  Electrically tunable devices contribute significantly to key functions of
photonics integrated circuits. Here, we demonstrate the tuning of the optical
index of refraction based on hybrid integration of multi-layered anisotropic
GaGeTe on a silicon micro-ring resonator (Si-MRR). Under static applied (DC)
bias and transverse-electric (TE) polarization, the device exhibits a linear
resonance shift without any amplitude modulation. However, for the
transverse-magnetic (TM) polarization, both amplitude and phase modulation are
observed. The corresponding wavelength shift and half-wave voltage length
product (V_{\pi}.l) for the TE polarization are 1.78 pm/V and 0.9 V.cm,
respectively. These values are enhanced for the TM polarizations and correspond
to 6.65 pm/V and 0.28 V.cm, respectively. The dynamic radio frequency (RF)
response of the devices was also tested at different bias conditions.
Remarkably, the device exhibits a 1.6 MHz and 2.1 MHz response at 0 V and 7 V
bias, respectively. Based on these findings, the integration of 2D GaGeTe on
the silicon photonics platform has great potential for the next generation of
integrated photonic applications such as switches and phase shifters.
