Thin film conductors for self-equalizing cables

Self-equalizing cables using hollow conductors with wall thickness less than the skin depth were proposed in 1929. However, they do not appear ever to have been widely used, although the idea has resurfaced and been refined from time to time. In the early 2000’s, self-equalizing conductors consisting of solid magnetic steel cores coated with silver were developed by W.L. Gore, and used in their 2.5 Gb/s “Eye-Opener” cables, although higher speed versions never appeared. We have revived the original 1929 idea, proposing to use glass as a solid insulating core. This technology can potentially work at frequencies of many 10’s of GHz. Possible uses include short range GHz links such as USB and Thunderbolt, and intra-rack interconnections in data centers. Our feasibility experiments have validated the principle. Copper coated glass fibers can, in principle, be manufactured, but in these tests, the conductors were capillaries internally coated with silver as these are easily obtainable, relatively inexpensive and serve to test the concept. The performance of these experimental twin lead cables corresponds to calculations, confirming the general principle. By calculation, we have compared the performance of cables made from copper-on-insulator conductors to that of similar cables made with solid copper conductors, and verified that copper-on-insulator cables have significantly less frequency dependent loss. We have also made and tested cables with copper on PEEK conductors as surrogates for copper on glass fiber

Analysis of Raman gain for focused Gaussian pump beams

Several theoretical and numerical models have been published which describe the evolution of a Stokes beam in a Raman medium excited by a focussed pump beam. Generally, the published theoretical departures from the plane-wave theory of Raman scattering are based on assumptions about the power of the pump beam. In this paper we present a theoretical model which is shown to be in excellent agreement with an exact numerical treatment, and which is valid without restrictions on the pump power. Its predictions are used to indicate the range of validity of earlier theories

Laser diode pumped solid state lasers

Solid state lasers have undergone a renaissance since the development of reliable and cheap laser diodes which can be used as pump sources. The result is compact, efficient laser sources which are attractive for a wide range of applications. This review summarizes the properties of laser diodes which are advantageous for pumping solid state lasers and describes the diverse laser materials and configurations of solid state lasers reported in the literature