Junction Lengths Research Articles

Optimum coupling junction and cavity lengths for coupled-cavity semiconductor lasers

In this paper we investigate the dependence of the mode suppression in coupled-cavity semiconductor lasers on coupling junction parameters and cavity lengths. An effective mirror formalism is developed and combined with exact numerical analysis to explore the mode behavior across the entire relative cavity gain operating range of coupled-cavity resonators. A gap coupling model is also presented which permits one to deduce the optimum gap spacing for best mode suppression, as well as the dependence of this optimum gap spacing on relative cavity lengths. Finally, the exact numerical analysis is combined with spectral gain roll-off to explore the mode suppression of all modes of the system versus cavity lengths. Long-long and long-short geometries are shown to be desirable as well as some interesting new intermediate cavity length ratios. Calculations indicate that coupled-cavity 1.55-μm lasers with mode suppression in excess of 10 cm−1 to both near in and repeat modes are realizable.

SEA equivalences between large platelike systems and their subparts

A procedure was developed to equate the properties of a large system, which is composed of a number of plates connected to each other in a variety of ways, with the properties of the smaller plates for use in Statistical Energy Analysis (SEA) modeling. Each small subsystem is a single plate, which can be characterized by a uniform thickness, an area, a material, and some internal losses. Each connection between systems is defined by a junction, with a length, a number of systems connected at that junction, and thicknesses of each system connected at that junction. Equivalents thicknesses, areas, loss factors, and junction lengths were determined for the larger composite system. The analysis was extended to the case where two composite systems are connected to each other.

Quantitation of terminal parameters and their interrelationships in maturing central synapses: A perspective for experimental studies

The development and maturation of synapses in the molecular layer of the occipital cortex of rats at 15, 20, 28, 75 and 224 days postnatal were examined and quantitative ultrastructural techniques were employed. The parameters evaluated display a diverse set of trends. A steady increase in mean terminal area is noted, the proportions of the smallest terminals declining progressively over this period. The mean length of the postsynaptic thickening fluctuates throughout the developmental series. A close association is found between terminal area and junction length, larger junction lengths being consistently associated with larger areas. Synaptic vesicle numbers within each terminal increase markedly between 15 and 28 days. There is an increase in the frequency of flat and positively curved junctions with increasing age, the bimodal distribution of negative and positive curvatures at 15 days being replaced by a normal distribution in the adult. When synaptic length is compared with curvature, flat junctions emerge as the longest and the most highly curved junctions as the shortest. The terminal areas of positive junctions are greater than those of negative ones. The consequences of these results for the flat disc model of synapses are discussed, and it is postulated that negatively curved synaptic junctions may be non-functional.

Diffraction patterns and vortex structure of asymmetrical and cross Josephson junctions

The critical current of an asymmetrical Josephson junction as a function of magnetic field has been computed for junction lengths of 2λJ and 6λJ. The boundary conditions for the asymmetrical and cross junction (with an assumed current distribution) are derived. Similarity between the computed asymmetrical junction diffraction patterns and experimental patterns for the cross junction plus identical boundary conditions indicate that the current flow in the cross junction is the same as in the asymmetrical junction. Profiles of the current density in the linear and asymmetrical Josephson junctions are compared.

Relationship between tooth-movement rate and estimated pressure applied.

The object of the experiments was to investigate the hypothesis that the pressure exerted by roots on the surrounding bone-periodontal-membrane complex, and not the force applied to the crown, is the critical factor in determining rate of tooth movement. As pressure is defined in terms of force per unit area, it was necessary to measure two quantities before any calculation of pressure could be made. These quantities are force and the projected area of the tooth root, provided that tipping and rotation are prevented. The distal movement of maxillary canine teeth was investigated in a group of twelveto fourteenyear-old male patients. In each case one canine was moved bodily while the other canine was tipped simultaneously as a comparison. A force of 450 gm. f. was exerted on each canine tooth by activating a helical torsion spring. A fixed point on a mandibular archwire was used as a reference point. Measurements of tooth movement and deflection of springs used in these experiments were accurate to 0.1 mm. The orthodontic experimental apparatus was similar to that used by Storey in his investigations in 1952 (E. STOREY, Aust. dent. J., 56:11, 1952). The projected areas of the roots of incisor teeth were determined with a planimeter after photographing extracted teeth normal to the axis, magnifying the image ten times, and tracing the outline. A study of the projected area of the mesial and distal surfaces and the labiolingual widths at the cemento-enamel junction and root lengths of incisor teeth showed that there was a highly significant relationship between the projected area of a root and these above-mentioned linear dimensions. Curves showing the rate of tooth movement of each patient against average force applied for bodily movement and tipping of the canine teeth were plotted (see fig.). The pressure is indicated for bodily movement. With decreasing force, and consequently pressure, due to the movement of the tooth and attached