Ultra-high modulation depth exceeding 2,400% in optically controlled topological surface plasmons.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 26514372.
- Also identified by DOI 10.1038/ncomms9814 and PMC identifier 4640142.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Modulating light via coherent charge oscillations in solids is the subject of intense research topics in opto-plasmonics. Although a variety of methods are proposed to increase such modulation efficiency, one central challenge is to achieve a high modulation depth (defined by a ratio of extinction with/without light) under small photon-flux injection, which becomes a fundamental trade-off issue both in metals and semiconductors. Here, by fabricating simple micro-ribbon arrays of topological insulator Bi2Se3, we report an unprecedentedly large modulation depth of 2,400% at 1.5 THz with very low optical fluence of 45 μJ cm(-2). This was possible, first because the extinction spectrum is nearly zero due to the Fano-like plasmon-phonon-destructive interference, thereby contributing an extremely small denominator to the extinction ratio. Second, the numerator of the extinction ratio is markedly increased due to the photoinduced formation of massive two-dimensional electron gas below the topological surface states, which is another contributor to the ultra-high modulation depth.