Polarization Degree Of Emission Research Articles

Effect of Dielectric Medium Anisotropy on the Polarization Degree of Emission from a Single Quantum Dash

This research was supported by the Polish Ministry of Science and Higher Education/the National Science Center Grant No. 2011/02/A/ST3/00152. The experiments have partially been performed within the laboratory infrastructure financed by the Polish Ministry of Science and Higher Education Grant No. 6167/IA/119/2012.

Polarization properties of photospheric emission from relativistic, collimated outflows

We consider the polarization properties of photospheric emission originating in jets consisting of a highly relativistic core of opening angle theta_j and Lorentz factor Gamma_0, and a surrounding shear layer where the Lorentz factor is decreasing as a power law of index p with angle from the jet axis. We find significant degrees of linear polarization for observers located at viewing angles theta_v \gtrsim theta_j. In particular, the polarization degree of emission from narrow jets (theta_j \approx 1/Gamma_0) with steep Lorentz factor gradients (p \gtrsim 4) reaches \sim 40%. The angle of polarization may shift by pi/2 for time-variable jets. The spectrum below the thermal peak of the polarized emission appears non-thermal due to aberration of light, without the need for additional radiative processes or energy dissipation. Furthermore, above the thermal peak a power law of photons forms due to Comptonization of photons that repeatedly scatter between regions of different Lorentz factor before escaping. We show that polarization degrees of a few tens of percent and broken power law spectra are natural in the context of photospheric emission from structured jets. Applying the model to gamma-ray bursts, we discuss expected correlations between the spectral shape and the polarization degree of the prompt emission.

ODMR Study of Zn1−x Mn x Se/Zn1−y Be y Se and (Cd1−x ,Mn)Te/Cd1−y Mg y Te Diluted Magnetic Semiconductor Quantum Wells

The effects of microwave pumping with a frequency of 60 GHz on the magneto-optical properties of diluted magnetic semiconductors (DMSs) are studied in (Zn,Mn)Se/(Zn,Be)Se and (Cd,Mn)Te/(Cd,Mg)Te quantum wells. Resonant heating of the Mn2+ ions in the electron spin resonance conditions leads to an increase in the Mn-spin temperature, which exceeds the bath temperature by up to 5.2 K, as detected by the shift of exciton emission line and decrease of its integral intensity. Nonresonant heating mediated by free carriers is also observed through variation of the polarization degree of emission. Direct measurements of spin–lattice relaxation times for both materials using time-resolved optically detected magnetic resonance (ODMR) technique have been performed. The mechanisms of ODMR in nanostructures of DMSs are discussed.

Optically detected magnetic resonance in (Zn,Mn)Se/(Zn,Be)Se quantum wells

The effects of microwave radiation with a frequency of 60 GHz on the magneto-optical properties of diluted magnetic semiconductors are studied on (Zn,Mn)Se/(Zn,Be)Se quantum wells. Resonant heating of the ${\text{Mn}}^{2+}$ ions leads to an increase in the Mn-spin temperature as detected by the shift of emission line and increase in emission intensity. Nonresonant heating mediated by free carriers is also observed through variation in the polarization degree of emission. The mechanisms of optically detected magnetic resonance in diluted magnetic semiconductors are discussed.

Emission polarization of roughened glass and aluminum surfaces

Ellipsometer measurements of the effective complex refractive index at a wavelength of 10.6 μm are made on a series of glass and aluminum surfaces of increasing surface roughness. The measured values are then used to calculate the degree of emission polarization and are shown to be in agreement with the experimentally determined values when depolarization is small. Comparisons are also made with calculations based on the Kirchhoff scattering theory. Both the theory and the experimental results indicate that it is the local surface slope and not the roughness magnitude that is the prime factor in determining the degree of emission polarization from the samples studied.

Temporal evolution of exciton resonant secondary emission spectrum

The exciton secondary emission spectrum of CdS crystals has been studied at 2 K under λ = 4765 A ̊ Ar + laser excitation in the samples with different exciton lifetime. In these conditions three distinct components of secondary emission — Raman scattering, hot and equilibrium luminescence were spectrally resolved. It has been shown that the exciton lifetime acts like a very fast optical shutter and permits one to observe in stationary conditions the temporal evolution of the exciton secondary emission spectrum. The energy relaxation of excitons is accompanied by its “phase” relaxation, the measure of the latter being the polarization degree of emission. With the aid of the Hanle effect the acoustic phonon relaxation time 3.5 × 10 -12 sec has been estimated. The exciton lifetime has been found to vary from 3 × 10 -12 to 1.6 × 10 -9 sec in the samples studied.