Linear optics, Raman scattering, and spin noise spectroscopy

Spin noise spectroscopy (SNS) is a new method for studying magnetic resonance and spin dynamics based on measuring the Faraday rotation noise. In strong contrast with methods of nonlinear optics, the spectroscopy of spin noise is considered to be essentially nonperturbative. Presently, however, it became clear that the SNS, as an optical technique, demonstrates properties lying far beyond the bounds of conventional linear optics. Specifically, the SNS shows dependence of the signal on the light power density, makes it possible to penetrate inside an inhomogeneously broadened absorption band and to determine its homogeneous width, allows one to realize an effective pump-probe spectroscopy without any optical nonlinearity, etc. This may seem especially puzzling when taken into account that SNS can be considered just as a version of Raman spectroscopy, which is known to be deprived of such abilities. In this paper, we clarify this apparent inconsistency.Comment: 7+ pages, 3 figure

High frequency electric field induced nonlinear effects in graphene (review)

The nonlinear optical and optoelectronic properties of graphene with the emphasis on the processes of harmonic generation, frequency mixing, photon drag and photogalvanic effects as well as generation of photocurrents due to coherent interference effects, are reviewed. The article presents the state-of-the-art of this subject, including both recent advances and well-established results. Various physical mechanisms controlling transport are described in depth including phenomenological description based on symmetry arguments, models visualizing physics of nonlinear responses, and microscopic theory of individual effects.Comment: 32 pages, 24 figures, revie

Exciton spin noise in quantum wells

A theory of spin fluctuations of excitons in quantum wells in the presence of non-resonant excitation has been developed. Both bright and dark excitonic states have been taken into account. The effect of a magnetic field applied in a quantum well plane has been analyzed in detail. We demonstrate that in relatively small fields the spin noise spectrum consists of a single peak centered at a zero frequency while an increase of magnetic field results in the formation of the second peak in the spectrum owing to an interplay of the Larmor effect of the magnetic field and the exchange interaction between electrons and holes forming excitons. Experimental possibilities to observe the exciton spin noise are discussed, particularly, by means of ultrafast spin noise spectroscopy. We show that the fluctuation spectra contain, in addition to individual contributions of electrons and holes, an information about correlation of their spins.Comment: 9 pages, 4 figures, Sec. IIB revised, Appendix adde

Light-matter interaction in doped microcavities

We discuss theoretically the light-matter coupling in a microcavity containing a quantum well with a two-dimensional electron gas. The high density limit where the bound exciton states are absent is considered. The matrix element of interband optical absorbtion demonstrates the Mahan singularity due to strong Coulomb effect between the electrons and a photocreated hole. We extend the non-local dielectric response theory to calculate the quantum well reflection and transmission coefficients, as well as the microcavity transmission spectra. The new eigenmodes of the system are discussed. Their implications for the steady state and time resolved spectroscopy experiments are analyzed.Comment: 7 pages, 2 figures; extended versio

Spin injection via (110)-grown semiconductor barriers

We study the tunneling of conduction electrons through a (110)-oriented single-barrier heterostructure grown from III-V semiconductor compounds. It is shown that, due to low spatial symmetry of such a barrier, the tunneling current through the barrier leads to an electron spin polarization. The inverse effect, generation of a direct tunneling current by spin polarized electrons, is also predicted. We develop the microscopic theory of the effects and show that the spin polarization emerges due to the combined action of the Dresselhaus spin-orbit coupling within the barrier and the Rashba spin-orbit coupling at the barrier interfaces.Comment: 7 pages, 2 figure

Suppression of spin beats in magneto-oscillation phenomena in two-dimensional electron gas

Theory of magneto-oscillation phenomena has been developed for two-dimensional electron systems with linear-in-k spin splitting. Both Dresselhaus and Rashba contributions are taken into account. It has been shown that the pattern of the magneto-oscillations depends drastically on the ratio between the above terms. The presence of only one type of the k-linear terms gives rise to the beats, i.e. two close harmonics corresponding to the spin-split subbands. However, if the strengths of both contributions are comparable, the third (central) harmonics appears in the spectrum of the magneto-oscillations. For equal strengths of the contributions, only the central harmonic survives, and the oscillations occur at a single frequency, although the k-linear terms remain in the Hamiltonian. Such suppression of the spin beats is studied in detail by the example of the Shubnikov-de Haas effect.Comment: 5 pages, 3 figure

Collective effects in emission of quantum dots strongly coupled to a microcavity photon

A theory of non-linear emission of quantum dot ensembles coupled to the optical mode of the microcavity is presented. Numerical results are compared with analytical approaches. The effects of exciton-exciton interaction within the quantum dots and with the reservoir formed by nonresonant pumping are considered. It is demonstrated, that the nonlinearity due to the interaction strongly affects the shape of the emission spectra. The collective superradiant mode of the excitons is shown to be stable against the non-linear effects.Comment: 17 pages, 5 figures, submitted to the focus issue of New J. Phys. on "Cavity and Circuit Quantum Electrodynamics in Solids

Resonant photonic crystals and quasicrystals based on highly doped quantum-well structures

A theory of light propagation through one-dimensional photonic crystals and deterministic aperiodic structures, including quasicrystals, based on doped quantum-well structures has been developed. The resonant Bragg condition, leading to the superradiant regime and formation of the widest optical reflection spectrum, has been formulated. The expressions for band gap edges for light waves in the Bragg structures have been obtained. The reflection and absorption spectra of such systems are calculated. The optical properties of the doped multiple-quantum-well structure are compared with the properties of undoped ones.Comment: 3 pages, 3 figures, Proceedings of 18th International Symposium Nanostructures: Physics and Technology 201

Effect of exchange interaction on the spin fluctuations of localized electrons

In this paper a microscopic theory of spin fluctuations in an ensemble of electrons localized on donors in a bulk semiconductor has been developed. Both the hyperfine interaction of the electron spin with spins of lattice nuclei and the exchange interaction between the electrons have been taken into account. We propose a model of clusters to calculate spin noise spectra of the ensemble of localized charge carriers. It has been shown that the electron-electron exchange interaction leads to an effective averaging of random nuclear fields and a shift of the peak in the spin-fluctuation spectrum towards lower frequencies.Comment: 9 pages, 3 figure

Spin noise in a quantum dot ensemble: from a quantum mechanical to a semi-classical description

Spin noise spectroscopy is a promising technique for revealing the microscopic nature of spin dephasing processes in quantum dots. We compare the spin-noise in an ensemble of singly charged quantum dots calculated by two complementary approaches. The Chebyshev polynomial expansion technique (CET) accounts for the full quantum mechanical fluctuation of the nuclear spin bath and a semi-classical approach (SCA) is based on the averaging the electron spin dynamics over all different static Overhauser field configurations. We observe a remarkable agreement between both methods in the high-frequency part of the spectra, while the low-frequency part is determined by the long time fluctuations of the Overhauser field. We find small differences in the spectra depending on the distribution of hyperfine couplings. The spin-noise spectra in strong enough magnetic fields where the nuclear dynamics is quenched calculated by two complimentary approaches are in perfect agreement.Comment: 6 pages, 3 figure