We present Keck-Adaptive Optics and Hubble Space Telescope high
resolution near-infrared (IR) imaging for 500 μm bright candidate
lensing systems identified by the Herschel Multi-tiered Extragalactic
Survey and Herschel Astrophysical Terahertz Large Area Survey. Out of 87
candidates with near-IR imaging, 15 (~17%) display clear near-IR lensing
morphologies. We present near-IR lens models to reconstruct and recover
basic rest-frame optical morphological properties of the background
galaxies from 12 new systems. Sources with the largest near-IR
magnification factors also tend to be the most compact, consistent with
the size bias predicted from simulations and previous lensing models for
submillimeter galaxies (SMGs). For four new sources that also have
high-resolution submillimeter maps, we test for differential lensing
between the stellar and dust components and find that the 880 μm
magnification factor (μ880) is ~1.5 times higher than the
near-IR magnification factor (μNIR), on average. We also
find that the stellar emission is ~2 times more extended in size than
dust. The rest-frame optical properties of our sample of
Herschel-selected lensed SMGs are consistent with those of unlensed
SMGs, which suggests that the two populations are similar.