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Showing papers in "Applied Optics in 1972"


Journal ArticleDOI
Smith Rg1
TL;DR: These effects of stimulated Raman and Brillouin scattering must be considered in the design of optical communication systems using low loss fibers especially when low loss optical fibers are used.
Abstract: The effect of stimulated Raman and Brillouin scattering on the power handling capacity of optical fibers is considered and found to be important especially when low loss optical fibers are used. A critical power below which stimulated effects may be neglected is defined for forward and backward Raman scattering and for backward Brillouin scattering. This critical power is determined by the effective core area A, the small signal attenuation constant of the fiber alpha, and the gain coefficient for the stimulated scattering process (gamma0), by the approximate relation P(crit) approximately 20Aalpha/(gamma0). For a fiber with 20-dB/km attenuation and an area of 10(-7) cm(2)P(crit) approximately 35 mW for stimulated Brillouin scattering. For stimulated Raman scattering P(crit) is approximately two orders of magnitude higher. It is concluded that these effects must be considered in the design of optical communication systems using low loss fibers.

1,080 citations


Journal ArticleDOI
TL;DR: A pulsed tunable dye laser with a bandwidth of less than 0.004 A, repetitively pumped by a nitrogen laser, is described and output peak powers in the kilowatt range at 5-100 nsec pulse width and repetition rates up to 100 pps can be generated from the near-ultraviolet throughout the visible spectrum.
Abstract: A pulsed tunable dye laser with a bandwidth of less than 0.004 A, repetitively pumped by a nitrogen laser, is described. An intracavity beam expanding telescope together with a diffraction grating in Littrow mount and a tilted Fabry-Perot etalon provide convenient, very reproducible wavelength tuning and good stability. Output peak powers in the kilowatt range at 5–100 nsec pulse width and repetition rates up to 100 pps can be generated from the near-ultraviolet throughout the visible spectrum.

598 citations


Journal ArticleDOI
TL;DR: A critical survey of the literature is presented and an empirical model of the complex refractive indices for ice and liquid water is constructed from this review.
Abstract: A critical survey of the literature is presented. An empirical model of the complex refractive indices for ice and liquid water is constructed from this review. The model is applicable from -20 degrees C to 0 degrees C for ice and from -20 degrees C to 50 degrees C for water. The spectral interval for which the model applies extends from 2 micro, to several thousand kilometers in wavelength for ice and from 2 micro to several hundred meters in wavelength for water.

595 citations


Journal ArticleDOI
TL;DR: A method for determining particle size, number density, and velocity utilizing a laser interferometer is analyzed and shows that when the fringe spacing is comparable to a particle diameter, size can be estimated and number density can be measured.
Abstract: A method for determining particle size, number density, and velocity utilizing a laser interferometer is analyzed. The results show that when the fringe spacing is comparable to a particle diameter, size can be estimated; and when the fringe spacing is much greater than the average particle diameter, number density can be measured. Since the optical arrangment for the interferometer is identical to that for a number of laser velocimeters, the effects of particle size on the velocimeter signal are discussed.

252 citations


Journal ArticleDOI
TL;DR: A general expression is derived for the mutual coherence function (MCF) of a finite optical beam propagating in a weakly inhomogeneous medium such that for distances much less than z(B), the MCF is well approximated by the plane (spherical) wave results.
Abstract: On the basis of the extended Huygens-Fresnel principle, a general expression is derived for the mutual coherence function (MCF) of a finite optical beam propagating in a weakly inhomogeneous medium. The results obtained here for the beam MCF are valid both in the near and far field of the laser transmitting aperture and for an arbitrary complex disturbance in the exit pupil of the aperture. A general expression is also derived for the propagation distance z(B) such that for distances much less (greater) than z(B), the MCF is well approximated by the plane (spherical) wave results. An analytic expression is pre-sented for a Gaussian beam such that a numerical error in previous results is corrected. Finally, some comments regarding higher order statistical moments of the field are given.

