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We report the experimental observation of Landau quantization of molecular beam epitaxy grown Sb2Te3 thin films by a low-temperature scanning tunneling microscope. Different from all the reported systems, the Landau quantization in Sb2Te3…
The newly-emergent two-dimensional topological insulators (TIs) have shown their unique electronic and optical properties, such as good thermal management, high nonlinear refraction index and ultrafast relaxation time. Their narrow energy…
The optical conductivity and the spectral weight of four topological insulators with increasing chemical compensation (Bi2Se3, Bi2-xCaxSe3, Bi2Se2Te, Bi2Te2Se) have been measured from 5 to 300 K and from sub-THz to visible frequencies. The…
Ultrathin (~3 quintuple layer) field-effect transistors (FETs) of topological insulator Bi2Se3 are prepared by mechanical exfoliation on 300nm SiO2/Si susbtrates. Temperature- and gate-voltage dependent conductance measurements show that…
Non-degenerate 2-photon excitation (ND-2PE) of a fluorophore with two laser beams of different photon energies offers an independent degree of freedom in tuning of the photon flux for each beam. This feature takes advantage of the infrared…
Creating materials with time-variant properties is critical for breaking reciprocity that imposes fundamental limitations to wave propagation. However, it is challenging to realize efficient and ultrafast temporal modulation in a photonic…
We demonstrate a robust low-loss optical interface by tiling passive (i.e., without doping of active ions) thin film lithium niobate (TFLN) and active (i.e., doped with rare earth ions) TFLN substrates for monolithic integration of…
We present the study of a proof-of-concept integrated device that can be used as a nonlinear broadband isolator. The device is based on the asymmetric loading of a highly-confining silicon-slot photonic coupler with graphene layers, whose…
Photonic integrated circuits are a paramount platform for optoelectronics and nonlinear optics, enabling high confinement nonlinear interactions, where advanced waveguide dispersion engineering can be leveraged to tailor broadband nonlinear…
Advanced photonic materials showing two-photon absorption (2PA) have been widely explored to develop three-dimensional imaging, micro and nanofabrication, all-optical switching, lithography on a nanoscale and many other enabling…
Optical microresonators with high quality ($Q$) factors are essential to a wide range of integrated photonic devices. Steady efforts have been directed towards increasing microresonator $Q$ factors across a variety of platforms. With…
Here, we present an in-depth theoretical analysis of the linear electrooptic effect in low-symmetry three-dimensional (3D) conductive materials with large Berry curvature dipoles. Our study identifies two distinct kinetic contributions to…
TiS3 nanosheets have proven to be promising candidates for ultrathin optoelectronic devices due to their direct narrow band-gap and the strong light-matter interaction. In addition, the marked in-plane anisotropy of TiS3 is appealing for…
Niobium telluride (NbTe$_2$), an emerging transition metal dichalcogenide material, has been theoretically predicted to have nonlinear absorption properties and excellent optical response. However, only a few studies of the utilization of…
Hybrid lead halide perovskites, such as CH$_3$NH$_3$PbX$_3$ (X=I, Br), are direct gap semiconductors that offer many superior optoelectronic properties combined with extremely simple solution-processing fabrication methods. This makes them…
We have performed angle-resolved photoemission spectroscopy on a heterostructure consisting of topological insulator Bi2Te3 and iron chalcogenide FeTe fabricated on SrTiO3 substrate by molecular-beam-epitaxy technique. This system was…
We measure the temperature dependence of the two-photon absorption and optical Kerr nonlinearity of a silicon waveguide over a range of temperatures from 5.5 to 300 K at a wavelength of 1.55 {\mu}m. The two-photon absorption coefficient is…
Conventional semiconductors such as silicon and InGaAs based photodetectors have encountered a bottleneck in modern electronics and photonics in terms of spectral coverage, low resolution, non-transparency, non-flexibility and…
Optical non-reciprocity, which breaks the symmetry between forward and backward propagating optical waves, has become vital in photonic systems and enables many key devices, such as optical isolators, circulators and optical routers. Most…
Using time- and angle-resolved photoemission, we investigate the ultrafast response of excited electrons in the ternary topological insulator (Bi$_{1 x}$Sb$_{x}$)$_2$Te$_3$ to fs-infrared pulses. We demonstrate that at the critical…