  The past few years have witnessed increased attention to the quest for
Majorana-like excitations in the condensed matter community. As a promising
candidate in this race, the one-dimensional chiral Majorana edge mode (CMEM) in
topological insulator-superconductor heterostructures has gathered renewed
interests during recent months after an experimental breakthrough. In this
paper, we study the quantum transport of topological insulator-superconductor
hybrid devices subject to light-matter interaction or general time-periodic
modulation. We report half-integer quantized conductance plateaus at
$\frac{1}{2}\frac{e^2}{h}$ and $\frac{3}{2}\frac{e^2}{h}$ upon applying the
so-called sum rule in the theory of quantum transport in Floquet topological
matter. In particular, in a photoinduced topological superconductor sandwiched
between two Floquet Chern insulators, it is found that for each Floquet
sideband, the CMEM admits equal probability for normal transmission and local
Andreev reflection over a wide range of parameter regimes, yielding
half-integer quantized plateaus that resist static and time-periodic disorder.
The $\frac{3}{2}\frac{e^2}{h}$ plateau has not yet been computationally or
experimentally observed in any other superconducting system, and indicates the
possibility to simultaneously create and manipulate multiple pairs of CMEMs by
light. The robust half-quantized conductance plateaus, due to CMEMs at
quasienergies zero or half the driving frequency, are both fascinating and
subtle because they only emerge after a summation over contributions from all
Floquet sidebands. Such a distinctive transport signature can thus serve as a
hallmark of photoinduced CMEMs in topological insulator-superconductor
junctions.
