Azat R. Gubaydullin

We report an experimental realization of a three-terminal photonic heat transport device based on a superconducting quantum circuit. The central element of the device is a flux qubit made of a superconducting loop containing three Josephson junctions, which can be tuned by magnetic flux. It is connected to three resonators terminated by resistors. By heating one of the resistors and monitoring the temperatures of the other two, we determine photonic heat currents in the system and demonstrate their tunability by magnetic field at the level of 1 aW. We determine system parameters by performing microwave transmission measurements on a separate nominally identical sample and, in this way, demonstrate clear correlation between the level splitting of the qubit and the heat currents flowing through it. Our experiment is an important step towards realization of heat transistors, heat amplifiers, masers pumped by heat and other quantum heat transport devices.

A theoretical study of structures with Tamm plasmons, where metal strips forming a one-dimensional periodic structure with a quasiperiodic unit cell on the surface of a structure are arranged in accordance with the Fibonacci sequence, have been theoretically studied. It has been shown that, when using the Fibonacci structure as a unit cell, additional band gaps appear in the band structure and the number of the bands, their total width, and the fraction of localized states in the eigenmode spectrum increase with the Fibonacci sequence number. In this case, all dispersion surfaces are combinations of paraboloids and hyperboloids, and the frequency of alternation of paraboloids and hyperboloids in the dispersion relation increases with the Fibonacci sequence number.

We have studied experimentally and theoretically spontaneous emission rate modification in Tamm plasmon structures with semiconductor(InAs/GaAs quantum dots) and organic (CBP) emitters. Time-resolved spectroscopy demonstrates that spontaneous emission rate is increased by one order in magnitude. Experimentally measured spontaneous emission pattern coincides with calculated dependence of modal Purcel factor on frequency and angle of emission.

We study Tamm plasmon structure based on GaAs/Al_0.95GaAs distributed Bragg reflector covered by thin silver layer, with active area formed by InAs quantum dots. We have measured the spectral and angular characteristics of photoluminescence and performed theoretical calculation of the spontaneous emission rate (modal Purcell factor) in the structure by using S-quantization formalism. We show that for Tamm plasmon mode the spontaneous emission can be enhanced by more than an order of magnitude, despite absorption in metallic layer.

We have demonstrated experimentally and theoretically that losses in Tamm plasmon structures can be reduced by using a subwavelength structuration of the metal layer. The structures consist of a GaAs/Al_0.95Ga_0.05As Bragg reflector covered with a sub-wavelength silver grating. An active quantum dot layer is inserted to perform photoluminescence experiments. Experimental results show that the quality factor of the Tamm plasmon mode with grating increases substantially, with respect to the same structure without a grating. Moreover, a fine-tuning of the Tamm spectral position is obtained by changing the grating parameters. Finite element method simulations are in good agreement with the experimental values. Our results will promote the realization of lasing with the TP based devices at room temperature.

We study the probability of spontaneous emission enhancement of the dipole emitter imbedded in the stratified metal-dielectric metamaterial, characterized by the hyperbolic isofrequency surface. We analyze the performance of finite-difference time-domain (FDTD) method implementations for a 3D simulation of the spontaneous emission of the dipole source embedded in the metal dielectric stratified media. We discuss boundary conditions applicability.

The rate of spontaneous emission of an emitter placed in a disordered one-dimensional photonic crystal is analyzed. It is shown that the spontaneous emission of a dipole placed in a disordered photonic crystal can either be enhanced (if the frequency corresponds to an optical eigenmode of the structure) or suppressed (if the frequency lies in the band gap or the position of the emitter corresponds to a node in the electric- field profile of the eigenmode). It is demonstrated that, for high levels of disorder, the photonic band gap is narrowed and the emission rate at the center of the band gap becomes significantly different from zero. Furthermore, for high levels of disorder, localized states featuring significantly enhanced spontaneous emission may appear within the photonic band gap.