Mach Zehnder

Fig. 1. Representative device configurations exploiting electrooptic second-order nonlinear optical materials are shown. Schematic representations are given for (a) a Mach-Zehnder interferometer, (b) a birefringent modulator, and (c) a directional coupler. In (b) the optical input to the birefringent modulator is polarized at 45 degrees and excites both transverse electric (TE) and transverse magnetic (TM) modes. The appHed voltage modulates the output polarization. Intensity modulation is achieved using polarizing components at the output.

Compared to the Mach-Zehnder modulator, the modulation efficiency of the birefringent modulator is lower because is 1.5 times higher, ie,... 

The Mach-Zehnder Interferometer operates in a similar way, except that the input hght is divided into two arms and the pinhole is placed in one of the arms (Fig. 4bb). A disadvantage here is the possibility of having non-common path errors between the two arms. This system was proposed for use in AO by Angel (1994). The Interferometer which has been most commonly used in AO systems is the Lateral Shearing Interferometer (LSI). In this device, the wavefronts are made to coincide with slightly shifted versions of themselves. Let nl(r) and u2(r) represent the original and shifted wavefronts. 

In the case of a space separation of the laser beams (i.e. if the atomic velocity is perpendicular to the direction of the laser beams), the interferometer is in a Mach-Zehnder configuration. Then, the interferometer is also sensitive to rotations, as in the Sagnac geometry (Sagnac, 1913) for light interferometers. For a Sagnac loop enclosing area A, a rotation Q, produces a phase shift ... 

Inoue, K., Komatsu, S., Trinh, X. A., Norisuye, T. and Tran-Cong-Miyata, Q. (2005) Local deformation in photo-crosslinked polymer blends monitored by Mach-Zehnder interferometry. J. Polym. Sci. Part B Polym. Phys., 43, 2898-2913. 

Resonant photoacoustic gas spectrometry was adapted to fiber optic sensor technology32 as early as in 1984. A Mach-Zehnder arrangement was combined with a resonant photoacoustic cell for gap analysis. The pollutant gas NO2 was detectable in a concentration of 0.5 ppm. In a smart optical fiber hydrogen sensor, the fiber is coated with palladium metal which expands on exposure to hydrogen. This changes the effective optical path length of the fiber, which is detected by interferometry33. 

Heideman R.G., H. Kooyman R. P., Greve J., Performance of a highly sensitive optical waveguide Mach-Zehnder interferometer immunosensor, Sensors and Actuators B 1993 10 209-217. 

One of the possibilities to interrogate the effect of the evanescent field on the propagation of the guided radiation in the waveguide is an interferometric approach. This approach uses so-called Mach-Zehnder interferometers5,11 shown in Figure 3. 

Figure 3. Mach-Zehnder interferometer One of the arms is covered by inert material (reference arm), the other arm exposes to the sample (measuring arm).

In the following, the application of these concepts is shown both for reffactometric and reflectometric measurements using Mach-Zehnder interferometers and reflectometric interference spectroscopy. 

Mach-Zehnder interferometers allow the monitoring of gas concentrations and even the determination of analytes in liquids. Normally one of the measurement arms is covered with a thin polymer film into which the analyte can sorp. According to Nemst s distribution law, we have an equilibrium between the mobile and the stationary phase if a gas or a liquid pass the measurement window . Figure 12 shows a variety of results. 

Figure 12. Measurement arm of the Mach-Zehnder interferometer covered by a sensitive polymer layer, resulting in a intensity modulation by a change of the refractive index. This schematic changes are combined with the experimental data on the right side on top the curve of uptake of analyte, and its diffuseion out of the layer (right part), in the middle the experimental modulation, and at the bottom the related changes in refractive index. Bottom left shows the result of intensity signal versus the amount of substance for eight different analytes.

Interferometric sensors frequently have also been applied to biosensor measurements. Thereby, the evanescent field technique (Mach-Zehnder interferometer) has been compared with other optical detection principles regarding information on layer structure and in case of biosensing30. The... 

Figure 13. A Mach-Zehnder interferometer used to measure the isomers para- and meta-xvlene at various concentrations.

Figure 15. Mach-Zehnder chip used to monitor the growth of a layer structure interchanging streptavidin and avidin molecules. This structure is shown on the right, on the left side,the modulation and the calculated thickness increase is given.

Figure 16. Determination of simazine concentration in water. In the upper part, the modulation of the Mach-Zehnder signal for one concentration, including the regeneration step. The lower part shows the calibration curve for six different simazine concentrations graphed for the slope of this signal versus the simazine concentration in the logarithmic scale.

Fabricius N., Gauglitz G. and Ingenhoff J., A gas sensor based on an Mach-Zehnder interferometer, Sensors Actuators B 1992 7 672-676. 

Drapp B., Piehler J., Brecht A.. Gauglitz G., Luff B.J., Wilkinson J.S., Ingenhoff J., Integrated optical Mach-Zehnder interferometers as simazine immunoprobes, Sensors Actuators B 1997 39 277-282. 

Here we will discuss in more detail the 10 Mach-Zehnder interferometer7. It is a nice vehicle for illustrating in what way the problem of looking for extremely high resolutions can be approached, an approach which appeared to be very successful. We will focus on the MZI used for bulk sensing and we will make some additional remarks on its utilization in surface sensing. 

Heideman R.G., Lambeck P.V., Remote opto-chemical sensing with extreme sensitivity design, fabrication and performance of a pigtailed integrated optical phase-modulated Mach-Zehnder interferometer system, Sens, and Actuat. B 1999 61 1 GO-127. 

The electron density of the produced plasma was diagnosed by means of a Mach-Zehnder interferometer, operated with a small portion of the main pulse, doubled in frequency [29,30]. The electron density along the pulse path was measured to be ne 2 x 1019 cm-3. At this density, the electron plasma wave has a period Tp 25 fs and wavelength Ap ss 7.5 j,m. 

Mach-Zehnder interferometer, 144 Medical applications, 153 Metal-insulator transitions, 52 Monte Carlo procedure, 135 Multi-energy X-ray imaging, 131 Multilayer targets, 131 Multiphoton absorption, 85 Multiphoton ionization, 82 Multiple filamentation, 91, 92 Multipulse techniques, 152... 

Paloczi, G. T. Huang, Y. Yariv, A. Mookherjea, S., Polymeric Mach Zehnder interferometer using serially coupled microring resonators, Opt. Express 2003, 11, 2666 2671... 

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