Showing papers on "Ring laser published in 1972"

Ring laser magnetic bias mirror compensated for non-reciprocal loss

Abstract: A ring laser incorporating a magnetic bias mirror forming a corner of the ring optical cavity for imparting a differential phase shift to the contradirectional oscillatory beams circulating in the ring to establish a frequency split therebetween. The bias mirror comprises a magnetic layer deposited on a substrate and overcoated with a plurality of dielectric layers which, exclusive of the layer adjacent the magnetic material, are adjusted in thickness so as to enhance the mirror reflectivity while the thickness of the remaining layer is adjusted to cancel non-reciprocal loss or differential reflection of the contradirectional beams caused by the presence of the magnetic material.

Continuous wave radar for range and velocity measurement

Abstract: A frequency modulated, continuous wave radar range measurement system using a laser oscillator is disclosed. A ring laser, carbon dioxide (CO2), laser oscillator allows target range and velocity measurement as either an active or a passive system. Nonlinear variation of laser output power is obtained by mixing the reflected signal with the energy within the laser cavity. In an active system the resulting beat frequency is sensed by a local receiver-detector and reduced to obtain the range and velocity data at the transmission site. The beat frequency is also superimposed on the transmitted laser beam and is therefore available at the target causing the beat frequency and is available to other detectors which may be positioned to receive a portion of the reflected energy, affording a passive system.

Natural fluctuations in lasers

Abstract: A review is presented of theoretical and experimental results of an investigation of natural fluctuations in gas and solid-state lasers. All the known theoretical results are obtained by a single method based on the equations of the quasiclassical laser theory. In the calculation of the fluctuations, the equations for the amplitudes and phases of the field are regarded as Langevin equations with suitably introduced fluctuation sources. The sources of the thermal fluctuations of the resonator are determined by the Kallen-Welton formula. The sources of the non-equilibrium fluctuations of the polarization of the working medium are calculated on the basis of the equations for the density-matrix elements. The fluctuations of the amplitudes and phases in linear and ring lasers are considered under arbitrary pump-to-threshold ratios. The natural line width of the laser radiation is calculated. The coupling of opposing waves in a ring laser, due to scattering by the mirrors, is taken into account. The maximum sensitivity of a laser gyroscope is estimated. The results of the theory are compared with the experimental data. A brief description of the status of the problem of calculating the natural fluctuations in lasers and an estimate of the possibilities of the quasiclassical method of calculating fluctuations are given in the conclusion.

Unidirectional Thin‐Film Ring Laser

Abstract: A light‐guiding thin polyurethane film, doped with rhodamine 6G, is coated on the surface of a cylindrical glass rod and pumped with a pulsed Ne laser. A prism‐film coupler produces two output beams corresponding to clockwise and counterclockwise oscillations around the circumference of the rod. Unidirectional operation is obtained when one of the output beams is reflected back into itself. A maximum directionality ratio of 17 was measured.

Single-isotope Laser Gyro

Abstract: A single-isotope He–Ne laser gyro has been constructed and operated, and the results have been compared with those obtained from a multi-isotope system. Strong mode competition in the single-isotope ring laser has been found in a region 10–30 MHz near line center. The sense of the mode competition has been found to depend on the direction of rotation of the laser cavity. Hence, by mechanical dithering of the laser, the time-averaged effect of the mode competition can be zero. However, with a current unbalance, a large dispersion-type null shift is found near line center. Unlike the linear laser and the multi-isotope ring laser, the single-isotope ring laser is characterized by strong mode competition such that only a single longitudinal mode oscillates over most of the free spectral range.

Unstable ring laser resonators

Abstract: Unstable resonator designs having totally reflecting optics which allow isolation of the parameters that control transverse mode discrimination from the parameters that control mode volume and output coupling are disclosed. Various asymmetric ring resonator geometries which include a pair of confocal curved reflecting surfaces and suitable techniques for promoting unidirectional oscillation in these geometries are discussed.

Effects of radiation trapping on mode competition and dispersion in the ring laser.

Abstract: By considering the phenomena of radiation trapping, corrections are obtained in the third order Lamb coefficients for the amplitude and frequency ring laser equations. The corrected coefficients allow the correct prediction of the shape of the experimentally measured Lamb dip. They also allow the prediction of mode competition between the oppositely directed traveling waves near the Doppler center. As found experimentally, this competition region is predicted to increase with increasing pressure. Expressions are given for the Lamb coefficients that are obtained from an exact third order integration.

Characteristics of a Tunable Travelling Wave Dye Ring Laser

Abstract: Abstract A flashlamp pumped dye ring laser using 4 Abbé prisms of constant 90 degree deviation has been built. Travelling wave operation is obtained when the counterclockwise wave is fed back by a beam-splitting output prism. The laser emission offers remarkable frequency stability when narrowed down to a linewidth of 7 pm by the use of an intracavity solid Fabry-Perot etalon.

Laser pulses in a system with a discrete loss

Abstract: An investigation is reported of a ring laser model employing a homogeneously broadened gain line and a discrete loss. For certain laser parameters the stable solutions consist of one or more pulses traveling around the ring. These pulses propagate at a velocity exceeding the phase velocity of light in the medium.

Competition between longitudinal modes in a ring laser with an anisotropic resonator

Abstract: A theoretical investigation is made of a ring laser subjected to a longitudinal magnetic field in the case when the anisotropy of the resonator is purely circular in nature. Four-wave emission is considered. Two separate cases are discussed: 1) two pairs of identically polarized circular waves traveling in opposite directions; 2) two orthogonal pairs of circular waves. A nonlinear interaction between the traveling waves and the stability of both cases are considered.

Deforming-Light-Path Ring-Laser Experiments

Abstract: Based on a thought experiment of Von Laue, a deforming-light-path ring-laser experiment is proposed. The thought experiment of Von Laue provides not only a well-founded explanation of rotating-mirror experiments with nondeforming light paths, but is also applicable to the problems of deforming-light-path devices. Von Laue’s experiment, in its original form, can probably be performed only as a deforming-closed-light-path experiment. Von Laue’s straight movable device may be used as an inseparable part of a ring interferometer or ring laser. In another possible form of a deforming-light-path experiment, the closed deforming light path is a fiber and beat frequencies are caused by the light-path-directed motion of the fiber.

Improvements in or relating to laser systems

Abstract: 1,262,293. Lasers. EMI Ltd. 21 April, 1969 [20 April, 1968], No. 18762/68. Heading H1C. In a ring laser, back scatter of the circulated light is reduced by prismatic corner reflectors 4, 5, 6 formed with their incident faces 12, 14 at the Brewster angle. Each side of the ring laser consists of a laser discharge tube 1, 2, 3 which is sealed to the incident faces of the adjacent corner prisms. Circulated light is extracted by a frustrated total internal reflection arrangement using a further optical surface positioned in near contact with the total internal reflection base 7 of one of the prisms. In operation the laser action is preferably maintained at a level just sufficient to generate and maintain the circulation of light plane polarized by the Brewster angle incident surfaces.