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Bloch gain in dc-ac-driven semiconductor superlattices in the absence of electric domains | | Timo Hyart
; Kirill N. Alekseev
; Erkki V. Thuneberg
; | | Date: |
19 Dec 2007 | | Abstract: | We study theoretically the feasibility of amplification and generation of
terahertz radiation in dc-ac-driven semiconductor superlattices in the absence
of electric domains. We find that if in addition to dc bias a strong THz pump
field is applied, Bloch gain profile for a small THz signal can be achieved
under conditions of positive static differential conductivity. Here the
positive differential conductivity arises, similarly to the case of
large-signal amplification scheme [H. Kroemer, cond-mat/0009311)], due to
modifications of dc current density caused by the application of high-frequency
ac field [K. Unterrainer extit{et al.}, Phys. Rev. Lett. extbf{76}, 2973
(1996)]. Whereas the sign of absorption at low and zero frequencies is
sensitive to the ac fields, the gain profile in the vicinity of gain maximum is
robust. We suggest to use this ac-induced effect in a starter for THz Bloch
oscillator. Our analysis demonstrates that the application of a short THz pulse
to a superlattice allows to suppress the undesirable formation of electric
domains and reach a sustained large-amplitude operation of the dc-biased Bloch
scillator. | | Source: | arXiv, 0712.3211 | | Services: | Forum | Review | PDF | Favorites | |
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