Quantum light emitters have been observed in atomically thin layers of transition metal dichalcogenides. However, they are found at random locations within the host material and usually in low densities, hindering experiments aiming to investigate this new class of emitters. Here, we create deterministic arrays of hundreds of quantum emitters in tungsten diselenide and tungsten disulphide monolayers, emitting across a range of wavelengths in the visible spectrum (610–680 nm and 740–820 nm), with a greater spectral stability than their randomly occurring counterparts. This is achieved by depositing monolayers onto silica substrates nanopatterned with arrays of 150-nm-diameter pillars ranging from 60 to 190 nm in height. The nanopillars create localized deformations in the material resulting in the quantum confinement of excitons. Our method may enable the placement of emitters in photonic structures such as optical waveguides in a scalable way, where precise and accurate positioning is paramount.

Synthetic single-crystal diamond has recently emerged as a promising platform for Raman lasers at exotic wavelengths due to its giant Raman shift, large transparency window and excellent thermal properties yielding a greatly enhanced figure-of-merit compared to conventional materials [1, 2, 3]. To date, diamond Raman lasers have been realized using bulk plates placed inside macroscopic cavities [3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13], requiring careful alignment and resulting in high threshold powers (~W-kW). Here we demonstrate an on-chip Raman laser based on fully-integrated, high quality-factor, diamond racetrack microresonators embedded in silica. Pumping at telecom wavelengths, we show Stokes output discretely tunable over a ~100nm bandwidth around 2-μm with output powers >250 μW, extending the functionality of diamond Raman lasers to an interesting wavelength range at the edge of the mid-infrared spectrum [14]. Continuous-wave operation with only ~85 mW pump threshold power in the feeding waveguide is demonstrated along with continuous, mode-hop-free tuning over ~7.5 GHz in a compact, integrated-optics platform.Diamond serves as a compelling material platform for Raman lasers operating over a wide spectrum due to its superlative Raman frequency shift (~40 THz), large Raman gain (~10 cm/GW @ ~1-μm wavelength) and ultra-wide transparency window (from UV (>220nm) all the way to THz, except for a slightly lossy window from ~2.6 -6 μm due to multiphonon-induced absorption) [1,15]. Furthermore, the excellent thermal properties afforded by diamond (giant thermal conductivity of ~1800 W/m/K @ 300K and low thermo-optic coefficient of ~10 -5 /K) [1,2] along with negligible birefringence [3,15] make it an ideal material for high-power Raman lasing with greatly reduced thermal lensing effects [1,3].The availability of CVD-grown, high-quality polished, single-crystal diamond plates has enabled the development of bulk Raman lasers using macroscopic optical cavities across the UV [6], visible [4, 5], near-infrared [7, 8, 9, 10, 11, 12] and even mid-infrared [13] regions of the optical spectrum. Although showing great performance with large output powers (many Watts) [12] and near quantum-limited conversion efficiencies [5,9], most operate in pulsed mode in order to attain the very high pump powers required to exceed the Raman lasing threshold [5,6,11,12]. Demonstration of continuous-wave diamond Raman lasing has been challenging, with very few reports [3,7,8]. Bulk cavity systems also require precise alignment and maintenance of optical components for the laser to function robustly.

Freestanding nanostructures play an important role in optical and mechanical devices for classical and quantum applications. Here, we use reactive ion beam angled etching to fabricate optical resonators in bulk polycrystalline and single crystal diamond. Reported quality factors are approximately 30 000 and 286 000, respectively. The devices show uniformity across 25 mm samples, a significant improvement over comparable techniques yielding freestanding nanostructures.

We investigate the effects of Raman and Kerr gain in crystalline microresonators and determine the conditions required to generate mode-locked frequency combs. We show theoretically that a strong, narrowband Raman gain determines a maximum microresonator size allowable to achieve comb formation. We verify this condition experimentally in diamond and silicon microresonators and show that there exists a competition between Raman and Kerr effects that leads to the existence of two different comb states.

For many emerging optoelectronic materials, heteroepitaxial growth techniques do not offer the same high material quality afforded by bulk, single-crystal growth. However, the need for optical, electrical, or mechanical isolation at the nanoscale level often necessitates the use of a dissimilar substrate, upon which the active device layer stands. Faraday cage angled-etching (FCAE) obviates the need for these planar, thin-film technologies by enabling in-situ device release and isolation through an angled-etching process. By placing a Faraday cage around the sample during inductivelycoupled plasma reactive ion etching (ICP-RIE), the etching plasma develops an equipotential at the cage surface, directing ions normal to its face. In this Article, the effects Faraday cage angle, mesh size, and sample placement have on etch angle, uniformity, and mask selectivity are investigated within a silicon etching platform. Simulation results qualitatively confirm experiments and help to clarify the physical mechanisms at work. These results will help guide FCAE process design across a wide range of material platforms.