Study On The End-coupling Of Optical Fiber And Waveguide Device

Optoelectronic integrated circuit (OEIC) is the development trend of optoelectronic devices due to their outstanding merits, such as low insertion loss, compact size, small crosstalk, high stability etc. However, Waveguide structures in optoelectronic integrated circuit have a small noncircular spot-size, and a fiber has a lager circular mode profile. Thus, there is high loss due to the mode mismatch if the fiber is simply butt-coupled to the OEIC. Therefore, there is typically 10dB or even greater power loss when OEIC is directly butt-coupled to single mode fiber (SMF). This becomes a challenging problem. 1dB mismatch tolerance is an important criterion (indicator) to determine the performance of optical coupling system。It is also the key to resolve coupled packaging issues. The so-called 1dB mismatch tolerance is the axial, lateral or angular offset when coupling efficiency decreased from the maximum. The greater 1dB mismatch tolerance means that the system allowed the bigger package alignment offset, so we can use a simple structure and low cost packaging technology. Conversely, if the 1dB mismatch tolerance is too small, precise alignment not only become considerable difficulty, but also be vulnerable to external disturbances (such as mechanical vibrations and other factors).This paper has studied several different kind of waveguide coupled packaging technologies, aiming to design the low insertion loss, easily alignment tolerance and compact spot size converter (SSC). From the content of this paper,it can be divided into three parts.For the first part of this thesis, we have studied the end-coupling of optical waveguide and fiber detailed theoretical analysis. 3D overlap integral method was used to calculate the mode coupling efficiency between the optical waveguide and fiber. This thesis theoretically analyzed the reasons and generation of insertion loss. In addition, butt-coupling of optical waveguide and fiber was discussed to analyze the coupling-related characters. In the second part, three types of spot size converter: simple laterally tapered SSC, two-layer SSC and Y-branch SSC, structure parameters of the three SSC are optimized, so that the maximum coupling efficiency, the transmission characteristics and the transmission loss of optical field and alignment tolerance to fiber are analyzed in detail. Finally, we gave a novel resonantly coupled spot-size converters for enhanced waveguide-fiber coupling based on resonant coupling between the"supermodes"in a coupled waveguides. This technology can greatly shorten the length of the device, and can significantly reduce the transmission loss.