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Showing papers in "Applied Physics Letters in 1968"


Journal ArticleDOI
TL;DR: In this paper, a model for superconducting Josephson junctions analogous to the driven simple pendulum with damping gives dc I•V curves displaying hysteresis for light damping.
Abstract: A model for superconducting Josephson junctions analogous to the driven simple pendulum with damping gives dc I‐V curves displaying hysteresis for light damping. Excess current and negative dynamic resistance can be obtained with heavy damping.

953 citations


Journal ArticleDOI
TL;DR: In this article, a type of surface wave with no counterpart in a purely elastic homogeneous material is shown to exist in a piezoelectric material and expressions for the velocity of propagation of this wave are obtained for various electrical boundary conditions on the free surface of a half-space.
Abstract: A type of surface wave with no counterpart in a purely elastic homogeneous material is shown to exist in a piezoelectric material Expressions for the velocity of propagation of this wave are obtained for various electrical boundary conditions on the free surface of a piezoelectric half‐space

606 citations


Journal ArticleDOI
TL;DR: In this paper, the ability of a nematic liquid crystal to cooperatively align in an electric field is used to orient "guest" dichroic dye molecules (molecules whose absorption spectrum is a function of the molecular orientation with respect to the polarization of the incident light).
Abstract: A new electro‐optic effect is presented, based on guest‐host interactions in nematic liquid crystals. The ability of a nematic liquid crystal to cooperatively align in an electric field is used to orient ``guest'' dichroic dye molecules (molecules whose absorption spectrum is a function of the molecular orientation with respect to the polarization of the incident light). Thus one can electrically switch the color of transmitted light using fields of the order of 104 V/cm.

462 citations


Journal ArticleDOI
TL;DR: In this article, a single-crystal lithium niobate has been used as a holographic storage medium and the high resolution obtained suggests that such material may be useful in high capacity, changeable optical information storage, processing and display devices.
Abstract: Single‐crystal lithium niobate has been used as a holographic storage medium. The material undergoes a change in refractive indices upon exposure to suitably intense light thus allowing it to act as a pure‐phase, volume‐holographic medium requiring no processing. The holograms formed have high diffraction efficiencies and are thermally erasable. The high resolution obtained suggests that such material may be useful in high‐capacity, changeable optical information storage, processing and display devices.

455 citations


Journal ArticleDOI
TL;DR: In this article, a single-crystal growth of gallium arsenide was achieved on a number of singlecrystal insulating oxide substrates, including sapphire, spinel, beryllium oxide, and thorium oxide.
Abstract: Chemical vapor deposition has been been used successfully for the attainment of a single‐crystal growth of gallium arsenide directly on a number of single‐crystal insulating oxide substrates. Several orientation relationships have been determined for GaAs grown on sapphire (α‐Al2O3), spinel (MgAl2O4), beryllium oxide (BeO), and thorium oxide (ThO2).

373 citations


Journal ArticleDOI
TL;DR: In this paper, a general method is presented for calculating the structural changes resulting from electric or magnetic fields acting on anisotropy of the anisotropic susceptibility of a liquid crystal.
Abstract: Electric or magnetic fields acting on the anisotropy of the electric or magnetic susceptibility exert torques within a liquid crystal which may compete with the elastic torques determining its internal structure. A general method is presented for calculating the structural changes thus produced. Two examples are given, and the field strength for the effects is estimated to be 105 V/cm or 105 G. Two experiments are suggested to test the theory.

292 citations


Journal ArticleDOI
TL;DR: In this paper, the Curie temperature, birefringence, and phase-matching temperature of LiNbO3 are shown to vary with the stoichiometry of the melt from which the crystals are pulled.
Abstract: The Curie temperature, birefringence, and phase‐matching temperature of LiNbO3 are shown to vary with the stoichiometry of the melt from which the crystals are pulled. The range of melt stoichiometry, indexed by the Li/Nb mole ratio, was varied from 1.20 to 0.80. This Li/Nb variation changes the Curie temperature, refractive index for the extraordinary ray, and the phase‐matching temperature by 120°C,.03, and 320°C respectively. The relevance of these changes are discussed in terms of the susceptibility of LiNbO3 to index inhomogeneities.

193 citations


Journal ArticleDOI
TL;DR: In this paper, metal-to-metal point contact diodes were used to obtain the 54 GHz beat notes between two adjacent 10.6μ CO2 laser transitions with a 337μ HCN laser.
Abstract: Metal‐to‐metal point contact diodes were used to obtain the 54‐GHz beat notes between two adjacent 10.6‐μ CO2 laser transitions. The speed of the diodes in the far‐infrared is at least 1000 GHz. This was tested with a 337‐μ HCN laser.

