Monday, November 18, 2019

Abstract-Graphene-based crack lithography for high-throughput fabrication of terahertz metamaterials

Sejeong Won, Hyun-June Jung, Dasom Kim, Sang-Hun Lee, DoVan Lam, Hyeon-Don Kim, Kwang-Seop Kim, Seung-Mo Lee, Minah Seo, Dai-Sik Kim, Hak-Joo Lee, Jae-Hyun Kim,

Unlabelled figure

Terahertz (THz) nanoantennas have significant potential for versatile applications in THz spectroscopy because of their capability for strong electromagnetic field localization. Electron-beam lithography or focused ion beam machining is typically employed to fabricate nanoantenna structures. These nanolithography methods present limitations in the widespread utilization of THz nanoantennas because of their high cost and low productivity. In this work, we proposed graphene-based crack lithography as a high throughput fabrication method for nanoantenna structures. A double-layer graphene interface was introduced to enable independent control of the nanoantenna dimensions and provide graphene-based nanoantenna structures. We analyzed the underlying mechanism of graphene-based cracking and developed an analytical model governing the geometric parameters of the fabricated nanostructures. As a vital application of the fabricated nanoantenna structures, we demonstrated the highly sensitive detection of d-Glucose molecules. Graphene-based crack lithography can provide a cost-effective method for generating nanoantenna structures with the desired characteristics and can accelerate the development of practical applications of electromagnetic metamaterials.

Sunday, November 17, 2019

Abstract-Tunable THz Graphene Filter Based on Cross-In-Square-Shaped Resonators Metasurface

Anton Zaitsev, ,Alexander Grebenchukov, Mikhail Khodzitsky,

The tunable terahertz (THz) Fano-resonant filter based on hybrid metal-graphene metamaterial was proposed. The optical parameters of metasurface with unit cell in the form of a cross-shaped graphene sheet in the center of a square gold ring were simulated by the finite element method using a surface conductivity model of a graphene monolayer. The narrowband modulation of the transmission by varying the Fermi level of the graphene and the position of graphene cross inside the metal ring was demonstrated. Simulation results were well explained theoretically using a three-coupled oscillator model. The proposed device can be used as a narrowband filter in wireless THz communication systems and sensing applications.

Abstract-Ferromagnetic resonance isolator based on a photonic crystal structure with terahertz vortices

Gianni Portela, Victor Dmitriev, Daimam Zimmer,

A new terahertz isolator based on the ferromagnetic resonance effect is suggested and analyzed. A two-dimensional photonic crystal consisting of a square lattice of gallium arsenide rods has been employed in the design of the device. Incident electromagnetic waves interact with one magnetized ferrite rod and two stubs inserted in the photonic crystal structure, generating a vortex-like field profile in the ferrite rod. Electromagnetic signals propagating in the forward direction are transmitted with low insertion losses, while their propagation in the backward direction is not allowed due to the high losses of the ferrite rod operating at the ferromagnetic resonance regime. Computational simulations show that the operating bandwidth is equal to 0.87 GHz around the central frequency 106.6 GHz. In this frequency band, the insertion losses are lower than − 1.68 dB, the reflection levels are better than − 16 dB, and the isolation levels are greater than − 15 dB.

Saturday, November 16, 2019

Abstract- Metal-graphene hybridized plasmon induced transparency in the terahertz frequencies

Anqi Yu, Xuguang Guo, Yiming Zhu, Alexey V. Balakin, Alexander P. Shkurinov,

(a) The proposed split T-shape metal/dielectric/graphene structure. (b) The top view of the proposed structure.

In this work, metal-graphene hybridized plasmon induced transparency (PIT) is systematically studied in the proposed simple metal/dielectric/graphene system. The PIT effect is the result of the coupling between the bright dipolar modes excited in the graphene regions under the shorter metallic bars and the dark quadrupolar modes excited in the graphene regions under the longer metallic bars. The coupled Lorentz oscillator model is used to help explain the physical origin of the PIT effect. Other than being tuned by the distance and the lateral displacement of the orthogonal metallic bars, the coupling efficiency can be further enhanced by the in-phase coupling or quenched by the out-of-phase coupling between the adjacent unit cells. Reduced barrier thickness will result in the enhancement of the coupling strengths and the scaling down of the device. Finally, we show that the PIT window can be actively tuned by changing the Fermi energy of graphene. The proposed structure has potential applications in actively tunable THz modulators, sensors and filters.
© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-High-performance and compact broadband terahertz plasmonic waveguide intersection

Mingrui Yuan, Yanfeng Li, Yongchang Lu, Ying Zhang, Ziying Zhang, Xueqian Zhang, Xixiang Zhang, Jiaguang Hah, Weili Zhang

THz plasmonic waveguides ...

For terahertz (THz) integrated systems, an intersection between waveguides is inevitable and is often accompanied by considerable crosstalk and loss. Here, we propose and experimentally demonstrate a novel type of crossing with a footprint less than 0.2 × 0.2  mm2 for THz surface plasmon polariton waveguiding. With an optimized crossover structure, the measured loss of the intersection is as low as 0.89 dB/crossing, and the crosstalk is less than −19.06 dB/crossing at 0.55 THz. The proposed crossing structure is compact and has low loss and crosstalk within a broad band, which will pave the way for a wide range of new applications for THz integrated systems.

Friday, November 15, 2019

Abstract-On the effect of third-order dispersion on phase-matched terahertz generation via interfering chirped pulses

Spencer W. Jolly, Frederike Ahr, Koustuban Ravi, Nicholas H. Matlis, Franz X. Kärtner, and Andreas R. Maier
Chirp-and-delay experimental setup (a), identical to the previous work in Ahr et al. [18]. This HR-PR combination produces a train of pulses rather than two pulses of equal energy. A waveplate is used to match perfectly the polarization of the IR light to the PPLN crystal axis. The beam is matched to the aperture of the PPLN crystal using a telescope, the parameters of which depend on the PPLN aperture. A Teflon plate separates the drive laser from the generated THz at the output of the crystal, whose energy is detector using a pyroelectric detector (b). The frequency of the generated THz is verified using an interferometer (c).

High-energy narrowband terahertz (THz) pulses, relevant for a plethora of applications, can be created from the interference of two chirped-pulse drive lasers. The presence of third order dispersion, an intrinsic feature of many high-energy drive lasers, however, can significantly reduce the optical-to-THz conversion efficiency and have other undesired effects. Here, we present a detailed description of the effect of third-order dispersion (TOD) in the pump pulse on the generation of THz radiation via phase-matching of broadband highly chirped pulse trains. Although the analysis is general, we focus specifically on parameters typical to a Ti:Sapphire chirped-pulse amplification laser system for quasi-phase-matching in periodically-poled lithium niobate (PPLN) in the range of THz frequencies around 0.5 THz. Our analysis provides the tools to optimize the THz generation process for applications requiring high energy and to control it to produce desired THz waveforms in a variety of scenarios.
© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement