Variable THz attenuator based on 5BDSR microparticles in synthetic 80W-90 oil

We present a prototype of the variable THz attenuator based on magnetophoretic driven 0.5 wt% 5BDSR microparticles solution of highly viscous 80W-90 synthetic oil. Two pairs of Helmholtz coils are used as a source of an external magnetic field that possesses to drive the ferrofluid in a real-time. Dependence of the transmittance on particles orientation was studied in the range 0.2-2 THz using a custom made THz-TDS. Ferrofluid solution in a standard 1 cm length quartz cuvette possesses extinction ratio up to 20:1 at 1.4 THz. The prospects for their use for THz photonics are discussed.