Single photon emitters (SPEs), or quantum emitters, are key components in a wide range of nascent quantum-based technologies, but creation and placement are difficult to control. We describe here a novel paradigm for encoding strain into 2D materials to create and deterministically place SPEs in arbitrary locations with nanometer-scale precision using an atomic force microscope. This quantum calligraphy allows deterministic placement and real time design of arbitrary patterns of SPEs. Because monolayer WSe2 is a direct gap semiconductor, SPE emission at a given wavelength is often intermixed with classical light, reducing the purity of the quantum emission. We show that this undesirable classical emission, arising primarily from defect bound excitonic processes, is significantly suppressed by electrostatic gating or incorporating the WSe2 layer in a simple van der Waals heterostructure, resulting in values of the autocorrelation function g(2)(t=0) as low as 0.07 at low temperature. In addition, the SPE intensity can be strongly modulated by changing the polarity of the gate bias, a feature of technological importance for practical applications.

Novel materials are the backbone of any technology. In this talk, I will discuss 2D materials that can be exfoliated down to a monolayer, as well as grown layer by layer, with applications ranging from the generation of quantum light to the detection of single photons at visible and near-infrared wavelengths. First part of the talk will focus on color centers in hexagonal Boron Nitride that have emerged as a promising candidate for single photon sources are room temperature. Experimental results on nanoscale localization of these color centers with 3D-dipole orientation characterized will be presented. Next, we will discuss iron chalcogenide-based 2D superconductor such as single photon detector.

Van der Waals materials, with their unique properties, have significantly advanced research in integrated photonics. Among these materials, hexagonal boron nitride (hBN) stands out for its optically and electronically desirable characteristics, including on-chip integration, availability, and manipulability. Particularly noteworthy are hBN's colour centres, which serve as single photon emitters in the UV and visible spectrums, essential for quantum communication and computing applications. Enhancing and controlling the emission wavelengths and quality is crucial. Plasmonic cavities, a common method for emission enhancement, are utilized in our study, employing plasmonic nanocones to investigate both the enhancement and the variability in emission wavelength. Our observations reveal a power dependence in emitter quenching. We substantiate our findings by comparing results from unstrained hBN without plasmonic enhancement with simulations. Additionally, we discuss the impact of gold emission on the quality of these emitters, providing valuable insights into the mechanisms at play.

Quantum degrees of freedom in flatland 2D materials are promising building blocks for quantum information processing, quantum communications, and quantum sensing. Especially quantum emitters in 2D materials, when compared to three-dimensional materials, have the advantage of reduced total internal reflection and easy coupling with interconnects. In this talk, I will share the story of the discovery and control of quantum emitters in two-dimensional materials. The possibility of leveraging van der Waals heterostructure for charging these emitters with a single electron will be discussed. This lays the foundation for optically addressable spin qubits in flatland materials. Further, I will also discuss the possibility of ab-initio prediction, deterministic generation, and integration with photonic devices, which offers a compelling solution to scalable solid-state quantum photonics. Our work opens the frontier of quantum optics in two-dimensional materials with the potential to revolutionize solid-state quantum devices.

Broadband photodetectors are of major significance in spectroscopy, imaging, and communication. Here, we demonstrate a waveguide integrated 1L-MoS2 photodetector for SWIR operating at zero bias with no dark current and having a responsivity up to ~100V/W. Our results pave the way for developing broadband MoS2 photodetectors from visible to IR.

Excitons in van der Waals semiconductors interact strongly with light and have been the subject of intense investigation for future optoelectronic applications. In this presentation, I will report our recent studies on excitons in MoSe2 and WSe2 heterostructures, including measurements on the spatial coherence of interlayer excitons, and the localization of excitons using lithographically defined graphene gates. I will also discuss our recent studies on a one-dimensional van der Waals semiconductor SbPS4. SbPS4 can be exfoliated using the scotch tape method to yield long (several micron) nanobundles with typical thicknesses of 1-100 nm. The nanobundles emit ultra-broadband and bright photoluminescence when excited with 400 nm light.

Metalorganic chemical vapor deposition (MOCVD) has emerged as a promising technique for scalable synthesis of transition metal dichalcogenides as it enables growth at high temperatures and chalcogen overpressures which are beneficial for epitaxial growth of monolayers and provides good control over precursor flux which is necessary for the synthesis of heterostructures. Our work has focused on MOCVD growth of epitaxial semiconducting TMDs (MoS2, WS2 and WSe2) on 2” diameter c-plane sapphire substrates. Steps on the sapphire surface can be used to control the orientation of TMD domains and reduce the number of inversion domain boundaries. In situ spectroscopic ellipsometry is demonstrated to be an effective real time monitor of TMD growth even at the sub-monolayer level which can be exploited to track surface coverage as a function of time under varying growth conditions. The ability to precisely control and modulate precursor flux during growth is used to synthesize in-plane heterostructures that enable localized exciton confinement and emission.

A fundamental requirement for photonic technologies is the ability to control the confinement and propagation of light. Widely utilized platforms include 2D optical microcavities in which electromagnetic waves are confined between either metallic or multi-layer distributed Bragg reflector dielectric mirrors. However, the fabrication complexities of thick Bragg reflectors and high losses in metallic mirrors have motivated the quest for efficient and compact mirrors. Recently, 2D transition metal dichalcogenides hosting tightly bound excitons with high optical quality were shown as promising atomically thin mirrors (a, b). In this work, we propose and experimentally demonstrate a sub-wavelength 2D nanocavity using two atomically thin mirrors (c-f). Remarkably, we show how the excitonic nature of the mirrors enables the formation of chiral and tunable cavity modes upon the application of an external magnetic field (g). Our work establishes a new regime for engineering intrinsically chiral sub-wavelength optical cavities and opens avenues for realizing spin-photon interfaces and exploring chiral many-body cavity electrodynamics.