236 citations


Journal ArticleDOI
TL;DR: A white-light interferometric thickness gauge has been developed that provides microinch sensitivity to gauge variations in moving transparent films and is relatively insensitive to variations in chemical composition, film temperature, haze level, and measurement geometry.
Abstract: A white-light interferometric thickness gauge has been developed that provides microinch sensitivity to gauge variations in moving transparent films. The new gauge that is suitable for on-line use can be adapted to monitor continuously the thickness profile of transparent films, the thickness of transparent coatings, and the birefringence of optically anisotropic materials. Its performance is relatively insensitive to variations in chemical composition, film temperature, haze level, and measurement geometry.

228 citations


Journal ArticleDOI
TL;DR: An analysis of the errors produced by emulsion movement, incorrect hologram size and position, and distortion in hologram plotter and photoreduction lens is given, and it is shown that all the errors are proportional to the slope of the aspheric wavefront.
Abstract: The use of computer generated holograms for the testing of aspheric wavefronts is described. An analysis of the errors produced by emulsion movement, incorrect hologram size and position, and distortion in hologram plotter and photoreduction lens is given, and it is shown that all the errors are proportional to the slope of the aspheric wavefront. Experimental results verifying the error analysis are shown for testing rotationally nonsymmetric wavefronts having slopes as large as 125 waves per radius and departures as large as sixty-five waves.

212 citations


Journal ArticleDOI
D. Gloge1
TL;DR: This paper shows that this grading affects the mode volume and the loss in bends very little, if the index difference of the graded core (between the core axis and the cladding) is twice that of the homogeneous core.
Abstract: Parabolic grading of the core index in a multimode fiber (Selfoc) diminishes mode dispersion and interface loss. This paper shows that this grading affects the mode volume and the loss in bends very little, if the index difference of the graded core (between the core axis and the cladding) is twice that of the homogeneous core. Curvature radii of several centimeters are tolerable. Mode coupling (or ray deflection) in random bends is slightly decreased by grading. Both the graded and the homogeneous multimode fiber are particularly sensitive to certain critical deviations of the guide axis from straightness. These deviations must be less than a fraction of a micrometer in order that catastrophic mode loss be avoided.

207 citations


Journal ArticleDOI
TL;DR: Experimental results are given for the photoionization of rubidium vapor using a ruby-laser-pumped dye laser and a doubled ruby laser radiation, and photodissociation of HCl using the Raman-shifted output and the fourth harmonic output of a tunable Nd-glass laser.
Abstract: The general considerations for two-step photoionization of atoms and photodissociation of molecules using tunable laser sources are discussed. Experimental results are given for the (1) photoionization of rubidium vapor using a ruby-laser-pumped dye laser and a doubled ruby laser radiation, and (2) photodissociation of HCl using the Raman-shifted output and the fourth harmonic output of a tunable Nd-glass laser. The possibilities for other laser systems are also discussed.

182 citations


Journal ArticleDOI
TL;DR: Comparisons show that the FLASH calculations for spherical-shell atmospheres are in good agreement with those for plane-parallel atmospheres within the range of zenith angles for which no differences could be attributed to the difference in the geometries of the two atmospheric models.
Abstract: A Monte Carlo procedure, designated as FLASH, was developed for use in computing the intensity and polarization of the radiation emerging from spherical-shell atmospheres and is especially useful for investigating the sunlit sky at twilight time. The procedure utilizes the backward Monte Carlo method and is capable of computing the Stokes parameters for discrete directions at the receiver position. Both molecular and aerosol scattering are taken into account as well as ozone, aerosol, water vapor, and carbon dioxide absorption within the atmosphere. The curvature of the light path due to the changing index of refraction with altitude is taken into account. Some comparisons are made between FLASH calculations for a pure Rayleigh atmosphere, a combined Rayleigh and aerosol atmosphere, and calculations reported by other authors for plane-parallel atmospheres. The comparisons show that the FLASH calculations for spherical-shell atmospheres are in good agreement with those for plane-parallel atmospheres within the range of zenith angles for which no differences could be attributed to the difference in the geometries of the two atmospheric models.

