Compact silicon photonics-based laser modules for FM-CW LIDAR and RFOG

Abstract

Narrow-linewidth semiconductor lasers, micro-optics, silicon photonics (SiP), low noise electronics and high-density packaging are key elements for the development of compact high-end light sources for sensing. A laser module for the interrogation of an RFOG (Resonant Fiber-Optic Gyroscope) includes three distributed feedback lasers coupled with micro-lenses to a multi-component SiP chip that performs beat note detection and several other functions. The lasers and SiP chip are packaged in a 2.6 cm³ multi-layer ceramic package, a 4x volume reduction over a first generation module. The package interfaces with 92 electrical pins and two fiber pigtails, one carrying the signals from a master and slave lasers, another carrying that from a second slave laser. The complete laser source including electronics is 60 mm in diameter and 23 mm in height, a 10x volume improvement over a previous version. The master laser can be locked to the RFOG resonator with a loop bandwidth greater than 1 MHz. The slave lasers are offset frequency locked to the master laser with loop bandwidths greater than 100 MHz. This high performance source is compact, automated, robust, and remains locked for days. A lighter version of this laser module for FM-CW LIDAR applications produces an output optical frequency that varies linearly as a function of the electrical drive. A triangular modulation at 100 kHz with a greater than 1 GHz amplitude has been demonstrated with a linearity noise near 1 MHz as measured through a 150 m unbalanced interferometer.