Type Of Interferometer Research Articles

Design of FT-IR for soft mode spectroscopy

Abstract A new instrument of far-infrared FT-IR spectrometer has been developed especially for high intensity throughput to observe the soft phonon which induces structural phase transition. The instrument has a new design of composite construction which allows to be alternatively utilized for the conventional Michelson type and also the Martin-Puplett type interferometer.

Sequential bidirectional differential interferometer

A new type of differential interferometer based on holographic optical elements is developed which allows a refractive index gradient field to be determined in two orthogonal directions obtained sequentially with a PLZT electrooptic modulator. The sign of the gradient is unequivocally determined by using a reference fringe pattern added to the interferogram. The sensitivity of the device is easily adjustable by changing the position of only one optical component.

Utilization of Fiber Optic Gyros in Inertial Measurement Units

Fiber optic gyro technology has been developed to a point where these gyros are now being introduced into advanced engineering models of the next generation of inertial measurement units (IMUs). This paper covers the operating principles of the interferometric type of fiber optic gyroscopes, together with a brief comparison against ring-laser gyroscopes. Recent flight test data of an IMU employing fiber optic gyro sensors are presented. Finally, the unique characteristics of the fiber optic gyro are discussed, with particular emphasis on the role they will play in future fault-tolerant IMUs.

表面形状検査測定用ホログラム干渉計 ホログラムガラス基板の光学的不均一性を補償した光学系

A new type of holographic interferometer, called hologram interferometer, for testing and measuring optical surface configuration is proposed. The interferometer mainly consists of a laser source, a microscope objective and a collimating lens to get a collimated beam, a hologram which serves both as an objective lens and a half mirror in a Twyman-Green type interferometer and a flat reference surface mirror. The optical inhomogeneity of hologram glass substrate is automatically compensated. Experimentally measured cofiguration error of a commercial spherical mirror whose diameter was 35 mm and radius of curvature was 200 mm were λ/10 in peak to valley and λ/50 in rms where λ was 0.632 8 μm. These values were the same as those obtained by using a commercial Fizeau type interferometer.

放物面鏡形状検査測定用ホログラム干渉計

A new type of hologram interferometer for null-testing and measuring a paraboloidal mirror configuration is proposed. In the interferometer a hologram causes a spherical reference wavefront which interferes with a spherical wavefront reflected by a paraboloidal mirror under test. The method to calculate the amount of configuration error of a paraboloidal mirror from the interferogram is also proposed. Almost straight and equally spaced tilt fringes obtained in the experiment for a commercial on-axis paraboloidal mirror shows the interferometer is useful.

Multichannel HCN laser interferometer for electron density measurements of the JIPP T-IIU tokamak

A six-channel HCN laser interferometer system has been developed for the measurement of the electron density profile in the JIPP T-IIU tokamak. The fringe shift of the probe beam is directly read out using a reference beam, the frequency of which is Doppler shifted by 50 kHz with a rotating grating. The optical configuration is of the Michelson interferometer type, of which reflecting mirrors are directly attached on the wall of the vacuum vessel. An effective area of the optical window is only φ40 mm. This optical configuration enables us to make the electron density profile measurements by the multichannel laser interferometer with a single small optical window.

Phase shifting thin film multilayers for Michelson interferometers

The design and construction of a set of four high reflectance metal-dielectric thin film multilayers which produce phase changes on reflection that differ by 90 degrees in the 0.55-0.77-microm spectral range are described. This provides the basis for a new type of optical Doppler Michelson imaging interferometer for use in upper atmospheric studies in which achromatic phase shifts are produced without mirror motions.

A ruggedized miniature UHV electron biprism interferometer for new fundamental experiments and applications

Electron interferometers are very sensitive to mechanical vibration and alternating magnetic fields. This is the reason why in the past their application was restricted to laboratories with very low disturbances of this kind. We present a novel type of electron biprism interferometer totally different in its technical realisation compared to conventional instruments. Its extremely low sensitivity to both types of disturbances is demonstrated and for the first time allows to make use of electron interferometry in virtually every environment. Experiments inconceivable with conventional electron interferometers are rendered possible with the new instrument. As an example, we hope to be able to demonstrate with it the rotational phase shift of charged matter waves (Sagnac effect with electrons) in the near future.

Simultaneous sensing of the acoustic wave and temperature using a polarization‐maintaining fiber

Many types of fiber‐optic sensors have been proposed and developed. In general, efforts have been made to detect a specific parameter of interest separately from other parameters. In the homodyne interferometric type of sensors, the fading of output caused by temperature variation is a serious problem, and several types of compensation schemes have been developed. In contrast, this paper describes the simultaneous sensing of acoustic wave and temperature change using a polarization‐maintaining fiber. The acoustic wave is detected by an optical heterodyne scheme and temperature change is detected by an optical homodyne scheme. The zeroth‐order diffracted light from a Bragg cell is directed into both the X and Y polarization axes of a polarization‐maintaining fiber. The homodyne interference of the X and Y components is utilized to detect the temperature variation. At the same time, the heterodyne interference of the X polarization component of the output light from the fiber and the first‐order diffracted light propagated in air is used to detect the acoustic wave. Simultaneous sensing of the acoustic wave and temperature variation was successfully demonstrated by this method.

