  When gravitational waves pass through the nuclear star clusters of galactic
lenses, they may be microlensed by the stars. Such microlensing can cause
potentially observable beating patterns on the waveform due to waveform
superposition and magnify the signal. On the one hand, the beating patterns and
magnification could lead to the first detection of a microlensed gravitational
wave. On the other hand, microlensing introduces a systematic error in strong
lensing use-cases, such as localization and cosmography studies. We show that
diffraction effects are important when we consider GWs in the LIGO frequency
band lensed by objects with masses $\lesssim 100 \, \rm M_\odot$. We also show
that the galaxy hosting the microlenses changes the lensing configuration
qualitatively, so we cannot treat the microlenses as isolated point mass lenses
when strong lensing is involved. We find that for stellar lenses with masses
$\sim 1 \, \rm M_\odot$, diffraction effects significantly suppress the
microlensing magnification. Thus, our results suggest that gravitational waves
lensed by typical galaxy or galaxy cluster lenses may offer a relatively clean
environment to study the lens system, free of contamination by stellar lenses.
We discuss potential implications for the strong lensing science case. More
complicated microlensing configurations will require further study.
