Enhancement of nonlinear functionality of step-index silica fibers combining thermal poling and 2D materials deposition.

This work proposes a new route to overcome the limits of the thermal poling technique for the creation of second order nonlinearity in conventional silica optical fibers. We prove that it is possible to enhance the nonlinear behavior of periodically poled fibers merging the effects of poling with the nonlinear intrinsic properties of some materials, such as MoS2, which are deposited inside the cladding holes of a twin-hole silica fiber. The optical waves involved in a second harmonic generation process partially overlap inside the thin film of the nonlinear material and exploit its higher third order susceptibility to produce an enhanced SHG.

Composite material anti-resonant optical fiber electromodulator with a 3.5 dB depth.

The hollow regions of an anti-resonant fiber (ARF) offer an excellent template for the deposition of functional materials. When the optical properties of such materials can be modified via external stimuli, it offers a method to control the transmission properties of the fiber device. In this Letter, we show that the integration of a ${{\rm MoS}_2}$MoS2 film into the ARF voids allows the fiber to act as an electro-optical modulator. We record a maximum modulation depth of 3.5 dB at 744 nm, with an average insertion loss of 7.5 dB.

Probing Excitons, Trions, and Dark Excitons in Monolayer WS2 Using Resonance Raman Spectroscopy.

We present temperature-dependent resonance Raman measurements on monolayer WS2 for the temperature range 4-295 K using excitation photon energies from 1.9 to 2.15 eV in ∼7 meV steps. These are analyzed to determine the resonance profiles of five previously assigned phonon based Raman peaks (A1', E', 2ZA, LA, 2LA) and a previously unassigned peak at 485 cm-1 whose possible attributions are discussed. The resonance profiles obtained are fitted to a perturbation theory derived model and it is shown that both excitons and trions are required to explain the profiles. The model is used to separate the contribution of exciton-exciton, trion-trion, and exciton-trion scattering to each of the Raman peaks at 4 K. This separation allows the ratios of the rates of scattering involving the A1' and E' phonons for each of the three types of scattering to be determined. The explanation of the multiphonon Raman peaks requires the coupling of bright excitons and trions to large wavevector dark states. The fitting of the resonance Raman profiles for these Raman peaks demonstrates scattering of bright excitons to bright trions via these large wavevector dark states.

Solid microstructured optical fiber.

An all-solid microstructured fiber based on two thermallymatched silicate glasses with a high index contrast has been fabricated for the first time. The microstructured cladding was shown to be essentially unchanged during fiber drawing. Fiber attenuation was measured as 5dB/m at 1.55m by the cutback method. High nonlinearity 230 W-1km-1 has been predicted and experimentally demonstrated in this fiber at 1.55m. In addition, modeling predicts that near-zero dispersion can be achieved between 1.5-1.6m in this class of high nonlinear fiber.