On the feasibility of a neutron Hanbury Brown—Twiss experiment with gravitationally-induced phase shift

It is shown that a gravitational potential difference between the two components of a split fermion beam in a Mach—Zehnder type interferometer can influence the fermion second-order, one-point correlation function and hence the conditional probability of fermion arrivals at one output port. Manifestation of the effect requires use of two statistically-inequivalent input beams. The configuration is a particle analogue of the optical Hanbury Brown—Twiss experiments. Contrary to previous report of a signal-to-noise performance orders of magnitude higher than that characterising the cross-correlation of particle fluctuations in two beams, it is shown that both types of measurements are characterised by comparable signal-to-noise expressions. The implications for observation of neutron antibunching are discussed.

AN AUTOMATED INTERFEROMETER FOR THE ANALYSIS OF ANAESTHETIC GAS MIXTURES

A microprocessor-controlled interferometer is described. The eyepiece of a conventional Jamin type interferometer has been replaced by an array of photocells which records the intensity across the interference pattern. Mathematical correlation procedures are used to locate the principal interference pattern maximum and, by sequential analysis of a fresh gas mixture followed by fresh gas plus vapour, it is possible to determine both oxygen and vapour concentrations. The instrument was used to analyse mixtures of oxygen and nitrous oxide and also oxygen, nitrous oxide plus halothane. It was found that the oxygen concentration could be determined to an accuracy of +/- 1% v/v and the vapour concentration to +/- 0.1% v/v. The instrument is suitable for monitoring concentrations delivered by an anaesthetic machine and may be included in a microprocessor-controlled anaesthetic machine.

Low-noise interferometer for microwave radiometry

A novel type of interferometer has been developed for precision measurements in microwave radiometry. The system employs two low-noise heterodyne receivers based on SIS (superconductor–insulator–superconductor) tunnel junction mixers in the band from 40 to 50 GHz. The rectangular horn antennas have adjacent apertures and are coaligned; the IF outputs of the receivers are multiplied together. The resulting antenna interference pattern has lobes which lead to positive output signals and lobes which give negative output. The radiometer measures the difference in the power from these lobes without beam switching or instrument motion. Other major features are: the cancellation of instrumental signals (horn emission, sidelobe pickup, etc.); very low 1/f noise in the output; and zero output signal when viewing a uniform source. The system achieves a sensitivity of ΔTrms =14.4±1.4 mK/(Hz)1/2 and is used to search for anisotropy in the cosmic background radiation on angular scales between 1° and 5°.

Silica-based single-mode waveguides on silicon and their application to guided-wave optical interferometers

Low-loss silica-based single-mode waveguides and directional couplers are fabricated on silicon substrates. Their application to Mach-Zehnder interferometer type guided-wave devices is demonstrated. Optical switches or tunable optical couplers are fabricated using the thermooptic effect. Asymmetrical Mach-Zehnder interferometers are successfully applied to multi/demultiplexers for optical FDM transmission systems. >

Novel ring interferometer for frequency stabilization of semiconductor lasers

A novel type of ring interferometer is proposed which is used as a reference for frequency stabilization of semiconductor lasers. This interferometer is fabricated by precisely polishing a block of synthesized quartz into the shape of an equilateral prism with multilayer dielectric films on each side. This interferometer has the advantage of drastic reduction of optical feedback to semiconductor lasers. The alignment of the optical axis of the interferometer is relatively easy compared with a conventional ring interferometer. The frequency fluctuation of an AlGaAs semiconductor laser is reduced to <1 MHz using this interferometer.

Performance data of the double pendulum interferometer

The paper describes the optical and electronical concept of a new type of interferometer. The performance of the instrument was demonstrated by measurements of gas absorption spectra and laser emissions. Measured data are compared to theoretical line-by-line calculations.

2-D differential interferometer

A new type of differential interferometer based on holographic optical elements is developed, which allows the exact determination of a refractive index gradient field in two orthogonal directions. This interferometer will be used in TEXUS experiments to determine the temperature field in a convective liquid cell in which the temperature may be known at only one point.

Laser diode feedback interferometer for stabilization and displacement measurements

Active laser diode interferometers in which the interference signal is fed back to the diode current are investigated for Twyman-Green and self-coupling interferometers. The Twyman-Green interferometer is stabilized with a stabilization factor of more than 100. By using the feedback signal of either type of interferometer, displacement is measured in a linear scale over a dynamic range of 8-9,microm with a precision of 10-60 nm. The feedback signal vs displacement shows hysteresis and multistable behavior, in accordance with theoretical results.

Diode laser direct modulation heterodyne interferometer

A new type of heterodyne interferometer was made through direct modulation of a diode laser wavelength. A measurement accuracy of better than lambda/50 and repeatability of lambda/100 were obtained. This interferometer shows promise for use in testing wavefront aberrations, especially in optical disk systems.

Interferometers, Aberration and the Sagnac Effect

In this note we show that the usual expression for diurnal aberration (see e.g. Woolard and Clemence 1966) is not valid for some types of radio interferometers. The difference (usual minus correct) is a constant of the instrument, and is absorbed in the calibration procedure. The analysis of multibaseline VLBI may also be affected.

Fiber-optic interferometer using frequency-modulated laser diodes

This paper describes an electrically passive fiber-optic interferometer which uses dual frequency-modulated laser diodes. Experimental results show that this type of interferometer can attain a displacement range of 100 μm with subnanometer resolution. This technique can serve as the basis for a number of high-precision fiber-optic sensors.