145 citations


Journal ArticleDOI
TL;DR: In this article, two stages of migration were found, the first corresponding to gross mass transport, the second to void growth and stripe failure, and activation energy for the first stage was determined to be 0.5-0.6 eV from change-in-rate, changein-temperature tests, indicating boundary diffusion.
Abstract: Resistance monitoring has been used to follow structural changes during electromigration in aluminum films. Two stages of migration were found, the first corresponding to gross mass transport, the second to void growth and stripe failure. An activation energy for the first stage was determined to be 0.5–0.6 eV from change‐in‐rate, change‐in‐temperature tests, indicating boundary diffusion. Transmission electron microscopy showed voids existing in areas of thinned aluminum. Corollary work on aluminum stripes on NaCl substrates showed nonadhesion to be a strong contributor to void formation, suggesting the possibility that the thinned regions were caused by hot spots at sites of nonadhesion.

145 citations


Journal ArticleDOI
TL;DR: The spontaneous polarizations in LiNbO3, LiTaO3 and Ba2NaNb5O15 have been measured directly at room temperature by a field reversal method as mentioned in this paper.
Abstract: The spontaneous polarizations in LiNbO3, LiTaO3, and Ba2NaNb5O15 have been measured directly at room temperature by a field reversal method and found to be Ps (LiNbO3) = 0.71 C/m2, Ps (LiTaO3) = 0.50 C/m2, and Ps (Ba2NaNb5O15) = 0.40 C/m2. Using these values we show that the linear electro‐optic effect in these materials is related fundamentally to a biased quadratic effect associated with each BO6 octahedron. Based on this result, predictions are made of the spontaneous polarization in other oxygen‐octahedra ferroelectrics.

142 citations


Journal ArticleDOI
TL;DR: In this article, a continuous 0.532μ solid-state source utilizing the nonlinear material Ba2NaNb5O15 inside the cavity of a 1.064μ YAlG:Nd laser has generated 1.1 W of coherent green power.
Abstract: A continuous 0.532‐μ solid‐state source utilizing the nonlinear material Ba2NaNb5O15 inside the cavity of a 1.064‐μ YAlG:Nd laser has generated 1.1 W of coherent green power. This represents 100% conversion to the green of the available infrared radiation from the YAlG:Nd laser utilized.

Journal ArticleDOI
TL;DR: In this paper, flashlamp-excited polymethyl methacrylate rods containing rhodamine dyes were reported to have light emission in the solid with respect to that observed for the same dyes in liquid solution.
Abstract: Laser emission is reported from flashlamp‐excited polymethyl methacrylate rods containing rhodamine dyes. Quenching of stimulated emission by the molecular triplet state is apparently reduced in the solid with respect to that observed for the same dyes in liquid solution.

Journal ArticleDOI
TL;DR: The experimentally observed distributions of surface state density versus energy is correlated with the existence of coulombic centers in the oxide as mentioned in this paper, where single charges give rise to peaks in surface state densities close to the band edges, deeper levels are introduced by two charges in close proximity.
Abstract: The experimentally observed distributions of surface state density versus energy is correlated with the existence of coulombic centers in the oxide. Single charges give rise to peaks in surface state density close to the band edges, deeper levels are introduced by two charges in close proximity.

Journal ArticleDOI
TL;DR: In this paper, a tunable, optical parametric oscillator using a continuous pump is reported, whose threshold was measured to be 45 mW of multimode power at.532 μ.
Abstract: A tunable, optical parametric oscillator using a continuous pump is reported. The threshold was measured to be 45 mW of multimode power at .532 μ. The efficiency was found to be 1% with 300 mW of pump power.

Journal ArticleDOI
TL;DR: In this paper, a new electro-optic effect based on the disruptive effects of ion transport through certain classes of nematic liquid crystals is presented, which scatters light strongly (appears white) when subjected to fields of 5 × 103 V/cm.
Abstract: A new electro‐optic effect based on the disruptive effects of ion transport through certain classes of nematic liquid crystals is presented. The initially transparent liquid scatters light strongly (appears white) when subjected to fields of 5 × 103 V/cm. Reflective contrast ratios of better than 20:1 with efficiencies of 45% of the standard white have been obtained.

