We present the use of holographic UV writing to fabricate 2D grating couplers in doped planar silica-on-silicon, enabling the creation of large (~1 cm) and efficient circular beam delivery into free space. Our fabrication process inscribes a channel waveguide with in-plane 60° blazed grating to expand a fibre-coupled beam within a planar core layer, followed by an out-of-plane 45° blazed grating to couple light out of the substrate. Our out-of-plane gratings are fabricated using a modified interferometric arrangement with a prism and index matching water layer, the arrangement and latest results will be presented here.
We present our research on utilizing weak Bragg grating reflectors to assess the uniformity of zinc-doped lithium niobate ridge waveguides, aiming to optimize frequency conversion. These gratings are fabricated through ablation using a pulsed 213nm laser within a phase-controlled interferometric system, providing sub-nanometer period accuracy. By employing gratings we spectrally and spatially characterize the modal properties of our waveguides, enabling direct analysis of process variability. Through this analysis, we aim to gain a deeper understanding of the effective index variation in periodically poled lithium niobate (PPLN) waveguides, with the ultimate goal of reducing it and improving frequency conversion.
We present the results of an extended study on the evolution of dicing blade dynamics to define the tolerances of the ductile regime for dicing optical quality facets with sub-nm surface roughness in optical materials. These results provide a route to determine the critical parameters, such as depth of cut, blade shape, and feed rate, to maintain stable ductile machining within a specific range of conditions. We will discuss our latest results and observations, including optical characterisation of waveguides in lithium niobate and other materials.
The Networked Quantum Information Technologies (NQIT) hub was one of the quantum hubs of the first round of the United Kingdom’s flagship scheme, bringing together academia, industry, and government. The Optical Engineering and Quantum Photonics Group at the University of Southampton’s Optoelectronics Research Centre has developed an interactive demonstrator of a key device within NQIT to bring quantum photonics technologies to a wider audience. The system was exhibited at the 2017 UK Quantum Showcase in London to an audience of industry and government. It also featured as part of the Quantum City stand at the 2018 Cheltenham Science Festival, one of the United Kingdom’s leading annual science events.
Novel research-inspired outreach activities allow scientists and members of the public to engage in a conversation, increasing the public’s understanding and interest in scientific research. This paper reviews outreach and public engagement initiatives undertaken by researchers from the University of Southampton’s Optical Engineering and Quantum Photonics Group during a 5-year research program grant entitled Building Large Optical Quantum States. The activities have been supported by a UK Engineering and Physical Sciences Research Council program grant and institutional, national and international professional organizations. The paper discusses activities and hand-outs that have been developed to increase the visibility and public understanding of integrated-photonics fabrication and testing facilities, including a cleanroom-based process for the design and fabrication of quantum outreach chips. More than 1,000 of these chips have been distributed to children, parents and government officials in public events and the activities have contributed towards the authors’ research group receiving the 2017 South East England Physics Network Highly Commended Award for Best Research Group. This paper also discusses the impact of these activities and lessons learned.
The Networked Quantum Information Technologies hub (NQIT) is one of the quantum hubs of the UK's agship scheme, bringing together academia, industry and government. The Optical Engineering and Quantum Pho- tonics group at the University of Southampton's Optoelectronics Research Centre have developed an interactive demonstrator of a key device within NQIT to bring quantum photonics technologies to a wider audience. The system was exhibited at the 2017 UK Quantum Showcase in London to an audience of industry and government. It also featured as part of the Quantum City stand at the 2018 Cheltenham science festival, one of the UK's leading annual science events.
Direct UV writing is a technique capable of fabricating low-loss channel waveguides, couplers and Bragg gratings in planar silica devices by translating an appropriate substrate through a tightly focused UV beam. To date direct UV written waveguides have been primarily formed using 244nm laser light, relying on the photosensitivity provided by doping with germanium and boron. To induce sufficient refractive index change, necessary for wave guiding, the substrates also require hydrogenation prior to UV writing. Not only does this require additional processing but over time the hydrogen present within the silica out-diffuses, which can cause variation of the final written structures. Deep-UV light, with a wavelength of 213 nm, has previously been used to inscribe strong fibre Bragg gratings (FBGs) in hydrogen-free Ge-doped fibres. Here we present the use of a 213 nm UV laser to write planar waveguide devices without the need for hydrogen loading.
