Research On Photonic Components Based On Surface Plasmons And Semiconductor Quasi-one Dimensional Nanostructures

The world has seen a tremendous development in integrated circuits (IC) in the past few decades. Electronics circuits keep shrinking in dimensions, according to Moore's law, with FET gate lengths in the laboratory being in the tens of nanometers range. In contrast, the progress of photonic integrated circuits has fallen far behind IC and photonic circuit elements and waveguides have lateral dimensions on the order of the wavelength. A key to make photonics have an electronics-like development is to confine the light into dimensions breaking the diffraction limit. Currently, there are several approaches that are condisered to be potentially promising for the further integration for photonic elements, including photonic crystal waveguides and devices, dielectric devices with high refractive index contrast and surface plasmon waveguides and devices. These approaches have attracted the interests of researchers around the world. In this thesis, we show our researches on the subwavelength photonic devices based on surface plasmons and semiconductor quasi-one dimensional structures grown with high temperature methods, and discuss the possibility for large scale photonic integration with the two methods.We first present the dispersive model for metals, and then analyse the property of surface plasmons on a single surface. Actually the surface plasmon devices are mostly based on multi-layer metallic structures, so we then analyze the properties of surface plasmons in two kinds of multi-layer structures, give their dispersion equations analytically and show their differences and potential applications. In the following part, we give our results about the coupling of two MIM waveguides, with a subsequent proposal on subwavelength optical directional couplers and Mach-Zehnder Interferometers. A theoretical analysis about their properties is presented. The effective index of a MIM waveguide is affected by the width of the insulator, larger when the width is smaller. We propose and numerically analyze surface plasmon Bragg gratings formed by a periodic variation of the width of the insulator in a metal-insulator-metal waveguide. Compared to similar plasmonic Bragg gratings proposed by other researchers, our gratings have great advantage in the ease of fabrication while maintaining a relatively better performance. To suppress the sidelobes in the transmission spectrum, we further propose S-shaped Bragg cells and find better performance. By introducing a defect into the grating, a defect state with high quality factor is introduced into the bandgap and a Fabry-Perot-like structure is formed and we have also conducted researches on this. We have studied the multimode interference (MMI) phenomena in the index guided surface plasmon waveguides. An ultra-compact MMI power splitter, is proposed, with the transverse size 2 and 1 orders of magnitude smaller than those with long range surface plasmon waveguides and silicon waveguides. We have also presented our result on the application of effective index method to index guided surface plasmon wavguides. Based on this method and the MMI effect in index guided surface plasmon waveguides, we use two dimensional FDTD method design and simulate 1×N MMI power splitters. 3D FDTD simulations validate the preciseness and efficiency of these designs. Our research has provided a quick and simple method for the efficient simulations of index guided surface plasmon waveguides and devices.We have proposed a metal gap surface plasmon waveguide with a good confining ability and light can propagate through a bend with 90 degrees effectively. This kind of waveguide can be utilized to realize a high photonic integration. For the experimental parts, we use the semiconductor manufacturing methods in our clean room to fabricate this kind of waveguides. Specifically speaking, we first use the electron beam lithography and then use lift off process or reactive ion echting method to transfer the pattern from the resist to the metal film.We have used a simple and cheap high temperature method to fabricate the InP, Ga₂O₃, ZnO and Ge nanowires. The fabricated nanowires have a smooth surface and a uniform diameter, thus suitable for subwavelength structures for light guiding. We use various materials characterization methods to characterize these nanowires, and we also measure the absorption spectrums and photoluminescence properties for some nanowires. By employing the evanescent coupling method, we manage to couple the He-Ne laser from a fiber taper to the Ga₂O₃ nanowire and we then measure the propagation loss of this nanowire waveguide, which we find in the same order with the reported value on other semiconductor nanowire waveguides.In the end of the theis, we have a conclusion on the whole contents and give the research plans for the future.