Journal ArticleDOI
TL;DR: In this article, a simple theory is proposed to explain the observed trapping of an argon laser beam when the beam passes through lead glass, and computer solutions have been obtained which reasonably agree with experimental determination of focal planes and spot radius.
Abstract: Strong thermal self‐focusing of an argon laser beam has been observed when the beam passes through lead glass. Focal lengths of less than 20 cm were obtained. The beams showed the effects of spherical aberration and at certain power levels beam trapping occurred. A simple theory is proposed to explain the observed trapping. Computer solutions have been obtained which reasonably agree with experimental determination of focal planes and spot radius.

Journal ArticleDOI
TL;DR: In this article, permanent magnet materials containing rare-earth elements (RE) have been discovered, which are based on the hexagonal intermetallic compounds Co5RE and Co5Sm-Cu5Sm systems.
Abstract: New permanent magnet materials containing rare‐earth elements (RE) have been discovered. For the most part, these alloys are based on the hexagonal intermetallic compounds, Co5RE. Replacement of cobalt with copper in some of these rare‐earth compounds results in solid materials with substantial permanent magnet properties. Coercive forces as high as 28,700 Oe have been obtained in heat‐treated samples of alloys in the Co5Sm–Cu5Sm system.

Journal ArticleDOI
TL;DR: In this paper, a 30MW Q-switched ruby laser was focused into water, and the resulting spark revealed a blackbody-like spectrum with a temperature of 15 000°K.
Abstract: Measurements have been taken of the radiative flux density, the spectrum, and the temporal behavior of laser induced underwater sparks. When a 30‐MW Q‐switched ruby laser was focused into water, the resulting spark revealed a blackbody‐like spectrum with a temperature of 15 000°K. The spark was delayed in time by 15 nsec with respect to the laser pulse and had a temporal behavior very similar to the laser pulse producing it.

Journal ArticleDOI
TL;DR: In this paper, a single isotope of Cd114 was used for the transition in Cd (II) using a tubular furnace at temperatures in the range of 200°C with He as a buffer gas.
Abstract: A gain of 20%/m and a power output of 50 mW have been measured on the 5s2 2D5/2 → 5p2P03/2 4416‐A laser transition in Cd (II) using a single isotope of Cd114. The system was operated in a tubular furnace at temperatures in the range of 200°C with He as a buffer gas. The laser output with respect to He pressure, discharge current, and furnace temperature are discussed along with a proposed excitation mechanism. The system appears to have the prospect of being one of the most efficient, high power lasers operating in the visible region of the spectrum.

Journal ArticleDOI
TL;DR: In this paper, the image information at 1.6 μ has been converted to the green by mixing it with highly collimated ruby laser radiation in lithium niobate and about 50 lines resolution was achieved, limited only by the laser beam quality.
Abstract: Image information at 1.6 μ has been converted to the green by mixing it with highly collimated ruby laser radiation in lithium niobate. About 50 lines resolution has been achieved, limited only by the laser beam quality. A tenfold increase on this should be attainable with a single transverse mode laser.

Journal ArticleDOI
TL;DR: It has been shown experimentally that it is possible to excite rare earth and transition metal ions included in a II-VI compound matrix as fluoride molecules by direct, hot-electron impact as mentioned in this paper.
Abstract: It is shown experimentally that it is possible to excite rare‐earth and transition metal ions included in a II‐VI compound matrix as fluoride molecules by direct, hot‐electron impact. Electron‐hole pairs in the matrix are unnecessary and even undesirable. AC excitation of a thin film structure has given external power conversion efficiency of about 10−4 at several optical frequencies including the 5480‐A line of Tb3+.

Journal ArticleDOI
TL;DR: In this paper, a stereoscopic camera technique is used to record the objects' parallax qualities in white light; this photographic information is transformed into a hologram with coherent light.
Abstract: Holograms of naturally illuminated objects are synthesized in two steps. A stereoscopic camera technique is used to record the objects' parallax qualities in white light; this photographic information is transformed into a hologram with coherent light. The image quality is excellent, and the method seems practical for making full‐color reconstructions using stereoscopic photographs taken with color film.

Journal ArticleDOI
TL;DR: The concept of the blazed hologram as a special case of the Denisyuk hologram is discussed in this paper, and the experimental production of blazed diffraction gratings has been described with 73% of the diffracted light concentrated in one first order maximum.
Abstract: The concept of the blazed hologram as a special case of the Denisyuk hologram is discussed. Experimental production of blazed holograms is described. Blazed diffraction gratings, a form of blazed hologram, have been produced with 73% of the diffracted light concentrated in one first‐order maximum.