Flame Hydrolysis Deposition (FHD) was used to deposit core and cladding layers of doped silica onto a thermally oxidised silicon wafer. Individual planar chips were diced from this wafer and a 5th harmonic Q-switched solid state laser operating at 213 nm wavelength was used to inscribe waveguides within the germanium-doped core layer of the chips without prior hydrogen loading.
We shall present our latest results of direct deep-UV written waveguides, including; the characterisation of single mode waveguides, detailed fluence and loss measurements, induced refractive index change and the first demonstration of planar Bragg gratings and photonic structures written with 213nm light.
Integrated Optical Fibre (IOF) allows for robust planar integration and seamless monolithic coupling. Fabrication is achieved through an adapted Flame Hydrolysis Deposition (FHD) technique, which forms a ruggedized glass alloy between the fibre and planar substrate. It has been previously demonstrated as a low linewidth external cavity lasers diode and a hot-wire anemometer, inherently suitable for harsh environments.
This work looks at implementing the platform for harsh environment refractometry, in particular monitoring hydrocarbon fuels in the C14 to C20 range (e.g. Jet A1 and diesel). The platform uses SMF-28 fibre and direct UV written Bragg gratings to infer refractive index and thus the quality of the fuel. A challenge arises as the refractive index of these fuels are typically greater than the refractive index of the waveguide. Therefore, the guided mode operation of FBG refractometers is unsuitable. This work uniquely reports leaky mode operation and a regression analysis, inferring propagation loss through changes in amplitude of successive gratings. In effect, the proposed methodology utilises the imaginary part of the effective index as opposed to the real part, typically used by such sensors.
Initial results have shown a 350 (dB/cm)/riu sensitivity is achievable above a refractive index of 1.45. This was measured for a SMF-28 fibre wet etched to 30 µm and planarized. Considering a 0.01 dB/cm propagation loss resolution, refractive index changes of the order 10-5 can be approached.
Work will be presented on the fabrication of an IOF platform for refractometers as well as metrics for survivability in harsh environments.
We present results from the development of a fiber-coupled Acousto-Optic modulator (Fiber-Q®) operating at near-UV and blue wavelengths.
A conventional TeO2 based Bragg diffraction design is introduced for short wavelengths optical input. Pure silica core single mode fibers (both Polarisation Maintaining (PM) and non-PM) are used as coupling fibers for their transmission at these wavelengths, and to avoid the possibility of photo darkening. The end of the fibers are fused with silica end-caps, lowering the power density on their fiber-air interfaces to achieve a higher power handling. The Fiber-Q® can be optimized for multiple wavelengths (including 397nm or 422nm) and can accept power levels of up to 100mW. A hermetically sealed package is selected to provide a clean in-package environment thus protecting the optics from damage caused by external contamination.
In this presentation we report details of the design, and test results of a fiber-coupled Acousto-Optic modulator that demonstrates the performance required for use in ion-trap quantum information processing applications.
Mode-locked Vertical External-Cavity Surface-Emitting Lasers (ML-VECSELs) have seen advances in pulse energy and peak power thanks to improved power handling techniques and structure designs. The significant increase in gain and intra-cavity power, coupled with the VECSEL's accessible external-cavity, has made the addition of intra-cavity elements for frequency conversion possible even for lossy conversion mechanisms. In this paper, we report a gold-patterned Semiconductor Saturable Absorbing Mirror (SESAM) that functions both as a slow saturable absorber in a ML-VECSEL and as an intracavity strip line Photo-Conductive Antenna (PCA) for THz emission. Here we describe the design of the strip emitter, THz-Time Domain Spectroscopy (TDS) performed with a ML-Yb fibre laser and the mode-locked characterisation of a ML-VECSEL built with the patterned SESAM.
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