Abstract-Quantifying the photothermal conversion efficiency of plasmonic nanoparticles by means of terahertz radiation

APL Photonics

 H. Breitenborn^,   J. Dong^,  R. Piccoli^,   A. Bruhacs^,   L. V. Besteiro^,  , Z. M. Wang^,   A. O. Govorov^,   L. Razzari^,   F. Vetrone^,   R. Naccache^,  R. Morandotti

(a) Schematic diagram of THz temperature measurements based on a THz-TDS system set in reflection geometry. The 786-nm NIR beam used to plasmonically heat the GNR dispersions is overlapped with the THz focusing spot. The power of the NIR illumination transmitted through the cuvette is recorded with a power meter. The inset depicts the THz raster-scans of the front- and back-side of the cuvette. During the scanning process, the THz beam is fixed and the cuvette moves together with the IR beam pixel-by-pixel. (b) Example of a recorded THz signal reflected from the cuvette. The well-separated first and second echoes after sparse deconvolution are also plotted, in which the influence of the “ringing” due to the ambient water vapor is eliminated. (c) Temperature-dependent reflectivity of the second THz echo as a function of temperature for GNR10. (d) Calibration curves featuring a linear relationship between THz amplitude and temperature for each of the GNR dispersions.

https://aip.scitation.org/doi/abs/10.1063/1.5128524

The accurate determination of the photothermal response of nanomaterials represents an essential aspect in many fields, such as nanomedicine. Specifically, photothermal cancer therapies rely on the precise knowledge of the light-to-heat transfer properties of plasmonic nanoparticles to achieve the desired temperature-induced effects in biological tissues. In this work, we present a novel method for the quantification of the photothermal effect exhibited by nanoparticles in aqueous dispersions. By combining the spatial and temporal thermal dynamics acquired at terahertz frequencies, the photothermal conversion efficiency associated with the geometry of the plasmonic nanoparticles can be retrieved in a noncontact and noninvasive manner. The proposed technique can be extended to the characterization of all those nanomaterials which feature a temperature-dependent variation of the refractive index in the terahertz regime.

Abstract-Invited Article: Ultra-broadband terahertz coherent detection via a silicon nitride-based deep sub-wavelength metallic slit

APL Photonics

A. Tomasino, R. Piccoli, Y. Jestin, S. Delprat1, M. Chaker,   M. Peccianti,   M. Clerici4, A. Busacca, L. Razzari,  R. Morandotti,

FIG. 1.3D sketch of the deep sub-λ slit (G) device embedded in a thin layer (T) of SiN, deposited on a quartz substrate. L and W are the length and the width of the metal pads, respectively.

https://aip.scitation.org/doi/abs/10.1063/1.5052628

We present a novel class of CMOS-compatible devices aimed to perform the solid-state-biased coherent detection of ultrashort terahertz pulses, i.e., featuring a gap-free bandwidth at least two decades-wide. Such a structure relies on a 1-µm-wide slit aperture located between two parallel aluminum pads, embedded in a 1-µm-thick layer of silicon nitride, and deposited on a quartz substrate. We show that this device can detect ultra-broadband terahertz pulses by employing unprecedented low optical probe energies of only a few tens of nanojoules. This is due to the more than one order of magnitude higher nonlinear coefficient of silicon nitride with respect to silica, the nonlinear material employed in the previous generations. In addition, due to the reduced distance between the aluminum pads, very high static electric fields can be generated within the slit by applying extremely low external bias voltages (in the order of few tens of volts), which strongly enhance the dynamic range of the detected THz waveforms. These results pave the way to the integration of solid-state ultra-broadband detection in compact and miniaturized terahertz systems fed by high repetition-rate laser oscillators and low-noise, low-voltage generators.

Abstract-Resonant nanoantennas for enhancing the interaction of terahertz radiation with nanomaterials

L. Razzari

https://ieeexplore.ieee.org/document/8364133/?denied

We present our investigation regarding the interaction of localized terahertz radiation with nanomaterials. Details about the design of metallic nanoantennas for THz field confinement will be given, together with some examples of applications.