Showing papers on "Mach–Zehnder interferometer published in 1993"

Interferometric detection of optical phase shifts at the Heisenberg limit.

Abstract: We show that the uncertainty in the relative quantum phase of two fields propagating in the arms of a Mach-Zehnder interferometer can be reduced to the Heisenberg limit by driving the interferometer with two Fock states containing equal numbers of photons. This leads to a minimum detectable phase shift far below that of any interferometer driven by a coherent light source.

Performance of a highly sensitive optical waveguide Mach-Zehnder interferometer immunosensor

Abstract: We describe a highly sensitive sensor which uses the evanescent field of a reusable planar optical waveguide as the sensing element. The waveguide used is optimized to obtain a steep dependence of the propagation velocity on the refractive-index profile near the surface. The adsorption of a layer of proteins thus results in a phase change, which is measured interferometrically using a Mach-Zehnder interferometer set-up. The stability of the interferometer is such that phase changes = (1 × 10-2)2pi per hour can be measured. Immunoreactions have been monitored down to concentrations of 5 × 10-11 M of a 40 kDa protein.

Single photon interference in 10 km long optical fibre interferometer

Abstract: Single-photon interference fringes with greater than 90% visibility were measured using a 10 km long optical fibre interferometer. The experiment employed a pulsed semiconductor laser source operating at a wavelength of 1.3 mu m and a novel single-photon counting scheme using high-speed germanium avalanche photodiodes. Interferometers of this type could form the basis of future quantum cryptography systems.

Efficient radially polarized laser beam generation with a double interferometer.

Abstract: Conversion of a linearly polarized CO2 laser beam into a radially polarized beam is demonstrated with a novel double-interferometer system. The first Mach–Zehnder interferometer converts the linearly polarized input beam into two beams with sin2 θ and cos2 θ intensity profiles, where θ is the azimuthal angle. This is accomplished by using two spiral-phase-delay plates with opposite handedness in the two legs of the interferometer to impart a one-wave phase delay azimuthally across the face of the beams. After these beams are interfered with, the resulting beams are sent directly into the second Mach–Zehnder interferometer, where the polarization direction of one beam is rotated by 90°. The beams are then recombined at the output of the second interferometer with a polarization-sensitive beam splitter to generate a radially polarized beam. The output beam is ≈ 92% radially polarized and contains ≈ 85% of the input power. This system will be used in upcoming laser particle acceleration experiments.

all optical switching devices based on large nonlinear phase shifts from second harmonic generation

Abstract: We show that the large nonlinear phase shifts obtained from phase‐mismatched second harmonic generation can be used to implement all‐optical switching devices such as a nonlinear Mach–Zehnder interferometer and a nonlinear directional coupler.

Quantum limits in interferometric detection of gravitational radiation

Abstract: A spectral analysis is given of the quantum fluctuations in an optical interferometer to detect gravitational radiation. Two different methods of beating the standard quantum limit are examined: directing a squeezed state into the nonlaser input port of the interferometer and placing a Kerr medium into both arms of the interferometer. For both the Kerr medium and large squeezing cases the interferometer system is limited ultimately by the damping noise in the mirrors, not by noise in the light.

10 Gbit/s, 1.56 mu m multiquantum well InP/InGaAsP Mach-Zehnder optical modulator

Abstract: 10 Gbit/s modulation using a III-V semiconductor Mach-Zehnder interferometer is reported for the first time. The modulator has a -3 dB bandwidth in excess of 15 GHz and is operated in a push-pull drive configuration with only 2 V peak to peak. 10 Gbit/s nonreturn to zero format eye diagrams with an extinction ratio>10 dB are demonstrated.

