Towards a CMOS Integrated Optically Controlled AlN Transducer

A framework for an ultrafast Sonic Fourier transform (SFT) physical computer leveraging the property that the Fourier transform of an image is its far-field pattern has been presented recently by our group. To represent different input images requires actuating a 2D array of transducers with controllable magnitude and phase. In this work, we demonstrate a CMOS-based optically controlled excitation approach for AlN transducers. This approach provides an optical pixel based amplitude modulation of electrically generated ultrasonic waves, providing a direct interface between an optical camera-like imager and ultrasonic waves, allowing for instantaneous control of the drive amplitude of all array transducers at the same time. The monolithic integration of this CMOS-based control circuitry and the AlN transducer array would enable the proposed SFT to instantly respond to the light from the environment or from an image mask, achieving real-time image recognition in the Fourier domain. In this work, we demonstrate the proposed single pixel architecture using an AlN transducer wire-bonded to the CMOS pixel circuitry comprised of a p+/n-well photodiode, a transimpedance amplifier, and a voltage controlled variable gain amplifier. We demonstrate the tuning of the pixel drive amplitude from 5 – 47.9mV by varying incident optical intensity from 0 – 250mW/mm2, resulting in receive amplitudes of 0.5 – 2.4 mV on an adjacent receive transducer located 200 um from the transmit pixel.