Nanoplasmonic‐Enhanced Spintronic Terahertz Emission

Abstract

operating at or below room temperature, Q is the order of meV, and this order corresponds to terahertz (THz) frequencies, which imply that future quantum devices working in THz frequency range will achieve low power consumption and high-speed performance. Electron spin, which is expected to break through the bottleneck of traditional microelectronic devices, has many excellent properties, [7,8] such as unique quantum properties, extremely low transmission energy consumption, high computing speed, high density storage, long spin relaxation time and fast response, nonvolatile, and so on. Spintronic devices can overcome the problems of heat dissipation and quantum effect caused by the miniaturization and integration of characteristic size based on the electronic charge properties. Along with the rapid progress of ultrafast laser technology and the increase of the device operating frequency, the development of ultrafast spintronic devices working in THz band is in full swing. [7,[9][10][11][12][13][14][15][16][17] When employing femtosecond laser pulses to illuminate magnetic materials, ultrafast spin currents can be produced. [18] High-efficiency conversion from spin currents to charge currents can be realized by using heterostructures such as topological materials or heavy metals. [19][20][21] THz emission spectroscopy can be used for contactless detect femtosecond Recently fashionable spintronic terahertz (THz) emission provides fresh pathways for contactless diagnosing femtosecond spin currents, opens the door for developing next-generation high-performance THz emitters, and accelerates the interdisciplinary of ultrafast THz optospintronics. However, one of the research highlights of ultrafast magnetism and the difficulty for further improving the spintronic THz emission productivity is how to efficiently reduce the energy consumption of all-optical magnetitic manipulation and improve the optical spin injection efficiency. Here, it is demonstrated, for the first time, gold nanorods (GNRs) plasmonic resonances can effectively increase the THz emission from W/CoFeB/Pt heterostructures by 140%. Systematic investigations of THz yield dependences on pumping laser incidence directionality, polarization, and the GNRs dimension parameter conclusively manifest the surface plasmon resonance validity. Theoretical interpretations combined with Drude-Lorentz model and numerical simulations semiquantitatively reproduce the experimental results. The observations prove that THz efficiency can be improved by nanophotonic technologies and may also spark inspiration for developing functional nano-THz optospintronic devices.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/admi.202101296.

Spintronics Based Terahertz Sources

“…The experimental results show that the intensity of the generated THz spectrum in the low-frequency band (0.1-0.5 THz) is enhanced by 2-3 orders of magnitude when the current is applied. Additionally, surface plasmonic resonance was also introduced to improve the performance for the STE by Liu et al [75]. They reported that gold nanorod (GNR) plasmonic resonance could effectively increase the terahertz emission of W/CoFeB/Pt heterostructures by 140%.…”

Spintronic terahertz emitters with unidirectional radiation

“…Then terahertz (THz) waves with polarization perpendicular to the magnetization direction of the FM layer will be radiated 3 . Spintronic terahertz emission with high efficiency belongs to the field of light-matter interaction in physics, and many efforts have been paid to improve the efficient THz emission of STEs [4][5][6] . However, most of these efforts aimed to the THz generation process, and little research was targeted at the control and modulation the THz waves generated by the STE to improve the THz emission process.…”

Coupling Broadband Terahertz Dipoles to Microscale Resonators

“…Furthermore, the quasi-two-dimensional geometry of the emitter allows for a direct emitter patterning ,,,− or a coupling of the emitter surface to metallic microstructures , and metasurfaces, , aiming for a spectral and angular tuning of the emitted radiation, an improved excitation or outcoupling efficiency, or enhanced sensitivity in local THz spectroscopy . Up to now, spectral tunability by employing two-dimensional resonators and antennas combined with large-area illumination of the spintronic emitter yielded only moderate effects.…”