11 research outputs found
Tunable plasmon-enhanced birefringence in ribbon array of anisotropic 2D materials
We explore the far-field scattering properties of anisotropic 2D materials in
ribbon array configuration. Our study reveals the plasmon-enhanced linear
birefringence in these ultrathin metasurfaces, where linearly polarized
incident light can be scattered into its orthogonal polarization or be
converted into circular polarized light. We found wide modulation in both
amplitude and phase of the scattered light via tuning the operating frequency
or material's anisotropy and develop models to explain the observed scattering
behavior
Anisotropic Acoustic Plasmons in Black Phosphorus
Recently, it was demonstrated that a graphene/dielectric/metal configuration
can support acoustic plasmons, which exhibit extreme plasmon confinement an
order of magnitude higher than that of conventional graphene plasmons. Here, we
investigate acoustic plasmons supported in a monolayer and multilayers of black
phosphorus (BP) placed just a few nanometers above a conducting plate. In the
presence of a conducting plate, the acoustic plasmon dispersion for the
armchair direction is found to exhibit the characteristic linear scaling in the
mid- and far-infrared regime while it largely deviates from that in the long
wavelength limit and near-infrared regime. For the zigzag direction, such
scaling behavior is not evident due to relatively tighter plasmon confinement.
Further, we demonstrate a new design for an acoustic plasmon resonator that
exhibits higher plasmon confinement and resonance efficiency than BP ribbon
resonators in the mid-infrared and longer wavelength regime. Theoretical
framework and new resonator design studied here provide a practical route
toward the experimental verification of the acoustic plasmons in BP and open up
the possibility to develop novel plasmonic and optoelectronic devices that can
leverage its strong in-plane anisotropy and thickness-dependent band gap
Twisted two-dimensional material stacks for polarization optics
The ability to control the light polarization state is critically important for diverse applications in information processing, telecommunications, and spectroscopy. Here, we propose that a stack of anisotropic van der Waals materials can facilitate the building of optical elements with Jones matrices of unitary, Hermitian, non-normal, singular, degenerate, and defective classes. We show that the twisted stack with electrostatic control can function as arbitrary-birefringent wave-plate or arbitrary polarizer with tunable degree of non-normality, which in turn give access to plethora of polarization transformers including rotators, pseudorotators, symmetric and ambidextrous polarizers. Moreover, we discuss an electrostatic-reconfigurable stack which can be tuned to operate as four different polarizers and be used for Stokes polarimetry.K. K and T.L. acknowledge partial support by the National Science Foundation, NSF/EFRI Grant No. EFRI-1741660, and the DDF UMN support for K. K.LM-MacknowledgesProjectPID2020-115221GB-C41 financed by MCIN/AEI/10.13039/501100011033 and the Aragon Government through Project Q-MAD. S.-H.O. acknowledges support from the Samsung Global Research (GRO) Program and the Sanford P. Bordeau Chair at the University of Minnesota.Peer reviewe
Midinfrared Electro-optic Modulation in Few-Layer Black Phosphorus
Black
phosphorus stands out from the family of two-dimensional
materials as a semiconductor with a direct, layer-dependent bandgap
spanning the visible to mid-infrared (mid-IR) spectral range. It is,
therefore, a very promising material for various optoelectronic applications,
particularly in the important mid-IR range. While mid-IR technology
has been advancing rapidly, both photodetection and electro-optic
modulation in the mid-IR rely on narrow-band compound semiconductors,
which are difficult and expensive to integrate with the ubiquitous
silicon photonics. For mid-IR photodetection, black phosphorus has
already been proven to be a viable alternative. Here, we demonstrate
electro-optic modulation of mid-IR absorption in few-layer black phosphorus.
Our experimental and theoretical results find that, within the doping
range obtainable in our samples, the quantum confined Franz–Keldysh
effect is the dominant mechanism of electro-optic modulation. A spectroscopic
study on samples with varying thicknesses reveals strong layer dependence
in the interband transition between specific pairs of sub-bands. Our
results show that black phosphorus is a very promising material to
realizing efficient mid-IR modulators