This PDF file contains the front matter associated with SPIE Proceedings Volume 12423, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

Despite its superior physical properties, graphene’s optical properties still possess crucial drawbacks for both classical and quantum photonics applications. For example, graphene’s gapless band structure prohibits efficient light emission, while its centrosymmetric nature renders it impossible to obtain strong second-order nonlinearity. In this work, we discuss our latest results on strained graphene that provides a new pathway towards solving the two key above-mentioned problems.

We present a strain engineering platform that allows the dynamic tuning of the emission wavelength of a monolayer WSe₂. A large and localized strain was induced in monolayer 2D materials by patterning a photoresist layer with internal stress into two elliptical shapes with a finite gap in between, which is referred to as a dimer in this work. By applying laser annealing on the dimer stressor while monitoring the exciton emission, we demonstrate the capability to dynamically tune the emission wavelength of the bright exciton in the monolayer WSe₂.

In this paper, we will outline the architectures of waveguide-integrated mid-infrared photodetectors, composed of black phosphorus-based van der Waals (vdW) heterostructures. The performed hybrid detector can detect broad spectral of light (λ: 3−4 μm) and show the feature of high operation speed (<10 MHz), high responsivity and long-term stability at room temperature. By exploiting this hybrid device platform, we further demonstrate that on-chip mid-infrared sources can be readily realized, showing great promise for on-chip sensing and spectroscopic applications.

In this work, we demonstrate a Sb₂Te₃/MoS₂ heterostructure photodetector for visible range detection or sensing applications with ultra-low dark current and high sensitivity at zero external bias. The photoresponsivity can reach to 156 mA/W at zero bias and can be enhanced 3 times at 1V bias voltage.

We use microscopic many-body models based on first principle density functional theory to investigate the high harmonic generation (HHG) in monolayer transition metal dichalcogenides (ML-TMDCs) at the example of MoS₂. A two-dimensional bandstructure model is utilized that allows for the realistic inclusion of Coulomb correlations. It is shown that for off-resonant mid-IR excitation Coulomb correlations lead to a dramatic enhancement of HHG intensity by up to two orders of magnitude. For resonant excitation near the fundamental excitonic resonance the Coulomb interaction leads to dressed harmonics. These have a sub-floor of broad spectral contributions. The amplitude of these contributions is about four to six orders of magnitude below the peak. The width scales linearly with the exciting field and can reach hundreds of meV.

The observation of the out-of-plane optical constants of a monolayer two-dimensional crystal is a challenging task. I illustrate an experimental procedure able to observe these quantities. We measure the out-of-plane surface susceptibilities of Graphene and Molybdenum disulfide monolayers. At a wavelength of 633 nm we find values of 0.6 and 1.1 nm respectively for these two atomic crystals.

Layered material such as Transition Metal Dichalcogenides (TMDCs) are known to exhibit very high refractive index making them an excellent candidate for building resonant optical structures that facilitate strong nonlinear optical interaction. In particular, third order nonlinear processes such as third harmonic generation and four wave mixing (FWM) can be significantly boosted in thick TMDC based nanodisks by exciting non-radiating Mie resonances such as anapole modes. Here, we report enhanced FWM from isolated MoS₂ disks supporting higher-order anapole resonances. The MoS₂ disks were fabricated by patterning an MoS₂ flake dry-transferred on a 2.2 micron thick thermal SiO₂ deposited on a silicon wafer. Scattering cross sectional FDTD simulations were performed to extract the dimension of the MoS₂ nanodisk to ensure higher order anapole modes lie within the desired signal wavelength range (1400-1600nm) with a fixed pump wavelength of 1040nm. The final dimensions of MoS₂ disk has a diameter of 1.62μm and a height of 108nm. FWM measurements involving two pump photon and one signal photon were performed by varying the input signal wavelength. Maximum experimental enhancement of 150 times at 1470nm when compared with the un-patterned MoS₂ flake region obtained. Such emerging optical nanostructure based on layered material has potential use as efficient wavelength converters across widely separated wavelength band.

We report on the synthesis of 2D GaN materials by the so-called liquid metal chemistry and tuning of their composition between oxide and nitride materials. This technique promises easier integration of 2D materials onto photonic devices compared to traditional “top-down” and “bottom-up” methods. Our fabrication method is carried out via a two-step liquid metal-based printing method followed by a microwave plasma-enhanced nitridation reaction. The synthesis of GaN relies on plasma-treated liquid metal-derived two-dimensional (2D) sheets that were squeeze-transferred onto desired substrates. We characterized the composition and optical properties of the resulting nm-thick GaN films using AFM, XPS, and ellipsometry measurements. Finally, the optical indices measured by ellipsometry are compared with theoretical results obtained by density functional theory (DFT). Our results represent a first step toward integrating 2D materials and semiconductors into electronics and optical devices.

In this work, partially etched amorphous silicon (a-Si) metasurface is designed and fabricated to enhance chiral THG from the a-Si nanodisks and SHG from integrated multilayer GaSe overlayers with spectrally tunable chirality. The metasurfaces are designed to support guided mode resonance in the 1500-1600 nm wavelength range. A minimum degree of circular polarization (DOCP) of -0.6 is obtained experimentally on-resonance for the inherent THG process from the silicon nanodisks with resonant enhancement of more than 5 orders. A spectrally tunable DOCP of -0.5 to 0.5 is obtained for the generated SHG from the GaSe layer on top of the silicon metasurface with resonant enhancement of more than 5 orders.

