Optical Amplification In Nanocrystalline Silicon Superlattices
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Optical Amplification In Nanocrystalline Silicon Superlattices J. Ruan1, H. Chen1, Philippe M. Fauchet2 1 Department of Physics and Astronomy 2 Department of Electrical and Computer Engineering University of Rochester, Rochester NY 14627, USA ABSTRACT Today, the overall performance of a multi-chip computing system is limited by the interconnection delay between chips. Conventional interconnects based on metal lines are expected to cause unmanageable problems with speed and power dissipation. Optical interconnects provide a solution to these problems. However, the low quantum efficiency associated with radiative recombination in silicon has so far prevented the demonstration of a practical laser. Recently stimulated emission has been demonstrated in Si nanocrystals prepared by ion-implantation. The reported material gain is high enough to realize a practical Si based laser. However, the optical filling factor in these samples was less than 10% due to the poor wave guiding nature of these structures. In this work, we explore a possible way to achieve optical gain in nanocrystalline silicon superlattices. The samples are produced by growing alternating layers of amorphous silicon and SiO2 and then using a two step crystallization method to transform each amorphous silicon layer into a high density array of silicon nanocrystals having identical size. The waveguide structure is formed by sandwiching the superlattice between cladding layers. To measure optical gain we use the variable stripe length method where the amplified spontaneous emission emitted from the edge is measured as a function of the excitation length. Tuning from loss to gain was observed by just varying the pump power. INTRODUCTION The ever-increasing integration density and operating frequency of electronic chips is causing an electrical interconnect bottleneck to emerge. Today, the overall performance of a multichip computing system is dominated by the limitations of the interconnections between chips and it is predicted that this problem will migrate to the single chip level after one decade. Interconnects are now the major bottleneck not only in terms of limiting performance, such as speed and signal integrity, but also in terms of power use and heat dissipation. Material innovations and traditional scaling will stop satisfying performance requirements when the feature size approaches 50 nm. Without a solution to the “interconnect problem,” the growth of the semiconductor industry may come to a halt. Finding a solution to this problem is at least as crucial as any breakthrough in individual device performance (e.g., silicon quantum dot transistors) or any revolutionary advance in computing architecture (e.g., quantum computing). Using optical means to provide the interconnect is an attractive solution because it offers many benefits [1]. For example, there is essentially no distance-dependent loss or distortion of the signal, there are no deleterious fringing-field effects, there is no heat dissipation in the interconnection itself, and fina
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