Provide background why we pursueplasmonic. For smaller dimension with faster speed.
Free-space light cannot be coupled directly to surface plasmon mode. One has to use either prism, or grating, etc, to couple the light. It will be beneficial if we have a plasmonic source similar to laser that can be coupled directly to surface plasmonpolariton wave.
Previous works. Akimov showed light emission from quantum dots can be coupled to a metallic nanowire and propagate as surface plasmonpolariton wave. Koller use LED connected directly to metal surface, Biasing the LED creates some electron-hole which can excite surface plasmonpolariton in the metal surface which can then propagate as SPP wave.
Walters use an MIM structure and bias to create hot electrons which then excite surface plasmonpolariton on the MIM waveguide.
We use a similar structure as Walters (MIM), but in a cavity structure, which will increase the intensity of the field inside before it is coupled to MIM waveguide and circuits.
To study the structure, we use FDTD simulation with realistic solid-state model and Lorentz-Drude model for metal.
The figure shows the whispering gallery mode of a conventional microdisk. The light travels circling the microdisk through internal reflection. The right figure shows the microdisklase at the mode at 1.47 um.
The left figure shows the total electric field distribution after attaching two metal layers. The mode is no longer a pure whispering gallery mode but hybridized by the surface plasmonpolariton mode. The right figure shows the field is increased by about 20,000 times at 1.47 um. The middle figure shows a comparison between whispering gallery mode and surface plasmonpolariton mode. In SPP mode, the maximum field is at the interface between the dielectric and the metal. The vertical black line indicates the interface between the metal (left side, < 400nm) and the semiconductor (right side, > 400nm)
Left figure shows that the SPP mode inside the microdisk can couple to the MIM waveguide. The right figure shows that the frequency spectrum inside the waveguide follows exactly the spectrum inside the microdisk. And the intensity is coupled directly by about 60%.
Surface Plasmon Hybridization of Whispering Gallery Mode Microdisk Laser
Surface Plasmon Hybridization of Whispering Gallery Mode Microdisk Laser<br />Oka Kurniawan<br />Iftikhar Ahmed<br />Er Ping Li<br />Photonics Global<br />14th to 16th December 2010<br />Singapore<br />
Plasmonics promises both high speed and miniaturization<br />2<br />NanoPlasmonics (A*STAR-SERC)<br />
Research on Plasmonics source is essential<br />3<br />kx<br />light cone = c k<br />w<br />k<br />
Previous works have shown progress though having low intensity<br />4<br />Akimov, A. V., A. Mukherjee, C. L. Yu, D. E. Chang, A. S. Zibrov, P. R. Hemmer, H. Park, and M. D. Lukin. “Generation of single optical plasmons in metallic nanowires coupled to quantum dots.” Nature 450, no. 7168 (November 2007): 402-406. <br />KollerD.M. “Organic plasmon-emitting diode.” Nat Photon 2, no. 11 (November 2008): 684-687.<br />
Metal-insulator-metal structure can excite surface plasmon and coupled directly to waveguide<br />5<br />Walters, R. J., R. V. A. van Loon, I. Brunets, J. Schmitz, and A. Polman. “A silicon-based electrical source of surface plasmonpolaritons.” Nat Mater 9, no. 1 (January 2010): 21-25. <br />
We use microdisk laser cavity structure to obtain high intensity output<br />6<br />metal<br />Radius = 1 µm<br />Layer thicknesses = 120 nm<br />semiconductor<br />metal<br />MSM<br />source<br />MIM<br />waveguide<br />MIM<br />circuits<br />
Finite-difference time domain method with realistic solid-state model and Lorentz-Drude model is used for simulation<br />7<br />Multi-electron multi-level model for modeling electron dynamic in semiconductor. The model can model stimulated emission in laser.<br />
Conventional microdisk shows whispering gallery mode<br />8<br />Total electric field at the centre plane of the microdisk<br />Electric field peak intensity at 1.47 µm.<br />
Attaching metal layers hybridize the whispering gallery mode with surface plasmonpolariton mode<br />9<br />Total electric field at middle plane of the plasmonicmicrodisk.<br />Comparison of whispering gallery mode and surface plasmonpolariton mode.<br />Electric field enhancement is about 20,000 times at 1.47 µm.<br />
We can couple the plasmonic source to an MIM waveguide with high efficiency<br />10<br />Metal<br />Metal<br />Semiconductor<br />Insulator<br />Metal<br />Metal<br />Gap = 20 nm<br />Side view<br />
We observed the surface plasmonpolariton wave traveling along the waveguide and the coupling efficiency is about 60%<br />11<br />Normalized electric field at the middle of the plane.<br />The intensity at the waveguide is 60% of the microdisk.<br />