Study Of Long-range Surface Plasmon Polariton Waveguide Thermo-optical Switch Devices

Surface plasmon polaritons(SPPs) are transverse magnetic(TM) wave generated by light waves coupled to oscillations of free electrons on the metal surface, which can propagate along the metal-dielectric interface, it decays exponentially into both media and metal. The penetration depth of surface plasmon wave in the adjacent medium is less than a half wavelength, this feature may be beyond the diffraction limit to manipulate photons and realize sub-wavelength scale photonic circuits. It has a great potential for optical communications research, such as high-speed data transmission, biological testing, optical integration. To reduce the propagation loss of device, in this paper, we use SU-8, P(MMA-GMA) as the cladding material and gold as core material. Using spin coating, lithography and wet etching process to fabricate Long-Range Surface Plasmon Polariton(LRSPP) waveguide devices, and they have been tested, experimental results are obtained. The main contents contain the following aspects:(1) Fabrication and performance test of Long-Range Surface Plasmon Polariton waveguide based on ultra-thin gold film. The gold films of different thickness were deposited on different substrates, and prepare waveguide by wet etching.AFM and SEM are used to characterize the morphology of gold films and waveguides. The end-fire excitation method is adopted to guide telecommunication wavelengths along the device. The results shown, the surface energy and electronegativity have significant effects on the growth of Au film.LRSPP waveguide based on the ultra-thin gold thin film having a lower propagation loss, the ultra-thin thin gold film may be applied to a variety of LRSPP waveguide device.(2) Fabrication and performance test of LRSPP waveguide are introduced. Using a thin P(MMA-GMA) as a mask to prepare gold waveguide by wet etching. It could avoid the damage from removal of photoresist on the gold waveguide. The software COMSOL 4.4 is used to simulate optical and thermal energy distribution of devices, and introduce the fabrication processes of device. The measurement of LRSPP waveguide have shown that, the switch has an extinction ratio of 20 d B with a driving power of 18 mw, the rise time and fall time are 2.5ms and 3.4 ms.(3) Fabrication and performance test of LRSPP waveguide with M-Z structure.Optimizing the device structure and draw the corresponding lithography layout,because of the need to introduce gaps in the device, the impact of gaps in LRSPP waveguide were studied. COMSOL was used to simulate power changes when the light passing through the gaps in LRSPP waveguide. Using the wet etching to remove photoresist on the electrode, the method can obtain high quality electrode surface, and simplifies the preparation process, improve the service life of device.The M-Z LRSPP waveguide thermo-optical switch and straight waveguide with different widths gaps were fabricated. The test results show that the induced optical loss is smaller than 3 d B when the gap width is lower than 10 μm. The fabricated switch exhibits an extinction ratio of 17 d B with a driving power of 13 m W, the rise time and fall time are 720 μs and 940 μs.