Journal ArticleDOI
TL;DR: In this paper, strong interaction between the wave on the surface of a piezoelectric crystal and the drift on the drifting carriers in a nearby semiconductor is reported, and two-port net terminal gain of 7 dB at 108 MHz with a delay of 9 μsec has been observed.
Abstract: Strong interaction between the wave on the surface of a piezoelectric crystal and the wave on the drifting carriers in a nearby semiconductor is reported. Amplification can result and two‐port net terminal gain of 7 dB at 108 MHz with a delay of 9 μsec has been observed.

Journal ArticleDOI
TL;DR: The second-harmonic phase-matching temperature of nonstoichiometric LiNbO3 crystals has been found to vary by as much as 75°C from crystal to crystal and 10°C within an individual crystal.
Abstract: The second‐harmonic, phase‐matching temperature of ``stoichiometric'' LiNbO3 crystals, for fundamental radiation at 1.06 μ, has been found to vary by as much as 75°C from crystal to crystal and 10°C within an individual crystal. Measurements on crystals grown in a controlled manner from nonstoichiometric melts have shown that the phase‐matching temperature, T, is an approximately linear function of melt composition, x, obeying the equation T = 50.5 + 32 × 102 (x − 0.50). Crystals with phase‐matching temperatures of as high as 186°C have been grown from melts containing excess lithia. Such a crystal has been operated as a second harmonic generator without damage, whereas a comparable radiation produced by a crystal with a low phase‐matching temperature damaged the crystal. A mechanism involving lithium ion vacancies is proposed to explain the results.

Journal ArticleDOI
TL;DR: In this article, the ambiguity in the return at the laser frequency (6943 A) due to the aerosol scatter component was avoided by monitoring the frequency-shifted Raman vibrational rotation band of the nitrogen component centered at 8285 A.
Abstract: Density profiles of the gaseous atmosphere up to 3 km have been measured using laser backscatter. The ambiguity in the return at the laser frequency (6943 A) due to the aerosol scatter component was avoided by monitoring the frequency‐shifted Raman vibrational‐rotational band of the nitrogen component centered at 8285 A.

Journal ArticleDOI
TL;DR: In this paper, the second harmonic pulse shape generated from ultrashort pulses is calculated in long dispersive crystals, where the pulse width may be much broader than the incident pulse and the power conversion ratio may saturate at a low value.
Abstract: The second harmonic pulse shape generated from ultrashort pulses is calculated In long dispersive crystals the pulse width may be much broader than the incident pulse and the power conversion ratio may saturate at a low value These effects should be prominent in LiNbO3 with 4 × 10−13 sec pulses

Journal ArticleDOI
TL;DR: In this article, it has been found that ferroelectric Sr1−xBaxNb2O6 has a pyroelectric coefficient at room temperature for 0.25 < x < 0.5 and a detector with a value of x=0.33 was successfully used at 300°K to detect single pulses of 10.6μ radiation from a Q•switched CO2 laser with a rise time of less than 30 nsec.
Abstract: It has been found that ferroelectric Sr1−xBaxNb2O6 has a very large pyroelectric coefficient at room temperature for 0.25 < x < 0.5. This suggested that the material may be useful as a detector of infrared radiation. A detector, constructed with a value of x=0.33 was successfully used at 300°K to detect single pulses of 10.6‐μ radiation from a Q‐switched CO2 laser with a rise time of less than 30 nsec. Detectors with a low frequency responsivity of better than 104 V/W and a minimum detectable power of 4 × 10−9 W‐cm−1‐cps−1/2 are easily constructed. Methods of improving on these results are discussed.

Journal ArticleDOI
TL;DR: In this article, nitrogen has been added to the grown layer to increase η, the room-temperature external quantum efficiency of the green emitting A line and its phonon replicas.
Abstract: P–N junctions have been formed in GaP using the liquid‐phase epitaxy process. In addition to the shallow donors and acceptors, nitrogen has been added to the grown layer to increase η, the room‐temperature external quantum efficiency of the electroluminescence of the green emitting A line and its phonon replicas. The measured value of η was as high as 0.1% dc and 0.2% pulsed. The nonradiative processes are reduced by using sulfur rather than other shallow donors to fabricate the n side of the junction.

Journal ArticleDOI
TL;DR: In this paper, a Q-switched ruby laser is used to generate surface elastic waves by transient surface heating of piezoelectric and non-piezoeelastic solids.
Abstract: The generation of surface elastic waves by the transient surface heating of piezoelectric and nonpiezoelectric solids is described. A Q‐switched ruby laser produces the surface heating; the frequencies of the resultant surface waves are Fourier components of the laser waveform. The use of a spatially periodic illumination is shown to increase the effectiveness of generation at a selected frequency. This method of generating surface waves appears suitable for microwave frequency operation as well as operation at high wave amplitudes at low frequencies.