Three-Step Molding Softlithographic Process for 1×2 Y-Branch Pof Coupler

Abstract

A three-step molding softlithographic process has been developed for the construction of a sharp Y-junction structure formation in a 1 × 2 Y-branch plastic optical fiber (POF) coupler design. The 1 × 2 Y-branch POF coupler is based on a Y-junction splitter which requires that the splitting part is constructed with sharp infinitesimal junction. The softlithographic process enables a PDMS mold to be constructed which then allows mass replication of the polymer-based POF coupler. A standard master mold based on PMMA material is fabricated using CNC milling. A secondary or auxiliarymold process step is then introduced in order to produce a sharp Y-junction structure which is then transferred to the final PDMS stamp prior to device replication. This step utilizes a free flowing, low viscosity casting-based resin, which after curing and hardening provide the auxiliary mold for PDMS mold fabrication. The result shows that a very fine and sharp Y-junction structure can be produced easily which cannot be produced via standard two step molding softlithographic process. Models for the Y-branch POF coupler produced with and without an auxiliary mold process are constructed which show that a 16% increased in optical performance with the device replicated with the auxiliary mold process. 1. INTRODUCTION Plastic Optical Fiber (POF) is a widely recognized optical medium for short distance optical data communication due to its favorably large-core size, multimode characteristics, low cost and robust features. Many applications for multimode fibers are well known. Nevertheless, waveguide-based POF devices development is limited because multimode devices have a smaller market especially for data communication application due to the high attenuation of POF devices compared to that of glass-based optical devices [1]. POF devices are produced with variety of new and economical materials for vast application which not only are for optical communications, but also include the entertainment, sensor, lighting and decoration system fields [2]. POF devices can be categorized in two parts: active and passive components. Active component are devices such as transmitter and receiver whereas passive component are devices such as filters, connectors, attenuators, and coupler or splitter, and other related passive devices [3]. Coupler or splitter as a passive device has great interest in applications in such as short length networks, optical sensors, and security system. These applications sometimes require that optical signals need to be split or divided. Standard fiber-based Y-branch couplers are normally made by polishing two fibers and gluing them together. These Y-branch couplers are vastly used in applications where incoming light signals need to be split. Nevertheless, this technique will be very impractical for producing asymmetrical-type couplers