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

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

Structural changes in chlorine-substituted SbSI

Article no. 14101The antimony sulphoiodide (SbSI) is considered a prospective and important ferroelectric material due to its unique properties below Curie temperature Tc. However, the fact that current practical applications require higher working temperatures has prompted new structural improvements that extend the ferroelectric state. In this ternary system, Tc is highly sensitive to any chemical modifications or stress. Therefore, one way to adjust the Tc is through selective substitution of the constituent elements. In this work, SbSI has been fractionally chlorine-substituted at the iodine site and examined using temperature-dependent x-ray diffraction and specific heat capacity methods. Although a considerable increase in Tc has been achieved, a more detailed analysis shows that the Tc increases with x from 0 to 0.2 and starts to decrease when x > 0.2. The maximum Tc increase in the range of x = 0–0.3 is - 15.3%. The reverse behavior, from increase to decrease, is thoroughly discussed with reference to the previously published data on SbSI1-xClx compoundsEdukologijos tyrimų institutasFizinių ir technologijos mokslų centrasMokytojų rengimo institutasVytauto Didžiojo universiteta