177 citations


Journal ArticleDOI
TL;DR: The principal optical characteristics of paraboloid-hyperboloid x-ray telescopes are evaluated by a ray-tracing procedure and it is found that results for resolution, focal plane curvature, and finite source distance effects may be approximated by simple empirical formulas.
Abstract: We have evaluated the principal optical characteristics of paraboloid-hyperboloid x-ray telescopes by a ray-tracing procedure; we find that our results for resolution, focal plane curvature, and finite source distance effects may be approximated in terms of the design parameters by simple empirical formulas.

Journal ArticleDOI
TL;DR: An investigation of new films made by an rf discharge polymerization process of organic chemical monomers, focused on films prepared from vinyltrimethylsilane and hexamethyldisilbxane, which exhibit very low loss for light-wave propagation and the possibility of controlling the refractive index of the films.
Abstract: The continued development of integrated optics is heavily dependent upon the availability of materials that are suitable for the construction of thin-film optical circuitry and devices We report here an investigation of new films made by an rf discharge polymerization process of organic chemical monomers We concentrate our discussion on films prepared from vinyltrimethylsilane and hexamethyldisiloxane These films are smooth, tough, pinhole-free, transparent from 04 μm to 075 μm, and exhibit very low loss (<004 dB/cm) for light-wave propagation More importantly, experiments demonstrate the possibility of controlling the refractive index of the films either by the mixing of the two monomers before deposition or by chemical treatment after the film is deposited The use of the prism–film coupler for studying the refractive index of each material is discussed in detail

Journal ArticleDOI
TL;DR: A simple model confirms the measured transmission of a coarse dry powder of water solubles and shows that the extinction by natural aerosol should have a minimum near 8 microm and a strong maximum near 9 microm.
Abstract: The optical constants in the ir from λ2.5 μm to 40 μm (4000–250 cm−1) of dry natural aerosol substances and of sea salt are presented. The aerosol substances were obtained from rain and snow water: dust and soot by sedimentation, and water soluble salts by evaporation. The spectra of the absorption index n′ were derived from our published transmittance measurements of potassium bromide disks. The real part n of the refractive index was calculated from the specular reflectance at near normal incidence of disks of pure aerosol substance. The observed spectral features are being related to chemical constituents, notably sulfates and alcohol soluble organics. Optical constants of composite and wet aerosol are discussed. A simple model confirms the measured transmission of a coarse dry powder of water solubles and shows that the extinction by natural aerosol should have a minimum near 8 μm and a strong maximum near 9 μm.

Journal ArticleDOI
Booth Bl1
TL;DR: An experimental Du Pont holographic photopolymer material produces an index modulation in excess of 10−2 utilizing a diffusion mechanism, which is exact for real-time holography.
Abstract: An experimental Du Pont holographic photopolymer material produces an index modulation in excess of 10−2 utilizing a diffusion mechanism. Optimum exposure in air is typically 30 mJ/cm2, in nitrogen 3 mJ/cm2. Composition, beam ratio, and exposure power all affect the index modulation. This, combined with thickness variations, permits diffraction efficiency to be preadjusted for a variety of desired angular responses and spatial frequencies. The material can be easily overmodulated according to Kogelnik’s phase grating theory. No wet processing is required. After total polymerization, storage at 100°C, −60°C, and under water does not significantly affect the diffraction efficiency. Image–object superposition is exact for real-time holography. Excellent copies of silver halide holograms with four times the original efficiency have been made. Grating devices with tailored peak or flat wavelength response can be constructed.

Journal ArticleDOI
TL;DR: A simple and inexpensive frequency stabilization system of a helium-neon two-mode laser with an internal mirror plasma tube and the relative uncertainty of the frequency stabilization is less than 1 part in 10(7).
Abstract: A simple and inexpensive frequency stabilization system of a helium-neon two-mode laser with an internal mirror plasma tube is described. The stabilization depends on the comparison of the light intensities of the two operating longitudinal modes. The corresponding frequencies of the modes are symmetrized about the emission line of neon at the transition 3s(2)-2p(4). Experimental results are given. The relative uncertainty of the frequency stabilization is less than 1 part in 10(7).

