Fig. 2. Acousto-optic modulator.

a A chip without AlN deposited so the waveguides are visible (left) and a completely fabricated chip with AlN and transducers (right). b An optical microscope image of a transducer next to a spiral. There are 19 waveguides visible on the transducer side of the spiral, corresponding to C = 38 modulated segments when counting both sides. Contrast and color has been modified to make the waveguides next to the transducer more visible. c ∣S₁₁∣² of the transducer reveals electromechanical coupling as the RF drive frequency is swept. d. Modulation efficiency as a function of transducer RF drive frequency for the spiral with C = 38 modulated segments. The RF drive power, P_RF, and optical wavelength, λ, are fixed. e Scaling of the waveguide length as a function of modulated segment count. f Scaling of the spiral area as a function of modulated segment count. Note that the spiral area is defined as the area of the smallest rectangle it can fit in. g Multiple spirals of varying modulated segment count are measured with identical transducer designs under the same drive power to ensure the measured modulation index increases multiplicatively with modulated segment count. h Scaling of the modulation efficiency for the first and second sidebands with respect to applied incident RF power following the expected trend for phase-modulation. The negative sidebands track identically to their positive counterparts.