Showing papers on "Waveplate published in 1980"

A spectrum scanning Stokes polarimeter.

Abstract: A photoelectric polarimeter for measuring line profiles in all four Stokes parameters has been built and operates on the SPO 40 cm coronagraph in a joint project with Sacramento Peak Observatory. A description of the optical and electronic systems and the calibration scheme is presented. Performance parameters determined from observations are also given. The polarimeter package consisting of a pair of KDP's, a quarter wave plate, and a polarizing beam splitter is located at the prime focus of the coronagraph. Modulation of the KDP's encodes polarization information into intensity signals that are electronically detected. The scanning of the spectrum, accomplished by rotating the grating, permits Stokes line profiles to be recorded on magnetic tape for processing. The instrument can be used to scan any line from 3900 to 7000 A with a spectral resolution of 0.01 A. Polarizations as small as 0.001% are detectable. The polarimeter and observing system are computer controlled.

Optical pressure sensor

Abstract: A system for sensing pressure features an electrically passive sensing head connected to electrically active components by a fiber optic cable. A preferred embodiment combines a polariscope bracketing a quarter wave plate and a photoelastic medium. The dependence of the intensities of two polarization components of light emerging from the photoelastic medium on the pressure applied to the medium permits the measurement of that pressure in a manner that has quadratic error dependence on optical misalignment.

Dual-frequency optical pumping for spin-polarizing a lithium atomic beam

Abstract: A lithium-6 atomic beam is spin-polarized by means of optical pumping with a single-mode dye laser operating on the resonance transition. Simultaneous pumping of both hyperfine substates is achieved by frequency-splitting the laser light with an acousto-optic modulator. A polarization dependent signal, obtained by probing the optical activity of the beam with linearly polarized light, is utilized in a microprocessor-controlled laser stabilization scheme. The polarization is analyzed with a sextupole magnet and its overall value is 0.70 for an intensity of 1×1014 atms s−1. By reversing the sense of circular polarization of the pumping light the atomic beam polarization is easily reversed in direction.

Optical modulators and apparatus including such modulators

Abstract: An optical modulator which is capable of passing the greatest intensity of light incident upon it when the light incident upon it is either unpolarized or has a partial or variable state of polarization, comprises a beam splitter (1) to resolve the light beam incident upon it into two plane polarized components having mutually perpendicular polarization states, one or more electro-optic cell or cells (2,18,19,22,23) which is or are arranged to receive both components of the light beam and, in use change the state of polarization of both of the components to a corresponding extent in dependence upon an electrical modulation signal applied to it or them. The optical modulator also includes analyzer means (1,17) arranged to receive the output from the electro-optic cell or cells (2,18,19,22,23) the arrangement being such that the intensity of the light output from the analyzer means (1,17) is a function of the change of the state of polarization generated in both components during their passage through the electro-optic cell or cells (2,18,19,22,23). The beam splitter and the analyzer means may be formed by the same piece of apparatus (1) and in this case the modulator preferably includes a half wave plate in the light path of both components to change their polarization states.

Semiconductor laser optical device

Abstract: PURPOSE:To prevent return of the reflected light of a laser beam to a semiconductor laser light source by using a polarizing plate and 1/4 wavelength plate. CONSTITUTION:A laser beam outputted by a semiconductor laser 1 and having the plane of polarization parallel to a P-N junction face passes through a polarizing plate 6, and is polarized to circularly polarized light by a 1/4 wavelength plate 7 disposed so as to increase a 45 deg. angle to the P-N junction face. A drum 5 is optically scanned by this circularly polarized light via a scanning part 3 and an imaging lens 4. When the reflected light from the drum 5 passes through the plate 7 via a reverse optical path, a 90 deg. change in phase is generated therein and this light is polarized to the linearly polarized light in the direction perpendicular to the P-N junction; therefore, it is shut off by the plate 6. Thereby, the return of the reflected light to the laser 1 is obviated and the fluctuation in the light source output is eliminated. Hence, the stable laser beam scanning is accomplished.

Tunable birefringent networks

Abstract: Consideration is given to mechanically tuned birefringent filters for the spectral range 4500-7500 A with bandpasses as narrow as 50 mA and stability of better than 5 mA. Two tuning techniques are described: optical path change and waveplate tuning. The tuning techniques are mechanically simple and require minimal demands on encoders and drive electronics. Tuning to a random wavelength can be accomplished in less than one second while adjacent wavelengths can be reached in a fraction of a second.

Laser optical system forming pulsed light beam - has Pockel cell oscillator between resonant mirrors and in line with quarter wave plate and linear polariser

Abstract: The laser optical system consists of a laser optical element (6) with its optical axis coincident with an opaque resonating mirror (2) on one side and, on the other side, a quarter-wave plate (5), a linear polariser (4), a laser-active medium (1) and a partly transparent resonating mirror (3). The laser active medium (1) is typically an Nd glass or Nd doped YAG crystal, the linear polarisium is of calcite and the quarter-wave plate of quartz. The laser optical element is constructed as a Pockel cell with side electrodes and a central KDP crystal. (Potassium-dihydrogen-phosphate). The cell has an electrical voltage applied to cause it to function as an oscillator and emit pulses of laser light for the irradiation of solid or liquid materials.

Application of a stress plate modulator to birefringence measurements in transparent films

Abstract: A stress plate modulator (SPM) is a waveplate, whose retardation varies sinusoidally with time depending on the supplied AC voltage. After describing how to construct the SPM and its oscillator circuit, an explanation has been given for the calibration and operation of the SPM in connection with the application to birefringence measurements of transparent films. The optical system consists of a He-Ne laser, a polarizer, the SPM, a sample, an analyzer and a photomultiplier tube (PMT). As pointed out by several investigators, such a system can allow us to determine a few tens of microradians in retardation by observing the AC component with a lock-in amplifier. The significant utilization of the DC component of the PMT output has been insisted. As performance illustrations, we have obtained the retardation of commercial cellophane films as a function of plies, demonstrating how to determine without using a standard quarter-wave or half-wave plate.

Selective optical ring resonator - includes active optical component in path between three mirrors and half-wave plates

Abstract: The optical system includes three mirrors (2, 3, 4) defining a resonator ring. Between two of the mirrors (2, 4) there is a partial polariser (6) which may for example be an inclined transparent plate favouring the shown direction of polarisation (P). Following this is a first half wave plate (8) having one of its two neutral lines making an angle a1 is approx. = theta with the direction of polarisation (P). This is followed by an optically active substance presenting a rotatory dispersion, with light being subject to rotation through an angle theta as it passes through. A second half wave plate (12) has one of its two neutral lines making an angle a2 is approx. = theta/2 with the polarisation direction(P). The optical resonator may be used in the formation of monofrequency lasers, and frequency stabilised lasers, providing a bandwidth of less than 0.01 angstrom.