structure. Reflection measurements demonstrate the pronounced formation of the lower and upper polariton modes with Rabi splitting of the magnitude of 0.3 eV, and the emission peak experiences a substantial red shift with respect to the lower polariton mode. Both radiative and nonradiative decay rates in the Tamm plasmon CBP structure are increased with respect to a bare CBP. Such peculiar behavior is attributed to the simultaneous manifestation of strong coupling and weak coupling of the CBP molecule emitters to the Tamm plasmons.
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| 6. |
- Morozov, Konstantin M., et al.
(författare)
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Opposite Sign of Polarization Splitting in Ultrastrongly Coupled Organic Tamm Plasmon Structures
- 2021
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Ingår i: The Journal of Physical Chemistry C. - : AMER CHEMICAL SOC. - 1932-7447 .- 1932-7455. ; 125:15, s. 8376-8381
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Tidskriftsartikel (refereegranskat)abstract
- The properties of the ultrastrongly coupled Tamm plasmon cavity filled with a high-oscillator-strength organic material DPAVBi (4,4-bis[4-(di-p-tolylamino)styryl]biphenyl) are studied using theoretical and experimental methods. An analytical model predicts the opposite sign of polarization splitting for the lower and upper polariton cases and a giant absolute value of the splitting. A set of organic Tamm plasmon cavities with different detuning parameters are fabricated. We demonstrate that all structures are operating in the ultrastrong coupling regime: the values of the Rabi splitting are close to a 20% fraction of the exciton energy. The measured angle-dependent reflectivity spectra structure for both transverse electric (TE) and transverse magnetic (TM) polarizations confirm the predicted theoretical model. We obtained a giant value of the polarization splitting of up to 180 meV for both polariton branches. We believe that it is the first demonstration of such peculiar polarization splitting behavior of polaritons in the ultrastrong coupling regime.
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| 7. |
- Pozina, Galia, et al.
(författare)
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Effect of Plasmonic Ag Nanoparticles on Emission Properties of Planar GaN Nanowires
- 2023
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Ingår i: Nanomaterials. - : MDPI. - 2079-4991. ; 13:8
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Tidskriftsartikel (refereegranskat)abstract
- The combination of plasmonic nanoparticles and semiconductor substrates changes the properties of hybrid structures that can be used for various applications in optoelectronics, photonics, and sensing. Structures formed by colloidal Ag nanoparticles (NPs) with a size of 60 nm and planar GaN nanowires (NWs) have been studied by optical spectroscopy. GaN NWs have been grown using selective-area metalorganic vapor phase epitaxy. A modification of the emission spectra of hybrid structures has been observed. In the vicinity of the Ag NPs, a new emission line appears at 3.36 eV. To explain the experimental results, a model considering the Frohlich resonance approximation is suggested. The effective medium approach is used to describe the enhancement of emission features near the GaN band gap.
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| 8. |
- Pozina, Galia, et al.
(författare)
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Enhancement of light emission in Bragg monolayer-thick quantum well structures
- 2019
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Ingår i: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Control over spontaneous emission rate is important for improving efficiency in different semiconductor applications including lasers, LEDs and photovoltaics. Usually, an emitter should be placed inside the cavity to increase the spontaneous emission rate, although it is technologically challenging. Here we experimentally demonstrate a phenomenon of super-radiance observed in a cavity-less periodic Bragg structure based on InAs monolayer-thick multiple quantum wells (MQW). The collective super-radiant mode shows enhanced emission rate for specific angles and frequencies. This behaviour correlates with the calculations demonstrating individual spots of the enhanced Purcell coefficient near the Bragg condition curve. This study provides a perspective for realization of surface emitting cavity-less lasers with distributed feedback.
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| 9. |
- Pozina, Galia, et al.
(författare)
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Fröhlich resonance splitting in hybrid GaN nanowire-Ag nanoparticle structures
- 2024
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Ingår i: New Journal of Physics. - : IOP Publishing Ltd. - 1367-2630. ; 26:5
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Tidskriftsartikel (refereegranskat)abstract
- Plasmonic nanoparticles (NPs) have attracted significant attention due to their unique optical properties and broad optoelectronic and photonic applications. We investigate modifications of emission in hybrid structures formed by 60 nm silver NPs and GaN planar nanowires (NWs). Bare GaN NWs exhibit photoluminescence (PL) spectra dominated by broad bands peaking at similar to 3.44 eV and similar to 3.33 eV, attributed to basal plane stacking faults. In hybrids, two new narrow PL lines appear at 3.36 and 3.31 eV, resulting in PL enhancement at these energies. While the 3.36 eV line in hybrid structures can be explained using the Fr & ouml;hlich resonance approximation based on the electric dipole concept, the appearance of two features at 3.36 and 3.31 eV indicates the splitting of resonance lines. This phenomenon is explained in framework of theoretical model based on the interaction of the dipole with its charge image, taking into account the quadrupole moment of the silver sphere and the quadrupole field of the charge image. A good agreement is obtained between the calculated Fr & ouml;hlich resonance frequencies and the experimental PL lines in hybrid structures.
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| 10. |
- Pozina, Galia, et al.
(författare)
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Purcell Effect and Nonlinear Behavior of the Emission in a Periodic Structure Composed of InAs Monolayers Embedded in a GaAs Matrix
- 2019
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Ingår i: Annalen der Physik. - : WILEY-V C H VERLAG GMBH. - 0003-3804 .- 1521-3889. ; 531:6
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Tidskriftsartikel (refereegranskat)abstract
- Enhancement of spontaneous emission in a resonant Bragg quantum well (QW) structure with 60 periods of triple InAs monolayers embedded in a GaAs matrix is studied experimentally and theoretically. From measurements of the time-resolved photoluminescence, besides the QW exciton at 1.47 eV, a specific super-radiant (SR) emission demonstrating nonlinear properties is found. The SR mode shows a near-quadratic dependence of intensity on excitation power, while its energy position follows the Bragg condition. It is revealed that the SR mode shows a peculiar non-monotonic dependence of intensity on direction, with a maximum observed at approximately 40 degrees. The enhancement in the SR emission at a specific direction is correlated well with suggested theoretical consideration of the modal Purcell factor for periodic quantum well structures.
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