Sub-nanosecond Pulse Generation from a Two-section Laser-thyristor: Theoretical Analysis

We have developed a theoretical model of a two-section laser-thyristor. It is shown that using a 4 µm weakly doped p-base can increase blocking voltage up to 50 V, which makes it possible to generate 2 ns 10 A current pulses. It is demonstrated that the proposed device utilizes passive Q switching to generate high-power short optical pulses that account for up to 80% of output power. By picking the optimal passive section length, we have achieved optical pulses of ∼30 ps full width at half maximum (FWHM) and ∼100 W peak power.     Keywords: pulsed laser, semiconductor N-p-N-i-P heterostructure, laser-thyristor, dynamic model of pulsed lase

A Microscopic Derivation of the SO(5)-Symmetric Landau-Ginzburg Potential

We construct a microscopic model of electron interactions which gives rise to both superconductivity and antiferromagnetism, and which admits an approximate SO(5) symmetry that relates these two phases. The symmetry can be exact, or it may exist only in the long-wavelength limit, depending on the detailed form of the interactions. We compute the macroscopic Landau-Ginzburg free energy for this model as a function of temperature and doping, by explicitly integrating out the fermions. We find that the resulting phase diagram can resemble that observed for the cuprates, with the antiferromagnetism realized as a spin density wave, whose wavelength might be incommensurate with the lattice spacing away from half filling.Comment: 29 pp., plain TeX, 7 figures, uses macros.tex (included) and epsf.tex; added subject clas

Photoluminescence Stokes shift and exciton fine structure in CdTe nanocrystals

The photoluminescence spectra of spherical CdTe nanocrystals with zincblende structure are studied by size-selective spectroscopic techniques. We observe a resonant Stokes shift of 15 meV when the excitation laser energy is tuned to the red side of the absorption band at 2.236 eV. The experimental data are analyzed within a symmetry-based tight-binding theory of the exciton spectrum, which is first shown to account for the size dependence of the fundamental gap reported previously in the literature. The theoretical Stokes shift presented as a function of the gap shows a good agreement with the experimental data, indicating that the measured Stokes shift indeed arises from the electron-hole exchange interaction.Comment: 8 pages, 4 figures, LaTe

Spin noise of a halide perovskite

We report on first observation of spin noise in a strongly birefringent semiconductor -- halide perovskite single crystal MAPbI$_3$. The observed spin noise resonance is ascribed to free holes with a record spin dephasing time of 4 ns. The spin dynamics is found to be affected by the residual light absorption of the crystal providing renormalization of the Larmor frequency. Extended spin noise spectroscopy with rotating magnetic field allowed us not only to evaluate the $g$-factor anisotropy, but also to distinguish two different spin subsystems tentatively associated to twinning of the crystal.Comment: 14 pages, 11 figure

Photon echoes from (In,Ga)As quantum dots embedded in a Tamm-plasmon microcavity

We acknowledge the financial support by the Deutsche Forschungsgemeinschaft through the Collaborative Research Centre TRR 142 and the International Collaborative Research Centre 160. S.V.P. and Yu.V.K. thank the Russian Foundation of Basic Research for partial financial support (contracts no. ofi_m 16-29-03115 and no. 15-52-12016NNIO_a). M.B. acknowledges partial financial support from the Russian Ministry of Science and Education (contract no. 14.Z50.31.0021). Yu.V.K. acknowledges Saint Petersburg State University for a research grant 11.42.993.2016. The project SPANGL4Q acknowledges financial support from the Future and Emerging Technologies (FET) programme within the Seventh Framework Programme for Research of the European Commission, under FET-Open grant no. FP7-284743.We report on the coherent optical response from an ensemble of (In,Ga)As quantum dots (QDs) embedded in a planar Tamm-plasmon microcavity with a quality factor of approx. 100. Significant enhancement of the light-matter interaction is demonstrated under selective laser excitation of those quantum dots which are in resonance with the cavity mode. The enhancement is manifested through Rabi oscillations of the photon echo, demonstrating coherent control of excitons with picosecond pulses at intensity levels more than an order of magnitude smaller as compared with bare quantum dots. The decay of the photon echo transients is weakly changed by the resonator indicating a small decrease of the coherence time T2 which we attribute to the interaction with the electron plasma in the metal layer located close (40 nm) to the QD layer. Simultaneously we see a reduction of the population lifetime T1, inferred from the stimulated photon echo, due to an enhancement of the spontaneous emission by a factor of 2, which is attributed to the Purcell effect, while non-radiative processes are negligible as confirmed from time-resolved photoluminescence.PostprintPeer reviewe

Photon echo transients from an inhomogeneous ensemble of semiconductor quantum dots

We acknowledge the financial support by the Deutsche Forschungsgemeinschaft, Project ICRC TRR 160 and the Russian Foundation of Basic Research (RFBR) in the frame of the Project No. 15-52-12016 NNIO_a. The project SPANGL4Q acknowledges financial support from the Future and Emerging Technologies (FET) programme within the Seventh Framework Programme for Research of the European Commission, under FET-Open Grant No. FP7-284743. S.V.P. thanks the RFBR for partial financial support (Project No. 14-02-31735 mol_a). S.V.P. and I.A.Yu. acknowledge partial financial support from the Ministry of Education and Science of the Russian Federation (Grant No. 11.G34.31.0067) and St-Petersburg State University (SPbU) (Grant No. 11.38.213.2014). M.B. acknowledges support from the Ministry of Education and Science of the Russian Federation (Grant No. 14.Z50.31.0021).An ensemble of quantum dot excitons may be used for coherent information manipulation. Due to the ensemble inhomogeneity any optical information retrieval occurs in form of a photon echo. We show that the inhomogeneity can lead to a significant deviation from the conventional echo timing sequence. Variation of the area of the initial rotation pulse, which generates excitons in a dot subensemble only, reveals this complex picture of photon echo formation. We observe a retarded echo for π/2 pulses, while for 3π/2 the echo is advanced in time as evidenced through monitoring the Rabi oscillations in the time-resolved photon echo amplitude from (In,Ga)As/GaAs self-assembled quantum dot structures and confirmed by detailed calculations.PostprintPeer reviewe