Theoretical Studies On Mode Properties Of Hybrid Surface Plasmonic Waveguide And Fabrication Of Microsphere

Electronic integrated circuit had developed rapidly since1960s, Ultra Large Scale Integrated Circuits can integrate millions scale of components. However, electronic integrated circuit encounters some bottlenecks during its way to small volume and high integration level. These bottlenecks include emitting, signal delay in high frequency and so on. Researchers pay attention to photonic integrated circuit and photonic integrated component in recent years. Compared to electronic integrated circuit, photonic integrated circuit has advantages of little emitting heat, wide operation bandwidth and anti-interference. Nevertheless, photonic integrated circuit needs to deal with ultra miniaturization problems in the fields of wave guiding and light source.As for wave guiding, photons suffer obvious diffraction when the space is as small as photons’ wavelength. In order to achieve high integration level, it is important to overcome diffraction effect. People focus on topics of photonic crystal waveguide and surface plasmonic waveguide. In addition, hybrid surface plasmonic waveguide has more advantages in field confinement. In the research of light source miniaturization, it is hard to create Fabry-Perot cavity in micron scale. light in certain wavelength turns into whispering gallery mode via total internal reflection of the internal surface of microsphere. Whispering gallery mode has features of small mode volume and strong mode confinement. These advantages provide theoretical support for fabrication of microsphere laser with small size and low threshold. On account of those problems above, the paper analyzes the creation of hybrid plasmonic waveguide and fabrication of quartz microsphere. Following several points:(1) A hybrid plasmonic waveguide that consists of a semiconductor nanowire and semicircular-top metal nanoridge was proposed. Finite element method was used to numerically calculate modal subwavelength field confinement and propagation loss. Numerical results indicate that mode area of0.00181(λ2/4) and relative long propagation distance are obtained at the wavelength of1.55μm. This kind of waveguides has potential in fabrication of integrated photonic circuits and components.(2) We study other kind of hybrid plasmonic waveguides. It’s main structure was an elliptical nanowire embedded in silica layer, two same rectangle surface plasmonic waveguides were placed in the up and down of silica layer. Mode properties of this waveguide were studied by varying the parameters of structure. Hybrid mode generated from coupling between two surface plasmonic modes and two dielectric modes. This specific mode possesses small mode volume. The paper analyzes coupling property of this kind structure of waveguide, this work makes foundation for coupling problem among waveguides in the photonic integrated component.(3) The research focus on fabrication and measurement of microsphere with high Q value and tapered fiber. In order to fabricate tapered fiber, we should fix a single mode fiber onto the sliding blocks of guide rail, sliding blocks was controlled by stepping motor and the single mode fiber was heated by hydrogen flame. Finally, power measurement system should be employed to verify the quality of the tapered fiber. Under the strictly controlling of experiment conditions, we fabricate tapered fiber with diameter of3μm and propagation loss of0.01dB. This quality fully meets our experimental demands. In addition, the paper studies two kinds of methods to fabricate microsphere. The first one named weight suspended method:fiber suspended by some weight and then heated by CO2laser. The other one named tapered fiber method:tapered fiber was cut properly and then heated by CO2laser also. We fabricate microspheres with diameters range from30to100μm. These microspheres have good sphericity and smooth surface. These properties satisfy demands of experiment very well.(4) In order to measure quality of microsphere, we construct our coupling system with broadband light source, optical spectrum analyzers and CCD monitoring device. Based on microsphere-tapered fiber measurement system, light wave which comes from the tapered fiber couples into microsphere and induces a resonance. We can observe a series of equal interval interference peaks on optical spectrum analyzers. Quality value of5000and free spectral range of8.4nm can calculate from these interference peaks of microsphere with diameter of50μm. Under the strict experiment conditions and measurement method, the Q value we calculated is smaller than its true value, so more works needed to be made in the next research. However, this work helps us to understand WGM well and it makes foundation of its sensing experiment through observing movement of interference peaks.