The photonics-based approach has recently become a strong candidate for realising a large-scale, practical quantum processor. Particularly in recent years, two-dimensional (2D) materials have become a strong candidate for developing an ideal integrated light source owing to their several unique advantages such as convenient on-chip integration. In this work, we study the effect of strain on the emission wavelength and carrier lifetime. We first show that the geometry of stressors can adjust the amount of strain and emission wavelength. Using this strain engineering technique, we demonstrate that the emission wavelength can be significantly shifted by ~10 nm while the carrier lifetime can also be engineered by ~30 %.

This manuscript aims to analyze the effect of bariumtitanate (BaTiO₃) and molybdenumdisulfide (MOS₂) along with gold (Au) on the sensing application of surface plasmon resonance (SPR) biosensors. The proposed multilayer structure has a BK7 prism, a bimetallic layer of Au, BaTiO₃, and a MOS² layer. BaTiO₃ and MOS₂ layers are used to improve the biosensor performance parameters by the Kretschmann configuration. The proposed configuration has enhanced the performance over the conventional sensor. The performance parameters like full width half maximum (FWHM), detection accuracy, and detection accuracy have been analyzed. The suggested biosensor can detect a wide range of analytes with an extensive refractive index range. The proposed sensor can be used to analyze chemical and biological analytes.

Transition metal dichalcogenides (TMDs) are highly efficient materials due to their vast applications in the domain of optoelectronics, photodetectors, catalysis, supercapacitors, and battery storage. Molybdenum disulfide (MoS₂) is the most important TMD material due to the existence of fascinating optical, electronic, and chemical properties. Herein, we have synthesized MoS₂ using a facile one-step hydrothermal technique resulting in low-cost 1T@2H MoS₂ flower-like nanosheets and examined the structural, electronic, and optical properties. The field emission gun-scanning electron microscopy (FEG-SEM) images confirm the flower-like nanosheet morphology of the synthesized MoS₂. Further, the Xray diffraction (XRD) peaks of MoS2 confirm the hexagonal phase with space group P63/mmc. The observed Transmission Electron Microscopy (TEM) image shows the formation of thin nanosheets of MoS₂ while the crystal planes of MoS2 can be noticed from the High-Resolution Transmission Electron Microscopy (HRTEM) images. Also, an interplanar distance (d) of 0.62 nm has been observed from the HRTEM images of MoS₂ nanosheets. The Raman spectrum confirms the vibrational modes corresponding to the 2H and 1T phase of MoS₂ indicating the formation of a mixed phase in the structure. An excellent luminescent behavior has been observed from the photoluminescence (PL) plot. The electronic nature of the material has been evaluated from the Tauc plot and an optical band gap of 1.69 eV has been observed indicating the formation of a few layers of semiconducting MoS₂. This rigorous study suggests the potential application of MoS₂ in nanoelectronic devices.

Transition metal dichalcogenides (TMDs) are a class of two-dimensional (2D) materials which has several applications in the domain of optoelectronic devices, catalyst, sensor, and energy storage devices. Tungsten disulfide (WS2) is one of the important TMD material exhibiting semiconducting and metallic nature in the 2H and 1T phases respectively. Herein, we report a one-step hydrothermally synthesized large-scale and low-cost WS₂ nanomaterial. Further, we have performed material characterization using X-ray diffraction (XRD), field emission gun-scanning electron microscopy (FEG-SEM), and transmission electron microscopy (TEM) to check the crystallinity, surface morphology, and shape of the nanomaterial. The XRD data matches very well with the mixed-phase 1T @ 2H of WS₂. Also, the formation of crystal planes can be clearly seen from the high-resolution transmission electron microscopy (HRTEM) image of the synthesized material. Further, the surface morphology of as-grown WS₂ nanomaterial has been investigated by field emission gunscanning electron microscopy (FEG-SEM) which shows the nanosheet-like morphology. Moreover, Raman spectroscopy has been done to check the presence of vibrational modes of the synthesized WS2. The Raman peaks were observed at 348.15 cm^-1 _{(E1 2g)} and 414.18 cm^-1 (A1g) corresponding to the in-plane vibrational mode and out-of-plane vibrational mode of 2H WS₂. In addition, Raman peaks corresponding to the 1T phase of WS₂ have also been obtained. This rigorous study on WS₂ nanomaterial suggests its usefulness in energy storage applications such as supercapacitors, photocatalysis, and electrochemical sensors.

Vanadium disulfide (VS₂) is a prominent metallic member of transition metal dichalcogenides (TMDs) family and has already demonstrated its flair in energy storage device applications such as supercapacitors and batteries. In this work, we have synthesized hexagonal shape VS₂ nanomaterial using a facile one step hydrothermal route and investigated the phase, morphology and structural properties of the material. The formation of phase has been confirmed from the X-ray diffraction (XRD) plot by correlating with the database of Joint Committee on Powder Diffraction Standards (JCPDS) 00-036-1139 of 1T VS₂. Further, the crystalline behavior of VS₂ nanomaterial can be seen from the high resolution transmission electron microscopy (HRTEM) measurement. Moreover, the morphology of the synthesized material is obtained from the field emission gun-scanning electron microscopy (FEG-SEM). Also, the characteristic Raman peaks of 1T VS₂ at 140.3 cm^-1 and 192.3 cm^-1 have been observed from the Raman spectrum indicating the metallic behavior of synthesized material. The peak at 281.8 cm^-1 is attributed to the in-plane vibrational mode (E_2g ¹) while the peak at 404.5 cm^-1 represents the out-of-plane vibrational mode (A1g) of V-S bond. The Fourier transform infrared (FTIR) spectrum shows the V-S-V and V=S vibrational modes around 534 cm_-1 and 982 cm^-1 respectively. The study introduces a low cost, large scale, highly crystalline, and metallic VS₂ nanomaterial with potential application for next generation supercapacitors and other energy storage devices.