Journal ArticleDOI
TL;DR: A system for extracting the phase components of an optical traveling wave field has been constructed using the Mach-Zehnder interferometer to capture the wave field as the hologram, a photoelectronic scanning system, and an analog computing circuit.
Abstract: A system for extracting the phase components of an optical traveling wave field has been constructed. This system consists of the Mach-Zehnder interferometer to capture the wave field as the hologram, a photoelectronic scanning system, and an analog computing circuit. The detected phase signal is immediately displayed on a cathode ray tube as continuous-tone patterns. The method has been confirmed through the experimental results.

Journal ArticleDOI
TL;DR: Implementation techniques are discussed and results shown that indicate good correlation with profilometer measurements for a wide range of roughness values produced with a variety of finishing procedures.
Abstract: An experimental investigation is made of a technique for measurement of surface roughness. A speckle pattern is formed near the image plane of a lens in spatially coherent light having a broad spectral bandwidth. The contrast of the speckle is found to be related to surface roughness when the roughness and the coherence length of illumination are comparable in magnitude. Implementation techniques are discussed and results shown that indicate good correlation with profilometer measurements for a wide range of roughness values produced with a variety of finishing procedures.

Journal ArticleDOI
Donald E Duffy1
TL;DR: An easily implemented method of measuring in-plane surface displacement by photographing an object through two laterally displaced apertures is described and the experimental results are presented.
Abstract: An easily implemented method of measuring in-plane surface displacement by photographing an object through two laterally displaced apertures is described and the experimental results are presented. The displacement is displayed as a pattern of moire fringes over the image. No previously constructed grids or rulings are required as in normal moire devices. The method is noncontacting and requires no special surface preparation. The sensitivity is easily adjusted and is shown to be equivalent to that obtained using double-exposure holography or speckle pattern interferometry techniques. The method has potential application in mechanically unstable environments or where the conditions are such that grids or strain gauges cannot be attached to the object.

Journal ArticleDOI
TL;DR: It is shown that monitoring Raman signals from atmospheric nitrogen aids in interpreting elastic scattering measurements by eliminating attenuation effects, and the experimental results show good agreement with independent meteorological measurements.
Abstract: Raman optical radar measurements of the atmosphere demonstrate that the technique may be used to obtain quantitative measurements of the spatial distribution of individual atmospheric molecular trace constituents (in particular water vapor) and of the major constituents. It is shown that monitoring Raman signals from atmospheric nitrogen aids in interpreting elastic scattering measurements by eliminating attenuation effects. In general, the experimental results show good agreement with independent meteorological measurements. Finally, experimental data are utilized to estimate the Raman backscatter cross section for water vapor excited at 3471.5 A.

Journal ArticleDOI
TL;DR: A computer-based method of finding ñ from chosen combinations of measured R or T values is described, which can give accurate results in some regions where other methods may be less sensitive.
Abstract: The reflectance R and transmittance T of thin absorbing films deposited on a transparent substrate are calculated for normal and oblique incidence, s and p polarization, and different film thicknesses. The results are presented as contours of constant R and T on the n plane, where n is the complex refractive index. The conditions for sensitive dependence of measured quantities on n are examined. A computer-based method of finding n from chosen combinations of measured R or T values is described. Oblique incidence measurements on thin films can give accurate results in some regions where other methods may be less sensitive. Accurate film-thickness values can be obtained from the optical measurements.

