Abstract-Terahertz pulse emission from GaInAsBi

Journal of Applied Physics

V. Pačebutasa, S. Stanionytė,  R. Norkus,  A. Bičiūnas, A. Urbanowicz,  A. Krotkus

https://aip.scitation.org/doi/abs/10.1063/1.5089855

Quaternary GaInAsBi alloy epitaxial layers were grown on InP substrates with 6% Bi. It was found that the thick layers remain fully strained. The measured carrier lifetimes were of the order of a few picoseconds. The terahertz (THz) emission was investigated using a GaInAsBi layer as an unbiased surface emitter and as a substrate for photoconductive antenna. It was observed that fabricated THz emitters were sensitive to the optical pulses with wavelengths longer than 2 μm. The demonstrated spectral characteristics of THz pulses obtained when using an Er-doped fiber laser for photoexcitation were comparable with those observed in other emitters used for THz-time-domain spectroscopy systems.

Abstract-THz-excitation spectroscopy technique for band-offset determination

V. Karpus, R. Norkus, R. Butkutė, S. Stanionytė, B. Čechavičius, A. Krotkus

Fig. 3 Experimental setup for THz excitation spectroscopy measurements.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-26-33807

The experimental THz-excitation spectroscopy technique for determining heterojunction band offsets is suggested. When photoexcited electrons gain sufficient energy to pass the potential barrier corresponding to a conduction band offset, an amplitude of THz-emission pulse sharply increases, which allows for direct measurements of the offset value. The technique is applied for determining GaAsBi-GaAs band offsets. The deduced conduction band offset of GaAsBi-GaAs heterojunction has about 45% of an energy gap difference at the Bi concentrations x <0.12 investigated.

© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Terahertz pulse generation from (111)-cut InSb and InAs crystals when illuminated by 1.55-μm femtosecond laser pulses

I. Nevinskas, K. Vizbaras, A. Trinkūnas, R. Butkutė, and A. Krotkus

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-42-13-2615

Terahertz (THz) pulse generation from p-InAs, p-InSb, and n-InSb epitaxial layers are investigated using 1.55-μm wavelength femtosecond laser pulses for photoexcitation. The samples are of (111) crystallographic orientation resulting in anisotropic photoconductivity. Experiments have shown that THz generation in InAs is mainly due to anisotropic photocurrent in the surface electric field while a dominant mechanism in InSb is optical rectification. At high optical excitation fluencies, InSb is more efficient than p-InAs. In the presence of an external magnetic field, (111) InSb has exhibited promising viability as an alternative to the photoconductive antenna emitter in a THz time-domain-spectroscopy (THz-TDS) system.

© 2017 Optical Society of America

Abstract-Terahertz radiation from an InAs surface due to lateral photocurrent transients

P. Cicėnas, A. Geižutis, V. L. Malevich, and A. Krotkus
https://www.osapublishing.org/ol/abstract.cfm?URI=ol-40-22-5164

We report on terahertz (THz) emission from a (111)-cut InAs crystal in the reflection and transmission directions, excited by femtosecond optical pulses in the direction of its surface normal. THz pulse amplitudes emitted from the crystal surface in this case were only ∼20% smaller than for optimal photoexcitation at a 45° angle. This observation evidences that THz emission from InAs is caused by lateral photocurrent transients appearing due to a crystal anisotropy rather than directly by the photo-Dember effect, which creates fast changing electric polarization perpendicular to the surface. Such a simple geometry of the photoexcitation could greatly enhance the fields of surface THz emitter applications.

© 2015 Optical Society of America

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Abstract-Physical mechanisms of terahertz pulse emission from photoexcited surfaces of tellurium crystals

A. Bičiūnas¹, A. Arlauskas¹, J. Adamonis¹, P. Cicėnas¹ and A. Krotkus¹
http://scitation.aip.org/content/aip/journal/jap/116/9/10.1063/1.4894514
1 Center for Physical Sciences and Technology, A. Goštauto 11, 01180 Vilnius, Lithuania
J. Appl. Phys. 116, 093102 (2014); http://dx.doi.org/10.1063/1.4894514

We report on terahertz (THz) emission from tellurium crystal surfaces excited by femtosecondoptical pulses. Measurements were performed on three differently cut Te samples and with different wavelength optical excitation pulses. THz pulse amplitude dependences on the azimuthal angle measured at various excitation wavelengths have evidenced that three different mechanisms are responsible for THz generation in tellurium: second order nonlinear optical rectification effect, dominating at lower excitation photon energies, as well as transverse and ordinary photo-Dember effects, which emerge at energies larger than 0.9 eV. The shapes of the azimuthal angle dependences were also explained by theoretical model.