Showing papers on "Ring laser published in 1969"

Compensated frequency biasing system for ring laser

Abstract: A compensated Faraday bias cell system is adapted to shift differentially the respective phases of the contradirectionally flowing light waves propagating in a ring laser cavity. The desired phase shift is produced by Faraday effect interaction occurring between the light waves and symmetrically disposed dual segments of the compensating bias cell system, the segments being specially oriented so as substantially to compensate for or to eliminate undesired reactions in the cell to the presence of disturbing ambient magnetic fields. The compensating bias cell may be employed as a corner mirror in a ring laser device of the type used for measuring rotation rate.

Spectrum and width of mode-locked laser pulses

Abstract: An analytical theory is given of the spectrum of the pulses generated by a ring laser that is mode locked by a synchronously modulated absorber. A steady-state solution is defined by requiring that, in a round trip, the joint effect of the active medium and the modulated absorber leave the pulses unchanged. The resulting integral equation is solved approximately, and the frequency spectrum of the pulses is obtained in closed form. Although the spectrum cannot be transformed analytically to obtain the pulse shape, the second moment of the shape, which gives a measure of the width, is found. The spectrum and width are found to depend on the curvature of the modulator waveform, near its maximum transmission, and on the gain and bandwidth of the active medium, which is assumed to have a Lorentzian line shape.

Minimizing frequency locking in ring laser gyroscopes

Abstract: A ring laser gyroscope utilizes a pair of oppositely rotating beams which are given a difference frequency in accordance with the rotation rate of their optical paths. A plurality of frequency modulated bias signals are imposed upon the beams, the modulation indices of these frequency modulation signals being chosen to minimize the effects of frequency locking at low rotation rates.

Ring laser having means for preventing mode locking

Abstract: A ring laser having laser beams traveling in opposite directions and a polarizer for circularly polarizing the beams in the same sense to reduce beam coupling within the lasing medium and for rejecting back scattered light to prevent oscillation of the back scattered light and reduce beam interaction.

Differential ring laser

Abstract: A differential ring laser comprising a disc on which a ring laser, an interferometer and a phototube are fixed. A second disc is arranged coaxially with the disc, under the same and provided with the same ring laser, interferometer and phototube as the disc. Means are provided for independently rotating the two discs and there is a counter for counting the difference between the number of beat waves detected by the phototubes on the two discs.

Ring-laser bias using reciprocal optical components

Abstract: Ring-laser biasing, to reduce nonlinear rotation sensitivity, normally requires either nonreciprocal optical components or rotation of the whole laser. It is shown that biasing can be achieved by using the finite transit time of light propagation between two time-varying optical phase shifters.

Solid state ring laser

Abstract: A solid state one-piece ring laser having a plurality of surfaces for converting broad band light to a ring laser beam. At least one surface is refractive and is arranged at a Brewster''s angle to the ring laser beam to linearly polarize the ring laser beam. Some of the surfaces may be reflective and are arranged at critical angles to the ring laser beam. With this arrangement, none of the surfaces needs to be coated with a dielectric which deteriorates with age and environment. In a preferred arrangement, as many of the surfaces as possible are refractive to provide a more coherent laser beam.

Sensing movement about a plurality of axes

Abstract: 1,143,033. Optical navigation. SPERRY RAND CORP. 8 June, 1967 [13 June, 1966], No. 26488/67. Heading H4D. In apparatus for sensing movement about a plurality of axes, e.g. three orthogonal axes, comprising a plurality of ring lasers 40, 41, 42 (42 out of sight), each mounted to be responsive to rotation about a respective one of said axes and having an output F 1 , F 2 , F 3 representing said respective rotation, each of said ring lasers has contra-rotating light beams tending to have a threshold below which the laser output is not proportional to sensed rotation and common rotational biasing means 54 is thus provided for simultaneously biasing all of said lasers whereby the contra-rotating beams always exceed said threshold and said proportional representation is maintained. A ring laser comprises an arrangement of laser gas discharge tubes optically connected in series by mirrors to form a closed path whereby two contra-rotating light oscillations are established in the closed path. The two oscillatory frequencies are equal if the ring laser is stationary with respect to an inertial frame, but commence to diverge in opposite directions when the ring laser is subjected to a rotation in its plane. Said divergence can be determined by an optical mixer and is proportional to said rotation for values of rotation above a threshold below which interference between the two beams occurs and the divergence drops to zero. A " bias " rotation is thus given to the ring laser such that it operates in the linear part of of its output characteristic, Fig. 2. The three ring lasers 40, 41, 42 (comprising three laser tubes and three mirrors) are mounted on the respective faces of a comer of a cube and the rotational bias is applied about an axis coincident with the diagonal comer to corner line of the complete cube. Equal components of this rotational bias occur for each ring laser. The frequency divergence signals F 1 , F 2 , F 3 are fed to a digital computer 43 to give position information and to frequency dscriminators 44, 45, 46 which produce D.C. signals indicating the deviations from a desired frequency divergence F 0 . Diodes 47, 48, 49 and negative source 51 cause the most positive discriminator output, corresponding to the lowest frequency divergences, and thus that nearest to the threshold value, to be applied to rotational bias drive 54, in such a sense that the bias is increased to take said lowest frequency divergence away from the threshold. The change in the rotational bias is fed to the computer. Accelerometers 60, 61 and 62 are also provided, feeding their outputs to the computer.