In this study, we present an all-optical reflection modulator for the
2 µm communication band exploiting a nanogear-array metasurface
and phase-change-material
G
e
2
S
b
2
T
e
5
(GST). The reflectance of the
structure can be manipulated by altering the phase of GST by employing
optical stimuli, and this paper provides details on the optical and
opto-thermal modeling techniques of GST. A numerical investigation
reveals that the metastructure exhibits a conspicuous changeover from
∼
99
%
absorption to very poor interaction
with the operating light depending on the switching states of the GST,
ending up with 85% modulation depth and only 0.58 dB insertion
loss. Due to noticeable differences in optical responses, we can
demonstrate a high extinction ratio of 28 dB and a commendable
figure of merit of 49, so far the best modulation performance in this
wavelength window, to our knowledge. In addition, real-time tracking
of reflectance during phase transition manifests high-speed switching
expending low energy per cycle, of the order of sub-nJ. Hence, given
its overall performance, the device will be a paradigm for optical
modulators for upcoming 2 µm communication technology.