Dielectric Structure with Periodic Strips for Increasing Radiation Power of Photoconductive Antennas: Theoretical Analysis

Low terahertz (THz) radiation power and low efficiency are the well-known drawbacks of photoconductive antennas (PCAs). To increase THz-radiation power of PCAs, a dielectric structure with periodic low-temperature-grown GaAs strips is proposed. Transmitted power of the proposed structure is obtained from a theoretical model, and further confirmed by finite element simulations. Results show that the structure is capable to transmit into the substrate 90 % of the power of transverse magnetic wave with wavelength as wide as from 0.7 to 1.0 μm. Favorability of this property gets amplified when power transmission in a wide range of frequency bandwidth is desired, e.g., for optical pulse with short duration time incident to PCA, which generates carriers in the semiconductor that create THz emission. Furthermore, the proposed dielectric structure with periodic strips, the whole structure placed in between electrodes of PCA is considered, and analyzed by the existing photoconductive antenna equivalent circuit model, to see how power radiation changes. Interestingly, THz-radiation power enhancements of 70 and 20 % are evinced for, respectively, 20 and 150 mW incident optical powers as instances, as compared to PCA without strips in the gap area.