Birefringence of orthorhombic DyScO3: Toward a terahertz quarter-wave plate

With growing interest in exploring fundamental phenomena at terahertz (THz) frequencies, the need for controlling the polarization state of THz radiation is indispensable. However, simple optical elements, such as waveplates that allow creating circularly-polarized THz radiation, are scarce. Here, we present THz quarter-wave plates (QWPs) made out of (110)-cut and (001)-cut DyScO3 (DSO) crystals. We examine the complex refractive indices along the in-plane axes and map the birefringence of both DSO crystals. Further, we demonstrate that both 50-mu m-thick (110)-cut DSO and 370-mu m-thick (001)-cut DSO crystals behave like a QWP over a broad frequency range of 0.50-0.70THz and 0.50-0.61THz, respectively, with a phase tolerance of +/- 3%.