Gravitational Lensing of Gravitational Waves: Effect of Microlens
  Population in Lensing Galaxies
  With increasing sensitivities of the current ground-based gravitational-wave
(GW) detectors, the prospects of detecting a strongly lensed GW signal are
going to be high in the coming years. When such a signal passes through an
intervening lensing galaxy or galaxy cluster, the embedded stellar-mass
microlenses lead to interference patterns in the signal that may leave
observable signatures. In this work, we present an extensive study of these
wave effects in the LIGO/Virgo frequency band ($10$-$10^4$ Hz) due to the
presence of the microlens population in galaxy-scale lenses for the first time.
We consider a wide range of strong lensing (macro) magnifications and the
corresponding surface microlens densities found in lensing galaxies and use
them to generate realisations of the amplification factor. The methodologies
for simulating amplification curves for both types of images (minima and saddle
points) are also discussed. We then study how microlensing is broadly affected
by the parameters like macro-magnifications, stellar densities, the initial
mass function (IMF), types of images, and microlens distribution around the
source. In general, with increasing macro-magnification values, the effects of
microlensing become increasingly significant regardless of other parameters.
Mismatch analysis between the lensed and the unlensed GW waveforms from
chirping binaries suggests that, while inferring the source parameters,
microlensing can not be neglected for macro-magnification $\gtrsim 15$.
Furthermore, for extremely high macro-magnifications $\gtrsim 100$, the
mismatch can even exceed $5\%$, which can result in both a missed detection
and, consequently, a missed lensed signal.
