Gerald B. Brandt

Image Plane Holography

Some of the unique reconstruction properties of image plane holography are derived from the well-known imaging equations of holography. These properties are illustrated experimentally with focused holograms using both external and locally generated reference beams. The relative advantages of lenses and hologram optical elements are presented with particular reference to local reference beam focused holography and some of the photographic film parameters which are important for optimum image reconstruction are presented. Image plane holography offers a practical technique for producing inexpensive,bright, white light displays.

Temperature sensing in optical fibers using cladding and jacket loss effects

A theoretical analysis is given of methods using transmission intensity effects in optical fibers as temperature sensors. The underlying mechanism involves temperature-dependent coupling of the evanescent field through a relatively thin cladding layer onto a lossy jacket. The temperature dependence comes about through the refractive indices of the core and cladding materials, which are chosen along with the fiber dimensions to give the desired response.

Fiber-optic temperature sensor based on internally generated thermal radiation.

This paper presents a theoretical and experimental study of a method of sensing temperature with optical fibers with the radiation thermally generated within the fiber. Using quartz fibers it is possible to read temperatures in the range from room temperature to over 1000 degrees C. We have demonstrated operation as low as 135 degrees C using nonoptimum fibers and detectors. The method also allows the determination of the location and length of a hot spot along the fiber. The purpose of this type of sensor is to monitor the development of hot spots in electrical machinery, such as generators and transformers, where conventional measurement techniques cannot be effectively applied. If such optical fibers can be incorporated in the manufacturing process of electrical equipment, these temperature monitors may contribute in avoiding catastrophic breakdown.

Role Of Hard Carbon In The Field Of Infrared Coating Materials

Amorphous hydrogenated hard carbon (a-C:H) is a promising new optical coating material for passive infrared materials. It offers the rare combination of extreme hardness, chemical inertness, and optical transparency over a wide spectral range. We give an overview of the optical properties of rf-plasma deposited a-C:H coatings and compare them with vacuum-evaporated infrared coatings. For many applications, a-C:H solves the problem of a mechanically and chemically resistant 8 to 12 Am coating despite its moderate absorption in the 6 to 20 Am range. The tunability of the refractive index between 1.8 and 2.2 allows single layer coatings on Si and Ge with zero reflection. State-of-the-art applications, possible future developments, as well as remaining technological problems of a-C:H are discussed.

Bulk acoustic wave interaction with guided optical waves

An interaction between longitudinal or shear bulk acoustic waves and guided optical waves has been observed in single‐mode and multimode polyurethane and sputtered glass optical waveguides. This interaction produces a number of effects — namely, mode conversion, amplitude modulation, and phase modulation — depending upon whether shear or longitudinal sound is present. Mode conversion between TE and TM waveguide modes occurs with shear sound; longitudinal sound produces amplitude and phase modulation of the guided light. The bulk acoustic wave effect offers promise for producing high‐data‐rate integrated optical modulators.

SPATIAL FREQUENCY DIVERSITY FOR COHERENT OPTICAL PROCESSING

Coherent optical noise can be suppressed by sending the desired signal through a number of channels and combining the result at the output. Channels coded by means of spatial frequency are particularly convenient for optical processing systems and offer some advantages additional to noise reduction. The mechanism of noise reduction is described for such spatial frequency diversity systems, and some experiments are described that illustrate noise reduction and multiple filtering possibilities of this technique.

An error analysis of holographic strains determined by cubic splines

Holographic measurements of an idealized cantilever beam under end-loading and uniform-loading conditions are simulated on a computer. Cubic splines are fitted to the simulated data and then used to evaluate the shear strain and bending moment. Controlled data errors are introduced into the simulated measurements and the strain and bending-moment results are compared with the known analytic results. When the data are not resolution limited, the accuracy of the results increases as more cubic splines are taken. However, when the data are resolution limited, the accuracy of the results is a maximum for an optimum number of cubic splines and the use of more splines actually decreases the accuracy.

In -plane scattering in glass and niobium oxide waveguides

Scattered light which remains in an optical waveguide to be guided to the detector is an important limiting factor to the performance of integrated optical devices. In sputtered glass and niobium oxide wavegu ides the principal mechanisms for scattering are refractive index variations in the wave-guide and surface roughness of the waveguide. Theories for scattering from surface roughness, in the regime expected for these wavegu ides, predict that the wavelength variation of the scattering should be proportional to the inverse square of the wavelength. Theory for scattering from refractive index variations predicts a wavelength dependence ranging from inverse fourth power of the wavelength to no dependence upon wavelength, when the range of possible scattering diameters is varied from small to le ge with respect to the optical wavelength. Experiments on a number of relatively lossy wavegu ides indicate that there is little relation between overall waveguide loss and the magnitude of the scattering in the near forward direction. Furthermore, overall loss and in-plane scattering have different variations with wavelength suggesting that the mechanisms involved in loss and scat-tering are different. Waveguide surface preparation prior to sputtering ap-pears to be an important factor in determining overall quality, but more as it influences the bulk properties of the waveguide film than as a direct scattering mechanism. Homogeneity of the waveguide film appears to be the controlling factor in production of low scatter wavegu ides.

Growth and characterization of mercurous halide crystals: mercurous bromide system

Abstract Mercurous bromide single crystals were grown by the physical vapor transport method in a sealed quartz tube. Growth rates were measured for crystals growing in different orientations. Experimental data followed the equation l t = l ∞ − A exp(− t / τ ), where l t is the length of the crystal at any time t , l ∞ is the final statio nary length, and A and τ are constants. Crystals growing in 〈001〉 orientation had much higher velocity than crystals growing in 〈110〉 orientation. Large crystals were grown in 〈110〉 orientation by using preoriented seeds, an orientation needed for acousto-optic devices. The optical quality of mercurous bromide crystals was evaluated by fabricating a 5 cm long crystals. The acoustic velocity measurement data showed that the value for the slow shear velocity propagating along 〈110〉 is 2.73 × 10 4 cm/s, consistent with the values reported earlier. This translates with a high value of photelastic coefficient, into a high acousto-optic diffraction efficiency; 2600 with respect to quartz. These results showed that mercurous bromide has potential as an efficient Bragg cell with a delay time greater than 200 μs in a compact package.

Purification and characterization of mercurous halides

Abstract Mercurous halides are extremely insoluble in most organic and inorganic solvents. This makes members of this class of compounds very difficult to purify by recrystallization from solution. The conventional directional freezing and zone melting methods also fail because all the mercurous halides decompose into the respective mercuric halide and mercury metal on melting. For this reason, we have developed a purification method based on repeated sublimation carried out in a hermetically sealed vessel. The materials prepared by this technique were analyzed following the purification. Metal contamination could be reduced below 10 ppm. Purified feed stock was found quite suitable for crystal growth.