arXiv subjects

Nikolay A. Gippius

Publications and source records attributed to Nikolay A. Gippius.

25 records · Page 2Linked to original sources

arXiv2019

Effects of tunneling and multiphoton transitions on squeezed states generation in bistable driven systems

Bistability of nonlinear resonantly driven oscillator in the presence of external noise is analyzed by means of classical Fokker-Planck equation in quasienergy space with account for tunneling effects and by quantum master equation in quasienergy states representation. Two time scales responsible for different stages of bistable system relaxation have been obtained. We found out that the slow relaxation rate caused by fluctuation--induced transitions between different stable states can be enhanced by several orders due to tunneling effects. It was also revealed that tunneling between nearly degenerate quasienergy states and resonant multiphoton transitions between the genuine eigenstates of the nonlinear oscillator are just the similar effects. It was demonstrated that the quasienergy states in the bistability region corresponding to higher amplitude are squeezed. The degree of squeezing is determined by the ratio between nonlinearity and detuning, so the uncertainty of one quadrature can be considerably smaller than the quantum limit. It was found out that tunneling effects can enhance the generation of output oscillator squeezed states. It is shown that 1D Fokker--Planck equation is a quasiclassical limit of a quantum master equation.

cond-mat.mes-hall↗

arXiv2017

Addressing the exciton fine structure in colloidal nanocrystals: the case of CdSe nanoplatelets

We study the band-edge exciton fine structure and in particular its bright-dark splitting in colloidal semiconductor nanocrystals by four different optical methods based on fluorescence line narrowing and time-resolved measurements at various temperatures down to 2 K. We demonstrate that all these methods provide consistent splitting values and discuss their advances and limitations. Colloidal CdSe nanoplatelets with thicknesses of 3, 4 and 5 monolayers are chosen for experimental demonstrations. The bright-dark splitting of excitons varies from 3.2 to 6.0 meV and is inversely proportional to the nanoplatelet thickness. Good agreement between experimental and theoretically calculated size dependence of the bright-dark exciton slitting is achieved. The recombination rates of the bright and dark excitons and the bright to dark relaxation rate are measured by time-resolved techniques.

cond-mat.mes-hall↗

arXiv2017

Optical properties of opaline photonic crystals covered by phase-change material Ge$_2$Sb$_2$Te$_5$

The physical origin of resonant Wood's anomalies in the reflection spectra of three-dimensional (3D) opaline photonic crystals covered with Ge$_2$Sb$_2$Te$_5$ (GST225) is discussed. For this purpose, the optical reflection spectra are studied for different incident angles of light both experimentally and theoretically. The performed eigenmode analysis reveals that the Wood's anomalies originate from the quasiguided modes which appear in the GST225 capping layer. This conclusion is supported by the simulated electromagnetic near-field distributions of incident light at resonant frequencies. The experimental reflection spectra are in a good agreement with theoretical calculations performed by the Fourier modal method in the scattering matrix form.

physics.optics↗

arXiv2015

Polarization control of quantum dot emission by chiral photonic crystal slabs

We investigate theoretically the polarization properties of the quantum dot's optical emission from chiral photonic crystal structures made of achiral materials in the absence of external magnetic field at room temperature. The mirror symmetry of the local electromagnetic field is broken in this system due to the decreased symmetry of the chiral modulated layer. As a result, the radiation of randomly polarized quantum dots normal to the structure becomes partially circularly polarized. The sign and degree of circular polarization are determined by the geometry of the chiral modulated structure and depend on the radiation frequency. A degree of circular polarization up to 99% can be achieved for randomly distributed quantum dots, and can be close to 100% for some single quantum dots.

physics.optics↗

arXiv2010

One-dimensional ZnO exciton polaritons with negligible thermal broadening at room temperature

Phonon damping is the main source of pure dephasing in the solid state, limiting many fundamental quantum effects to low temperature observations. Here we show how excitons in semiconductors can be totally decoupled from the phonon bath, even at room temperature, thanks to their strong interaction with photons. To do so, we investigated ZnO microwires, a new semiconductor nanostructure made of large band-gap material where the light can be trapped and guided into whispering gallery modes. In this system, the very large coupling regime between exciton and photon results in unusual exciton-polariton of one-dimensional character and Rabi splitting as large as 300meV. We find that polariton modes of excitonic fraction up to 75% exhibit no thermal broadening up to room temperature. We show that this remarkable behavior is due to the very large Rabi splitting as compared to the LO phonon energy.

cond-mat.mes-hall↗

arXiv2009

Transverse Photo-Voltage Induced by Circularly Polarized Light

We discovered that when circularly polarized light is obliquely incident on a two-dimensional metallic photonic crystal slabs, electrical voltage is induced perpendicularly to the incident plane. Signal sign is reversed by changing the sense of polarization or incident angle. The origin of this transverse photo-induced voltage is explained in terms of the force linear in light intensity induced by the asymmetry brought by angular momentum of incident light.

physics.optics↗

arXiv2008

Entangled photons from a strongly coupled quantum dot-cavity system

A quantum dot strongly coupled to a photonic crystal has been recently proposed as a source of entangled photon pairs [R. Johne et al., Phys. Rev. Lett. 100, 240404 (2008)]. The biexction decay via intermediate polariton states can be used to overcome the natural splitting between the exciton states coupled to the horizontally and vertically polarized light modes, so that high degrees of entanglement can be expected. We investigate theoretically the features of realistic dot-cavity systems, including the effect of the different oscillator strength of excitons resonances coupled to the different polarizations of light. We show that in this case, an independent adjustment of the cavity resonances is needed in order to keep a high entanglement degree. We also consider the case when the biexciton-exciton transition is also strongly coupled to a cavity mode. We show that a very fast emission rate can be achieved allowing the repetition rates in the THz range. Such fast emission should however be paid for by a very complex tuning of the many strongly coupled resonances involved and by a loss of quantum efficiency. Altogether a strongly coupled dot-cavity system seems to be very promising as a source of entangled photon pairs.

quant-ph↗