THz generation with photoconductive emitters with a low-noise GHz repetition rate laser

Abstract

Photoconductive emitters and receivers are widely accepted as the best combination for applications requiring broadband and high dynamic range and are nowadays deployed in most commercially available systems. Novel laser sources with higher repetition rate and power levels are a promising route towards further improvements in this area. We present our first steps in this direction by combining state-of-the-art emitters and receivers with an ultra-stable commercial fs laser (MENHIR-1550 SERIES) at 1 GHz repetition rate as the optical source. The output of the laser is amplified and compressed by a commercial fiber amplifier setup. In this experiment, we use 17 mW as the probe beam and 30 mW as the pump beam with a pulse duration of 150 fs, as these are the best operation points for the emitter and receiver available. The emitter is based on iron doped InGaAs in a strip line geometry with an active region of 50 μm x 50 μm while a fiber coupled dipole antenna with a 10 μm gap is used as the receiver. We demonstrate a 1 GHz repetition rate terahertz time-domain spectroscopy (THz-TDS) system with a dynamic range of 73 dB and a bandwidth of 3.5 THz using state-of-the-art THz photoconductive emitter and receiver with a measurement time of 60 s. This result is part of a larger effort to understand the compromises to be realized in terms of repetition rate and average power to take photoconductive emitters and receivers to the next step in dynamic range enhancement.