A robust and tuneable mid-infrared optical switch enabled by bulk Dirac fermions.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 28106037.
- Also identified by DOI 10.1038/ncomms14111 and PMC identifier 5263875.
- 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
Pulsed lasers operating in the mid-infrared (3-20 μm) are important for a wide range of applications in sensing, spectroscopy, imaging and communications. Despite recent advances with mid-infrared gain platforms, the lack of a capable pulse generation mechanism remains a significant technological challenge. Here we show that bulk Dirac fermions in molecular beam epitaxy grown crystalline Cd<sub>3</sub>As<sub>2</sub>, a three-dimensional topological Dirac semimetal, constitutes an exceptional ultrafast optical switching mechanism for the mid-infrared. Significantly, we show robust and effective tuning of the scattering channels of Dirac fermions via an element doping approach, where photocarrier relaxation times are found flexibly controlled over an order of magnitude (from 8 ps to 800 fs at 4.5 μm). Our findings reveal the strong impact of Cr doping on ultrafast optical properties in Cd<sub>3</sub>As<sub>2</sub> and open up the long sought parameter space crucial for the development of compact and high-performance mid-infrared ultrafast sources.