Planar Lightwave Circuit Balanced Optical Fanout Using a Thin Film Photodetector Array Embedded in a Polymer MMI Coupler

摘要

Planar lightwave circuits are an attractive miniaturized, integrated implementation of optical interconnections and functionality for use in optical subsystems and for insertion into electrical board and chip level systems. As the demand of high data rate interconnection on boards increases, electrical systems face a variety of interconnection bottlenecks which may be addressed with optical interconnections [1]. Heterogeneous integration of planar lightwave circuit (PLC) components, including optoelectronic (OE) active devices with polymer waveguides and optical components, offers the versatility of optimization of substrate, OE device, and optical components for low cost implementation with materials which are compatible with electronic subsystems. The heterogeneous integration of thin film OE devices embedded in the PLC structure offers a fully planar integrated structure that can be directly or evanescently coupled, and which requires no beam turning out of the plane of the PLC [2], In this paper, a balanced optical fanout using a 1x4 thin film metal-semiconductor-metal (MSM) photodetector array embedded in a photoimageable polymer multi-mode interference (MMI) coupler is fabricated, demonstrated, and compared to theoretical estimates. This is the first MMI coupler reported with an integrated photodetector array, and the first MMI coupler reported that has been fabricated with a photoimageable polymer. For optical signal distribution (e.g. optical clock distribution), balanced signal routing is an important optical function, and MMI couplers provide compact design, low splitting loss, and balanced output [3].