Terahertz Radiation Modulated by Confinement of Picosecond Current Based on Patterned Ferromagnetic Heterostructures

Jin, Zuanming; Zhang, Shunnong; Zhu, Weiren; Li, Qin; Zhang, Wenjie; Zhang, Zongzhi; Lou, Shitao; Dai, Yong; Lin, Xian; Ma, Guohong; Yao, Jianquan

doi:10.1002/pssr.201900057

Cited by 29 publications

(31 citation statements)

References 40 publications

(58 reference statements)

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“…Our findings here are distinct from past works, which only focused on the amplitude modulation and the spectral shift of the terahertz waves from the stripe-patterned terahertz emitters. 38,47 Instead, our results clearly show that the directions parallel and perpendicular to the stripes define a set of canonical coordinates, in which the terahertz waveforms of E ∕∕ and E ⊥ are decoupled from each other and possess a broadband quarter-wave phase difference. This is the key for the generation and manipulation of the chiral terahertz waves.…”

Section: Resultsmentioning

confidence: 74%

“…Clearly, the perpendicular electric-field amplitude E ⊥ is strongly suppressed compared to E ∕∕ , which is consistent with previous work. 38,47 The results of the peak-to-peak amplitude V pp [see Figs. 2(a) and 2(b)] as a function of θ H are summarized in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…2(d), which displays identical spectral shapes for each polarization, although the spectrum of E ⊥ is blue-shifted compared to E ∕∕ . 38,47 The coherent detection of EOS allows us to retrieve the phase information, and, most interestingly, the phase difference (φ ⊥ − φ ∕∕ ) stays close to AEπ∕2 throughout the entire spectrum [see Fig. 2(e)].…”

Section: Resultsmentioning

confidence: 99%

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Active spintronic-metasurface terahertz emitters with tunable chirality

et al. 2021

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The ability to generate and manipulate broadband chiral terahertz waves is essential for applications in material imaging, terahertz sensing, and diagnosis. It can also open up new possibilities for nonlinear terahertz spectroscopy and coherent control of chiral molecules and magnetic materials. The existing methods, however, often suffer from low efficiency, narrow bandwidth, or poor flexibility. Here, we propose a novel type of laser-driven terahertz emitters, consisting of metasurface-patterned magnetic multilayer heterostructures, that can overcome the shortcomings of the conventional approaches. Such hybrid terahertz emitters combine the advantages of spintronic emitters for being ultrabroadband, efficient, and highly flexible, as well as those of metasurfaces for the powerful control capabilities over the polarization state of emitted terahertz waves on an ultracompact platform. Taking a stripe-patterned metasurface as an example, we demonstrate the efficient generation and manipulation of broadband chiral terahertz waves. The ellipticity can reach >0.75 over a broad terahertz bandwidth (1 to 5 THz), representing a high-quality and efficient source for few-cycle circularly polarized terahertz pulses with stable carrier waveforms. Flexible control of ellipticity and helicity is also demonstrated with our systematic experiments and numerical simulations. We show that the terahertz polarization state is dictated by the interplay between laser-induced spintronic-origin currents and the screening charges/ currents in the metasurfaces, which exhibits tailored anisotropic properties due to the predesigned geometric confinement effects. Our work opens a new pathway to metasurface-tailored spintronic emitters for efficient vector-control of electromagnetic waves in the terahertz regime.

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Section: Resultsmentioning

confidence: 74%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Active spintronic-metasurface terahertz emitters with tunable chirality

et al. 2021

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“…Anisotropic emission was observed with higher intensity for the perpendicular configuration and a blue shift in frequency compared to the parallel configuration. Further, modulation of THz radiation in terms of magnitude, bandwidth and center frequency was achieved based on W/CoFeB/Pt stripe patterns [51]. The patterns had dimensions of 5 μm width and 5 μm spacing (see Figure 9, upper panel).…”

Section: Future Perspectives Of Thz Spintronic Emittersmentioning

confidence: 99%

“…By changing the angle between the applied magnetic field and the stripe direction, modulation of the THz emission was measured. Interestingly, Jin et al [51] attributed this effect to nanoconfinement of the charge current due to nanopatterning. For a specific configuration of stripe and magnetic field at 90°, the spatial separation of the photo-induced positive and negative charges accumulate and then create a nonequilibrium electric potential U(t) at the edge of the stripe.…”

Section: Future Perspectives Of Thz Spintronic Emittersmentioning

confidence: 99%

THz spintronic emitters: a review on achievements and future challenges

2020

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The field of THz spintronics is a novel direction in the research field of nanomagnetism and spintronics that combines magnetism with optical physics and ultrafast photonics. The experimental scheme of the field involves the use of femtosecond laser pulses to trigger ultrafast spin and charge dynamics in thin films composed of ferromagnetic and nonmagnetic thin layers, where the nonmagnetic layer features a strong spin–orbit coupling. The technological and scientific key challenges of THz spintronic emitters are to increase their intensity and to shape the frequency bandwidth. To achieve the control of the source of the radiation, namely the transport of the ultrafast spin current is required. In this review, we address the generation, detection, efficiency and the future perspectives of THz emitters. We present the state-of-the-art of efficient emission in terms of materials, geometrical stack, interface quality and patterning. The impressive so far results hold the promise for new generation of THz physics based on spintronic emitters.

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Qualitative Identification of the Spin‐to‐Orbital Conversion Mechanism Modulated by Rare‐Earth Nd, Gd, and Ho Metals via Terahertz Emission Measurements

Liu,

Jiang,

Zhao

et al. 2024

Adv Funct Materials

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It is crucial to study the materials that could effectively facilitate the inter‐conversion between charge, spin, and orbital degrees of freedom. In this work, the conversion among these three types of degrees of freedom in Pt/CoFeB/rare‐earth (RE, represents Nd, Gd, and Ho)/Ti multilayers is manipulated. Through terahertz (THz) emission measurements, it is found that the spin current induced by a femtosecond laser is converted into an orbital current via the spin‐orbit coupling of the RE layer. Notably, the light RE (Nd) and heavy RE (Gd and Ho) induce the orbital current with opposite polarization directions, ultimately leading to a weakening or enhancement of the THz emission intensity, respectively. Moreover, the fast Fourier transform reveals that Gd exerts the most significant influence on increasing the whole THz spectrum within the Pt/CoFeB/RE/Ti structure. The findings of RE‐modulated spin‐to‐orbital conversion provide valuable insights into the fundamental transport mechanism of the orbital current.

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Terahertz Radiation Modulated by Confinement of Picosecond Current Based on Patterned Ferromagnetic Heterostructures

Cited by 29 publications

References 40 publications

Active spintronic-metasurface terahertz emitters with tunable chirality

Active spintronic-metasurface terahertz emitters with tunable chirality

THz spintronic emitters: a review on achievements and future challenges

Qualitative Identification of the Spin‐to‐Orbital Conversion Mechanism Modulated by Rare‐Earth Nd, Gd, and Ho Metals via Terahertz Emission Measurements

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