Lithuanian Journal of Physics article / Lietuvos fizikos žurnalo straipsnis

SUM-FREQUENCY GENERATION AND AMPLIFICATION PROCESSES IN SEMICONDUCTOR SUPERLATTICES
Vladislovas Čižas^a, Natalia Alexeeva^a, Kirill Alekseev^a, and Gintaras Valušis^a,^b
^aDepartment of Optoelectronics, Center for Physical Sciences and Technology, Saulėtekio 3, 10257 Vilnius, Lithuania
^bPhotonics and Nanotechnology Institute, Faculty of Physics, Vilnius University, Saulėtekio 3, 10257 Vilnius, Lithuania
Email: vladislovas.cizas@ftmc.lt

Received 27 September 2023; accepted 28 September 2023

Semiconductor superlattices are very well-known structures due to their specific electron transport properties, making them extremely attractive to be employed in electronic or optoelectronic devices. The interest in such structures has been recently additionally stirred up due to the first successful experimental demonstration of parametric gain in GaAs/AlGaAs superlattices, resulting in the generation of harmonics, half-harmonics and fractional harmonics. This invention paves the way for a successful realization of superlattice-based generators and amplifiers up to the terahertz frequency range. Despite the emerging experimental results and decade-long theoretical research, unresolved aspects, related to the physical processes inside the superlattices, persist. Lately, the biasing effect was extensively analysed for the case of degenerate processes in the superlattice; however, the non-degenerate case was left out of frame until now. Within this research, we further expand the boundaries of previous investigation by exploring the differences of non-degenerate processes. The study uncovers the asymmetry appearance of the probe field vs. relative phase dependences as well as the possibility of parametric fractional frequency generation. Finally, the concept of energy reflow between two participating probes is predicted and discussed.
Keywords: superlattice, non-degenerate process, parametric gain, Bloch gain

SUMINIO DAŽNIO GENERAVIMO IR STIPRINIMO PROCESAI PUSLAIDININKINĖSE SUPERGARDELĖSE
Vladislovas Čižas^a, Natalia Alexeeva^a, Kirill Alekseev^a, Gintaras Valušis^a,^b

^aFizinių ir technologijos mokslų centro Optoelektronikos skyrius, Vilnius, Lietuva
^bVilniaus universiteto Fizikos fakulteto Fotonikos ir nanotechnologijų institutas, Vilnius, Lietuva

Puslaidininkinės supergardelės dėl ypatingos struktūros ir elektronų pernašos pasižymi retais fizikiniais efektais, kurie leidžia kurti skirtingiausius prietaisus, veikiančius terahercų (THz) dažnių ruože. Šiame darbe tiriamos puslaidininkinių supergardelių aukštadažnio signalo stiprinimo galimybės neišsigimusiojo proceso metu. Skirtingai nuo ankstesnių darbų, kai tyrimui buvo naudotas mažo signalo modelis, šiame darbe buvo panaudotas didelio signalo stiprinimo modelis, kuris taikomas atvejams, kai generuojamo signalo elektrinio lauko stipris yra palyginamas su priešįtampio signalu. Gauti rezultatai palyginti su anksčiau atliktais išsigimusiųjų procesų skaičiavimais. Parodyta, kad neišsigimusiojo proceso atveju galimas parametrinis trupmeninių harmonikų generavimas. Taip pat parodyta, kad išsigimusiajam procesui būdingas dominuojančio generavimo mechanizmo perėjimas iš Blocho stiprinimo į parametrinį ne tik išlieka ir neišsigimusiojo proceso atveju, bet ir sustiprėja. Galiausiai parodytas energijos pertekėjimas tarp dviejų neišsigimusiajame procese dalyvaujančių skirtingo dažnio elektrinių laukų. Gauti rezultatai, tikėtina, leis geriau suprasti supergardelėje vykstančius generavimo ir (ar) stiprinimo procesus, leisiančius sukurti mažą, našų, ir galingą THz dažnių ruožo šaltinį ar stiprintuvą.

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