Drift correction in a multichannel integrated optical young interferometer

We demonstrate that in a sensor based on a multichannel Young interferometer, the phase information obtained for different pairs of channels can be used to correct the long-term instability (drift) due to temperature differences between measuring and reference channels, the drift in the alignment of the setup, etc. Experiments show that the nature of a major part of the drift is such that the drift present in one of the channels can be determined by interpolation of the drift measured in the two adjacent channels. It is shown that a drift reduction of 10 times can be achieved as compared with the situation in which no correction is applied. We anticipate that these findings will permit the exploitation of the extreme sensitivity of interference-based sensors to a much greater extent.     

Fast, ultrasensitive virus detection using a Young interferometer sensor

We report the application of an integrated optical Young interferometer sensor for ultrasensitive, real-time, direct detection of viruses. We have validated the sensor by detecting herpes simplex virus type 1 (HSV-1), but the principle is generally applicable. Detection of HSV-1 virus particles was performed by applying the virus sample onto a sensor surface coated with a specific antibody against HSV-1. The performance of the sensor was tested by monitoring virus samples at clinically relevant concentrations. We show that the Young interferometer sensor can specifically and sensitively detect HSV-1 at very low concentrations (850 particles/mL). We have further demonstrated that the sensor can specifically detect HSV-1 suspended in serum. Extrapolation of the results indicates that the sensitivity of the sensor approaches the detection of a single virus particle binding, yielding a sensor of unprecedented sensitivity with wide applications for viral diagnostics.     

Polarization invariance in a Young interferometer

Conditions ensuring that the polarization properties at the output plane of a Young interferometer fed by an electromagnetic partially coherent beam are the same as those at the pinholes are derived. Such a behavior is interpreted in terms of the vector modes of the electromagnetic source corresponding to the field emerging from the Young pinholes.     

Integrated optical Young interferometer

The integrated optical configuration of a Young interferometer is proposed for refractometry and chemical sensing. We coupled light into an integrated optical Ybranch by fixing a laser diode directly at the input of the optical device. We solved the problem of ambiguity in the interference order by operating the laser diode at currents below threshold, resulting in visibility modulation of the interference fringes caused by the low coherence length of the emitted light. A very compact device results that measures the refractive index of liquids or gases. An electronic scanning technique by means of a CCD array provides a fast readout without the need for moving parts.     

Development of a multichannel fluorescence affinity sensor system

A multichannel fluorometer is proposed for analysis of biochemical reactions. The sensor is based on the luminescence generation in the evanescent field of a totally reflected laser beam. For transduction, multiple reflection elements are used. Multichannel operation is realized, including the possibility of applying different solutions to each channel at the same time. First experimental results, obtained with fluorescein or Cy5 as labels in a model hybridization assay, demonstrate the applicability and allow the detection of 3-10 fmol injected fluorescently labeled oligonucleotide.     

Optical amplification in a planar multichannel Mach-Zehnder interferometer based on metal-semiconductor-metal structures

This paper describes a new optoelectronic device—an optical transistor that provides power amplification of output visible radiation. The optical transistor is structurally based on a metallized semiconductor plate with a microchannel gap in the form of a planar Mach-Zehnder interferometer. A device of the light-light type is controlled by modulating the refractive index in one arm of the interferometer. Pis’ma Zh. Tekh. Fiz. 24, 17–21 (January 26, 1998)     

Reciprocal reflection interferometer for a fiber-optic Faraday current sensor

A reciprocal fiber-optic reflection interferometer for remote measurement of electrical current through the Faraday effect is described. The effects of polarization cross coupling because of nonideal elements are eliminated with a low-coherence source. Nonreciprocal birefringence phase modulation is employed for detection of the Faraday phase shift. The theoretical predictions are confirmed by measurements with a piece of straight fiber as the sensing element in a 100-turn solenoid. Currents from 0 to 40 A have been measured with a linear response and a noise limit of ~0.015 A/√Hz.     

