Laser Directional Emission Based On Hybrid Plasma In Nano Microcavity

In past decade, surface plasmon polaritons based nanolasers(also known as spasers) have been intensively studied. Compared with their all-dielectirc counterparts, spasers have several intrinsic advantages. They can break the diffraction limit and localize light into a nanoscale volume. Conseuquntly, the local field and the corresponding light-matter interaction have been significantly improved. In 2009, two types of spasers have been experimentally realized and ultrasmall mode volumes have been demonstrated. Up to now, spasers have been observed in a number of systems and they have shown bright futures in practical applications, e.g. biological sensing, data storage, lithography and optical communication field brings new features. However, the researches on spasers are mostly relied on the chemically synthesized nanoparticles, nanowires, or nanoplates. These nanodevices are typically randomly distributed on the wafer and hard to be precisely aligned to the on-chip integrated nanophotonic circuites.To solve this problem, we have studied the spaser structures that can be fabricated by the well-developed top-down fabrication process. Our design consists of a semiconductor nanodisk and a silver film, which are separted by a ultrathin low refractive index insulating layer. Due to the continuity of electric displacement in vertical direction and the capacity effect, most of energy is well confined within the insulating layer and forms the well-known hybrif plasmonic modes. By carefully tuning the parameters such as surface roughness and shape deformations, we have studied the main characteristics of such kind of nancavity, e.g. cavity quality(Q) factor, resonant wavelength, effective mode volume, Purcell factor, and the directionality.In this thesis, we have mainly obtained the following results:1. Based on the top-down fabrication process for mass-manufaction, we have re-designed the cavities of well known hybrid plasmonic nanolasers.The thicknesses of gain mateirals and insulating layer have been carefully optimi zed to achieve smaller effective mode volume and relative high Q factors.2. By tailoring the cavity boundary from a perfect circular disk to deformed cavities or replacing the disk with a ring cavity, we have observed similar Q factors and effective mode volumes. Similarly, the cavity Q factor and effective mode volumes are also well kept after introducing surface roughnesses to the nanocavities. These results clearly illustrate the robustness of nanocavities to the possible deviations of un-expected errors in real fabrications.3. Based on the robustness of nanocavities, we have proposed a new type of cavity structure. By directly connecting a waveguide to a nanocavity, we have successfully observed unidirectional emission along the waveguide. And the unidirectionality is also found to have very nice fabrication tolorence.Overall, we have numerically studied a new kind of top-down fabricated nanocavity. Our numerical calcualtions show that the designed nanocavity is quite robust to the possible fabrication deviations such as deformation and roughness. Mostimportantly, for the first time, we have designed a type of nanocavity that has unidirectional emission along a waveguide. All of these results are very important for the avances of spasers in mass-fabrication.