Gigahertz Metamaterial Ultrasonic Lens Characterization Using GHz CMOS Integrated Ultrasonic Micro Imager

Recently we have developed a Gigahertz ultrasonic metamaterial lens that can focus the incoming ultrasonic waves. These lenses are critical components of SonicFFT to compute the fast Fourier transform [1]–[3] at high speeds and low energy consumption. The ultrasonic lens consists of silicon dioxide pillars in a silicon matrix, with spatially varying oxide density to realize ultrasonic phase shifts. The Sonic FFT operation requires complex 3D stacking and CMOS chips, which work under development. Here we demonstrate the use of 2D 128×128 AlN CMOS integrated T/R pixels to verify lens operation. The GHz Micro-Imager enables measurement of the return magnitude and phase to characterize the lens phase shifting operation [4]. This demonstration establishes a methodology to characterize and optimize complex silicon-based 2D ultrasonic impedances at high GHz frequencies.