Showing papers on "Mach–Zehnder interferometer published in 1982"

Passive compensation scheme suitable for use in the single-mode fibre interferometer

Abstract: The feasibility of a passive compensation scheme for the SMFI is investigated using a conventional Mach-Zehnder interferometer. Problems normally associated with active feedback stabilisation are eliminated, resulting in infinite range compensation. Minimum detectable phase sensitivities less than 10?6 rad are achievable at frequencies > 1 kHz with the interferometer working in an unshielded environment.

Analysis of integrated-optics near 3 dB coupler and Mach-Zehnder interferometric modulator using four-port scattering matrix

Abstract: The scattering matrix formalism for a lossless four-port device is used to describe the interferometric performance of the integrated-optics near 3 dB coupler and, consequently, the Mach-Zehnder interferometric modulator as a function of coupler and/or power imbalance. For the case of a coupler consisting of three single-mode dielectric guides forming a Y junction, a fourth port is incorporated which takes all the power radiated out of the guided-wave system in the vicinity of the junction. The interferometric properties of the coupler are shown to be relatively insensitive to fabrication and/or design errors of a magnitude which would make the use of this junction in the reverse direction as a 3 dB divider very marginal. A coupler with an extinction ratio as an interferometer better than -26 dB corresponds to a power divider which couples 22 percent more power into one arm than the other. It is also shown that the near 3 dB coupler used as the output of an interferometric modulator is similarly insensitive to the inequality of the powers in the two arms.

Stabilization mechanism for optical interferometer

Abstract: A stabilizer for the relative mirror separation and inclination in a Michelson (two beam) or a Fabry-Perot (multiple beam) interferometer that generates at least three reference beams and in one embodiment an optional monitor beam. The reference beams are disposed substantially around the interferometer signal beam and are directed through the interferometer. The resultant intensity from the interference within each reference beam (transmission) is detected and compared to a fixed reference, in one embodiment the monitor beam. Based upon the ratio of reference intensity to fixed reference, the mirror position is controlled to maintain a constant spacing with respect to the wavelength of the reference source. A stepped mirror surface in the interferometer is used in one embodiment and provides a constant difference between effective mirror spacing encountered by a signal beam and the spacing encountered by reference beams. A servo system is provided to adjust mirror spacing to maintain a constant transmission ratio for each of the reference beams in response to distortion in the interferometer or changes in reference wavelength. A method of stabilizing a Michelson and a Fabry-Perot interferometer utilizing reference beams derived from an independent reference source of nearly monochromatic radiation is also disclosed.

Fiber Optic Accelerometer

Abstract: At NRL the primary interest in optical fiber sensors has been the acoustic [1] and magnetic sensor [2]. However, the optical fiber sensor can be configured to act as a sensitive accelerometer with sensitivities of 1 μg or better for sinusoidal accelerations [3]. Although many different configurations of accelerometer are possible, the configurations tested so far have been in the form of a simple harmonic oscillator (sho) consisting of a mass suspended between two fibers as shown in Fig. la or a mass suspended from a single fiber as in Fig. 1b. These two configurations are attractive in the sense that they employ the standard fiber Mach Zehnder configuration used in the acoustic and magnetic sensors. Another possible configuration is that of a Michel son interferometer in which the mirrored ends of the fiber (replacing the two mirrors in the bulk device) are attached to the mass as shown in Fig. 1c. The success of the accelerometer is contingent on the following: a) an interferometer of rugged construction with μrad sensitivity, b) a fiber configuration to maximize sensitivity in one preferred direction with a crosstalk (to the other orthogonal directions) of better than 10–5, c) a large dynamic range (105 → 106) over which the accelerometer will respond linearly.

Michelson interferometer with a photorefractive mirror

Abstract: The invention relates to the interferometric detection of reciprocal and non-reciprocal effects affecting the propagation of optical radiation in a two-armed interferometer. The invention relates to a two-armed interferometer terminating by a photorefractive medium used as an interactive reflector according to the four-wave interferometer principle. The invention particularly applies to the measurement of physical quantities such as displacement, linear velocity, angular velocity, magnetic field, pressure and temperature.

