Scientists at the University of Marburg have developed a wave plate which can turn the polarization state of terahertz waves. The Prof. Martin Koch group reports on this in the scientific journal Optics Express (B. Scherger, et al. Optics Express 19, 24884 (2011)). The wave plate consists of paper and is based on the principle of the so-called form birefringence.
Thin strips of paper are stacked in a way that there is a thin gap of air between every other piece. If polarized terahertz waves transmit through this paper structure under a certain angle, their polarization state is turned. For certain frequencies the turning amounts to 90 degrees. In this case, the device acts as a half wave plate. The paper wave plate is more efficient and markedly cheaper than more elaborately produced counterparts, e.g. from metamaterials.
In order to prove that production of this terahertz component is as easy as child’s play, Benedikt Scherger and Prof. Martin Koch visited a local kindergarten near Marburg. The preschoolers devotedly produced paper strips which were combined to form a wave plate. Afterwards, the children could convince themselves of the operational reliability of their construction in the lab.