Ray picture of polarization and coherence in a Young interferometer

We apply a polarization Wigner formalism to the propagation of polarization in a Young interferometer within paraxial approximation. With a very simple ray picture, we obtain complete and rigorous information about polarization evolution via the superposition of the spatial-angular Stokes parameters associated with three light rays. We compare the degree of polarization in the interference region with several measures of the degree of coherence for vectorial fields.     

Optical and electronic design of a calibrated multichannel electronic interferometer for quantitative flow visualization

Calibrated multichannel electronic interferometry is an electro-optic technique for performing phase shifting of transient phenomena. The design of an improved system for calibrated multichannel electronic interferometry is discussed. This includes a computational method for alignment of three phase-shifted interferograms and determination of the pixel correspondence. During calibration the phase, modulation, and bias of the optical system are determined. These data are stored electronically and used to compensate for errors associated with the path differences in the interferometer, the separation of the phase-shifted interferograms, and the measurement of the phase shift.     

Design methodology for a Fabry-Perot interferometer used as a concentration sensor

We present the design methodology for a sensor that can nonintrusively monitor target gas concentration levels in a power plant exhaust flow. The measurement is based on radiative emission by rovibrational transitions that are well isolated from emission features of other constituents and requires both moderate spectral resolution (typically 1 nm or below) and relatively high optical throughput. A Fabry-Perot interferometer provides this capability, and its conceptual design is discussed at length. High-temperature radiative emission of nitric oxide in a background of water was used as a sample system for the design of a prototype Fabry-Perot interferometer. Predictions for the instrument are a minimum resolvable NO column density of 100 parts per million times meter based on a simple background subtraction scheme with a gas temperature of 800 K. Improved order sorting can dramatically lower this minimum. The prototype instrument was calibrated and tested with a laboratory simulator; results are presented and compared with predictions.     

Fundamental performance comparison of a Hartmann and a shearing interferometer wave-front sensor

The performance of ground-based optical imaging systems is severely degraded from the diffraction limit by the random effects of the atmosphere. Adaptive-optics techniques have been used to compensate for atmospheric-turbulence effects. A critical component in the adaptive-optics system is the wave-front sensor. At present, two types of sensors are common: the Hartmann-Shack wave-front sensor and the shearing interferometer wave-front sensor. In this paper we make a direct performance comparison of these two sensors. The performance calculations are restricted to common configurations of these two sensors and the fundamental limits imposed by shot noise and atmospheric effects. These two effects encompass the effects of extended reference beacons and sensor subaperture spacings larger than the Fried parameter r(0). Our results indicate comparable performance for good seeing conditions and small beacons. However, for poor seeing conditions and extended beacons, the Hartmann sensor has lower error levels than the shearing interferometer.     

Two-chamber integrated multichannel narrowband filter prepared by a multistep etching method

A new, to the best of our knowledge, method, which combines the multistep ion-etching method with a traditional narrowband filter coating technique, is developed to prepare a two-chamber integrated multichannel filter. The influence of film deposition and etch technique on the shape and height of the narrow transmittance peaks is analyzed. A 32-channel narrowband integrated filter is fabricated with a homemade ion-etching machine and a coating machine. Every channel is distinctly separated and the FWHM is 1% of its central wavelength. The feasibility of the technique will be useful in the fabrication of a higher integrated multichannel narrowband filter.     

Analysis of a shift interferometer as a component of a fiberoptic acoustic pressure sensor

Translated from Izmeritel'naya Tekhnika, No. 10, pp. 24–26, October, 1992.     

Fourier transform near-infrared spectrometer using a corner-cube integrated prism scanning interferometer

This paper describes a Fourier transform (FT) near-infrared spectrometer that uses an integrated prism scanning interferometer whose optical paths are stabilized by corner cubes. A combination of corner cubes and a retroreflection mirror, which is sometimes used in the conventional interferometer for FT spectrometers, is adopted and adapted to the integrated prism scanning interferometer through a special design. Without any degradation of spectroscopic properties, the optical path in the interferometer is highly stabilized and the moving distance of the stage is halved. These advantages provide a robust and portable FT spectrometer for field use.     

