Generation and detection of coherent terahertz waves using two photomixers

Abstract

A general technique has been demonstrated at microwave and submillimeter-wave frequencies for photoconductive sampling in the frequency domain using photomixers and continuous-wave laser diodes. A microwave version in which two photomixers were coupled by a transmission line was developed to quantitatively test the concept from 0.05 to 26.5 GHz. A quasioptical version using antenna-coupled photomixers was demonstrated from 25 GHz to 2 THz. Such a system can outperform systems based on time-domain photoconductive sampling in frequency resolution, spectral brightness, system size, and cost.

Continuous Wave Terahertz Systems Based on 1.5 μm Telecom Technologies

“…First CW systems have been assembled at 800 nm [3,4]. It looked very promising to replace the expensive Ti:Sapphire lasers by more simple CW lasers while using the low temperature grown (<200°C) LT GaAs photoconductive antennae (PCA) available from pulsed systems also as photomixers.…”

Investigations of various cw terahertz photomixers

“…Optical heterodyne down-conversion (photomixing) in ultrafast photodetectors is one of the most promising sources for high-resolution THz spectroscopy systems. Narrow-band radiation at the optical beat frequency was observed from photodetectors illuminated by two optically delayed parts of linearly chirped laser pulses [2,3], by a single laser emitting simultaneously at two wavelengths [4], or by heterodyne mixing of two individual cw lasers in a photoconductor [5,6]. Low-temperature-grown GaAs photomixers pumped by two cw, tunable, frequency-offset solid-state lasers have been used to generate coherent cw far-infrared radiation tunable to 3.8 THz with high conversion efficiency [5].…”

Generation of Terahertz radiation with two color semiconductor lasers

“…Since one is interested in cost-effective and robust THz sources, this approach is particularly attractive using compact fiber lasers or diode lasers. For example, continuous wave THz radiation has been successfully realized with two DBR laser diodes [18]. However, the stable superposition of two independent lasers still introduces a considerable effort.…”

“…The difference frequency of the two wavelengths is the desired THz frequency. When these two laser sources are spatially overlapped and sent onto nonlinear mixing devices as photoconductive antennas [17,18] or nonlinear optical crystals [19], the THz difference frequency is generated. The concept of photomixing will be addressed in more detail below.…”