Enhanced single photon fringe visibility in a 10 km-long prototype quantum cryptography channel

Abstract: High visibility (V = 0985) single photon fringe measurements in a 10 km long, optical fibre-based, time- and polarisation-division Mach-Zehnder interferometer are reported The ability of the system to transmit key data in a quantum cryptography scheme is assessed

An all-optical switch employing the cascaded second-order nonlinear effect

Abstract: A new, ultrafast, low loss, all-optical switch based on the cascaded second-order nonlinearity is proposed. The device is based on an integrated Mach-Zehnder interferometer where quasi-phase matching produces a nonlinear phase shift with a different sign in each arm of the interferometer. A full treatment of the nonlinear phase shift indicates that the proposed device, if fabricated in AlGaAs, could switch with powers around 1.3 W in a length of approximately 1 cm. >

Interferometers and minimum-uncertainty states

Abstract: Minimum-uncertainty states in variables which are quadratic in mode creation and annihilation operators can be used to increase the accuracy of interferometric measurements. For a general interferometer we show how to find the relevant uncertainty relation. We consider two specific examples, a Mach-Zehnder interferometer and a Mach-Zehnder interferometer in which the first beam splitter has been replaced by a four-wave mixer. For both devices su(2) squeezed minimum-uncertainty states can be used to achieve phase-measurement accuracies of 1/N, where N is the total photon number at the input. We also describe a method of producing approximate versions of these states.

Phase contrast and amplitude pseudoheterodyne interference near field scanning optical microscopy

Abstract: Pseudoheterodyne detection of sample light in near field optical microscopy is demonstrated in an actively stabilized Mach–Zehnder interferometer. This results in a significant signal enhancement. Three distinct imaging modalities are described, which are based on the various stabilization feedback parameters, and scan speeds. A number of images are presented, demonstrating both amplitude and phase contrast imaging modalities.

Sub-shot-noise measurement with fiber-squeezed optical pulses.

Abstract: A novel scheme employing two pulses separated by a short time delay is used to cancel the phase noise from guided-acoustic-wave Brillouin scattering in a fiber ring interferometer. The dual-pulse-excited fiber ring is used to generate squeezed vacuum that, when injected into a measuring Mach–Zehnder interferometer, improves its sensitivity by 3 dB beyond the shot-noise limit.

Biosensors using integrated optical devices

Abstract: A label-free, homogeneous immunoassay can be realised using surface single-mode wave guide structures. The evanescent field of the guided mode penetrates the adjacent vicinity of the wave guide, the biochemical layer. Thus, changes in its thickness and refractive index during an antigen-antibody interaction cause a change in the effective refractive index of the wave guide itself. Such small changes can be transformed into intensity modulations using an interferometric set-up. Investigations are described using an integrated optical Mach-Zehnder interferometer (IO-MZ-chip) and the experimental results are compared with model calculations. The theoretical sensitivity of the IO-MZ-chips used was determined applying Maxwell's equations to the propagation of light in stripe wave guides. For the experimental formation of a protein adlayer a three-step biotinavidin protocol for the immobilisation of biotinylated immunoglobulins was employed.

Optical pressure sensor based on a Mach-Zehnder interferometer integrated with a lateral a-Si:H p-i-n photodiode

Abstract: We have fabricated an optical pressure sensor consisting of a Mach-Zehnder (MZ) interferometer and a thin membrane anisotropically etched into the silicon substrate underneath the measuring arm of the interferometer. The oxynitride rib-waveguides are single mode both for the TE and the TM polarization. To measure the constructive and destructive interferences at the output section of the interferometer we have integrated the rib waveguide with a lateral a-Si:H p-i-n photodiode. The number of constructive interferences measured for a given membrane deflection differs depending on TE or TM polarization. >

Optical Mach-Zehnder type logic element which performs an XOR operation

Abstract: An optical logic element is disclosed which performs an XOR operation through utilization of the high-speed property of light. On each branched waveguide of a Mach-Zehnder interference type optical waveguide there is provided a phase modulating element whose refractive index undergoes a change when it is irradiated by light. The interference type optical waveguide is adapted to provide different optical output levels when the refractive index changes of the phase modulating elements are both zero or a predetermined value and when they differ from each other. Thus, the optical logic element is capable of performing the XOR or XNOR operation at an ultrahigh speed.

Multilevel registered polymeric Mach–Zehnder intensity modulator array

Abstract: Described here is the first known demonstration of a registered two level guided wave polymeric electro‐optic Mach–Zehnder intensity modulator array. The device consists of two complete vertically stacked levels. Both levels were independently poled and operated. There was no measurable optical or electrical cross talk due to a high resistivity thermoset polymer buffers layer employed. Fabrication and performance of the device is discussed.

Spectral Changes in the Mach-Zehnder Interferometer

Abstract: The spectral interference law for a Mach-Zehnder interferometer is derived and is used to illustrate spectral changes arising by interference between beams having different degrees of correlation. The results are compared with those pertaining to Young's interference experiment.

