We propose and investigate the performance of integrated photonic isolators based on non-reciprocal mode conversion facilitated by unidirectional, traveling acoustic waves. A triply-guided waveguide system on-chip, comprising two optical modes and an electrically-driven acoustic mode, facilitates the non-reciprocal mode conversion and is combined with modal filters to create the isolator. The co-guided and co-traveling arrangement enables isolation with no additional optical loss, without magnetic-optic materials, and low power consumption. The approach is theoretically evaluated and simulations predict over 20 dB of isolation and 2.6 dB of insertion loss with 370 GHz optical bandwidth and a 1 cm device length. The isolator utilizes only 1 mW of electrical drive power, an improvement of 1-3 orders of magnitude over the state-of-the-art. The electronic driving and lack of magneto-optic materials suggest the potential for straightforward integration with the drive circuitry, possibly in monolithic CMOS technology, enabling a fully contained `black box optical isolator with two optical ports and DC electrical power.
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