Optical spot-size transformer interfaces for photonic microsystem packaging with relaxed optical tolerance
As packaging density of photonic microsystems increases, so do demands upon the number and coupling efficiency for optical interfaces. Spot-size transformers reduce optical loss of fibers to waveguides and relax spatial tolerances which, in turn, reduce the loss increase due to the creep usually experienced after attaching the fibers to the chip. A flexible design methodology has been developed based upon a high-potential-yield wafer-scale post-processing technology for polymer optical waveguide interfaces with the ability to adapt to a wide range of waveguide shapes and sizes. This method can potentially eliminate the need for individually tailored optical transformer designs for each device commonly realized during III-V semiconductor epitaxial growth. In addition the method allows for the use of non-epitaxial materials, such as active and passive doped glass, in large-scale hybrid photonic microsystems. Various polymeric spot size transformers based on established as well as novel processing methods have been fabricated and will be reported. The technology developed is amenable to economic manufacturing of photonic microsystems at a wafer scale with a large number of optical I/Os.