Frequency Selective Optoelectronic Downconversion of a Terahertz Pulse Using ErAs:In(Al)GaAs Photoconductors

Anuar De Jesus Fernandez Olvera,Pablo Acedo,Andres Betancur-Perez,Benedikt Leander Krause,Uttam Nandi,Sascha Preu,Cristina De Dios

doi:10.1109/access.2021.3094358

Anuar De Jesus Fernandez Olvera, Pablo Acedo + Show 5 more

Open Access

https://doi.org/10.1109/access.2021.3094358

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Abstract

We introduce a new scheme for the detection of terahertz pulses based on the frequency selective optoelectronic downconversion of its individual modes with a continous-wave (CW) ErAs:InGaAs photoconductive antenna (PCA) driven by a comb-based CW photonic signal. The detection scheme can be used as metrology tool for the analysis of the fundamental resolution and stability limits of terahertz pulses and the mode-locked-lasers (MLLs) that drives them, as well as an ultra-high-resolution measurement technique for terahertz components or gas spectroscopy. We demonstrate both applications by measuring the linewidth of two frequency components of the particular terahertz pulse analyzed here (one at 75 GHz and one at 340 GHz) and by measuring a very narrowband filter between 70 and 80 GHz. The main advantage of this technique with respect to other terahertz pulse detection schemes is its capability of performing ultra-high-resolution measurements without the need of unpractically long scanning ranges or synchronization of two MLLs.

Highlights

P OTONIC terahertz pulsed systems, known as terahertz time-domain spectrometers (TDS), have become a powerful tool for non-destructive testing
Most modern TDS systems use a single mode-locked laser (MLL) with a repetition rate that ranges between several tens of megahertz and a few hundreds of megahertz in order to generate an optical pulse with a duration of several tens of femtoseconds
EXPERIMENTAL DEMONSTRATION In the subsections we show the experimental demonstration of the two possible applications of Frequency Selective Optoeletronic Downconversion (FreSOD): the precise phase noise characterization of terahertz pulses, and the realization of extremely high-resolutionterahertz measurements using terahertz pulses

Summary

INTRODUCTION

P OTONIC terahertz pulsed systems, known as terahertz time-domain spectrometers (TDS), have become a powerful tool for non-destructive testing. We employ two lines of an electro-optically (EO) generated frequency comb to produce a continuous wave (CW) terahertz signal that acts as a photonic local oscillator for the optoelectronic downconversion of the individual frequency components of a terahertz pulse We call this scheme Frequency Selective Optoeletronic Downconversion (FreSOD), feasible thanks to the recent developments in telecom-wavelength compatible PCAs [11]–[15]: when acting as emitters in pulsed operation, telecom-wavelength PCAs are capable of delivering powers in excess of 0.5 mW [16], while CW receivers have shown noise equivalent powers (NEPs) as low as 1.8 fW/Hz [17].

THEORETICAL FRAMEWORK

APPLICATION 1

APPLICATION 2

CONCLUSION