Design and characterization of individual addressing optics based on multi-channel acousto-optic modulator for $^{171}$Yb$^+$ qubits

We present the design and characterization of individual addressing optics based on a multi-channel acousto-optic modulator (AOM) for trapped ytterbium-171 ions. The design parameters of the individual addressing system were determined based on the tradeoff between the expected crosstalk and the required numerical aperture of the projection objective lens. The target beam diameter and separation were 1.90 $\mu$m and 4.28 $\mu$m, respectively. The individual beams shaped by the projection optics were characterized by an imaging sensor and a field probe ion. The resulting effective beam diameters and separations were approximately 2.34--2.36 $\mu$m and 4.31 $\mu$m, respectively, owing to residual aberration.