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Electronically doped metal oxide nanocrystals exhibit tunable infrared localized surface plasmon resonances (LSPRs). Despite the many benefits of IR resonant LSPRs in solution processable nanocrystals, the ways in which the electronic structure of the host semiconductor material impact metal oxide LSPRs are still being investigated. Semiconductors provide an alternative dielectric environment than metallically bonded solids, such as noble metals, which can impact how these materials undergo electronic relaxation following photoexcitation. Understanding these differences is key to developing applications that take advantage of the unique optical and electronic properties offered by plasmonic metal oxide NCs. Here, we use the two-temperature model in conjunction with femtosecond transient absorption experiments to describe how the internal temperature of two representative metal oxide nanocrystal systems, cubic WO 3−x and bixbyite Sn-doped In 2 O 3 , change following LSPR excitation. We find that the low free carrier concentrations of metal oxide NCs lead to less efficient heat generation as compared to metallic nanocrystals such as Ag. This suggests that metal oxide NCs may be ideal for applications wherein untoward heat generation may disrupt the application's overall performance, such as solar energy conversion and photonic gating.
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Coherent Networks of Si Nanocrystals: Tunable Collective Resonances with Narrow Spectral Widths
The ultralong coherent networks of Si nanocrystals (NCs) via lattice‐enhanced dipole–dipole coupling and the formation of disordered arrays of phase‐correlated field hotspots are studied. Such arrays occur in structures consisting of Si NCs randomly positioned inside long strips that are periodically repeated. The theoretical results predict the formation of all‐dielectric coherent networks of Si NCs, formed via in‐phase coupling of the resonances generated by diffraction of light. Such networks are extended along the lengths of the strips while supporting high field enhancement associated with the phase‐correlated chains of field hotspots between the nanocrystals. It is shown that these phenomena occur at the wavelengths where the Rayleigh anomaly condition is satisfied. Under this condition the electric field is squeezed between two field‐impenetrable regions, causing efficient concentration of electromagnetic energy along the disordered arrays of Si NCs in each strip. The results show that these arrays act as coherently assembled units that are efficiently coupled with the lattice modes, forming highly tunable collective resonances with spectral widths less than 5 nm. These results pave the way for all‐dielectric‐tunable optical filters with very small losses and near‐perfect reflectivity and laser systems based on Si NCs.
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- Award ID(s):
- 1917544
- PAR ID:
- 10214532
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Photonics Research
- Volume:
- 2
- Issue:
- 4
- ISSN:
- 2699-9293
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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