Generation and Detection of THz Radiation With Scalable Antennas Based on GaAs Substrates With Different Carrier Lifetimes

We report on scalable photoconductive antennas for both emission and detection of terahertz (THz) radiation. The concept yields THz emitters with high efficiencies for the conversion of near-infrared into far-infrared radiation, and provides detectors that do not require tight focusing of both the THz beam and the near-infrared gating beam. GaAs substrates implanted with dual energy implants of N⁺ and As⁺ ions of various doses are compared with semiinsulating (SI) and low-temperature-grown GaAs. We discuss which material properties are desirable for emitters and detectors and identify which material is optimal as either emitter or detector substrate. Best results for detectors are found for implanted samples with doses in the range of 10¹³ cm^-2 for GaAs:N and for LT-GaAs. Best emitters for typical excitation conditions with a Ti: sapphire oscillator system are based on SI-GaAs.