Abstract: An optical radar operating in the infrared region of the spectrum and adad to efficiently detect elongated targets such as wires. The pulsed transmitter is preferably passively Q-switched and produces optical pulses polarized in one direction. A CW local oscillator laser is locked to a frequency slightly offset from the transmitter frequency. A Brewster angle duplexer and a quarter wave plate in the transmit/receive path of the radar permit the transmitter flux to pass to a scanner and direct the orthogonally polarized echo signals to the heterodyne receiver which includes a display or alarm circuit. The transmitter and local oscillator lasers include frequency control circuits. Either wedge or ball joint type scanners may be used to scan the radar beam over a target area of interest.

Abstract: A waveplate is any optical device which retards one polarization component of an incident wave relative to the orthogonal component. This subject is much too general for our purposes so we will restrict the discussion to retardations of one quarter or one half of a wavelength. In particular, we will be concerned with phase retarders which are constant or nearly so over a significant spectral region.© (1982) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Abstract: In a number of measuring methods such as ellipsometry, linearly polarized light of changing orientation is used. Several techniques have been utilized for the production of variable linear polarization: a rotating polarizer illuminated by unpofarized light, a rotating halfwave plate illuminated by linearly polarized light, electrooptic and magnetooptic effects, and also polarization switching of the source itself. The techniques involving rotating components suffer from the inconveniences induced by mechanical movement and are limited in rotation frequency, while the other techniques are usually restricted to the switching between two distinct states of polarization. The present Letter describes a new method for the production of a linearly polarized light beam in a plane that rotates uniformly at high frequencies. The method is based on the superposition of two circularly polarized waves that differ in frequency. It can be shown in an elementary way that if the two waves are polarized in opposite sense the result is a linearly polarized wave, the polarization of which rotates at the difference frequency. The electric field component of a right-circularly polarized wave that propagates in the positive z direction may be represented in the form

Abstract: A variable ratio power combiner employs, as its major coupling component, one or more septum polarizers and associated 90° differential phase shifters or quarter waveplates in place of conventional OMTs. Advantageously, a septum polarizer is a relatively simple component that serves the same function as an OMT and polarizer combination. Because it has an essentially T-shaped configuration, it can bring a pair of waveguide arms together in the same plane back-to-back, so that the resulting power combiner may provide the desired symmetrical coupling. Normally the variable ratio power combiner requires only symmetrical inputs for the sources and not both symmetrical inputs and outputs, so that only a single septum polarizer and associated quarter waveplate are employed, with an OMT used for the output. For a completely symmetrical configuration, however, the other OMT may be replaced by a separate septum polarizer/rotatable quarter waveplate arrangement.

Abstract: A nuclear magnetic resonance gyroscope which derives angular rotation thef from the phases of precessing nuclear moments utilizes a single-resonance cell situated in the center of a uniform DC magnetic field. The field is generated by current flow through a circular array of coils between parallel plates. It also utilizes a pump and read-out beam and associated electronics for signal processing and control. Encapsulated in the cell for sensing rotation are odd isotopes of Mercury Hg199 and Hg201. Unpolarized intensity modulated light from a pump lamp is directed by lenses to a linear polarizer, quarter wave plate combination producing circularly polarized light. The circularly polarized light is reflected by a mirror to the cell transverse to the field for optical pumping of the isotopes. Unpolarized light from a readout lamp is directed by lenses to another linear polarizer. The linearly polarized light is reflected by another mirror to the cell transverse to the field and orthogonal to the pump lamp light. The linear light after transversing the cell strikes an analyzer where it is converted to an intensity-modulated light. The modulated light is detected by a photodiode processed and utilized as feedback to control the field and pump lamp excitation and readout of angular displacement.