Electromagnetic (EM) Mie resonances in high-index nanomaterials have garnered significant interest for their potential to confine EM fields and therefore enhance optical effects. Phonon polaritons in boron nitride (hBN) nanostructures (NNs) have been heavily studied as low-losses hyperbolic metamaterials in the midinfrared within the Reststrahlen band. In this work, we show that hBN NNs can also be used as extremely high positive dielectric material near the transversal optical mode, making them attractive candidates for dielectric resonators. This study investigates the infrared Mie resonances of hBN NNs of varying sizes through numerical and experimental analyses. Notably, a strong magnetic dipole resonance is observed, which energy and strength depends on the size and geometry of the hBN NN, as well as the substrate properties. Harnessing Mie resonances offers a path for manipulating light confinement for applications such as lasers, flat optics, imaging, and chemical sensing.

2D materials and specifically Transition Metal Dichalcogenides have received much attention as photoactive materials in photodetectors. These materials possess attractive properties, including a direct bandgap in the visible range and mechanical resilience to strain, making them an attractive material for flexible photodetectors. Here we demonstrate 4x4 pixel photodetector arrays on flexible and non-flexible substrates based on mechanically exfoliated flakes of MoS2. The arrays have a minimum pitch between array pixels of 9.5 µm in both vertical and horizontal directions. Demonstrating, to our knowledge, the densest 2D material based photodetector array to date.

Here, we present a vanadium carbide (V₂C) mid-infrared (mid-IR) photodetector. Drop casting and spin coating a silicon substrate with a thin silicon oxide layer produced the V2C photodetector. Isopropyl alcohol and nitrogen gas drying increased material quality. E-beam lithography and metal deposition of Au/Ti contacts on V₂C flakes carefully made electrical connections. Electrical bias and 2 μm laser light evaluated the V₂C photodetector’s dark current and photocurrent responses. Photocurrent response changed dramatically, matching FTIR spectroscopy findings. V₂C’s peak responsivity of 2.65 A/W demonstrated mid-IR photodetection. To test scalability, we created devices with 2-5 μm channels. For specialized sensing, photocurrent increases with channel length. Onchip waveguides and photonic circuits might use V2C photodetectors. V₂C’s mid-IR photodetector exhibits its promise as a cutting-edge optoelectronics and integrated photonics material. This work expands mid-IR-sensing photodetector technology.

We demonstrate MoTe2/ReS2 and WSe2/ReSe2 van der Waals heterostructures for linear polarization photodetection. The MoTe2/ReS2 photodiode shows excellent electrical performance with ideality factor or 1.3 and high ON/OFF ratio of 10^4 and exhibit broad spectral photo response up to 1310 nm illumination. The WSe2/ReSe2 device also exhibits excellent performance: an ideality factor of 1.67, a broad spectral photoresponse of 405–980 nm with significant photovoltaic effect, remarkable linearity with a linear dynamic range wider than 100 dB, and rapid photoswitching behavior with cutoff frequency up to 100 kHz. These two type of heterostructure shows clear linear polarization sensitive photodetection and we finally demonstration NIR digital incoherent holography.

In this work, a vertically stacked metal/2H-MoTe2/metal structure was fabricated to take advantage of the optical and electrical properties of two phases of MoTe2. By applying an electric-field, we triggered a reversible, non-volatile phase transition from the 2H phase to the lower-resistance 1T' phase, resulting in a resistance difference of 104 times and an 80% shift in optical reflectance, suitable for active reflective light modulation. When operated as a photodetector, its responsivities at near-infrared wavelengths around 975 nm significantly depend on its phase state, indicating its potential as an active reconfigurable photodetector.

This talk will highlight recent visible photonic integrated circuits based on silicon nitride including switching networks, optical phased arrays, chip-scale lasers, modulators and ongoing challenges for their practical application in neuroscience, imaging, and quantum systems. For scaling up these systems, frequency and spatial multiplexing architectures and techniques to overcome loss and fabrication challenges in the visible spectrum down to blue wavelengths will be discussed. Finally, the future of hybrid integrated platforms that incorporate active material properties including electro-optic modulation and optical gain will be discussed for expanding the platform’s functional capabilities.

In this talk I will discuss novel emergent functions for deeply subwavelength optics with bulk van der Waals materials. I will discuss novel integrated photonics circuits, light squeezing in atomically thin waveguides, and strong photon-phonon coupling at a fraction of a wavelength.

Iridium (Ir) is a refractory metal commonly seen in industrial applications, but has great potential for optical applications including metasurfaces. Metasurfaces are used to control the optical properties of an interface via sub-wavelength surface structures. These patterns require sharply defined features to create precise optical phase interactions. For high-temperature environments, most materials are insufficient candidates for metasurfaces because the sharpness of the surface structures are lost due to edge-rounding or oxidation. Ir is better suited for metasurface applications in high-temperature environments but the patterning of Ir using nanofabrication techniques has not been thoroughly investigated. In this work, Ir metasurfaces were fabricated and characterized for optical applications in the infrared.