Showing posts with label black phosphorus. Show all posts
Showing posts with label black phosphorus. Show all posts

Tuesday, April 21, 2020

NSF Funds Multidisciplinary U of A Team to Improve Imaging Technology


From left: Magda El-Shenawee, principal investigator and professor of electrical engineering; Hugh Churchill, assistant professor of physics; and Robert Coridan, assistant professor of chemistry.
https://news.uark.edu/articles/52782/nsf-funds-multidisciplinary-u-of-a-team-to-improve-imaging-technology

University of Arkansas researchers received funding from the National Science Foundation to advance imaging technology that could help improve breast cancer treatment, protect airline travelers and advance the nation's 5G network.
Three professors were awarded $456,070 from the NSF to support their research into high-frequency antennas, which are a critical part of imaging technology. The team is composed of Magda El-Shenawee, principal investigator and professor of electrical engineering, Hugh Churchill, assistant professor of physics, and Robert Coridan, assistant professor of chemistry.
Researchers are working to create more effective terahertz photoconductive antennas by using a new material — black phosphorus. The research includes three main components, modeling, fabrication, and measurements.
Terahertz radiation falls between infrared and microwave radiation on the electromagnetic spectrum. It is useful for a variety of applications because it can penetrate non-conductive materials like clothing, cardboard and wood, however, its penetration of body tissue is in micrometers.
El-Shenawee's research has been focused for years on terahertz technology to improve imaging for use in identifying breast cancer tumor margins to help doctors make better decisions when assigning treatments. She previously developed terahertz antennas based on plasmonic nano-disks using low temperature Gallium Arsenide (GaAs). The idea to use black phosphorous in this new project came from Churchill, a physicist whose research interests include 2-D semiconductors, like black phosphorous. The collaboration began through a project made possible by the Chancellor's Fund for Innovation and Collaboration.
That collaboration allowed the pair to examine whether black phosphorous would work as a component of terahertz antennas, and computer simulations suggested it could be 10 times more effective than current technology. They'll also work with dielectric nanoparticle coatings, which Coridan uses in his solar cell research, to increase the efficiency of the new antenna.  
"We want to maximize the fraction of the incident light that is absorbed in the black phosphorous layer," Coridan said. "Adding a layer of nanoparticles will scatter light in directions that will make the black phosphorous seem to be thicker than it is. This passive structure increases the light absorption in the black phosphorous layer, while reducing reflection or absorption of other parts of the device."
Black phosphorous could also increase the speed of communication between devices on the 5G network, which has a wide variety of applications. 
"If your car has 5G technology, it has an antenna to communicate with other vehicles to detect its location. This detection allows the vehicle to stop automatically when it needs to, so improving the signal speed between these devices can help vehicles sense objects faster, reducing the chances of an accident," El-Shenawee said.
El-Shenawee said the project is a unique collaboration.
"This is my first time working with three different disciplines on a promising idea like this one," El-Shenawee said. "The three of us think differently, but it is quite interesting."
Churchill said the team is excited and grateful for the support they have received.
"I would like to express our team's gratitude for the phenomenal institutional boost our team received to catalyze this interdisciplinary effort, which included Chancellor's Fund support to obtain preliminary data and Arkansas Biosciences Institute support to obtain crucial equipment to test our novel devices," he said.

OUTREACH TARGETING UNDERREPRESENTED STUDENTS

The NSF funding will also support outreach initiatives geared toward underrepresented K-12 students and their teachers in Arkansas.
"When we presented the concepts of antennas and wave traveling to students in K-12 summer camps, they were very excited," El-Shenawee said. 
The camps are coordinated by Amy Warren, assistant director of outreach and summer programs in the College of Engineering.
El-Shenawee said the team will work with Warren on creating unique opportunities and activities for underrepresented students in Arkansas.
"Even the youngest students are familiar with technologies that utilize antennas, but most do not gain any understanding of the concepts underlying this technology until high school," Warren said. "The outreach initiatives will give K-8 teachers and students the tools needed to teach these complex concepts earlier."
El-Shenawee, Churchill and Coridan said they hope this will encourage students to consider majoring in science and engineering-based fields.
The team hopes to have the project completed by 2023.

Monday, January 27, 2020

Abstract-Comparative investigation of two-dimensional materials for the design of non-reciprocal antennas in terahertz band


Aymen Hlali, Zied Houaneb, Hassen Zairi,

Fig. 2. Variation of BP conductivity versus frequency: (a) Real and (b) imaginaryFig. 5. Structure of the candidate antennaFig. 3. Equivalent model of single-layer black phosphorus

https://www.sciencedirect.com/science/article/pii/S0030402620301017

Two-dimensional materials have already demonstrated their potentials in the making of non-reciprocal components. In this paper, we compared the performance of terahertz non-reciprocal antennas made up of magnetized graphene, black phosphorus, and hybrid structure in a view to choose a suitable material for effective non-reciprocal THz antennas. A classical patch antenna is used as the reference antenna to effect the comparisons. The performances of these antennas are analyzed and it was found that the proposed strategy of hybridization of graphene and BP shows better electromagnetic performance with their counterparts. The response of the antenna can be controlled conveniently by adjusting the chemical potential of graphene and it is significantly decreased by adjusting the electron doping of black phosphorus.

