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Transition metal dichalcogenides (TMDCs) with high refractive index at the near-infrared wavelengths are predicted to have superior performances in photonic devices compared with conventional semiconductors. Postdoctoral fellow Jingang Li and PhD student Rundi Yang investigated the optical waveguiding properties of colloidal MoS2 nanowires by scattering-type scanning near-field optical microscopy (s-SNOM). The combined experiments and simulations showed highly tunable waveguide modes, which can be modulated by nanowire thickness, incident wavelength, and environmental temperature, highlighting the potential for active optical components and integrated photonic devices. This work was published in Advanced Functional Materials
https://onlinelibrary.wiley.com/doi/10.1002/adfm.202312127 |
PhD students Brian Blankenship and Timon Meier, along with undergraduate Naichen Zhao, have developed a technique to image internal deformations in polymeric metamaterials using confocal microscopy. Many metamaterials are composed of complex micro- and nanoscale architectures that give these materials enhanced, and often unnatural material properties over their bulk counterparts. While SEM is commonly used for high-resolution imaging of such small-scale features, its limitations in probing deep within these materials hinders our ability to understand their internal behavior. In turn, we demonstrate an optical confocal microscopy-based approach that allows for high-resolution optical imaging of internal features, deformations and fracture processes in microscale metamaterials under mechanical load. The work has been published in Nano Letters, doi.org/10.1021/acs.nanolett.3c04421
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PhD students Timon Meier, Jacky Li, Stefanos Mavrikos and Brian Blankenship, in collaboration with former LTL PhD student Zacharias Vangelatos and Dr. Erden Yildizdag from Instabul Technical University, have demonstrated new ways to inverse design metamaterials with tailored elastic properties. The research introduces a methododology that combines automated modeling, FEA, multi-objective optimization, 2PP fabrication and experimental validation. Utilizing their flexible framework, they successfully developed metamaterials featuring both isotropic and auxetic properties, offering new potential in material science and engineering applications.
The work was published in npj Computational Materials, https://doi.org/10.1038/s41524-023-01186-2 |
The quantitative analysis of s-SNOM experiments usually relies on analytical models, whose accuracy can be impaired by simplifications made on the system. PhD student Rundi Yang and postdoctoral fellow Jingang Li developed a numerical approach to study the carrier dynamics in pump-probe near-field nanoscopy, which could directly simulate the time-resolved near-field response and bypass the limitations of the analytical models. This method provides a validated and versatile framework to investigate the carrier behaviors in a broad range of semiconductor materials. The work was published in Journal of Physical Chemistry C,
https://pubs.acs.org/doi/10.1021/acs.jpcc.3c06824 |
PhD Student Brian Blankenship develops a method for incorporating and imaging nanodiamonds containing NV centers into two photon polymerization structures. He then demonstrates how these particles can be used for taking precise measurements of temperature and magnetic field in microscale environments. This has significant applications in the field of quantum information science for building practical sensors that work at room temperature. The work has been published to Nano Letters,
https://pubs.acs.org/doi/epdf/10.1021/acs.nanolett.3c02251 |
PhD Students Brian Blankenship and Jacky Li develop a novel, neuromorphic sensor that relies on heating a substrate made out of the phase change material, vanadium dioxide. This sensor is shown to have several neuromorphic functionalities and capabilities such as memory, non-linear thresholding, and the potential for sending information via spike-encoding. This work has been published to Nano Letters, https://doi.org/10.1021/acs.nanolett.3c02681
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Biomimetic and Bioinspired designs have been investigated due to the advances in modeling, mechanics and experimental characterization of structural features of living organisms. The deep sea sponge Euplectella Aspergillum has been of interest due to its complex and hierarchical lattice structure. Former LTL PhD student Zacharias Vangelatos characterized and modeled the mechanical behavior of this sponge from a structural standpoint. Dr. Erden Yildizdag of Instabul Technical University and University of L'Aquila, Italy contributed on the FEA modeling. The research enabled a deeper understanding of Nature’s tailored hierarchy and the design of metamaterials. The work was reported in Extreme Mechanics Letters, https://doi.org/10.1016/j.eml.2023.102013.
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GHz femtosecond (fs) lasers have opened exciting new possibilities for engineering the physicochemical properties of materials. Former LTL PhD student and current LBNL post-doc Minok Park investigated the ablation dynamics of copper (Cu) by GHz fs bursts using in situ multimodal diagnostics; time-resolved scattering imaging, emission imaging, and emission spectroscopy. He showed that GHz fs bursts rapidly remove molten liquid Cu from the irradiated spot due to the recoil pressure exerted by following fs pulses. The insight gained will be critical in selecting optimal processing conditions. The work was done at LBNL with Professor Vassilia Zorba and Dr. Xianglei Mao. A detailed report was published in Science Advances
https://www.science.org/doi/10.1126/sciadv.adf6397 |
Nonlinear optical response of materials can provide powerful fingerprints of physicochemical properties, including crystallography, interfacial state, and carrier dynamics. Former LTL PhD student and postdoctoral fellow Yoonsoo Rho showed efficient second harmonic generation (SHG) nanoscopy for ZnO NWs using a SHG-active plasmonic nanotip. The experimental results combined with EM modeling and theoretical analysis suggest quantum mechanical nonlinear energy transfer between the tip and the sample. In terms of an application, this method could probe nanoscale corrosion of ZnO NW. Professor Seokjae Yoo of Inha U. in Korea developed the framework for the analysis of the experimental results. The work was done in collaboration with Dr. Daniel Durham and Professor Andy Minor of UCB MSE and supported by Laser Prismatics LLC under a DOE STTR/SBIR Phase II grant. The paper was published in Nano Letters,
https://pubs.acs.org/doi/pdf/10.1021/acs.nanolett.2c04748. |
The Laser Thermal Lab is directed by Prof. Costas P Grigoropoulos of the Mechanical Engineering Department, UC Berkeley. Current research interests are focused on laser materials interactions, nanomanufacturing and the fundamental study of microscale and nanoscale transport phenomena.
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For a full list go to the Publications/Journals
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