  This study centers on Line-of-Sight (LoS) MIMO communication enabled by a
Transmissive Reconfigurable Intelligent Surface (RIS) operating in the
Terahertz (THz) frequency bands. The study demonstrates that the introduction
of RIS can render the curvature of the wavefront apparent over the transmit and
receive arrays, even when they are positioned in the far field from each other.
This phenomenon contributes to an enhancement in spatial multiplexing. Notably,
simulation results underline that the optimal placement of the RIS in the
near-field is not solely contingent on proximity to the transmitter (Tx) or
receiver (Rx) but relies on the inter-antenna spacing of the Tx and Rx.