Journal ArticleDOI
TL;DR: Improvements in materials and techniques for storage of high efficiency phase holograms in electrooptic crystals offer a simple means of achieving nondestructive readout for holographic information stored in these crystals.
Abstract: This paper describes recent improvements in materials and techniques for storage of high efficiency phase holograms in electrooptic crystals. The storage performance of lithium niobate and barium sodium niobate was greatly enhanced by introducing transition metal impurities or by subjecting the undoped crystals to irradiation treatments. The latest materials combine good sensitivity with diffraction efficiencies that reach well over 50% for sample thickness of a few millimeters. In addition, the fixing techniques that were developed offer a simple means of achieving nondestructive readout for holographic information stored in these crystals.

Journal ArticleDOI
TL;DR: An optical wind sensor that uses the motion of the scintillation pattern to measure the transverse component of wind blowing across a laser beam is reported, which is more useful than the more commonly used delay to the peak.
Abstract: We report the successful construction and testing of an optical wind sensor that uses the motion of the scintillation pattern to measure the transverse component of wind blowing across a laser beam. As is done for measuring ionospheric and interplanetary winds, we use a correlation method. However, in our application, the slope at zero lag of the time-lagged correlogram proves to be more useful than the more commonly used delay to the peak. The reason is that, in the atmosphere, irregularities are distributed along the entire propagation path. We use a detector spacing of 0.33 of the diameter of the first Fresnel zone to obtain a nearly uniform weighting function along the path, though the center of the path is still more effective than the ends. The sensor has been used extensively over 1-km and 15-km paths, and field tests of various applications are planned.

Journal ArticleDOI
TL;DR: The theory and experimental evidence of a shearing interferometer based on the Talbot effect, which can be reduced to triple-shearing or doubleshearing interferences by the addition of simple spatial filtering, is presented.
Abstract: The theory and experimental evidence of a shearing interferometer based on the Talbot effect are presented. Multiple-shearing interferences are obtained that can be reduced to triple-shearing or doubleshearing interferences by the addition of simple spatial filtering. When the shear is less than the width of the details in the object, these interferences become either the second or first derivative of the object under test, respectively. Either lateral or constant radial shear can be introduced by choosing Ronchi rulings or circular gratings. Thus both lateral and radial derivatives are easily obtained. If white light is used as a source, color fringes of high contrast are observed.

Journal ArticleDOI
TL;DR: A multichannel phase modulator is described which employs the electrooptic roperties of lithium tantalate to achieve phase modulation and the beam steering results for a forty-six-channel modulator are given.
Abstract: A multichannel phase modulator is described which employs the electrooptic properties of lithium tantalate to achieve phase modulation. The modulator’s speed and 2π voltage are compatible with high speed microelectronics The beam steering properties of this one-dimensional optical phased array antenna are described, and the beam steering results for a forty-six-channel modulator are given.

Journal ArticleDOI
Reinhard Ulrich1, H. P. Weber1
TL;DR: Low optical loss, in combination with the hotographic sensitivity of the KPR, offers the possibility of fabricating integrated optical circuits directly in the photoresist films.
Abstract: Light-guiding thin films of various materials have been deposited on glass substrates from liquid solutions by slow evaporation of the solvent. The attenuation of the guided light wave in some of these films is as low as that in the best films prepared by other methods. Film deposition from solution is done at or near room temperature. Therefore, this technique allows us to dope the thin films with organic molecules, e.g., laser dyes. The preparation and light-guiding properties of the doped and undoped films are described. The materials studied were epoxy, lead-silica, polyurethane, and Kodak photoresist KPR. Films of the first and second material have shown losses as low as 0.3 dB/cm at wavelengths of 0.633 microm and 1.064 microm, respectively. Films of polyurethane have been prepared with rhodamine 6G doping. When pumped with a pulsed nitrogen laser, the doped films showed optical gains of up to 100 dB/cm. The KPR films have an attenuation of ~1 dB/cm at 1.064 microm. This low optical loss, in combination with the hotographic sensitivity of the KPR, offers the possibility of fabricating integrated optical circuits directly in the photoresist films.

