Fig. 3. High-speed temporal modulation.
a Time domain response (orange) to a small-signal square wave (gray) with 2 V Vpp, 1 MHz repetition rate, and a 50% duty cycle. The sharp peaks at tuning edges are caused by mechanical ringing of acoustic resonances. b Time domain response to short pulses with 20 V Vpp, 5 MHz repetition rate, and a 20 ns pulse width, demonstrating ultra-fast (sub-ns) tuning speed. The inset shows the normalized cross-correlation (black) between input and output signals and the auto-correlation (red) of the input signal. The right Y axis in a, b denotes the resonant wavelength shifting relative to 0 V voltage, according to a measured linear tuning of −0.2 pm V−1. c Response to a 6 GHz square wave driving at the frequency where mechanical resonances disappear due to the low mechanical Q. The electrical input signal (gray) is measured by an oscilloscope after 20 dB attenuation of the original signal. The optical output (orange) shows clear oscillations with a frequency equal to the driving field, illustrating GHz level piezoelectric actuation.