Electrical control of optical orientation of neutral and negatively charged excitons in n-type semiconductor quantum well

We report a giant electric field induced increase of spin orientation of excitons in n-type GaAs/AlGaAs quantum well. It correlates strongly with the formation of negatively charged excitons (trions) in the photoluminescence spectra. Under resonant excitation of neutral heavy-hole excitons, the polarization of excitons and trions increases dramatically with electrical injection of electrons within the narrow exciton-trion bias transition in the PL spectra, implying a polarization sensitivity of 200 % per Volt. This effect results from a very efficient trapping of neutral excitons by the quantum well interfacial fluctuations (so-called "natural" quantum dots) containing resident electrons.Comment: 18 pages, 4 figure

Fine structure and optical pumping of spins in individual semiconductor quantum dots

We review spin properties of semiconductor quantum dots and their effect on optical spectra. Photoluminescence and other types of spectroscopy are used to probe neutral and charged excitons in individual quantum dots with high spectral and spatial resolution. Spectral fine structure and polarization reveal how quantum dot spins interact with each other and with their environment. By taking advantage of the selectivity of optical selection rules and spin relaxation, optical spin pumping of the ground state electron and nuclear spins is achieved. Through such mechanisms, light can be used to process spins for use as a carrier of information

Electrically tunable g-factors in quantum dot molecular spin states

We present a magneto-photoluminescence study of individual vertically stacked InAs/GaAs quantum dot pairs separated by thin tunnel barriers. As an applied electric field tunes the relative energies of the two dots, we observe a strong resonant increase or decrease in the g-factors of different spin states that have molecular wavefunctions distributed over both quantum dots. We propose a phenomenological model for the change in g-factor based on resonant changes in the amplitude of the wavefunction in the barrier due to the formation of bonding and antibonding orbitals.Comment: 5 pages, 5 figures, Accepted by Phys. Rev. Lett. New version reflects response to referee comment

Spin Fine Structure in Optically Excited Quantum Dot Molecules

The interaction between spins in coupled quantum dots is revealed in distinct fine structure patterns in the measured optical spectra of InAs/GaAs double quantum dot molecules containing zero, one, or two excess holes. The fine structure is explained well in terms of a uniquely molecular interplay of spin exchange interactions, Pauli exclusion and orbital tunneling. This knowledge is critical for converting quantum dot molecule tunneling into a means of optically coupling not just orbitals, but spins.Comment: 10 pages, 7 figures, added material, (published

Современные аспекты фотодинамической терапии при базальноклеточном раке кожи

Photodynamic therapy (PDT) is one of the most effective treatments for basal cell skin cancer (BCC). As the incidence rate of BCC is increasing worldwide, interest in developing new methods for diagnosing and treating this disease, taking into account long-term cosmetic results, is growing. The review article presents the results of domestic and foreign studies on the treatment of BCC with PDT. The presented results of studies from various domestic and foreign clinics indicate the high efficiency of independent PDT and a combination of PDT with other treatment methods. PDT is proposed to be used in combination with surgical methods and radiation therapy, immunomodulating and chemotherapeutic agents, and inhibitors of molecules involved in the carcinogenic process. These new strategies open the way to increasing the effectiveness of treatment and prevention of BCC. Moreover, in all studies, the safety of this non-invasive treatment, a low level of adverse reactions during therapy, good tolerance for the patient and excellent cosmetic treatment results are noted. The guidelines currently being developed in Europe and the United States provide consistent expert advice that reflects current published evidence of treatment outcomes for BCC using PDT. Moreover, the recommendations emphasize that the treatment plan for patients with “difficult to treat” BCC should be discussed at an interdisciplinary oncological council.Фотодинамическая терапия (ФДТ) является одним из наиболее эффективных методов лечения базальноклеточного рака кожи (БКРК). По мере роста показателей заболеваемости БКРК во всём мире всё больше возрастает интерес к разработке новых методов диагностики и лечения данного заболевания с учётом отдалённых косметических результатов. В обзорной статье приводятся результаты отечественных и зарубежных исследований по лечению БКРК с помощью ФДТ. Представленные результаты исследований различных отечественных и зарубежных клиник свидетельствуют о высокой эффективности самостоятельной ФДТ и комбинации ФДТ с другими методами лечения. ФДТ предлагается применять в сочетании с хирургическими методами и лучевой терапией, иммуномодулирующими и химиотерапевтическими агентами, ингибиторами молекул, участвующих в канцерогенном процессе. Эти новые стратегии открывают путь к повышению эффективности лечения и профилактики БКРК. При этом во всех исследованиях отмечается безопасность данного неинвазивного лечения, низкий уровень побочных реакций при проведении терапии, хорошая переносимость для пациента и превосходные косметические результаты лечения. В разработанных в настоящее время в Европе и США руководствах представлены согласованные экспертные рекомендации, отражающие текущие опубликованные доказательства результативности лечения БКРК с использованием ФДТ. При этом в рекомендациях подчеркивается, что план терапии пациентов с трудно поддающимися лечению БКРК должен обсуждаться на междисциплинарном онкологическом совете

Optical Orientation in Ferromagnet/Semiconductor Hybrids

The physics of optical pumping of semiconductor electrons in the ferromagnet/semiconductor hybrids is discussed. Optically oriented semiconductor electrons detect the magnetic state of the ferromagnetic film. In turn, the ferromagnetism of the hybrid can be controlled optically with the help of the semiconductor. Spin-spin interactions near the interface ferromagnet/semiconductor play crucial role in the optical readout and the manipulation of ferromagnetism.Comment: The review is written for a special issue "Spin Orientation" of Semiconductor Science and Technology journal dedicated to the memory of B.P. Zakharcheny