Impact of Optical Illumination on Transmission of Subterahertz Electromagnetic Waves by Bi12GeO20 Crystals

In this paper, we have investigated the impact of optical illumination on the transmission of subterahertz waves through Bi12GeO20 crystals. At the investigated frequency range (220-330 GHz) at different intensities of optical illumination (440-465 nm), we received a change in transmittance of the Bi12GeO20 crystal of about 0.6 dB. The transmission recovery time after the optical illumination stops was 2 min. The optical illumination with the intensity I = 3.0 W/cm(2) leads to changes in the resistance of the test sample by three orders of magnitude, i.e., to the values of similar or equal to 10(4) Omega, and hence to the conductivity sigma = 10(-5) (Omega cm)(-1). Using light illumination with the photon energy > 3.2 eV and the intensity I >= 1 W/cm(2), it is possible to achieve a concentration of free carriers (electrons and holes) that will lead to a more significant modulation of terahertz illumination by Bi12GeO20 crystals. The obtained results were analyzed and compared with the results of other scientific groups.