Abstract: A novel optical head for digital audio disks has been successfully developed. The headconsists of a GaAlAs laser diode, a quadrant PIN photodiode and a single -beam opticalsystem for focusing and radial tracking. All of the data (RF), focusing, and radial track-ing signals are derived from a single quadrant PIN photodiode. Focusing and radial trackingservocontrol of the head are characterized by two -dimensional actuation of an objective lens. The detection method of the error signals and their dependence upon both the movementof the objective lens and the tilt of the disk are described.The optical configuration ofthe head is shown in Fig. 1. Theoptical system consists of a laserdiode as a light source, acollimator lens, a combinationof a polarizing prism andquarter -wave plate used to preventthe light reflected by the diskfrom returning to the laser diode,an objective lens focusing thelight beam into a diffractionlimited spot, a critical anglereflecting prism and finally, aquadrant PIN photodiode havingfour light sensitive segments,PDa, PDb, PDc, and PDd. Thecritical angle prism is used todetect the focal displacement ofthe disk from the focal point.Focus control and radial trackingare achieved by driving theobjective lens in the directionof the light path and radiallywith respect to the disk, respec-tively, i.e. in the z- directionand r- direction shown in Fig. 1.Fig. 2 shows an overall view of the optical head, the parameters of each component beinggiven in Table 1.ConfigurationLaser diode Objective

Abstract: The design and preliminary test results for the spectropolarimeter for the Faint Object Spectrograph (FOS) for the Space Telescope are presented. The mechanical design and optical specifications of the spectropolarimeter are described noting that a Wollaston prism with an internal wedge angle of 20 deg is fixed behind each of two rotatable waveplate retarders of different retardations. Either waveplate/prism combination can be positioned at either of the two FOS entrance ports. Magnesium fluoride is chosen as the birefringent crystal for the polarizing elements to allow linear and circular polarization measurements down to Lyman-alpha at 1216 A. Mechanical stability and repeatability were determined by operational testing to give polarization-position angles of + or - 0.5 deg, corresponding to degree-of-polarization measurements of + or - 0.1 percent. Faint-object accuracy, dependent on photoelectron statistics and hence on observation time, is calculated to be one percent in each 100-A-wide spectral band for a 20-min observation of an AO star with V = 15th magnitude.

Abstract: When a Raman active medium is irradiated simultaneously with an elliptically polarized pump laser beam of frequency oil and a linearly polarized Stokes laser beam as probe of frequency ωL ωs a Stokes component is produced which is perpendicularly polarized to the incident, probe beam. This perpendicular component shows resonance for ωL -ωs = ωj, where ωj is a Raman active eigen frequency of the medium, and can therefore be used to observe the Raman spectrum.

Abstract: In an optical gyroscope comprising a coil of an optical fiber having opposite ends on which linearly polarized input light beams are incident and from which output light beams are derived which create an interference pattern to be detected, the optical fiber has orthogonal principal axes along which the light beams propagate at a large propagation constant difference. The application of the linearly polarized input light beams to the opposite ends of the optical fiber coil is such that the polarization plane of the linearly polarized light beam coincides with the same principal axis on the opposite ends. Thus, polarization characteristics of the output light beam from the optical fiber coil becomes time invariant and the light paths for the two light beams coincide with each other. In particular, in order to minimize the influence of external disturbances, the optical fiber has a structure defined by |N.sub.x -N.sub.y |>λ/R.sub.o where N x and N y are refractive indices of said optical fiber in directions of the orthogonal principal axes, R o is the radius of said optical fiber coil, and λ is the wavelength of the light beam.

Abstract: A new analytical technique is constructed by using circularly polarized waves. And further, it is applied to calculate and interpret the polarization characteristics of optical fiber.

Abstract: A laser machining apparatus includes an optical resonator for generating a laser beam and two polarizers disposed in the form of a V within the optical resonator to linearly polarize the laser beam. The linearly polarized laser beam is focussed on a workpiece for cutting purposes while the workpiece is moved in two orthogonal directions. The polarizers are rotated about the optical axis of the laser beam in correspondence with the two dimensional movement of the workpiece to rotate a plane of polarization of the beam to coincide with a cutting direction of the beam. Alternatively, a linearly polarized laser beam from a laser oscillator is circularly polarized with a quarter wave plate and then linearly polarized by a rotatable quarter wave plate to form a cutting beam. The rotatable quarter wave plate is rotated in the same manner as the polarizers to rotate a plane of polarization of the cutting beam.

Abstract: For a given modal skew ray in a graded-index optical fiber, the intrinsic angular momentum associated with the direction of circular polarization in space can, as we know, have two different orientations, and the states of the polarization or the directions of the polarization have been considered so far to be invariant. This paper shows that this is valid only for high frequencies but fails for low frequencies and in certain special optical fibers. A critical frequency is calculated at which the direction of rotation of its circular polarization changes. It is pointed out that the feature of this anomalous polarization critically depends on the inhomogeneity of the medium. Some profiles of refractive index are examined.