Degree Of Optical Polarization Research Articles

Coherent Aharonov-Bohm oscillations in type-II (Zn,Mn)Te/ZnSe quantum dots

The magneto-photoluminescence of type-II (Zn,Mn)Te quantum dots is presented. As a result of the type-II band alignment, Aharonov-Bohm (AB) oscillations in the photoluminescence intensity are evident. In addition, an interesting interplay between the AB effect and the spin polarization in these diluted magnetic semiconductor quantum dots is observed. The intensity of the AB oscillations increases with both magnetic field and the degree of optical polarization, indicating that the suppression of spin fluctuations improves the coherence of the system.

Spin and carrier relaxation dynamics in InAs/GaAs quantum-dot spin-LEDs

We investigate the dynamics of electrons injected into InAs/GaAs quantum dots by initializing and further observing the spin state of the electrons. For this purpose, we use spin polarized light-emitting diodes where the electron spin is set in a semimagnetic ZnMnSe layer. We find that the degree of optical polarization depends strongly on the ground state energy of the quantum dot. A dependence of polarization on dopant concentration in the spin aligner suggests an influence of residual electrons in the quantum dots.

Electrical spin injection from ZnMnSe into InGaAs-based quantum structures

We report on electrical spin injection into InGaAs-based nanostructures through a semi-magnetic ZnMnSe layer in a magnetic field. We show an optical polarization degree of the electro-luminescence of up to 35% in InGaAs quantum wells and up to 14% in InGaAs quantum dots. To be able to attribute the polarization of the emitted photons to the spin alignment in the semi-magnetic layer, we have fabricated reference devices and performed all-optical measurements.

Analysis of correlations between polarimetric and photometric characteristics of young stars

We present the results of the investigation of correlations between the polarimetric and photometric characteristics of a sample (496 objects) of young Herbig Ae/Be (HAEBE) stars and T Tauri (TT) stars. It is shown that, for 85% of the sample stars there is a gen- eral relation between the degree of optical polarization and the infrared colour index (V L)obs and the colour excess E(V L) due to the contribution of a circumstellar dust shell. Polarimetric data were also compared with the value of v sini to search for a possible correlation between the polarization and an inclination of circumstellar disks. Polarimetric data as well as IR excesses are considered and compared for dierent subgroups of young stars namely: HAEBE and TT stars with Algol{like minima of bright- ness (26 objects), Vega{type stars and post HAEBE stars (114 objects) and young solar{type stars (58 objects). For statistical purposes the data for young stars were com- pared with those collected for dierent groups of evolved objects such as: classical Be stars (300 objects), Mira Ceti stars (39 objects), early{type supergiants from the Serkowski et al. (1975) catalogue (120 objects) and main sequence (MS) stars within 50 pc from the Sun from the Leroy (1993) catalogue (68 objects). The value of polar- ization is discussed in context with the stages of evolution of circumstellar shells which were established by compari- son of spectral energy distribution in the far IR (using the IRAS data). It is shown that most young stars have sta- tistically larger value of polarization in comparison with the stars which are on a stage of evolution close to MS. We are able to contend that the changes in polarimetric behaviour of young stars are connected with evolution of their circumstellar shells.

Demonstration of electrical spin injection into a semiconductor using a semimagnetic spin aligner

Spin injection into semiconductors has been a field of growing interest during recent years, because of the large possibilities in basic physics and for device applications that a controlled manipulation of the electrons spin would enable. However, it has proven very difficult to realize such a spin injector experimentally. Here we demonstrate electrical spin injection and detection in a GaAs/AlGaAs p-i-n diode using a semimagnetic II–VI semiconductor (Zn1−x−yBexMnySe) as a spin aligner. The degree of circular polarization of the electroluminescence from the diode is related to the spin polarization of the conduction electrons. Thus, it may be used as a detector for injected spin-polarized carriers. Our experimental results indicate a spin polarization of the injected electrons of up to 90% and are reproduced for several samples. The degree of optical polarization depends strongly on the Mn concentration and the thickness of the spin aligner. Electroluminescence from a reference sample without spin aligner as well as photoluminescence after unpolarized excitation in the spin aligner sample show only the intrinsic polarization in an external magnetic field due to the GaAs bandstructure. We can thus exclude side effects from Faraday effect or magnetic circular dichroism in the semimagnetic layer as the origin of the observed circularly polarized electroluminescence.

Temporal gating in highly scattering media by the degree of optical polarization

The temporal profiles of polarized laser pulses propagating through a scattering medium differ for scattered light parallel and perpendicular to the incident polarization. The degree of polarization is conserved over 100 ps after the arrival of the ballistic component. This observation can be used as a time gate for the early portion of the scattered light, reducing the diffusive component.

A survey of ultraviolet variability in blazars

This is the first comprehensive, consistent survey of the ultraviolet variability properties of a large sample of blazars. All of the 14 blazars with five or more observations in a single IUE camera showed significant variability. The strength of the ultraviolet variability is positively correlated with both the apparent ultraviolet luminosity and the degree of optical polarization of the source. This is the first clear indication that the ultraviolet continua of blazars are beamed. A search for rapid variability yielded nine 'events' with doubling time scales of 0.5-7 days. These rapid flux variations and correlations argue for the standard synchrotron self-Compton model, and against the accretion disk model, which would predict slower variations and the opposite sense of correlation.

Optical nuclear polarization in heavy-doped silicon

The unusual behaviour of the optical polarization degree of 29Si nuclei as a function of the illumination time has been found in silicon single crystals heavily doped with gadolinium. The effect of an external magnetic field on the process of optical nuclear polarization has been studied. It has been shown that the presence of second phase precipitations in heavily doped silicon leads to the complex unexponential establishment of the optical nuclear polarization degree with illumination time.

1400 + 162 - an extended radio source identified with a BL Lacertae object in a group of galaxies

view Abstract Citations (51) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS 1400+162 - an extended radio source identified with a BL Lacertae object in a group of galaxies. Baldwin, J. A. ; Wampler, E. J. ; Burbidge, E. M. ; O'Dell, S. L. ; Smith, H. E. ; Hazard, C. ; Nordsieck, K. H. ; Pooley, G. ; Stein, W. A. Abstract This paper presents optical, infrared, and radio observations of the radio source 1400 + 162, which has been identified with a neutral stellar object. This source is classified as a BL Lacertae object based on the absence of broad emission features, its high degree of optical polarization, and its steep optical continuum. A weak narrow emission line is identified as the 3727-A feature of forbidden O II at z = 0.244, in agreement with the redshift of the nearest and brightest galaxy in a small adjacent group. The radio source 1400 + 162 differs from the sources associated with the majority of BL Lacertae objects in that, even at high frequencies, a significant fraction of its emission arises in extended components. The implications of the properties of 1400 + 162 for the interpretation of the physical conditions in BL Lacertae objects are briefly discussed. Publication: The Astrophysical Journal Pub Date: July 1977 DOI: 10.1086/155370 Bibcode: 1977ApJ...215..408B Keywords: Galactic Clusters; Radio Sources (Astronomy); Red Shift; Spectral Energy Distribution; Astronomical Photometry; Emission Spectra; Infrared Radiation; Light Emission; Polarization Characteristics; Radio Emission; Astronomy full text sources ADS | data products SIMBAD (3) NED (3)