Nanomedicine has attracted increasing attention in recent years, because it offers great promise to provide personalized diagnostics and therapy with improved treatment efficacy and specificity. In this study, we developed a gold nanostar (GNS) probe for multi-modality theranostics including surface-enhanced Raman scattering (SERS) detection, x-ray computed tomography (CT), two-photon luminescence (TPL) imaging, and photothermal therapy (PTT). We performed radiolabeling, as well as CT and optical imaging, to investigate the GNS probe's biodistribution and intratumoral uptake at both macroscopic and microscopic scales. We also characterized the performance of the GNS nanoprobe for in vitro photothermal heating and in vivo photothermal ablation of primary sarcomas in mice. The results showed that 30-nm GNS have higher tumor uptake, as well as deeper penetration into tumor interstitial space compared to 60-nm GNS. In addition, we found that a higher injection dose of GNS can increase the percentage of tumor uptake. We also demonstrated the GNS probe's superior photothermal conversion efficiency with a highly concentrated heating effect due to a tip-enhanced plasmonic effect. In vivo photothermal therapy with a near-infrared (NIR) laser under the maximum permissible exposure (MPE) led to ablation of aggressive tumors containing GNS, but had no effect in the absence of GNS. This multifunctional GNS probe has the potential to be used for in vivo biosensing, preoperative CT imaging, intraoperative detection with optical methods (SERS and TPL), as well as image-guided photothermal therapy.

Dynamic polarization control of light is essential for numerous applications ranging from enhanced imaging to materials characterization and identification. We present a reconfigurable terahertz metasurface quarter-waveplate consisting of electromechanically actuated micro-cantilever arrays. Our anisotropic metasurface enables tunable polarization conversion cantilever actuation. Specifically, voltage-based actuation provides mode selective control of the resonance frequency, enabling real-time tuning of the polarization state of the transmitted light. The polarization tunable metasurface has been fabricated using surface micromachining and characterized using terahertz time domain spectroscopy. We observe a ~230 GHz cantilever actuated frequency shift of the resonance mode, sufficient to modulate the transmitted wave from pure circular polarization to linear polarization. Our CMOS-compatible tunable quarterwaveplate enriches the library of terahertz optical components, thereby facilitating practical applications of terahertz technologies.

Terahertz perfect absorbers represent an essential photonic component for detecting, modulating, and manipulating terahertz radiation. We utilize single-layer H-shaped all-silicon arrays to demonstrate tunable ultra-broadband terahertz wave absorption. Experiment and simulation reveal near unity absorption at 1 THz, with a bandwidth of ∼913 GHz for ≥90% absorbance. The absorption is optically tunable, exhibiting a resonance frequency blueshift by 420 GHz, while the peak absorbance remains over 99%. The dynamic response upon optical excitation depends on the penetration depth of the pump beam in silicon, as demonstrated through simulations that take into account the depth dependence of the carrier concentration in the all-silicon metamaterial perfect absorber. Notably, our all-silicon and ultrabroadband metamaterial perfect absorber is compatible with CMOS processing, potentially facilitating the development of terahertz detectors. Furthermore, the demonstrated tunable response may find potential applications toward creating dynamic functional terahertz devices, such as modulators and switches.

We demonstrate nonlinear metamaterial split ring resonators (SRRs) on GaAs at terahertz frequencies. For SRRs on doped GaAs films, incident terahertz radiation with peak fields of ∼20 -160 kV/cm drives intervalley scattering. This reduces the carrier mobility and enhances the SRR LC response due to a conductivity decrease in the doped thin film. Above ∼160 kV/cm, electric field enhancement within the SRR gaps leads to efficient impact ionization, increasing the carrier density and the conductivity which, in turn, suppresses the SRR resonance. We demonstrate an increase of up to 10 orders of magnitude in the carrier density in the SRR gaps on semi-insulating GaAs substrate. Furthermore, we show that the effective permittivity can be swept from negative to positive values with increasing terahertz field strength in the impact ionization regime, enabling new possibilities for nonlinear metamaterials.Nonlinear metamaterials is a rapidly developing field of fundamental interest with significant technological implications spanning from microwave through the visible spectral ranges [1][2][3][4][5][6][7]. As with tunable and reconfigurable metamaterials [8,9], the combination of the metamaterial structure with the local environment is crucial. This is because significant nonlinearities result from local field enhancement within the active region of the subwavelength metamaterial elements which, in the case of split ring resonators, are the capacitive gaps. While the active volume of the enhanced gaps is small in comparison to the unit cell volume, the field enhancement can dominate volumetric effects leading to global nonlinearities enhanced by two to four orders of magnitude [5]. This, in turn, results in useful nonlinear effects at low incident fields.Advances in nonlinear metamaterials coincide with the development of high-field terahertz sources capable of generating electric fields sufficient to induce significant nonlinearities in conventional matter [10][11][12][13][14]. For example, in doped GaAs, highly nonlinear effects such as velocity saturation and impact ionization have been observed [11,14] at peak electric fields of several hundred kV/cm. Further, with metamaterial THz field enhancement to MV/cm fields an insulator-metal phase transition has been induced in vanadium dioxide, a prototypical correlated electron material [7].In this letter, we experimentally demonstrate a nonlinear response in metamaterial split ring resonators (SRRs) on n-type GaAs and semi-insulating (SI) GaAs at terahertz frequencies. The nonlinear response arises from THz electric field-induced carrier dynamics that increase or decrease the substrate conductivity upon which the SRR arrays are fabricated. This modifies the SRR electromagnetic response as a function of field strength. For peak incident THz fields (E in ) from ∼20-160 kV/cm, mobility saturation by intervalley scattering (IVS) dominates leading (for doped GaAs) to a conductivity decrease and a corresponding increase in the metamaterial oscillator strength. In this regime, e...

In this single-institution phase II study, administration of 100 mCi of 131I-m81C6 to recurrent malignant glioma patients followed by chemotherapy is associated with a median survival that is greater than that of historical controls treated with surgery plus iodine-125 brachytherapy. Furthermore, toxicity was acceptable. Administration of a fixed millicurie dose resulted in a wide range of absorbed radiation doses to the SCRC. We are now conducting a phase II trial, approved by the US Food and Drug Administration, using patient-specific 131I-m81C6 dosing, to deliver 44 Gy to the SCRC followed by standardized chemotherapy. A phase III multicenter trial with patient-specific dosing is planned.