Two-wavelength interferometric technique for measuring the refractive index of salt-water solutions.

Abstract: An experimental test system capable of measuring the refractive index variation of a salt-water solution at two wavelengths, with temporally varying temperature and concentration, is constructed by using a Mach–Zehnder interferometer. An experimental data-reduction method is developed to take the data generated in the experimental test program and to determine the variation of the refractive index with temperature and concentration. The experimental data obtained from the test system are reduced and the results are fitted by using a nonlinear regression algorithm to determine the functional dependence of the refractive index with temperature and concentration.

High-accuracy differential interferometry for the investigation of phase objects

Abstract: The authors present an interferometric method for the investigation of phase objects which employs a Mach-Zehnder arrangement with objects being located outside. It functions as a differential interferometer with the practical advantage that the sensitivity and the carrier fringe system can be chosen arbitrarily and independently. The computerized evaluation is well adapted to the experimental set-up, which helps to achieve high accuracy of the results. For the case of radially symmetrical objects a numerical method is presented for calculating the refractive index distribution from data measured with the above mentioned type of differential interferometer. The results of a demonstration experiment are shown and further applications of this differential interferometer are discussed.

Polarization-insensitive low-voltage optical waveguide switch using InGaAsP/InP four-port Mach-Zehnder interferometer

Abstract: Polarization-independent operation is highly desirable for optical-waveguide switches It can be realized with directional couplers, digital optical switches (DOS’s),1 and Mach-Zehnder interferometric (MZI) devices MZI switches2 have spatially separated regions for electro-optic phase shifting and mode coupling that may permit independent optimization Multimode- interference (MMI) couplers were recently demonstrated to be promising as polarization-insensitive and fabrication-tolerant power splitter-combiners3 Zucker et al4 realized a polarization- insensitive MZI switch by applying MMI couplers and introducing strain in quantum wells

Method for linearizing an unbalanced Mach Zehnder optical frequency discriminator

Abstract: An unbalanced Mach Zehnder optical frequency discriminator is linearized to suppress third order nonlinear distortion. An optical carrier that is modulated in optical frequency is input to an unbalanced Mach Zehnder interferometer to discriminate RF information signals carried on the carrier. The Mach Zehnder interferometer has an adjustable operating point. The operating point is adjusted to a point where the output intensity of the Mach Zehnder interferometer is no more than about ten percent of its maximum value. In order to avoid problems with second order distortion, the optical carrier is modulated with RF signals that do not occupy more than a single octave. The operating point of the device can be adjusted by adjusting an electrical bias thereof, by adjusting the wavelength of the optical carrier, or by adjusting the temperature of the device.

Magnetostrictive transducer system having a three dual-strip fiber optic magnetostrictive transducers bonded into a single fiber mach-zehnder interferometer

Abstract: The fiber-optic magnetostrictive transducer system consists of a sensing element having three dual-strip fiber optic magnetostrictive transducers bonded into a single fiber Mach-Zehnder interferometer operating single mode mounted in a symmetrical orthogonal geometry. The dual-strip fiber optic magnetostrictive transducers have predictable and consistent reproducibility and are comprised of a pair of field annealed metallic glass strips bonded to a coil of optical fiber. This structure is in turn mounted on a bobbin structure where the fiber ribbon is attached to the bobbin only at the two ends of the bobbin. This reduces the possible loading of the transducer due to friction between the optical fiber and the surface of the mounting structure and at the same time provide a long sensing fiber in contact with the magnetostrictive element for high sensitivity. The symmetrical orthogonal arrangement of the transducers minimizes magnetic crosstalk and the strip form of the transducer elements maintain high directional sensitivity.

Two-photon interference in a standard Mach–Zehnder Interferometer

Abstract: Two-photon interferometry (polarization correlation included) provides an efficient tool for studying the foundations of quantum mechanics and the fundamental properties of the electromagnetic field. It has been pointed out that the study of two-photon interferometry may bring new hope to the development of quantum-measurement theory. Several two-photon-interfercncc experiments by using Mach–Zehnder interferometers have been reported.1,2 In these experiments the light-quanta pairs generated from parametric downconversion are degenerate in frequency but nondegenerate in propagation direction. The photon pairs were directed to two input ports of a Mach-Zehnder interferometer, Higher than 50% second-order interference visibility (second order in intensity, fourth order in field) was observed when the pairs take equal optical paths to reach the input beam splitter of the interferometer from the down con version crystal. This phenomenon was considered to be a quantum effect.

