This article presents a device capable of generating different or hybrid orbital angular momentum (OAM) modes at 225 GHz using a mechanically tunable configuration of two reflectionless plates. High precision microfabricated metallic traces on the plates form a miniaturized-element frequency-selective surface structure. Rotating one plate relative to the other produces different combined phase profiles to generate different orbital angular momentum (OAM) modes. Transmission phase measurements of individual and combined plates in the near field confirmed simulations with good agreement. This innovative OAM generation approach finds potential applications in near-field communications and high-resolution radar imaging systems.