Sub-wavelength Metal-Clad Semiconductor Lasers.

摘要

There has been a growing interest in the field of optoelectronics for sub-wavelength lasers due to an increased interest in better integration between optoelectronic and electronic components. Although advances have been made in the field of nanolasers with novel structures, further scaling of optical cavities beyond a sub-wavelength scale has been challenging due to the optical diffraction limit on the order of an optical wavelength. In this regard, the use of metal has been proven promising because electromagnetic wave rapidly decreases to zero within metal. However, it comes at a high cost of metal loss. Therefore, it is critical to optimize the optical cavity structure such that the overlap between the cavity and the electromagnetic field is maximized, thereby allowing the highest possible modal gain. In addition, to make the integration of the two possible, a sub-wavelength laser must have the following features: site-controllability, fine-tunability and out-coupling capability. In this Thesis, the use of metal for obtaining sub-wavelength nanolasers with the above features has been investigated in two different ways: surface plasmon mode and hybrid dielectric-plasmonic mode.;Surface plasmon-enabled sub-wavelength injection laser (SPESIL) uses a pure surface plasmon mode. Due to the location of electromagnetic field at the interface between metal and semiconductor, it suffers from tremendous amount of metal loss. Metal loss compensation by a gain medium nearby has been investigated and found to be true; however, it was shown to fall short of providing enough gain to reach lasing.;In a metal-clad semiconductor nanoring laser, the surface plasmon mode is replaced with a hybrid dielectric-plasmonic mode, in which the peak of the electromagnetic field is moved away from the metal interface. Therefore, metal loss is reduced. Furthermore, optical confinement factor (Gamma) is around 0.65, compared to 0.4 for SPESIL, providing a higher modal gain. Optically-pumped lasing in a metal-clad semiconductor nanoring laser was observed, and electrical injection was also investigated. Additionally, metal-clad nanoring laser is experimentally proven to possess fine-tuning capability with its two design parameters---ring width and ring diameter, which nanolasers often lack due to their high spectral range.