Narrowband multichannel filters and integrated optical filter arrays

We propose and demonstrate three approaches to achieve narrowband multichannel filters. These are multiple heterostructures with defects, guided-mode resonance (GMR) Brewster filters with multiple channels, and integrated narrow bandpass filter arrays. Transmission studies for multiple heterostructures with defects are presented. We show that the enlargement of the forbidden band and multiple-channel filtering can be reached simultaneously with these configurations. GMR Brewster filters with multiple channels can be obtained with a single-layer grating. The same properties can be obtained by use of double-layer structures that consist of a homogeneous layer and a grating with equal refractive index. We developed a combinatorial etching technique that has 32 elements on a single substrate with which to fabricate integrated narrow bandpass filters. Single- and double-chamber integrated optical filter arrays were fabricated by use of this etching technique. These narrowband multichannel filters and narrow bandpass filter arrays show good filtering features and can be utilized in many optical applications.     

Experimental comparison of a Shack-Hartmann sensor and a phase-shifting interferometer for large-optics metrology applications

We performed a direct side-by-side comparison of a Shack-Hartmann wave-front sensor and a phase-shifting interferometer for the purpose of characterizing large optics. An expansion telescope of our own design allowed us to measure the surface figure of a 400-mm-square mirror with both instruments simultaneously. The Shack-Hartmann sensor produced data that closely matched the interferometer data over spatial scales appropriate for the lenslet spacing, and much of the <20-nm rms systematic difference between the two measurements was due to diffraction artifacts that were present in the interferometer data but not in the Shack-Hartmann sensor data. The results suggest that Shack-Hartmann sensors could replace phase-shifting interferometers for many applications, with particular advantages for large-optic metrology.     

An integrated magnetotransistor sensor

The initial voltage offset between the collectors in integrated circuits, including an npn-type dual-collector lateral bipolar magnetotransistor, formed in a well, and polysilicon resistors, is investigated experimentally. The choice of the switching circuit of the magnetotransistor determines the mode of operation and its effect on the offset. The initial offset between the voltages on the collectors is less than 1 mV, which enables the relative value of the useful signal in a weak magnetic field to be increased. Translated from Izmeritel’naya Tekhnika, No. 4, pp. 50–54, April, 2009.     

Fiber bragg grating strain sensor demodulation with quadrature sampling of a mach-zehnder interferometer

A simple and highly sensitive phase-demodulation technique is proposed, and its use for a fiber Bragg grating strain sensor is experimentally demonstrated. Sampling a phase-modulated Mach-Zehnder output with controlled time delay produced two quadrature data streams that have relative quadrature phase difference (90 degrees ). The Bragg wavelength-dependent phase information is extracted by application of digital arctangent function and phase unwrapping to the quadrature signals. By use of this technique with a reference grating, strain sensing at as much as a 30-kHz sampling rate was obtained with strain resolution of 3.5 microstrains and 6 nanostrains/ Hz in quasi-static and dynamic strain measurements, respectively.     

Extrinsic optical-fiber ultrasound sensor using a thin polymer film as a low-finesse Fabry-Perot interferometer

Theoretical and experimental aspects of an extrinsic optical-fiber ultrasound sensor are described. The sensor is based on a thin transparent polymer film acting as a low-finesse Fabry-Perot cavity that is mounted at the end of a multimode optical fiber. Performance was found to be comparable with that of a piezoelectric polyvinylidene dinuoride-membrane (PVDP) hydrophone with a sensitivity of 61 mV/MPa, an acoustic noise floor of 2.3 KPa over a 25-MHz bandwidth, and a frequency response to 25 MHz. The wideband-sensitive response and design flexibility of the concept suggests that it may find application as an alternative to piezoelectric devices for the detection and measurement of ultrasound.