Integrated optical switches in silicon based on SiGe-waveguides

Abstract: The realization of switches in silicon base on monomode Ge-indiffused SiGe waveguides is reported. At a wavelength of 1.3 mu m a Mach-Zehnder interferometer switch with a modulation depth of -10 dB at a current of 150 mA is obtained. This is the lowest value reported so far for single-mode optical switches in silicon. >

Analysis of symmetric directional couplers and asymmetric Mach-Zehnder interferometers as 1.30- and 1.55-um dual-wavelength demultiplexers/multiplexers

Abstract: Two difterent concepts for 1.30- and 1 .55-μm dual-wavelength demultiplexers/multiplexers, based on glass waveguides, the symmetric directional coupler, and the asymmetric Mach-Zehnder interlerometer, are analyzed and compared. Attention is given mainly to the sensitivity to fabrication parameter changes. The rather strict fabrication conditions needed to obtain satisfactory performance from directional couplers are examined. With Mach-Zehnder interferometers, the sensitivity is considerably lower, which indicates that the fabrication of these devices is uncomplicated.

Integrated optic sensor with macro-flow cell

Abstract: An integrated-optic channel waveguide device is configured as a biosensor. The device measures a refractive index change on the waveguide surface, so it is called a biorefractometer. With an appropriate overlay or selective coating, the device can monitor proteins in blood or pollutants and bio-warfare agents in water. We describe the design, fabrication, and testing of a sensor employing a waveguide Mach-Zehnder interferometer configuration. The device is fabricated in a glass substrate using potassium ion exchange. A patterned glass buffer layer defines the sensing and reference arms of the interferometer. A silicone-rubber macro-flow cell confines the liquid above the integrated-optical waveguide device. Salt solution data show that the biorefractometer has a sensitivity ((Delta) neff/(Delta) nLiquid) of 2 X 10-3 and can measure refractive index changes of about 0.005. Data obtained for antigen-antibody binding of the protein IgG indicate that a 10 percent signal change occurs in approximately 1 minute for a 10 (mu) g/ml concentration level.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A subcarrier-multiplexed coherent FSK system using a Mach-Zehnder modulator with automatic bias control

Abstract: A subcarrier-multiplexed coherent optical transmission system using a push-pull Mach-Zehnder intensity modulator is demonstrated. Six subcarrier channels cover a six-octave bandwidth and are frequency-shift keying (FSK) modulated at 45 Mb/s. With an optical phase modulation index of 0.38, a receiver sensitivity of -36 dBm is obtained. Second-order intermodulation is canceled by more than 20 dB due to the balanced structure of the modulator. This results in an 8-dB improvement in the receiver sensitivity compared to the system using an optical phase modulator. A simple automatic bias-control scheme for the Mach-Zehnder modulator is also demonstrated. It utilizes the optical signal from the complementary output port of the dual-output modulator. >

High‐speed all‐optical switching experiment in Mach–Zehnder configuration using GaAs waveguide

Abstract: We report the results of a high‐speed all‐optical switching experiment in Mach–Zehnder configuration using a GaAs waveguide. The all‐optical switching is based on the nonlinear refractive index change induced by the band‐filling effect in the GaAs waveguide. To achieve high‐speed operation without being limited by the slow carrier relaxation time, a dc electric field is externally applied to the nonlinear waveguide to sweep carriers away from the light guiding region. The FWHM (full width at half maximum) of the switching waveform without the externally applied electric field is about 800–900 ps. As the electric field is increased, the FWHM is reduced to about 80–90 ps.

Compact Mach–Zehnder fiber interferometer incorporating photoinduced gratings in elliptical-core fibers

Abstract: A new type of Mach–Zehnder interferometer has been fabricated in an elliptical-core high-birefringence fiber. The directional couplers of a conventional fiber interferometer are replaced by two photoinduced polarization rocking filters written on the same fiber. The resonant wavelength of the interferometer was 787 nm, with an operational bandwidth of 18 nm. The device can be used in two different modes for temperature sensing.