Ph.D Thesis

Ph.D StudentArbel David
SubjectActive Nano Plasmon-Optics in Silicon and Indium-Phosphide
DepartmentDepartment of Electrical and Computer Engineering
Supervisor PROF. Meir Orenstein
Full Thesis textFull thesis text - English Version


Surface Plasmon Polariton (SPP) optical waves on a metal-dielectric interface are confined to sizes much below the optical wavelength, and offer a route to overcome the diffraction-limit, and allow the integration of electronic and optical circuits in a sub-100nm scale. While most previous studies were related to passive SPP optical circuitry in metal-on-glass, this research is focused on active plasmonic nano-optical structures in semiconductor, i.e., silicon and InP. In the research I studied plasmon enhanced emission from InP, optical modulation in silicon plasmonic structures, and the coupling from micro-to-nano plasmonic waveguides.

For the study of enhanced emission from InP we designed and manufactured using E-beam lithography gold nano-antenna arrays on InP substrate with MQW gain layer. Measured photoluminescence from the MQW showed enhancement of the emission by a factor of 9 using dipole nano-antennas, where maximum enhancement wavelength was tuned due to coupling to the plasmon nano-antennas. Theoretical analysis and simulation results show that most of the enhancement is attributed to the coupling to the nano-antennas, altering the density of states such that radiative recombination times are reduced by a factor of ~25, shortening the overall recombination time by a factor of ~3. This effect is extremely important for the development of multi-GHz directly modulated nano-LEDs.

For the integration of nano plasmon-devices with standard micron-size dielectric waveguides, a tapered gap plasmon waveguide and the interplay of related plasmonic and oscillating modes was analyzed and simulated. This compact non-adiabatic plasmon device shows high micron-to-nano coupling efficiency of more than 70%.

Plasmon nano-optical modulation in silicon by free-carrier induced index change was analyzed, showing increased response due the tight confinement of the plasmon mode. Theoretical analysis of several amplitude and phase modulation schemes was performed, showing good results for compact gap plasmon waveguides in silicon. Structured plasmon waveguides V and W shaped with tight confinement at the tips were manufactured in silicon, and the plasmon modes were measured, showing excellent agreement with simulations. A V-MOS modulation structure was manufactured in silicon, integrating a V-groove plasmon waveguide with MOS capacitor for free-carrier modulation. The V-MOS plasmonic nano-modulator did not exhibit the predicted electro-optical effect due to process and manufacturing problems, and an improved structure was proposed.

We can summarize that plasmon enhanced modulation and emission in silicon and InP show great potential for future silicon nano-photonics, and for the implementation of critical optical interactions over several microns scale where metal losses are controllable.