Получены алгебраические выражения для вероятности спонтанного излучения в утекающие моды для эмиттеров в нанопроводе, ориентированных радиально, аксиально и азимутально по отношению к оси нанопровода. Рассчитаны диаграммы направленности и зависимости вероятности спонтанной эмиссии от положения эмиттера. Показано, что при определенных значениях диаметра нанопровода вероятность спонтанной эмиссии на границе нанопровода может увеличиваться на порядок, и возможно формирование узкой диаграммы направленности. Ключевые слова: нанопровод, спонтанная эмиссия, утекающие моды.

Metal-dielectric photonic structures with organic materials 4,4-bis(N-carbazolyl)-1,1-biphenyl and 4,4′-bis[4-(di-ptolylamino)styryl] biphenyl) as light emitting layers were investigated. The formation of the polaritonic modes in the investigated structures was experimentally demonstrated and a correlation between theoretical and experimental dispersion was shown. Was shown, that increase in interaction between organic exciton and optical mode leads to a significant decrease in the lower polariton emission bandwidth.

The work presents robust and fast numerical method for calculation of complex-valued energies and wave functions of carriers in one-dimensional electrically biased periodic structures. Using this method optical transitions were studied in a superlattice (Bloch oscillations). Transition probabilities were shown to disobey linear dependence from applied field when it is large enough; in this case transitional with double and triple Bloch frequency can be more intensive than on single frequency. In a superlattice with a split miniband the same holds, with non-linearity being more pronounced in wider split case.

The GaN planar hexagonal microcavities were grown by a selective vapor phase epitaxy. The spectra were measured by the low-temperature cathodoluminescence method in-situ scanning electron microscope. The obtained spectra show a huge Rabi splitting (in order of 100 meV). Numerical simulation of the spatial distribution of the modes’ intensities of a hexagonal resonator is shown. Some modes can have strong spatial localization, leading to strong coupling with the exciton and huge Rabi splitting. Theoretically, we calculated the fraction of excitons in polariton modes, which correlates with the intensity of exciton radiation associated with these modes, for microcavities of a hexagonal shape. Thus, we have obtained the form of the dependence of the radiation probability on the eigenfrequencies of the structure.

A theoretical study of the properties of a microcavity structure with intracavity metal layers and an organic active region (material CBP(4,4′-Bis(N-carbazolyl)-1,1′-biphenyl)) was done. The structure consisted of a layer of organic material CBP, sandwiched between two silver layers, thin phase matching layers (dph=26 nm) and two quarter-wave Bragg reflectors. It was shown that hybrid modes localized in the central layer of the structure can significantly increase the decay rate of the luminescence of an organic emitter by means of the Purcell effect. A shift in the hybrid modes spectral position was shown upon their interaction with the exciton resonance in CBP. This fact may indicate the appearance of a strong coupling regime.

The effect of annealing temperature and time on the luminescence intensity of the InGaN/GaN heterostructure subjected to ion beam etching was studied. We show that annealing at a temperature of 1100°C makes it possible to eliminate the radiation defects in the GaN layers that arise in the etching process with a focused Ga+ ion beam (30 keV).

Методом селективной газофазной эпитаксии были выращены плоские гексагональные микрорезонаторы одиночные и двойные. Проводилось измерение спектров методом низкотемпературной катодолюминесценции на сканирующем электронном микроскопе. На полученных спектрах видно огромное расщепление Раби (порядка 100 мэВ). При высокой температуре два пика сливаются в один пик. Показано численное моделирование распределения интенсивности мод резонатора гексагональной формы. Некоторые моды могут иметь сильную пространственную локализацию, приводящую к сильному взаимодействию с экситоном и огромному расщеплению Раби. Теоретически мы рассчитали долю экситонов в поляритонных модах, которая коррелирует с интенсивностью экситонного излучения, связанного с этими модами, для нескольких микрорезонаторов гексагональной формы. Таким образом, мы получили вид зависимости вероятности излучения от собственных частот структуры.

AbstractThe interaction of a Tamm plasmon with an exciton in an organic material in the strong coupling mode is investigated theoretically. The structure consists of five pairs of layers of silicon oxide and tantalum oxide, an organic light-emitting layer of 4,4'-bis( N -carbazolyl)-1,1'-biphenyl, and a silver layer. It is shown that the splitting of polariton modes (Rabi splitting) with a magnitude of >400 meV can occur in such a structure, which can be accompanied by an increase in the luminescence bandwidth up to 700 meV.

AbstractIn the Si_3N_4 layer, coaxial and single submicrometer GaN structures of hexagonal shape with pyramidal facets are formed by selective vapor-phase epitaxy in windows produced with a focused ion beam. It is found that coaxial hexagonal structures are formed during the growth process in ring-shaped mask windows.

