Terahertz time-domain-spectroscopy system based on 1.55 μm fiber laser and photoconductive antennas from dilute bismides

A Urbanowicz,S Stanionytė,V Pačebutas,A Krotkus,A Geižutis

doi:10.1063/1.4942819

Abstract

We describe a terahertz time-domain-spectroscopy system that is based on photoconductive components fabricated from (GaIn)(AsBi) epitaxial layers and activated by femtosecond 1.55 μm pulses emitted by an Er-doped fiber laser. (GaIn)(AsBi) alloy grown on GaAs substrates contained 12.5%In and 8.5%Bi – a composition corresponding to a symmetrical approach of the conduction and valence band edges to each other. The layers were photosensitive to 1.55 μm wavelength radiation, had relatively large resistivities, and subpicosecond carrier lifetimes – a set of material parameters necessary for fabrication of efficient ultrafast photoconductor devices. The frequency limit of this system was 4.5 THz, its signal-to-noise ratio 65 dB. These parameters were comparable to their typical values for much bulkier solid-state laser based systems.

Highlights

We describe a terahertz time-domain-spectroscopy system that is based on photoconductive components fabricated from (GaIn)(AsBi) epitaxial layers and activated by femtosecond 1.55 μm pulses emitted by an Er-doped fiber laser. (GaIn)(AsBi) alloy grown on GaAs substrates contained 12.5%In and 8.5%Bi – a composition corresponding to a symmetrical approach of the conduction and valence band edges to each other
At 1 μm wavelength photoconductive antennas (PCA) can be fabricated from LTG GaInAs on GaAs substrates,[9] but their performance is greatly reduced by low electron mobility in this material
As alternative solutions for PCA activated by femtosecond 1.55 μm wavelength pulses, superlattices consisting of GaInAs absorption and AlInAs carrier recombination layers[15] as well as AsGa mediated absorption in a LTG GaAs photoconductor[16] were proposed