James C. Hone

Waveguides play a key role in the implementation of on-chip optical elements and, therefore, lie at the heart of integrated photonics. To add the functionalities of layered materials to existing technologies, dedicated fabrication protocols are required. Here, we build on laser writing to pattern grating structures into bulk noncentrosymmetric transition metal dichalcogenides with grooves as sharp as 250 nm. Using thin flakes of 3R-MoS2 that act as waveguides for near-infrared light, we demonstrate the functionality of the grating couplers with two complementary experiments: first, nano-optical imaging is used to visualize transverse electric and magnetic modes, whose directional outcoupling is captured by finite element simulations. Second, waveguide second-harmonic generation is demonstrated by grating-coupling femtosecond pulses into the slabs in which the radiation partially undergoes frequency doubling …

Over the past decade, the discovery of intriguing quantum phenomena such as non-trivial topology, superconductivity, and quantum Hall effects have generated intense interest in layered transition metal dichalcogenides (TMDs). Unlike in graphene, poor contacts have impeded the thorough study of TMD systems at millikelvin temperatures. We have developed a novel “contactless capacitance” method to circumvent the issue of poor contacts and enable compressibility and charge transport measurements on these materials at very low temperatures and carrier densities inaccessible to current electronic measurement techniques. We demonstrate our new technique on mono-and few-layer WSe 2 flakes, demonstrating high device quality and our ability to measure delicate quantum phenomena without the need for low-resistance contacts.* This work is supported by the Basic Energy Sciences Program of the Office …

We have developed a local capacitance technique using capacitively coupled electrodes to study the electronic properties of transition metal dichalcogenide materials. This approach does not rely on making ohmic contacts to the material and thus makes measurements at low temperature and low density possible presenting a significant advantage over conventional dc transport. Our local capacitance technique provides sensitivity to layer polarization in bilayer systems as the density and displacement field can be varied independently under the local measurement electrode. We have implemented our technique to study monolayer and bilayer WSe 2 in which contact resistance has been a major impediment to transport measurements. In this talk, we will present the results of our local capacitance techniques down to low carrier densities (< 10 12 cm-2) and temperatures and high magnetic fields.* This work is …

In this talk, we will describe an experimental framework that leverages quantum phenomena to inform and explore the unique role that material physics can play in developing more sensitive and efficient quantum devices. The overarching challenge of utilizing novel materials in quantum devices is the integration of the material into the device in such a way that unlocks new functionality. We address this challenge by leveraging the characteristics of two-dimensional (2D) van der Waals (VdW) materials such as gate-tunability, pristine interfaces, and emergent electronic properties of their heterostructures to welcome a new era of hybrid superconducting devices. To this end, we present our latest measurements of the internal energy of a single photon and describe a method to directly detect the quantum states of a photon. We will also discuss how basic physics principles impose fundamental limitations on sensitivity …

Van der Waals (vdW) structures of two-dimensional materials host a broad range of physical phenomena. New opportunities arise if different functional layers may be remotely modulated or coupled in a device structure. Here we demonstrate the in-situ coherent modulation of moir\'e excitons and correlated Mott insulators in transition metal dichalcogenide (TMD) homo- or hetero-bilayers with on-chip terahertz (THz) waves. Using common dual-gated device structures, each consisting of a TMD moir\'e bilayer sandwiched between two few-layer graphene (fl-Gr) gates with hexagonal boron nitride (h-BN) spacers, we launch coherent phonon wavepackets at ~0.4-1 THz from the fl-Gr gates by femtosecond laser excitation. The waves travel through the h-BN spacer, arrive at the TMD bilayer with precise timing, and coherently modulate the moir\'e excitons or the Mott states. These results demonstrate that the fl-Gr gates, often used for electrical control of the material properties, can serve as effective on-chip opto-elastic transducers to generate THz waves for the coherent control and vibrational entanglement of functional layers in commonly used moir\'e devices.

In addition to wavelength and polarization, coherent light possesses a degree of freedom associated with its spatial topology that, when exploited through nonlinear optics, can unlock a plethora of new photonic phenomena. A prime example involves the use of vortex beams, which allow for the tuning of light's orbital angular momentum (OAM) on demand. Such processes can not only reveal emergent physics but also enable high-density classical and quantum communication paradigms by allowing access to an infinitely large set of orthogonal optical states. Nevertheless, structured nonlinear optics have failed to keep pace with the ever-present need to shrink the length-scale of optoelectronic and photonic technologies to the nanoscale regime. Here, we push the boundaries of vortex nonlinear optics to the ultimate limits of material dimensionality. By exploiting second and third-order nonlinear frequency-mixing processes in van der Waals semiconductor monolayers, we show the free manipulation of the wavelength, topological charge, and radial index of vortex light-fields. We demonstrate that such control can be supported over a broad spectral bandwidth, unconstrained by traditional limits associated with bulk nonlinear optical (NLO) materials, due to the atomically-thin nature of the host crystal. Our work breaks through traditional constraints in optics and promises to herald a new avenue for next-generation optoelectronic and photonics technologies empowered by twisted nanoscale nonlinear light-matter interactions.

Atomic defects in two-dimensional (2D) materials impact electronic and optoelectronic properties, such as doping and single photon emission. An understanding of defect–property relationships is essential for optimizing material performance. However, progress in understanding these critical relationships is hindered by a lack of straightforward approaches for accurate, precise, and reliable defect quantification on the nanoscale, especially for insulating materials. Here, we demonstrate that lateral force microscopy (LFM), a mechanical technique, can observe atomic defects in semiconducting and insulating 2D materials under ambient conditions. We first improve the sensitivity of LFM through consideration of cantilever mechanics. With the improved sensitivity, we use LFM to locate atomic-scale point defects on the surface of bulk MoSe2. By directly comparing LFM and conductive atomic force microscopy (CAFM …

Compact and high-speed electro-optic phase modulators play a vital role in various large-scale applications including optical computing, quantum and neural networks, and optical communication links. Conventional electro-refractive phase modulators such as silicon (Si), III-V and graphene on Si suffer from a fundamental tradeoff between device length and optical loss that limits their scaling capabilities. High-finesse ring resonators have been traditionally used as compact intensity modulators, but their use for phase modulation has been limited due to the high insertion loss associated with the phase shift. Here, we show that high-finesse resonators can achieve a strong phase shift with low insertion loss by simultaneous modulation of the real and imaginary parts of the refractive index, to the same extent, i.e., Δ n Δ k∼1. To implement this strategy, we demonstrate an active hybrid platform that …