Fig. 1.

Schematic of the experimental setup. AOM, acousto-optic modulator; BSO, ${\mathrm{Bi}}_{12}{\mathrm{SiO}}_{20}$; EOM, electro-optic modulator; HWP, half-wave plate; L, lens; M, mirror; $O$, signal light; $O^{*}$, time-reversed signal light; PBS, polarizing beam splitter; PD, photodiode; $R$, reference beam; $R^{*}$, conjugated reference beam; S, shutter; T, ultrasound transducer. Coordinates: $X=\text{optical\hspace{0.17em}axis}$, and $Z=\text{acoustic\hspace{0.17em}axis}$ of T1. The pressure at the ultrasound focus was 1.0 MPa peak-to-peak. To enhance the phase conjugation efficiency, a 2.1-kHz, $8\text{-}\mathrm{k}{\mathrm{V}}_{\mathrm{pp}}$ square waveform external electric field was applied across the BSO.