Optically pumped spintronic terahertz emitters (STEs) have, in less than a decade, strongly impacted terahertz (THz) source technology, by the combination of their Fourier‐limited ultrafast response, their phononless emission spectrum and their wavelength‐independent operation. However, the intrinsic strength of the inverse spin Hall effect governing these devices introduces a challenge: the optical‐to‐terahertz conversion efficiency is considerably lower than traditional sources. It is therefore primordial to maximize at least their electromagnetic efficiency independently of the spin dynamics at play. Using a rigorous time‐domain treatment of the electromagnetic generation and extraction processes, an optimized design is presented and experimentally confirmed. With respect to the strongest reported spintronic THz emitters it achieves a 250% enhancement of the emitted THz field and therefore an 8 dB increase of emitted power. This experimental achievement brings STE close to the symbolic barrier of mW levels. The design strategy is generically applicable to any kind of ultrafast spin‐to‐charge conversion (S2C) system. On a broader level, our work highlights how a rigorous handling of the purely electromagnetic aspects of THz spintronic devices can uncover overlooked aspects of their operation and lead to substantial improvements.

In this work, we propose a sensor based on Tamm plasmonic resonance; the structure is composed of gold nanoribbons deposited on a Distributed Bragg Reflector (DBR) (SiO 2 /Si 3 N 4 ) 6 .We have enhanced the sensitivity of our sensor from 40 nm/RIU to 200 nm/RIU for a refractive index change of 1% by replacing the last layer of Si 3 N 4 in contact with gold with porous Si 3 N 4 with a porosity of p = 40%.

In this article, we introduce a gas sensor concept consisting of a nanostructured gold grating coupled with a distributed Bragg reflector (DBR). This coupling makes it possible to obtain plasmonic Tamm states, where excitation is possible at normal incidence and does not require the use of the Kretschmann configuration. Through parameters optimization of the gold nanostructured grating, we achieved well-defined and localized Tamm resonances between the gold nanostructured grating and the distributed Bragg reflector composed of SiO2/Si3N4 . To exploit the spatial confinement of the energy of the Tamm states in order to measure the change in refractive index, we propose three configurations, in which we substitute the last nitride layer in the Bragg reflector with porous materials. In the first configuration, we use a porous nitride portion with 30% porosity, producing sensitivity S=170 nm/RIU and figure of merit FOM=27.1 RIU-1 . In the second configuration, we use a porous nitride layer with a porosity of 30% ( S=175 nm/RIU and FOM=27.3 RIU-1 ). Finally, the third configuration adopts a 66% porous silicon layer ( S=268 nm/RIU and FOM=43.6 RIU-1 ). These values show the significant potential for sensing applications.

We numerically explore optical Tamm states (OTS) supported by a photonic structure composed of a nanostructured metallic layer on top of a distributed Bragg reflector (DBR). Several polarizations, incidences and patterning are assessed to map OTS and their properties. We then gain magnetic control of the OTS by adding a cobalt layer below the metal pattern and switching its magnetization. This control, widely used in plasmonics, takes advantage of the Transverse Magneto-Optical Kerr Effect (TMOKE). The simulated TMOKE signal of this structure has an amplitude of the order of 10 -3 and, compared to conventional magnetoplasmonic structures, provides high energy confinement between the metal stripes. In addition to the opening of the metallic layer that allows better access of the analyte to the sensitive area, this paves the way for higher sensitivities in bio- and chemical sensing applications.

The boom in terahertz technologies of the last few decades is now not limited to the use of electric charge, but also fully exploits spin. Revolutionary spintronic terahertz emitters (STEs) offer versatile usage under a wide range of visible and infrared excitation wavelengths, arbitrary reflection/transmission excitation geometries, and utilization with most femtosecond oscillators and amplifiers. STE emission results in a 30THz-broad and gapless spectrum with easily controllable polarization. However, the optical-to-terahertz conversion efficiency is lower than traditional THz sources. Here, we demonstrate experimentally the enhancement of factor 6 in STEs power, which is the highest improvement nowadays. We integrate STEs with our optimized photonic cavities and provide procedures on how to dramatically increase efficiency.