Optical: systems and elements – Polarization without modulation – By relatively adjustable superimposed or in series polarizers
Patent
1998-08-27
1999-11-09
Epps, Georgia
Optical: systems and elements
Polarization without modulation
By relatively adjustable superimposed or in series polarizers
359352, 359498, 353 20, 349 9, G03B 2114, G02F 11335
Patent
active
059825413
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
Background of the Invention
Polarizers and polarizing beam-splitters (PBS) are optical components that are currently widely used in optical instruments, lasers, electro-optic displays, optical recording and in the fabrication of other optical components. There are several parameters that can be used to describe the performance of a polarizer or polarizing beam-splitter. These parameters are: the wavelength range over which the polarizer or polarizing beam-splitter is effective, the angular field of the incident light in which the polarizer or polarizing beam-splitter is effective and the extinction ratio of the desired polarized light to the unwanted polarized light after the light passes through a polarizer or polarizing beam-splitter.
Commonly available polarizers and polarizing beam-splitters can be divided into several types that depend upon different physical principles: pile-of-plates polarizers, reflection polarizers, dichroic sheet polarizers, polarizers based on birefringent crystals, metallic grid polarizers, and thin film interference polarizers.
Pile-of-plates polarizers consist of a stack of parallel transparent plates that are placed in series. They are mainly used in the ultraviolet and infrared parts of the spectrum. Normally, light is incident at each interface at the Brewster angle such that all the p-polarized light and only some of the s-polarized light is transmitted. If a sufficient number of such plates are placed in series, the transmitted light can be highly polarized and have a high extinction ratio. Although these polarizers act over a very broad spectral region, their angular field is limited.
Reflection polarizers are based on a similar principle but use light reflected from one or more surfaces to polarize a light beam. One advantage of this polarizer is that its performance is independent of the wavelength. However, its performance is very sensitive to the angle of the incident beam. An additional complication is that the reflected light propagates in a different direction from that of the incident light.
Dichroic polarizers are both wide-angle and broad-band and are based on the absorption of light of one polarization. They can be very thin and are convenient to use. They are made of plastic and can be produced in large sizes and at low cost. However, at least 50% of light is lost by absorption in these polarizers and the extinction ratio is not very high. Therefore, these polarizers are typically used in low power applications in which damage to the device due to light absorption is not a concern.
Polarizers based on birefringent materials also perform well over a broad band of wavelengths and a wide range of angles. These polarizers are based on the total internal reflection of light in birefringent crystals. Normally these polarizers are comprised of two birefringent crystal prisms that are in contact with each other. The optical axes of the two prisms are arranged in such a way that the refractive indices at both sides of the contact surface are the same for the ordinary light (polarized in one direction) and are higher in the first prism and lower in the second prism for the extraordinary light (polarized in the other direction), or vice versa. When unpolarized light is incident upon the interface between the two prisms and if the angle of incidence is larger than the critical angle for the extraordinary light, the ordinary light will be substantially transmitted while the extraordinary light will be totally reflected. Therefore, a very high extinction ratio is achieved. Many different arrangements for such polarizers exist. However this type of polarizer is costly and cannot be made in large sizes because of the limited availability of birefringent crystal materials.
Metallic grid polarizers transmit light whose electric field vector is parallel to the grid lines and reflect light whose electric field vector is perpendicular to the grid lines. These polarizers are effective over a wide spectral region and a wide range of angles. However, beca
REFERENCES:
patent: 5181054 (1993-01-01), Nicolas et al.
patent: 5453859 (1995-09-01), Sannohe et al.
patent: 5517340 (1996-05-01), Doany et al.
Bergstein, "Novel Thin-Film Polarizer for the Visible and Infrared," Journal of the Optical Society of America, Paper No. TUD18 of the 1971 Spring Meeting of OSA, vol. 61, Apr. 1971.
Lees, et al, "Versatile Frustrated Total Internal Reflection Polarizer for the Infrared," Optics Letters, vol. 4, No. 2, Feb., 1979, pp. 66-67.
Dobrowolski Jerzy A.
Li Li
Sullivan Brian Thomas
Burke Margaret
Epps Georgia
Nationsl Research Council of Canada
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