Enhanced terahertz emission from a femtosecond-laser-ablated photoconductor

Terahertz (THz) emission properties from bow-tie antennas fabricated on a femtosecond-laser-ablated, semi-insulating gallium arsenide (SI-GaAs) photoconductor are investigated. The ablated material demonstrates increased photoabsorption resulting in increased photocurrent leading to a more efficient optical to THz efficiency. We use THz time-domain spectroscopy (THz-TDS) in order to compare the relative efficiency of the two fabricated devices. The influence of the excitation power and applied bias on the antennas electrodes for both ablated and non-ablated substrates is studied, highlighting the better performances of the ablated devices. A 60{\%} enhancement in THz emission amplitude is observed in the frequency range 0.5 - 4 THz of the ablated SI-GaAs antenna, compared to untreated SI-GaAs. Our experimental results are in agreement with Drude-Lorentz numerical simulations using previously reported absorption and photocurrent properties of femtosecond laser ablated SI-GaAs based photoconductors. This material treatment provides a new way to achieve THz-TDS systems based on SI-GaAs antennas with an improved signal-to-noise ratio.