Friday, September 20, 2019

Abstract-Negative terahertz conductivity and amplification of surface plasmons in graphene–black phosphorus injection laser heterostructures



V. Ryzhii, T. Otsuji, M. Ryzhii, A. A. Dubinov, V. Ya. Aleshkin, V. E. Karasik, and M. S. Shur

https://journals.aps.org/prb/accepted/9b078O08Pf81783789dd94946bdb6e0d63736de90

We propose and evaluate the heterostructure based on the graphene-layer (GL) with the lateral electron injection from the side contacts and the hole vertical injection via the black phosphorus layer (PL) (p+P-PL-GL heterostructure). Due to a relatively small energy of the holes injected from the PL into the GL (about 100 meV, smaller than the energy of optical phonons in the GL which is about 200 meV), the hole injection can effectively cool down the two-dimensional electron-hole plasma in the GL. This simplifies the realization of the interband population inversion and the achievement of the negative dynamic conductivity in the terahertz (THz) frequency range enabling the amplification of the surface plasmon modes. The later can lead to the plasmon lasing. The conversion of the plasmons into the output radiation can be used for a new types of the THz sources.

Thursday, June 13, 2019

Abstract-Tunable asymmetric spin splitting by black phosphorus sandwiched epsilon-near-zero-metamaterial in the terahertz region



Yanmei Lin, Xiaohe Liu, Huifeng Chen, Xinyi Guo, Jintao Pan, Jianhui Yu, Huadan Zheng, Heyuan Guan, Huihui Lu, Yongchun Zhong, Yaofei Chen, Yunhan Luo, Wenguo Zhu, Zhe Chen, 


Fig. 1 (a) Schematic of in-plane asymmetric spin splitting. A horizontal incident polarization can be considered as a superposition of two opposite spin, which undergo displacements X ± along x-axis thus separate spatially, after transmitted through the BP-ENZ metamaterial-BP structure. The incident plane makes angles of ϕ1and ϕ2 to the armchair axes of top and bottom BP layers, respectively. (b) A single BP layer surrounding by two dielectrics with refractive index of nj and nj+1. (c) A stack of NBP layers separated by different dielectrics.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-27-11-15868



In-plane photonic spin splitting effect is investigated in tunneling terahertz waves through an epsilon-near-zero metamaterial sandwiched between monolayer black phosphorus (BP). The strong in-plane anisotropy of BP layers will induce in-plane asymmetric spin splitting. The asymmetric spin splitting can be flexibly tuned by the angles between the incident plane and the armchair crystalline directions of the top and bottom BP layers, i.e., ϕ1 and ϕ2. Based on this, an angle-resolved barcode-encryption scheme is discussed. For the special case of ϕ1 = ϕ2 = 0 or 90°, the transmitted beam undergoes Goos-Hänchen shift, which varies with the carrier density of BP. We believe these findings can facilitate the development of novel optoelectronic devices in the Terahertz region.
© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Tuesday, November 27, 2018

Abstract-Tailoring anisotropic perfect absorption in monolayer black phosphorus by critical coupling at terahertz frequencies




Ye Ming Qing, Hui Feng Ma, and Tie Jun Cui

Fig. 1 (a) Schematic of the proposed structure. (b) Schematic of monolayer BP. (c) The single port resonator model in coupled mode theory. Frequency dependent surface conductivity along (d) the x-direction and (e) the y-direction. Solid lines and dashed lines denote the real part and imaginary part, respectively.


https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-25-32442


A metamaterial perfect absorber composed of a black phosphorus (BP) monolayer, a photonic crystal, and a metallic mirror is designed and investigated to enhance light absorption at terahertz frequencies. Numerical results reveal that the absorption is enhanced greatly with narrow spectra due to critical coupling, which is enabled by guided resonances. Intriguingly, the structure manifests the unusual polarization-dependent feature attributable to the anisotropy of black phosphorus. The quality factor of the absorber can be as high as 95.1 for one polarization while 63.5 for another polarization, which is consistent with the coupled wave theory. The absorption is tunable by varying key parameters, such as period, radius, slab thickness, incident angle, and polarization angle. Furthermore, the state of the system (i.e., critical coupling, over coupling, and under coupling) can be tuned by changing the electron doping of BP, thus achieving various applications. This work offers a paradigm to enhance the light-matter interaction in monolayer BP without plasmonic response, and this easy-to-fabricate structure will provide potential applications in BP-based devices.
© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Friday, May 11, 2018

