A Compact Soft-lithography Based Y-branch Optical Power Splitter

Driven by increasing demand for broadband services and access network, fi-ber-to-the-home (FTTH) has been intensively investigated for its potential application in access network. Passive Optical Network (PON) is an ideal choice for FTTH because of its unlimited bandwidth and cost-effective system. As one of the key elements of PON, a great deal of optical power splitters with high quality and low cost are required to ensure large-scale deployment of PON. We develop a novel structure for Y-branch splitter, which is much smaller compared to a traditional one. In addition, we fabricate this newly designed splitter using soft lithography technique, which can dramatically reduce cost, simplify production procedures and increase efficiency.First, the basic theories of optical waveguides are thoroughly investigated. The waveguide propagation condition and analytical methods are deduced from Maxwell's equations. The ray optics and wave optics methods for slab waveguides are also explained while the Marcatili's method and the effective index method are introduced for channel waveguides. Especially, we discuss the frequently used numerical simulation method for waveguides—Beam Propagation Method (BPM). All of the work above can shed light on subsequent analysis and experiment.Then, detailed design for the structure of Y-branch optical power splitter is followed. It includes independent design of input waveguide, output waveguide, Y-branch module and connecting waveguide module. We use the waveguide simulation software BeamPROP? to analyze the effects of the Y-branch angle, the radius and central angle of arc waveguides, and the length of straight waveguide on insertion loss and nonuniformity. Based on these analyses, we develop the whole structure of 1 by 8 and 1 by 16 splitter, both of which are proven to be with low insertion loss and low non-uniformity.At last, we use soft lithography technique to fabricate this structure. The origin mold was made by computer-controlled carving machine with high precision of 0.1μm. The negative PDMS mold was developed through two steps of molding. Then, we filled this PDMS mold with UV curable polymer by using MIMIC method, and placed them on an optical substrate where UV light can cure the polymer to form anidentical structure of the mold. Finally, a stand-alone optical power splitter was formed after peeling the mold off. The laboratory test indicates that this splitter can be applied to optical networks. In addition, we also propose the potential methods to further improve the characteristics of this optical power splitter.