Knowledge of polarized light
1.1 Polarized light definition
When the electromagnetic wave is acting with the substance, the effect of the electric vector is much more powerful than the magnetic vector, so the electric vector is used to describe the electromagnetic wave. In the two-dimensional plane perpendicular to the direction of light propagation, there are various vibration states of electric vector E, which is called polarization state. There are usually five kinds of polarization states, that is, natural light, partially polarized light, polarized light, circularly polarized light and elliptically polarized light.
(1)Natural light, usually light emitted by the light source, it is not limited to the surface vibration of a fixed direction, but in every direction of uniform distribution, this light is called natural light light emitted by the light source, usually, the vibration of the electric vector of random orientation in the propagation direction perpendicular to the light, but the statistical average, in the space of all possible directions, the distribution of the electric vector can be regarded as equal opportunity, combined with the light propagation direction of the electric vector is symmetrical, with Amplitude Axial Symmetry uniform distribution of each direction of the vibration of the same, this light is called natural light.
(2)Partial polarized light, if the vibration of light wave vector in the propagation process has a relative advantage in a certain direction, this polarized light is called partial polarized light.
(3)The plane composed of linearly polarized light, the direction of the vibration and the direction of the light wave is called the vibrating surface. The vibration surface of the light is only limited to a fixed direction. It is called plane polarized light. And because the electric vector vibration track is a straight line in the propagation process, it is also known as linearly polarized light.
(4)Circular polarized light, if the light wave electric vector varies regularly change, namely electric vector trajectory in the plane perpendicular to the propagation direction of the round, it is called in circularly polarized light propagation direction, if the electric vector endpoints counterclockwise for right-hand circular polarization; if the electric vector endpoint clockwise then, for the left-hand circular polarization.
(5)Elliptically polarized light, if the light wave electric vector with time change rules, namely electric vector trajectory in the plane perpendicular to the propagation direction of the oval, is called the elliptically polarized light also, elliptically polarized light are also elliptical handelliptically polarized state and elliptically polarization of circularly polarized light application example is ellipsometer for the measurement of refractive index film material thickness rate of extinction coefficient, in many materials science research is an important research tool.
1.2 Polarized light test
The polarization of light is the most direct and most powerful evidence of the transverse wave of light, and the polarization of light can be observed with the aid of an experimental device. Using P and A two copies of the same polarizer, a polarizing film P by direct observation of natural light (such as light or sunshine), through the polarizer light though become polarized, but due to the ability of the human eye without discrimination of polarized light, so it can not detect if we take the Polaroid P's position and fixed. The Polaroid A slow rotation can be found that the intensity of the transmitted light with A rotation periodic changes, and each turned 90 degrees will be repeated from the maximum luminous intensity (brightest) gradually reduced to the minimum (the dark);
Continue to turn A, then the intensity is increased from near to zero to the maximum. From this, we can see that the transmitted light of P is different from the original incident light. This indicates that the vibration of P transmission has no symmetry to the propagation direction. Natural light through the polarizer, change into a certain vibration direction of the light, this is because there is a characteristic direction of polarizer, called polarization transmission direction (referred to light), polarizer only allowed by vibration parallel to the transmission direction of the electric vector.
At the same time, the absorption is perpendicular to the direction of the electric vector of light vibration light transmitted through the polarizer, the electric vector vibration limit in a direction of vibration, we put the first polaroid polarizer is called P (Polarizer), it is the role of the natural light into polarized light, but the human eye can not distinguish polarized light. We must rely on second pieces of Polaroid A to check, Polaroid polarizer is called A (Analyzer) A rotation, when the parallel polarization direction of its light and polarized surface, polarized light can be passed, then behind A have a bright light when the vertical polarization direction and polarized light through the face of A when the polarized light can not pass, behind A and darkens the second polarizer A helps us identify the polarized light, this is why it is called a polarizer in optical reversible, A and P can only swap Polarizer can check whether the exit light is plane polarized light, but it can not separate the natural light from the circularly polarized light, nor can it separate the partial polarized light from the elliptically polarized light.