Waveguide-type Optical Filters And Photodetectors On Silicon Substrate For Visible Light

Information and communication technology has changed people's lives and way of thinking. And the growing demand for information and communication technology has put forward higher requirements. Traditional electronic technology has been difficult to meet the requirements of mass information transmission. The long-distance optical communication can achieve massive data requirements. It is hoped that this technology also extend to the short-distance communication and interconnection areas. So people are focusing on the photonics integration technology which is very much alike the traditional microelectronics technology to achieve such kind of requirements. We want to reduce the costs and improve the device's performance, and at the same time make the device smaller and higher the level of the integration. We can use the materials with high refractive index to reduce the device size. On the other hand, with the continued development of photonics integration, its use is not limited to traditional communication applications. The application of optical sensing also has broad prospects. However, conventional infrared communication band has a few limitations as the sensing wavelength. Shorter wavelength(such as visible light) and long wavelength(such as far infrared wavelength) have their superiority when using as the sensing wavelength. This requires us to do the relevant research, which includes the platform of the waveguide materials and structures.This article first reviews relevant technologies about photonics integration. After, there is a brief introduction of the basic theory of planer waveguides, including the commonly used numerical methods for a brief introduction, which contains the finite difference method and the beam propagation method. Then, there is a brief introduction of the processes of photonics integration.There are two main parts of this subject. First is the silicon based SU-8 polymer waveguide-type filter design. The purpose of this part is to design and fabricate a special kind of array waveguide grating using the MMI coupler to replace the traditional FPR region. Since SU-8 polymer materials is a particularly good material for visible light transmission, which makes it a good candidate to realize visible light waveguide and visible light waveguide-type filter. The designed device's channel spacing is 4nm, and channel number is 4. The testing result of the cross talk is about 12dB,3dB bandwidth is about 3.3nm, and FSR is 16nm which all are in good agreement with the design value. The second part is the design and fabrication of one special suspended optical waveguide using silica as its waveguide material. Compared to the traditional weak confine silica waveguide, such kind of suspended optical waveguide structure has improved the refractive index difference. Since it uses air as its cladding. So the waveguide's dimension and bending radius has been significant decreased. Compares with the ridge waveguide, using such kind of waveguide structure to realize optical sensing system can obtain higher sensitivity. Because of the larger contact area with the media. At the same time, compared to conventional waveguide, the vertical dimension of the suspended optical waveguide is hung in the air. Therefore it has the vertical dimensional freedom. Since silica nanostructure has excellent mechanical properties, it is possible to introduce MEMS to regulate the performance of the photonics integration devices and further study the interaction between photons and nano-structures and other physical problems. Also, because the special structure of such suspended optical waveguide, achieving monolithic integration of silicon-based visible light detector becomes very easy. The substrate material is silicon, as long as we do not etch the silicon below the waveguide, the guided mode in the waveguide will soon leak into the substrate. Adding with the appropriate electrodes design, we can achieve high efficient of the photoelectric conversion. Because of its flat structure, metal-semiconductor-metal type silicon-based photodetector device is very suitable to achieve monolithic integration with the front suspended optical waveguide. Also, compared with the other type photodetector, it has the advantage of high speed, easier realization of detector array and so on.