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Abstract The carrier excitation, relaxation, energy transport, and conversion processes during light‐nanocrystal (NC) interactions have been intensively investigated for applications in optoelectronics, photocatalysis, and photovoltaics. However, there are limited studies on the non‐equilibrium heating under relatively high laser excitation that leads to NCs sintering. Here, the authors use femtosecond laser two‐pulse correlation and in‐situ optical transmission probing to investigate the non‐equilibrium heating of NCs and transient sintering dynamics. First, a two‐pulse correlation study reveals that the sintering rate strongly increases when the two heating laser pulses are temporally separated by <10 ps. Second, the sintering rate is found to increase nonlinearly with laser fluence when heating with ≈700 fs laser pulses. By three‐temperature modeling, the NC sintering mechanism mediated by electron induced ligand transformation is suggested. The ultrafast and non‐equilibrium process facilitates sintering in dry (spin‐coated) and wet (solvent suspended) environments. The nonlinear dependence of sintering rate on laser fluence is exploited to print sub‐diffraction‐limited features in NC suspension. The smallest feature printed is ≈200 nm, which is ≈¼ of the laser wavelength. These findings provide a new perspective toward nanomanufacturing development based on probing and engineering ultrafast transport phenomena in functional NCs.
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Reducing feature size in femtosecond laser ablation of fused silica by exciton-seeded photoionization
We demonstrate a method of laser ablation with reduced feature size by using a pair of ultrashort pulses that are partially overlapped in space. By tuning the delay between the two pulses, features within the overlapping area are obtained on the surface of fused silica. The observed dependence of the feature position on delays longer than the free-carrier lifetime indicates an ionization pathway initiated by self-trapped excitons. This method could be used to enhance the resolution of laser-based lithography.
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- Award ID(s):
- 1846671
- PAR ID:
- 10140822
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Optics Letters
- Volume:
- 45
- Issue:
- 7
- ISSN:
- 0146-9592; OPLEDP
- Format(s):
- Medium: X Size: Article No. 1994
- Size(s):
- Article No. 1994
- Sponsoring Org:
- National Science Foundation
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