Abstract-Black-Phosphorus Terahertz Photodetectors




The discovery of graphene and the related fascinating capabilities have triggered an unprecedented interest in inorganic two-dimensional (2D) materials. Despite the impressive impact in a variety of photonic applications, the absence of energy gap has hampered its broader applicability in many optoelectronic devices. The recent advance of novel 2D materials, such as transition-metal dichalcogenides or atomically thin elemental materials, (e.g. silicene, germanene and phosphorene) promises a revolutionary step-change. Here we devise the first room-temperature Terahertz (THz) frequency detector exploiting few-layer phosphorene, e.g., a 10 nm thick flake of exfoliated crystalline black phosphorus (BP), as active channel of a field-effect transistor (FET). By exploiting the direct band gap of BP to fully switch between insulating and conducting states and by engineering proper antennas for efficient light harvesting, we reach detection performance comparable with commercial detection technologies, providing the first technological demonstration of a phosphorus-based active THz device.

Sunday, March 4, 2018

Abstract- Tunable terahertz/infrared coherent perfect absorption in a monolayer black phosphorus



Xi Wang, Qian Ma, Leiming Wu, Jun Guo, Shunbin Lu, Xiaoyu Dai, and Yuanjiang Xiang

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-5-5488

Black phosphorus (BP), a promising new two-dimensional (2D) material, has drawn a lot of attentions in academia and industry due to its extraordinary physical and chemical properties. In this paper, we theoretically demonstrate a monolayer BP that achieves coherent perfect absorption (CPA) at the THz/infrared band. It is found that quasi-CPA point does exist at the THz/infrared band. The CPA, which has a relative bandwidth of 141.3% and a coherent absorptivity of more than 90%, can be implemented at the quasi-CPA wavelength through a proper phase modulation. Moreover, the coherent absorptivity can be modulated with a high modulation depth by means of the phase difference between the two coherent counter-propagating beams. The angular selectivity of the monolayer BP is also investigated. The CPA wavelength is divided into two wavelength branches for TE and TM polarization at oblique incidence. In addition, the CPA wavelength can be tuned from THz to infrared band by adjusting the electron doping of the BP while maintaining the modulation depth of 104. Hence, our results may be potentially used for coherent modulations in terahertz/infrared detections and signal processing with 2D materials.
© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Friday, January 26, 2018

Abstract-Strong coherent coupling between graphene surface plasmons and anisotropic black phosphorus localized surface plasmons



Jinpeng Nong, Wei Wei, Wei Wang, Guilian Lan, Zhengguo Shang, Juemin Yi, and Linlong Tang

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-2-1633&origin=search

The anisotropic plasmons properties of black phosphorus allow for realizing direction-dependent plasmonics devices. Here, we theoretically investigated the hybridization between graphene surface plasmons (GSP) and anisotropic black phosphorus localized surface plasmons (BPLSP) in the strong coupling regime. By dynamically adjusting the Fermi level of graphene, we show that the strong coherent GSP-BPLSP coupling can be achieved in both armchair and zigzag directions, which is attributed to the anisotropic black phosphorus with different in-plane effective electron masses along the two crystal axes. The strong coupling is quantitatively described by calculating the dispersion of the hybrid modes using a coupled oscillator model. Mode splitting energy of 26.5 meV and 19 meV are determined for the GSP-BPLSP hybridization along armchair and zigzag direction, respectively. We also find that the coupling strength can be strongly affected by the distance between graphene sheet and black phosphorus nanoribbons. Our work may provide the building blocks to construct future highly compact anisotropic plasmonics devices based on two-dimensional materials at infrared and terahertz frequencies.
© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Wednesday, September 20, 2017

Abstract-Surface plasmons in a nanostructured black phosphorus flake



Xinyue Ni, Lin Wang, Jinxuan Zhu, Xiaoshuang Chen, and Wei Lu
Recent rediscovered layered material-black phosphorous with a puckered honeycomb atomic structure has experienced an upsurge in demand owing to its exotic physical properties such as layer-independent direct bandgap and linear dichroism. This Letter presents plasmonic properties of the nanostructured BP flake and its unprecedented capability of wide-band photon manipulation within the deep subwavelength scale. Owing to its anisotropic characteristic in band structure and moderate mobility, a strong layer number and polarization dependences of the plasmon resonance with frequencies ranging from infrared (IR) to terahertz have been found. Oblique plasmons have been observed in the square array of a black phosphorus (BP) flake, with the resonant frequency tuned in-situ, either electrically or optically, plus strong plasmon-induced absorption. Such advantages place BP as the best alternate candidate of plasmonic materials for ultra-scaled optoelectronic integration from terahertz to mid-IR.
© 2017 Optical Society of America