Infrared Optical-Field-Driven Luminescence in Quantum Dots

A recent study on CdSe-CdS core-shell colloidal quantum dots (QDs) showed that extreme electric fields from ultrafast THz-frequency electromagnetic pulses alone can produce QD luminescence [1, 2]. Unlike multi-photon absorption, which occurs at much higher optical frequencies, such emission was shown to be associated with large energy shifts of the absorption edge (more than 25%) – much like electro-luminescence (EL) driven by a quasi-DC field. While details of the mechanism of THz driven-EL are still under investigation, the effects of high optical electric fields of mid- to long- wavelength infrared (IR) radiation on the optical properties of QDs remain largely unexplored. To expand our understanding of the responses of QDs to extreme optical fields, we investigated the interaction of visible bandgap QD materials with sub-picosecond infrared-frequency pulses in the 3.5 to 12 micron wavelength range, at electric field levels that exceeded 1 MV/cm. We observed significant luminescence, resulting in up-conversion of the IR light to visible wavelengths, throughout the IR range that we explored. Preliminary results suggests similar EL induced by strong THz and IR fields.

[1] B.C. Pein et al., Nano Lett. 17, 5375 (2017).
[2] https://doi.org/10.1021/acs.nanolett.9b03342.