Optimization of electro-optic phase shifters for integrated optical phased arrays

Abstract

A low-loss, high-speed optical phased array (OPA) has been designed and fabricated. Two different platforms have been utilized in combination to leverage electro-optic (EO) tuning. A lithium niobate (LiNbO3) optical phased array was fabricated and used in conjunction with a silicon nitride (Si3N4) 8x8 waveguide array that condenses the output pitch and utilizes the TriplexTM waveguide technology. This OPA allows for the non-mechanical beam steering (NMBS) of 1550 nm light on an edge coupled optic platform and takes advantage of the high electro-optic coefficient and high speed capability of LiNbO3 for electro-optic phase tuning. This coupled OPA has an overall insertion loss of ~3.5 dB which is advantageous to silicon-on-insulator OPAs that have shown overall insertion losses of ~14 dB. To characterize and tune this device, a 3 lens imaging system was employed to produce both near- and far- field intensity patterns of the output of the OPA on a static image plane. At the image plane, a high resolution infrared camera was used to observe the resulting intensity pattern. The control software for tuning the OPA reads the intensity incident at a specified position on the detector array, and has a PWM interface to drive the electro-optic phase controls. Beam steering was accomplished using an iterative tuning algorithm.