Journal ArticleDOI
TL;DR: The photodimers formed by polycyclic aromatic hydrocarbons, such as anthracene, and their derivatives can be photodissociated to the original monomers, making such a system attractive for reversible phase holographic recording with nondestructive readout.
Abstract: The photodimers formed by polycyclic aromatic hydrocarbons, such as anthracene, and their derivatives can be photodissociated to the original monomers. When the photodimer is held in a rigid matrix, the dimer can be remade efficiently because the two monomers are held in the proper relationship for photodimerization. The absorption spectra of monomer and photodimer differ substantially, and associated with this is a difference in refractive index. These characteristics as well as the stability of both states at room temperature make such a system attractive for reversible phase holographic recording with nondestructive readout. We have investigated several photodimer systems as solutions in rigid transparent polymer matrices, as well as some single crystals of photodimers. We have been able to write and erase diffraction gratings repeatedly. The photosensitivities ( 0.1 J cm(-2)), which are close to the maximum possible for a system with no gain, are high enough to be useful. Grating scattering efficiencies in the range of 0.01-5% have been observed. The physical, chemical, and photochemical characteristics of these systems, as well as some basic general considerations, are discussed.

Journal ArticleDOI
TL;DR: The emission spectra of single particles of inorganic solids as a function of particle size have been recorded and are of particular interest for interpreting the spectral behavior of circumstellar silicate particles.
Abstract: The emission spectra of single particles of inorganic solids as a function of particle size have been recorded from 6 μ to 11.8 μ. For small optically thin particles, an emission maximum is produced in the reststrahlen region. The emission behavior is dominated by scattering and can be adequately described in terms of Mie absorption efficiency factors. As the particle size is increased, the emission band reverses its polarity, and the spectrum approaches that of a polished plate. The data provide source functions necessary for determining the emission behavior of particulate samples in which temperature gradients exist, such as on the lunar surface. The data are of particular interest for interpreting the spectral behavior of circumstellar silicate particles.

Journal ArticleDOI
TL;DR: The coated sphere scattering pattern is more structured and quite sensitive to core sphere size, suggesting a possible method of distinguishing types of biological cells that are similar in gross size but different in internal detail.
Abstract: Efficient methods for the calculation of light scattering intensity functions for concentrically coated spheres (~10-μ diam) are discussed. This model represents many types of biological cells whose nuclei have a low refractive index (~1.1) and cytoplasms with a slightly lower refractive index. Studies are made on the relationships between the scattering coefficients for nonabsorbing, spherically symmetric scatterers. The physical origin of these coefficients is examined for absorbingscatterers. A comparison of the angular half-width of the scattered intensity functions for the coated sphere and an equivalent homogeneous sphere shows that diffraction dominates the small angle scattering in both cases. At larger angles, the coated sphere scattering pattern is more structured and quite sensitive to core sphere size, suggesting a possible method of distinguishing types of biological cells that are similar in gross size but different in internal detail.

Journal ArticleDOI
TL;DR: The theory of periodic couplers is examined from the point of view of the reciprocity theorem and a modified Born scattering approach and design equations for several coupler configurations are presented.
Abstract: The theory of periodic couplers is examined from the point of view of the reciprocity theorem and a modified Born scattering approach. Design equations for several coupler configurations are presented. Efficiency and aperture size calculations are compared with previously published data for grating and Bragg couplers.

Journal ArticleDOI
TL;DR: Techniques for designing infinite conjugate two mirror aplanats and computing their image properties are developed and design configurations corrected for a third Seidel aberration are identified and their properties discussed.
Abstract: The properties of two-conic reflecting aplanats are analyzed and discussed on the basis of third order aberration theory. Techniques for designing infinite conjugate two mirror aplanats and computing their image properties are developed. The secondary mirror alignment characteristics of Ritchey-Chretien and aplanatic Gregorian telescopes are examined and neutral point locations defined. Design configurations corrected for a third Seidel aberration (astigmatism, image curvature, or distortion) are identified and their properties discussed. The properties of Ritchey-Chretien and aplanatic Gregorian telescopes are compared.