Centro de Investigaciones en Optica, Leon, Mexico
September 17, 2019 @ 11:00am
Two-photon absorption spectroscopy and anisotropy of silicon quantum dots and bulk semiconductors
Brandon J. Furey1
1University of Texas at Austin
Nanocrystalline silicon (Si) exhibits optical properties of quantum dots (SiQDs) that differ from bulk Si, including efficient emission of photoluminescence (PL). The peak PL wavelength varies with the size of the SiQDs. In addition, SiQDs are biologically inert and thus have potential applications in bioimaging. Recent research also shows that they can potentially be useful for cancer therapy by selectively targeting cancer cells and disrupting them with shock waves from collapsing bubbles formed when the SiQDs are strongly excited and heated to very high temperatures. For biological theranostic applications, it is preferable to excite the SiQDs by two-photon absorption (2PA); this allows excitation with lower-energy infrared photons which have deeper penetration depth in biological samples, and enables localizing the excitation volume in 3D by focusing the beam and exploiting the nonlinear intensity dependence of 2PA. We seek to map the size- and spectral-dependence of 2PA in SiQDs to identify spectral resonances using two-photon induced PL and pump-probe modulation spectroscopy (PPMS). We also study 2PA spectra and anisotropy in bulk Si (and other semiconductors) using z-scan and PPMS and are developing a model for relating the bulk response to the nanocrystalline response.
Link to host institution: https://www.cio.mx/
Brandon J. Furey 