Showing papers on "Waveplate published in 1981"

Waveplate for correcting thermally induced stress birefringence in solid state lasers

Abstract: Thermally induced stress birefringence in laser resonators is eliminated by inserting a waveplate in the resonating cavity. The waveplate is chosen by matching its polarization transmission matrix to the polarization transmission matrices of the laser rod and a Porro prism used as an end reflector in the resonating cavity. This produces a total polarization transmission matrix in the resonating cavity which is independent of ray coordinates. Additional control of the polarization transmission matrix is provided using a Porro prism as a cavity reflector that has an antireflection coating on its roof to change the required phase advance angle of the waveplate.

Polarization-insensitive optical switch apparatus

Abstract: Polarization-insensitive optical switch and dual channel carrier multiplexer includes a polarization beam splitter for receiving an input collimated beam which has arbitrarily polarized components, splitting the beam into the two components. One of the components is rotated by a 1/2 wave plate so as to yield a polarized beam which is polarized in the same direction as the other beam. The two polarized beams are then applied to a polarization sensitive interferometric multimode fiber optic switch and modulator. The output of the interferometric multimode fiber optic switch and modulator contains two beams, both polarized in the same direction. One of the beams is rotated ninety degrees by a 1/2 wave plate, and the two mutually perpendicularly polarized beams are then recombined by a polarization beam splitter operated in reverse to yield an output beam containing mutually perpendicular components.

Optical system for enregistration and restitution from an information carrier comprising two laser sources with different wavelengths

Abstract: System comprising means of transmitting two radiations polarised in the same direction and of different wavelengths lambda 1 and lambda 2). This system also comprises optical means comprising at least one splitter element (20), a quarter wave plate (21) and focusing optics (L3 and L4) making it possible to focus onto two photodetector units (DA and DB) the reading and enregistering components of the composite beam reflected on the information medium (5).

Optical pickup device for use in a video and/or audio disc player

Abstract: An optical pickup device is placed in a video and/or audio disc player operative to reproduce information recorded in the form of an optical pattern such as a train of pits on a recording disc, in which the direction of light beam emitted from a light source is parallel to the propagation path of light impinging onto and reflected from the recording disc toward a photosensor. A polarization prism is used to deflect the light from the light source toward the recording disc, which prism cooperates with a quarter wave plate to act as a beam splitter.

Simplified wave plate measurements

Abstract: A simple method for evaluating wave plates has been developed. The equipment required is a source at the appropriate wavelength, a detector, and a pair of polarizers. The accuracy of the measurement is independent of any angular measurement; it is only dependent upon the extinction ratio of the polarizers. The method is based on the principle that a waveplate with orthogonal fast and slow axes, placed with the fast axis 45° to the plane of polarization (POP) of the source, will produce elliptical polarization whose major axis lies either in the POP of the source or orthogonal to the source POP. With this condition it can be shown that the square root of the ratio of the intensity in the POP orthogonal to the input (Iy) to the intensity in the POP of the input (Ix) is equal to the tangent of the retardation half-angle of the plate. Further, it can be

Drawing apparatus for optical fiber

Abstract: PURPOSE:To continuously measure the tension of a drawn optical fiber all over by attaching a tension detector detecting the tension by a photoelastic effect in a noncontact state to an apparatus for softening glass for an optical fiber in the heating furnace and for drawing it. CONSTITUTION:A base material 1 is gradually fed into a drawing furnace 3 with a base material feeder 2 and softened by heating. The diameter of the material 1 is made smaller, and the material 1 is continuously drawn into an optical fiber 4 with a capstan 7. At this time, the outside diameter of the fiber 4 is measured with an outside diameter measuring device 5, and the tension is detected with a tension detector 6 between the furnace 3 and the capstan 7 or a drum 8. For example, light from a light source 9 using He-Ne laser is converted into circularly polarized light by a polarizer 10, passed through a quarter- wave plate 11, converged by a lens 12, and passed through the center of the fiber 4. Since the passed light undergoes double refraction according to tension applied to the fiber 4, the tension of the fiber 4 is detected with an analyzer 13 and a photodetector 14. Thus, an optical fiber of high strength can be manufactured.

A wide field, low light level TV system to measure the state of polarisation of light

Abstract: A low light level television system has been designed to measure the general state of polarisation of light. The instrument incorporates a portable television camera with a wide field of view (22 degrees vertical*29 degrees horizontal) which images the light transmitted by a rotating quarter wave plate and a stationary linear polariser combination. The data, stored on video tape, are analysed later using a video integrator to measure the variations in the light intensity at any point of the TV image from which the polarisation parameters of the incident light beam are determined. The principal advantage of this technique over other, more conventional, methods is that it enables spatial as well as temporal variations in the polarisation of the incident light to be measured. The system was developed to observe noctilucent clouds and proved to be capable of detecting small amounts of circular polarisation in an otherwise predominantly linearly polarised signal.