Continuous-wave 1550 nm operated terahertz system using ErAs:In(Al)GaAs photo-conductors with 52 dB dynamic range at 1 THz

Abstract

Telecom-wavelength compatible photoconductors benefit strongly from the large amount and affordability of telecom lasers and components but there are demanding requirements on material development. We demonstrate continuous-wave (CW) photomixing with a setup that only uses ErAs:In(Al)GaAs devices with a peak dynamic range (DNR) of 78 dB and a bandwidth of ∼3.65 THz at an integration time of 300 ms and only 26 mW laser power on each device. The ErAs:InGaAs receiver further features a factor of two lower noise equivalent power (NEP) than a state-of-the-art photoconductor, despite an antenna mismatch.

International System of Units (SI) Traceable Noise-Equivalent Power and Responsivity Characterization of Continuous Wave ErAs:InGaAs Photoconductive Terahertz Detectors

“…As discussed in Ref. [14], the NEP saturates at high laser powers, P L , and then variations of P L have no influence on the NEP. For low laser powers, the NEP is proportional to P −1 L according to Equation (12), resulting in a (worst case) NEP uncertainty of 3.6%.…”

“…The photoconductive material consists of a periodic structure of alternating layers of 10 nm of InGaAs and Be-delta-doped 0.8 monolayers of ErAs repeated 90 times. The third detector, used only for the DC comparison, is identical to the first two but instead of being Be-doped, it was C-doped, as described in [14]. All three detectors were designed and processed at Technische Universität Darmstadt with material grown at the University of California, Santa Barbara solely for research purposes.…”

Continuous Wave THz System Based on an Electrically Tunable Monolithic Dual Wavelength Y-Branch DBR Diode Laser

“…Generally, compact homodyne CW THz systems are attractive for real-time THz applications. Simple and cost-efficient systems for thickness measurements and spectroscopic application have already been demonstrated based on two colour distributed feedback (DFB) diode lasers operating in the optical communication windows of 1300 nm and 1550 nm [5][6][7][8][9][10]. Such systems allow for a real-time operation employing frequency scanning either with or without a delay stage [5,6].…”

Terahertz gas phase spectroscopy using a high-finesse Fabry–Pérot cavity

“…Numerous applications such as, breath analysis [4], environmental surveillance [5,6], food spoilage monitoring [7], or detection of explosive taggants [8], should be feasible if sufficient instrument sensitivity and spectral resolution can be obtained. Despite numerous advances observed at THz frequencies including THz Quantum Cascade Lasers [9][10][11], solid-state electronic devices [12], photonic conversions [13], detectors [14,15], this spectral region remains hindered by its immature technology compared to the neighbouring microwave and infrared domains. At present, there is no versatile tool for THz or sub-millimetre chemical analysis, the development of such an instrument has without doubt been held up by the limited achievable sensitivity.…”