Analysis of Integrated-Optics Near 3 dB Coupler and Mach-Zehnder Interferometric Modulator Using Four-Port Scattering Matrix

Abstract: The scattering matrix formalism for a lossless four-port device is used to describe the interferometric performance of the integrated optics near 3dB coupler and, consequently, the Mach-Zehnder interferometric modulator as a function of coupler and/or power imbalance. For the case of a coupler consisting of three single-mode dielectric guides forming a Y junction, a fourth port is incorporated which takes W the power radiated out of the guided-wave system in the vicinity of the junction. The interferometric properties of the coupler are shown to be relatively insensitive to fabrication and/or design errors of a magnitude which would make the use of this junction in the reverse direction as a 3 dB divider very marginal. A coupler with an extinction ratio as an interferometer better than -26 dB corresponds to a power divider which couples 22 percent more power into one arm than the other. It is also shown that the near 3 dB coupler used as the output of an interferometric modulator is similarly insensitive to the inequality of the powers in the two arms.

Fiber optic gyroscope with alternating output signal

Abstract: A Sagnac rotation sensing interferometer that uses a Mach-Zehnder interferometer to provide incident light beams that counter-propagate through an optical-fiber loop. The Sagnac interferometer operates at maximum sensitivity for zero rotation rates when the Mach-Zehnder is adjusted so that the intensities of the incident light beams are equal. By peiodically varying the position of a mirror in the Mach-Zehnder the interferometer is switched into and out of quadrature so that the amplitude of the interferometer output signal is modulated at frequency f o . Phase sensitive detection at 2f o or multiples thereof reduces the background noise level several orders of magnitude below the level for dc operation.

A High-Efficiency Polarizing Interferometer for Far-Infrared Spectroscopy

Abstract: A new interferometer based on the principle of the Martin and Puplett polarizing interferometer was constructed for Fourier spectroscopy in the far-infrared region. In principle, all the radiation entering the interferometer can be utilized without loss and the bias level of the interferogram is reduced to zero. The figure of merit in the signal is estimated to be about 6 times greater than that of the standard Michelson interferometer using a dielectric film as the beam-splitter. The experimental results in the 10–70 cm-1 range are described.

Large cross-section pulsed TEA-CO(2) interferometer for plasma diagnostics.

Abstract: A large cross-section Mach-Zehnder interferometer is illuminated by a 30-nsec CO(2) laser pulse. The line-integrated density sensitivity is 2 x 10(19) m(-2). Spatial features down to 150 microm can be identified within a usable field of view of 50 mm. An example of a typical interference pattern obtained on a plasma column is shown together with its corresponding Abel deconvoluted density profile.

CO2 laser interferometer for temporally and spatially resolved electron density measurements

Abstract: A 10.6‐μm Mach–Zehnder interferometer has been constructed to make temporally and spatially resolved measurements of electron densities in plasmas. The device uses a pyroelectric vidicon camera and video memory to record and display the two‐dimensional fringe pattern and a Pockels cell to limit the pulse width of the 10.6‐μm radiation. A temporal resolution of 14 ns has been demonstrated. The relative sensitivity of the device for electron density measurements is 2×1015 cm−2 (the line integral of the line‐of‐sight length and electron density), which corresponds to 0.1 fringe shift.

Thermal physics of transverse-discharge copper vapor lasers

Abstract: One of the factors determining the ultimate characteristics of copper vapor lasers is the heating of the active medium by the pulse-periodic discharge providing the excitation. The gas temperature was measured on the axis of the discharge gap of a transversely excited copper vapor laser. Two methods were used: a spectroscopic method (based on the Doppler width of an emission line of the neon buffer gas) and an interferometric method (based on the fringe shift in a Mach–Zehnder interferometer at the instants when the discharge was switched abruptly on and off). Both methods yielded values close 2200 °K. The temperature distribution in the active zone with a rectangular cross section was computed numerically. The results of a theoretical calculation were used to estimate the efficiency of conversion of the discharge energy into heat, which was around 40%.

Effect of partial polarizations in interferometry

Abstract: Studies the propagation of an electromagnetic wave through a dielectric medium (transparent or not) isotropic or anisotropic, for all angles of incidence. The author deduces coefficients which allow one to determine the transmission and reflection conditions of a beam splitter, a mirror or a birefringent medium. The results obtained are applied to a Mach-Zehnder interferometer and the author shows the influence of partial polarization in transmitted light intensity and of perturbations of the observed fringes patterns.

Heterodyne Fibre Gyro With Complete Reciprocity

Abstract: This paper describes an optical fibre gyroscope which uses a completely reciprocal heterodyne detection technique. The system is based on the Mach Zehnder interferometer and provides a phase and polarisation reference for the beams transmitted through the fibre. Initial measurements have been made on the system and its feasibility demonstrated. Further developments are being made to the system to produce an instrument which will investigate the noise limitations imposed by environmental effects on the fibre loop.