Probing Dark Excitons in Monolayer MoS_{2} by Nonlinear Two-Photon Spectroscopy.

We report a new dark exciton in monolayer MoS_{2} using second harmonic generation spectroscopy. Hereby, the spectrally dependent second harmonic generation intensity splits into two branches, and an anticrossing is observed at ∼25  meV blue detuned from the bright neutral exciton. These observations are indicative of coherent quantum interference arising from strong two-photon light-matter interaction with an excitonic state that is dark for single photon interaction.

Lasing of moiré trapped MoSe/WSe interlayer excitons coupled to a nanocavity.

We report lasing of moiré trapped interlayer excitons (IXs) by integrating a pristine hBN-encapsulated MoSe/WSe heterobilayer into a high- (>10) nanophotonic cavity. We control the cavity-IX detuning using a magnetic field and measure their dipolar coupling strength to be 78 ± 4 micro-electron volts, fully consistent with the 82 micro-electron volts predicted by theory. The emission from the cavity mode shows clear threshold-like behavior as the transition is tuned into resonance with the cavity.

Extending the coherence of spin defects in hBN enables advanced qubit control and quantum sensing.

Negatively-charged boron vacancy centers ([Formula: see text]) in hexagonal Boron Nitride (hBN) are attracting increasing interest since they represent optically-addressable qubits in a van der Waals material. In particular, these spin defects have shown promise as sensors for temperature, pressure, and static magnetic fields. However, their short spin coherence time limits their scope for quantum technology.

Thickness insensitive nanocavities for 2D heterostructures using photonic molecules.

Two-dimensional (2D) heterostructures integrated into nanophotonic cavities have emerged as a promising approach towards novel photonic and opto-electronic devices. However, the thickness of the 2D heterostructure has a strong influence on the resonance frequency of the nanocavity. For a single cavity, the resonance frequency shifts approximately linearly with the thickness.

Coupling of MoS_{2} Excitons with Lattice Phonons and Cavity Vibrational Phonons in Hybrid Nanobeam Cavities.

We report resonant Raman spectroscopy of neutral excitons X^{0} and intravalley trions X^{-} in hBN-encapsulated MoS_{2} monolayer embedded in a nanobeam cavity. By temperature tuning the detuning between Raman modes of MoS_{2} lattice phonons and X^{0}/X^{-} emission peaks, we probe the mutual coupling of excitons, lattice phonons and cavity vibrational phonons. We observe an enhancement of X^{0}-induced Raman scattering and a suppression for X^{-}-induced, and explain our findings as arising from the tripartite exciton-phonon-phonon coupling.

Unveiling the Zero-Phonon Line of the Boron Vacancy Center by Cavity-Enhanced Emission.

Negatively charged boron vacancies () in hexagonal boron nitride (hBN) exhibit a broad emission spectrum due to strong electron-phonon coupling and Jahn-Teller mixing of electronic states. As such, the direct measurement of the zero-phonon line (ZPL) of has remained elusive. Here, we measure the room-temperature ZPL wavelength to be 773 ± 2 nm by coupling the hBN layer to the high- nanobeam cavity.

Nonlocal Exciton-Photon Interactions in Hybrid High-Q Beam Nanocavities with Encapsulated MoS_{2} Monolayers.

Atomically thin semiconductors can be readily integrated into a wide range of nanophotonic architectures for applications in quantum photonics and novel optoelectronic devices. We report the observation of nonlocal interactions of "free" trions in pristine hBN/MoS_{2}/hBN heterostructures coupled to single mode (Q>10^{4}) quasi 0D nanocavities. The high excitonic and photonic quality of the interaction system stems from our integrated nanofabrication approach simultaneously with the hBN encapsulation and the maximized local cavity field amplitude within the MoS_{2} monolayer.

Enhanced Strong Interaction between Nanocavities and p-shell Excitons Beyond the Dipole Approximation.

Large coupling strengths in exciton-photon interactions are important for the quantum photonic network, while strong cavity-quantum dot interactions have been focused on s-shell excitons with small coupling strengths. Here we demonstrate strong interactions between cavities and p-shell excitons with a great enhancement by the in situ wave-function control. The p-shell excitons are demonstrated with much larger wave-function extents and nonlocal interactions beyond the dipole approximation.

Two-Photon Rabi Splitting in a Coupled System of a Nanocavity and Exciton Complexes.

Two-photon Rabi splitting in a cavity-dot system provides a basis for multiqubit coherent control in a quantum photonic network. Here we report on two-photon Rabi splitting in a strongly coupled cavity-dot system. The quantum dot was grown intentionally large in size for a large oscillation strength and small biexciton binding energy.

High-Responsivity Photodetection by a Self-Catalyzed Phase-Pure p-GaAs Nanowire.

Defects are detrimental for optoelectronics devices, such as stacking faults can form carrier-transportation barriers, and foreign impurities (Au) with deep-energy levels can form carrier traps and nonradiative recombination centers. Here, self-catalyzed p-type GaAs nanowires (NWs) with a pure zinc blende (ZB) structure are first developed, and then a photodetector made from these NWs is fabricated. Due to the absence of stacking faults and suppression of large amount of defects with deep energy levels, the photodetector exhibits room-temperature high photoresponsivity of 1.

Gain enhanced Fano resonance in a coupled photonic crystal cavity-waveguide structure.

Systems with coupled cavities and waveguides have been demonstrated as optical switches and optical sensors. To optimize the functionalities of these optical devices, Fano resonance with asymmetric and steep spectral line shape has been used. We theoretically propose a coupled photonic crystal cavity-waveguide structure to achieve Fano resonance by placing partially reflecting elements in waveguide.

Ultrafast optical switching using photonic molecules in photonic crystal waveguides.

We study the coupling between photonic molecules and waveguides in photonic crystal slab structures using finite-difference time-domain method and coupled mode theory. In a photonic molecule with two cavities, the coupling of cavity modes results in two super-modes with symmetric and anti-symmetric field distributions. When two super-modes are excited simultaneously, the energy of electric field oscillates between the two cavities.