Optical design of a miniature semi-integrated tunable laser on a silicon optical bench

Abstract

There is an increasing demand for tunable lasers in telecommunications networks for test equipment, optical components and other applications. In DWDM systems, multiple data streams propagate concurrently on a single mode fiber. DWDM networks are based on a DFB lasers operating at a wavelength defined by ITU wavelength grid. Statistical variations associated with the manufacture of DFB laser results in yield losses. Continuously tunable external lasers are developed to overcome the limitations of DFB lasers. Various laser tuning mechanisms are being explored to provide external cavity tunable lasers to provide a stable single mode output. The packaged tunable laser source (TLS) for DWDM network also need to include several optical elements for isolation and data modulation like collimator, focusing lens, fiber pigtail, a modulator and output fiber segment. In this publication, we propose a novel semi integrated miniature high frequency tunable laser design based on Silicon Optical Bench (SiOB) concept. One of the mirrors is a movable MEMS structure changing the optical path length. We propose micro optical design between laser diode and the MEMS mirror for efficient optical coupling and side mode suppression. We also present the compatibility between the optical coupling and MEMS actuation range. We present the coupling efficiency results over the tuning range. We also propose a method of monitoring the output power of the tunable laser using waveguide coupler structures which are integrated in the silicon wafer and method of packaging in a miniature package compatible to the industry standard form factor.