  We demonstrate the magnetically-induced transparency (MIT) effect in
Y$_3$Fe$_5$O$_{12}$(YIG)/Permalloy(Py) coupled bilayers. The measurement is
achieved via a heterodyne detection of the coupled magnetization dynamics using
a single wavelength that probes the magneto-optical Kerr and Faraday effects of
Py and YIG, respectively. Clear features of the MIT effect are evident from the
deeply modulated ferromagnetic resonance of Py due to the
perpendicular-standing-spin-wave of YIG. We develop a phenomenological model
that nicely reproduces the experimental results including the induced amplitude
and phase evolution caused by the magnon-magnon coupling. Our work offers a new
route towards studying phase-resolved spin dynamics and hybrid magnonic
systems.
