Lithuanian Journal of Physics article / Lietuvos fizikos žurnalo straipsnis

DEPOPULATION MECHANISM FOR INCOHERENT TERAHERTZ SOURCE – THz TORCH – BASED ON GaAsBi/GaAs QUANTUM WELL IN GaAs/AlGaAs PARABOLIC QUANTUM WELL
Mindaugas Karaliūnas^a, Andres Udal^b, and Gintaras Valušis^a
^aDepartment of Optoelectronics, Center for Physical Sciences and Technology, Saulėtekio 3, 10257 Vilnius, Lithuania
^bDepartment of Software Science, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia
Email: mindaugas.karaliunas@ftmc.lt

Received 29 November 2019; revised 7 February 2020; accepted 10 February 2020

Parabolic quantum wells (PQWs) are known as a promising candidate for a compact terahertz (THz) source. PQWs have equidistant subbands that can be designed to be separated by few meV to meet the THz frequency range. To enhance the efficiency and power of THz emission from PQWs, a new approach is proposed by employing depopulation of the lowest subbands of PQW. In this work, the theoretical analysis of an incoherent THz torch device is presented. The findings suggest that the introduction of narrower band-gap GaAsBi/GaAs rectangular quantum well within the GaAs/AlGaAs PQW can alter subbands arrangement to enable a faster depopulation mechanism exploiting LO phonon scattering. The calculated radiative power spectra show the increase of oscillator strength between the rearranged subbands of PQW due to the added GaAsBi rectangular potential. The increased intersubband radiative transition probability can lead to an efficient compact incoherent THz source – THz torch.

Keywords: terahertz emission, parabolic quantum well, GaAsBi/GaAs/AlGaAs nanostructures, incoherent THz source
PACS: 03.65.Ge, 73.21.Fg, 78.67.De, 33.20.Ea

DEPOPULIACIJOS MECHANIZMAS NEKOHERENTINIAM TERAHERCŲ ŠALTINIUI – THz ŽIBINTUI, PAGRĮSTAM GaAsBi/GaAs KVANTINE DUOBE PARABOLINĖJE GaAs/AlGaAs KVANTINĖJE DUOBĖJE
Mindaugas Karaliūnas^a, Andres Udal^b, Gintaras Valušis^a

^aFizinių ir technologijos mokslų centras, Vilnius, Lietuva
^bTalino technikos universitetas, Talinas, Estija

Parabolinės kvantinės duobės (PKD) yra žinomos kaip tinkama priemonė kompaktiškiems terahercų (THz) šaltiniams. PKD turi vienodais energiniais tarpais pasiskirsčiusias pajuostes, kurios gali būti išdėstytos taip, kad būtų atskirtos kelių meV energiniu atstumu, – tai atitinka THz dažnių ruožą. THz spinduliuotės iš PKD našumui ir galiai padidinti siūlomas naujas būdas išnaudojant žemiausių PKD pajuosčių depopuliaciją. Darbe pateikiama nekoherentinio THz žibinto kaip prietaiso teorinė analizė. Rezultatai rodo, kad siauresnės draustinių energijų juostos GaAsBi / GaAs stačiakampės duobės įterpimas į GaAs / AlGaAs PKD gali pakeisti pajuosčių išsidėstymą taip, kad būtų įjungiamas greitesnis depopuliacijos mechanizmas, paremtas LO fononų sklaida. Suskaičiuoti spindulinės galios spektrai atskleidžia osciliatoriaus stiprio padidėjimą tarp dėl pridėto GaAsBi stačiakampio potencialo persiskirsčiusių PKD pajuosčių. Išaugusi tarppajuostinio spindulinio šuolio tikimybė gali tapti našaus, kompaktiško, nekoherentinio THz šaltinio – THz žibinto – veikimo pagrindu.

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