UC Santa Barbara

Optical beam steering is increasingly utilized for many applications – a well-known example being terrestrial navigation light detection and ranging for autonomous vehicles. The performance requirements for this application and others, including remote sensing for climate monitoring and disaster relief, and even industrial machining for printed circuit board manufacturing and integrated circuit repair, are pushing the limits of existing beam steering solutions. Steering speed is an especially demanding requirement which cannot be met by traditional beam steering methods, and optical phased arrays are the only feasible solution for obtaining GHz-class steering speeds.

By utilizing integrated photonics technology, optical phased arrays can be cost-effectively realized compared to other methods. Yet, typical integrated photonic solutions impose additional restrictions on wavelength and struggle to meet steering speed requirements. Group III-V semiconductor-based integrated photonics platforms, in contrast, are able to provide increased steering speed, and gallium arsenide platforms in particular offer a wide wavelength range covering traditional optical beam steering wavelengths. Moreover, gallium arsenide based materials enable efficient integrated light sources and optical amplification in 900-1300 nm wavelengths and beyond, leading to the possibility of a fully monolithically integrated optical phased array solution.

In this work, a gallium arsenide photonic integrated circuit platform has been developed with fast electro-optic phase modulators to enable GHz-class beam steering, with demonstrated single-sided Vπ∙L phase modulation efficiency ranging from 0.5 V∙cm to 1.22 V∙cm at wavelengths from 980 nm to 1360 nm. This platform was leveraged to fabricate and demonstrate a 16-channel optical phased array with phase control, with a one-dimensional optical phased array output featuring 0.92° beamwidth, 15.3° grating-lobe-free steering range, 12 dB sidelobe level, and ≥770 MHz single-element electro-optical bandwidth when operating at 1064 nm.

Further development has integrated active material to provide the possibility of on-chip lasers and per-channel gain in an active-passive platform. While still in development, this platform has successfully demonstrated an active-passive fabrication process and produced fully functional of phase modulators and passive elements, paving the way for a fully monolithically integrated photonic integrated circuit platform for optical phased array applications.