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Light therapy, also called phototherapy or bright light therapy is the exposure to direct sunlight or artificial light at controlled wavelengths in order to treat a variety of medical disorders, including seasonal affective disorder (SAD), circadian rhythm sleep-wake disorders, cancers, and skin wound infections.
Polarization is observed in the light of the sky, as this is due to sunlight scattered by aerosols as it passes through Earth's atmosphere. The scattered light produces the brightness and color in clear skies. This partial polarization of scattered light can be used to darken the sky in photographs, increasing the contrast.
A typical hysteresis cycle containing the Voigt effect is shown in figure 1. This cycle was obtained by sending a linearly polarized light along the [110] direction with an incident angle of approximately 3° (more details can be found in [4]), and measuring the rotation due to magneto-optical effects of the reflected light beam. In contrast to ...
The fact that light could be polarized was for the first time qualitatively explained by Newton using the particle theory. Étienne-Louis Malus in 1810 created a mathematical particle theory of polarization. Jean-Baptiste Biot in 1812 showed that this theory explained all known phenomena of light polarization. At that time polarization was ...
Initially, the laser light induces coherent polarization in the sample, i.e., the transitions between electron and hole states oscillate with the laser frequency and a fixed phase. The polarization dephases typically on a sub-100 fs time-scale in case of nonresonant excitation due to ultra-fast Coulomb- and phonon-scattering. [15]
Structure of KTP crystal, viewed down b axis, used in second harmonic generation.. Nonlinear optics (NLO) is the branch of optics that describes the behaviour of light in nonlinear media, that is, media in which the polarization density P responds non-linearly to the electric field E of the light.
Polarizers which maintain the same axes of polarization with varying angles of incidence [clarification needed] are often called [citation needed] Cartesian polarizers, since the polarization vectors can be described with simple Cartesian coordinates (for example, horizontal vs. vertical) independent from the orientation of the polarizer surface.
In general, the polarization of monochromatic light is completely described via four Stokes parameters, which form a (non-orthonormal) vector space when the various waves are incoherent. For light propagating in the z direction, with electric field: In cosmology, no circular polarization is expected, so V is not considered.