Properties of metal-dielectric-metal surface plasmon polaritons and their potential application in optoelectronics

When a metal with a negative dielectric function is in contact with another material with a positive dielectric constant, a particular class of guided modes – surface plasma waves (SPWs) –can exist at the interface due to the coupling of electromagnetic field and oscillation of charges on metal surface. The quantization of this wave is called surface plasmon-polariton (SPP). The field of a SPP has a maximum at the interface and only extends a very short distance into both the metal and the dielectric medium. Recently, SPPs are known to be beneficial for light emitters since SPPs can enhance the spontaneous emission rate of a radiative dipole due to the Purcell effect. However, the inclusion of SPPs into light emitters typically encounters four difficulties. The first difficulty is that the highest energy of SPPs is bounded by the SPP resonant energy. Thus, the energy of the photon radiated from the dipole should be lower than the SPP resonant energy if the spontaneous emission rate is intended to be enhanced. Second, the SPP density of states increases with the increase of energy and reaches a maximum at the resonant energy. Thus, the energy of the photon radiated from the dipole should be close to the resonant energy since Purcell enhancement is proportional to the SPP density of states. Third, if the energy of the photon radiated from the dipole is very close to the resonant energy, the extension of the corresponding SPPs into the dielectric material, i.e. the enhanced region, become minimal. This difficulty is generally known as wave vector cutoff problem. The fourth difficulty is resulted from the fact that SPPs are nonradiative in nature, and this is the reason why a specific coupling method, such as a prism, grating or corrugation, is typically found in such applications. However, our simulation indicates that all of these difficulties can be resolved if metal-dielectric-metal structures are adopted. Accordingly, a two-year project is proposed. The theoretical foundation will be established. Then, the samples of metal-SiO2-metal structures will be prepared for demonstrating the obtained theory. Finally, light emitters based on metal-direct band gap semiconductor-metal structures will be realized.

Project ID:PB10202-1064
External Project ID:NSC101-2221-E182-037-MY2