Fig. 2: Electrical architecture with the measured and calculated performance of the light-activated phase shifter.
A Simplified circuit diagram of the programmable pixel unit where the loaded transducer element has a complex impedance of ZT, which we approximate by the capacitive reactance XT. B Electrical characteristics of the photoresistive element embedded in the pixel unit, where the resistance R is measured for different values of light intensity IL. C The phase shift of the emitted ultrasound wave when the light is switched on (IL = 65.7 mW cm−2) and off at 1 Hz. Insets (i) and (ii) show zoomed views of the rise and fall times Δtr and Δtf, respectively. D Experimentally measured range of the total phase shift ΔϕT in the electrical signal presented for several different frequency values F. The experimental results corresponds to the operation of transducers at 2.25 MHz where data are presented as mean value ± standard deviation in the mean value of the phase shift. E The experimental and theoretical curves of the relative amplitude of electrical signal presented for several different values of R. The resistance is controlled by the light intensity IL. The data are presented as mean value ± standard deviation in the mean value of the relative amplitude. F The experimental and theoretical curves of the phase shift obtained in the ultrasound wave presented for several different values of R. The data are presented as mean value ± standard deviation in the mean value of the phase shift.
