Natalia Malkova

Electro-optic control of the superprism effect in photonic crystals

We have designed a two-dimensional photonic crystal in electro-optic materials that can actively control the superprism effect. By applying an electric field to the photonic crystal, the electro-optic effect will change the dielectric constant of the material, which modifies both the band structure and the dispersion surfaces. In the proposed structures, we show that electric fields of up to 6 V/μm in (Pb0.09La0.91)(Zr0.65Ti0.35)O3-based photonic crystals can deflect light up to 49°. This device concept can be used for a class of optical modulation devices that can provide a local control of dispersion surfaces within a photonic crystal.

Strain tunable light transmission through a 90° bend waveguide in a two-dimensional photonic crystal

We report a device based on strain-tunable light propagation through a 90° bend waveguide based on a two-dimensional photonic crystal. This is achieved by the splitting of a doubly degenerate defect state, by means of a symmetrical distortion of the lattice, locally near the bend. The resonant coupling of the photon modes between the two waveguide arms across the bend can be tuned by the symmetry and the magnitude of the local distortion of the lattice.

Tunable resonant light propagation through 90° bend waveguide based on strained photonic crystal

The degenerate state in two-dimensional photonic crystal is studied. The photonic analogue of the static Jahn–Teller effect is utilized for realizing tunable propagation through photonic crystal waveguide bends. It is shown that the resonant coupling of the photon modes at the corner can be tuned by the symmetry and magnitude of the distortion of the lattice.

Symmetrical analysis of the defect level splitting in two-dimensional photonic crystals

In this paper doubly degenerate defect states in the band gap of the two-dimensional photonic crystal are studied. These states can be split by a convenient distortion of the lattice. Through analogy with the Jahn–Teller effect in solids, we present a group theoretical analysis of the lifting of the degeneracy of doubly degenerate states in a square lattice by different vibronic modes. The effect is supported by the supercell plane-wave model and by the finite difference time domain technique. We suggest ways for using the effect in photonic switching devices and waveguides.

Negative‐Band‐Gap Quantum Dots

The spectrum of quantum dots (QDs) made from semiconductors like HgTe and HgS changes from negative gap to positive gap with decreasing size. Furthermore, intrinsic surface states, which are not related to dangling bonds, appear in the negative gap regime. We investigate theoretically the evolution of the spectrum of HgS QDs with decreasing size and show how states evolve from a negative gap to a positive gap as confinement is increased. The lowest confined electron level evolves into an intrinsic surface state with increasing size. This surface state is not derived from a bulk HgS bands. We demonstrate that surface states found do not have characteristic topological properties.

Resonant light propagation through 90°-bend waveguide based on a strained two-dimensional photonic crystal

The abstract for this paper has been replaced with the following editorial note: It has come to the attention of the Optical Society of America that this article should not have been submitted for publication owing to its substantial replication of an earlier paper: N. Malkova, “Tunable resonant light propagation through 90° bend waveguide based on strained photonic crystal,” J. Phys.: Condens. Matter 16, 1523–1530 (2004).

Spin Properties of Quantum wells Incorporating Semimagnetic Semiconductors

The electronic band-edge spectrum of magnetic semiconductor quantumwells containing a diluted magnetic semiconductor as one of the constituents is studied within the envelope-function formalism. Quantum wells with normal and mutually inverted band arrangements are considered. The sp – d hydribization between the bare sp -electron states and the d -states of the Mn atoms is shown to lead to a spin-splitting effect. The spin-splitting effect is studied as a function of external magnetic field, well width, valence band offset and fraction of magnetic atoms. The results have bearing on the perspective for using the magnetic semicondutor structures in spin electronics.