AbstractA technique for quantization of the electromagnetic field in photonic nanostructures with three-dimensional modulation of the dielectric constant is developed on the basis of the scattering matrix formalism ( S quantization in the three-dimensional case). Quantization is based on equating the eigenvalues of the scattering matrix to unity, which is equivalent to equating each other the sets of Fourier expansions for the fields of the waves incident on the structure and propagating away from the structure. The spatial distribution of electromagnetic fields of the modes in a photonic nanostructure is calculated on the basis of the R and T matrices describing the reflection and transmission of the Fourier components by the structure. To calculate the reflection and transmission coefficients of individual real-space and Fourier-space components, the structure is divided into parallel layers within which the dielectric constant varies as a function of two-dimensional coordinates. Using the Fourier transform, Maxwell’s equations are written in the form of a matrix connecting the Fourier components of the electric field at the boundaries of neighboring layers. Based on the calculated reflection and transmission vectors for all polarizations and Fourier components, the scattering matrix for the entire structure is formed and quantization is carried out by equating the eigenvalues of the scattering matrix to unity. The developed method makes it possible to obtain the spatial profiles of eigenmodes without solving a system of nonlinear integro-differential equations and significantly reduces the computational resources required for calculating the probability of spontaneous emission in three-dimensional systems.

AbstractSpontaneous-emission enhancement in a Tamm plasmon microcavity with an active region with organic material 4.4'-bis( N -carbazolyl)-1.1'-biphenyl (CBP) is theoretically and experimentally studied. The microcavity consisted of a Bragg reflector made of silicon oxide and tantalum oxide, over which CBP and silver layers are applied. The dependences of the Purcell modal factor on the emission direction and frequency, as well as the Purcell factor spectrum are calculated. The emission and fluorescence decay spectra in time are measured in the ultraviolet range. It is found that the probability of spontaneous emission increases and the maximum Purcell factor reaches three at frequencies corresponding to eigenmodes of the Tamm plasmon.

Graphene crystals, containing arrays of disclination defects, are modeled and their energies are calculated using molecular dynamics (MD) simulation technique. Two cases are analyzed in details: (i) pseudo-graphenes, which contain the alternating sign disclination ensembles and (ii) graphene with periodic distribution of disclination quadrupoles. Electronic band structures of disclinated graphene crystals are calculated in the framework of density functional theory (DFT) approach. The evolution of the Dirac cone and magnitude of band gap in the band structure reveal a dependence on the density of disclination quadrupoles and alternating sign disclinations. The electronic properties of graphene with disclination ensembles are discussed.

AbstractThe time-resolved photoluminescence of a Bragg structure formed by InAs single-layer quantum wells in a GaAs matrix is investigated experimentally. The comparison of photoluminescence spectra recorded from the edge and the surface of the sample indicates that Bragg ordering of the quantum wells leads to substantial modification of the spectra, in particular, to the appearance of additional modes. The spectrum recorded at the edge of the sample features a single line corresponding to the exciton ground state. In the spectrum recorded at the surface, an additional line whose frequency and propagation angle correspond to the Bragg condition for quantum wells, appears at high excitation levels. The calculation of the modal Purcell factor explains the fact that spontaneous emission is enhanced only for specific propagation angles and frequencies, rather than for all angles and frequencies satisfying the Bragg condition.

Исследована зависимость затухания собственной оптической моды вертикально-излучающего лазера с внутрирезонаторными металлическими контактами от геометрических параметров системы. Показано, что наименьшее затухание имеет место для частоты собственной моды резонатора, отличной от брэгговской частоты зеркал. Методом S-квантования рассчитана вероятность спонтанной эмиссии, и показано, что для высокоэнергетической нечетной моды вероятность спонтанной эмиссии увеличивается на 2 порядка по сравнению с вероятностью эмиссии в свободном пространстве. DOI: 10.21883/FTP.2017.04.44350.8419

A method for calculating the spontaneous-emission probability for arbitrary layered structures in the waveguide mode has been developed based on the scattering matrix formalism. The results of calculating the mode Purcell factor for the TE and TM modes of a planar waveguide are shown. Analytical estimates for the mode Purcell factor are obtained, and the conditions for achieving maximum amplification of spontaneous emission in a waveguide are determined.

Проведено исследование изменения вероятности спонтанной эмиссии для излучателя, помещенного в одномерный разупорядоченный фотонный кристалл. Показано, что для диполя, помещенного в разупорядоченный фотонный кристалл, возможно как усиление спонтанной эмиссии (если частота соответствует собственной оптической моде структуры), так и подавление спонтанной эмиссии (в случае запрещенной зоны или когда позиция соответствует узлу в профиле электрического поля собственной моды). Показано, что при большом уровне разупорядочения фотонная запрещенная зона сужается, а вероятность эмиссии в центре фотонной запрещенной зоны становится существенно отличной от нуля. Показано, что при большом уровне разупорядочения в фотонной запрещенной зоне возможно появление локализованных состояний, для которых спонтанная эмиссия значительно усилена. DOI: 10.21883/FTP.2017.07.44659.8479