A dielectric optical polarizer which is operable at high peak and average power, with greater than 95 percent transmission of the desired P polarized radiation, and also greater than 95 percent reflectance of the S polarized radiation. The polarizer comprises a radiation transmissive substrate with a first dielectric layer disposed on at least one side of the substrate. The first dielectric layer has an index of refraction higher than the substrate. A second dielectric layer of low index of refraction material is disposed atop the first dielectric layer. A third dielectric layer of the same high index of refraction material as the first layer, is disposed atop the second layer. Each of the dielectric layers is one quarter wavelength thick at the operating wavelength. The dielectric polarizer operates at a very high Brewster angle associated with the dielectric layers rather than that of the substrate.
A polarization conversion optical system converts light having a nonuniform plane of polarization into light having a uniform plane of polarization. The system includes a multilayer dielectric film at the side upon which the target light is incident. The film exhibits the property that it reflects one polarized component of the light and transmits a second polarized component of the light at a first angle of incidence, but transmits the first component at a second angle of incidence. Incident target light that is transmitted through the film at the first angle of incidence passes through a quarter-wavelength plate and is reflected at the second angle, whereupon it is retransmitted through the quarter-wavelength plate to be converted from one plane of polarization to the other. It is then emitted from the dielectric film in the same plane of polarization as light reflected by the film.
A laser adapted to operate at a constant, predetermined wavelength includes the following elements disposed in order within a laser cavity and aligned along the path of light flow therethrough: a highly reflective rear mirror, a halfwave plate, a Brewster window, an active laser medium, and an output coupler. The halfwave plate is designed to rotate incident light beams by 180.degree. at the predetermined wavelength and to rotate incident light beams by an amount other than 180.degree. at wavelengths other than the predetermined wavelength. In a preferred embodiment, the Brewster window is a thin film polarizer designed for the predetermined wavelength.
The polarizer of the present invention is composed of mediums having different refractive indices, by which ordinary light in incidented light is wholly reflected at a boundary between laminated medium I and medium II and extraordinary light is transmitted through the medium II. The medium II is so arranged as to be almost 45.degree. to the light axis, and thickness of the medium II is selected as a value with which the medium II works as a half wave length plate to the transmitting light. The polarizer, which has high transparency by reduction of absorption and is able to make most of incident light be similarly polarized light, is obtained. A polarizer for and apparatus for bright liquid crystal display, which is able to be enlarged to a large size display without light absorption, can be provided.
A fiber-optic acoustical sensor system includes a light source, an elongate optical cable conducting light from the light source to an optical acoustical transducer located at a distance from the light source along this cable, and a polarizer at the acoustical transducer. The sensor system includes a polarizer providing orthogonally-polarized light along the optical cable to the polarizer located adjacent to the transducer. Because of the polarizer adjacent to the transducer, disturbances of the optical cable and resulting polarization perturbations of the light transmitted along this cable do not affect the optical acoustical transducer. The acoustic transducer is responsive to sound energy to provide an optical return signal indicative of this sound energy. An in-line fiber-optic polarizer suitable for use in this acoustical transducer includes a pair of confronting optical fiber portions aligned along an optical axis and which each define end surfaces disposed at a Brewster polarizer angle with respect to light transmitted along this optical axis. The end surface of one of these optical fibers carries plural alternating sub-layers of high-index and low-index dielectric material, which are effective to p-polarize the transmitted light and substantially eliminate s-polarized light transmission to the optical acoustical transducer.
A beam splitter having an optical multilayer thin film is disclosed. The optical multilayer thin film is formed by laminating six layers in sequence. The laminated six layers comprise: a first layer, a third layer and a fifth layer each having a refractive index from 1.63 to 1.64; a second layer and a sixth layer each having a refractive index from 1.37 to 1.38, a fourth layer having a refractive index from 1.9 to 2.3; in which light is allowed to be incident upon the first layer of the optical multilayer thin film at the angle of incidence equal to or greater than 40.degree.. The reflectances of S and P polarized components of reflected light are substantially equal to each other over a wide wavelength range and substantially no phase difference exists between the S and P polarized components. The beam splitter having a multilayer polarizing light separating film formed between an incoming side prism and an outgoing side prism is extremely high in the reflectance of the P polarized component of reflected light, in comparison with that of the S polarized component of the same reflected light.
