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.
The possibility of fabricating all-fiber nonlinear devices based on periodically poled silica fibers allows for overcoming most of the issues of free space nonlinear optics, such as thermal instabilities and high costs of nonlinear crystals. In this talk the most recent results related to the topic are presented, including some interesting applications of periodically poled fibers, such as the generation of high harmonics and of Frequency Combs when exploited in cavity configuration.
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.
We present an investigation into the resolution of blazed chirped Bragg grating spectrometers. These are dispersive spectrometers that diffract light out of a waveguide at a wavelength dependent angle, whilst focusing the light. The spectral resolution is found to be inversely proportional to grating length; previously used fabrication schemes limited the grating length (and hence resolution) when creating compact devices. We propose and implement a solution to this problem by varying the blaze angle of a Bragg grating along its length. Initial results show the fabrication of longer gratings (while preserving focal length) and an increase in FWHM resolution from
0.57 nm to 0.52 nm. This increase in resolution is thought to be limited by the appearance of aberrations which can be corrected for in future devices.
Thermal poling, a technique to create permanently effective second-order susceptibility in silica optical fibers, has recently been improved by the discovery of an “induction poling” technique1 and the adoption of liquid electrodes2, allowing for poling fibers of any length and geometry. Nevertheless, the nonlinearity created via thermal poling is always limited by the 𝜒(3)of the optical fiber material and by the maximum electric field that can be frozen inside the glass. For these reasons research is ongoing to determine routes for further improving the nonlinear effects due to the thermal poling process. In this work, we propose to enhance the effects of the thermal poling by exploiting the intrinsic nonlinear properties of some 2D materials3, which are deposited inside the cladding holes of a twin-hole silica fiber. The materials we focused on are 2D Transition Metal Chalcogenide (2D TMDC) MoS2 and WS2 and the technique adopted to realize the deposition inside the cladding channels of a twin-hole step index silica fiber consists of a thermal decomposition process4 of the precursor ammonium tetrathiomolybdate (NH4)2MoS4 in 6% H2/Ar flow. The technique has allowed us to uniformly coat the two cladding channels for a length of ≈25 cm with a film nominally consisting in a bi-layer of the 2D materials. A Raman based analysis has been used to test the morphology of the coating. The fiber deposited with 2D materials was later thermally poled and periodically erased via exposure to UV light to reach the QPM condition at a wavelength of ≈1550 nm. The effective 𝜒(2) of the fiber was measured via SHG for both the deposited and the pristine fiber, showing an enhancement of the nonlinearity in favor of the deposited one. The phenomenon can be explained by the exploitation of a higher 𝜒(3) seen by the pump wave due to the presence of the 2D layer deposited inside the cladding holes and opens the possibility of exploiting the higher intrinsic material 𝜒(2), in case of a periodic patterning/synthesis of the TMDC.
For over a decade the field of quantum photonics has increasingly looked towards optical integrated platforms to perform more complex and sophisticated experiments. Silica integrated optics is an ideal material for this area, offering low propagation and fibre-coupling losses. To date many of the key on-chip experiments have been carried out in this platform, using bespoke monolithic devices. In this work we propose an alternative approach, implementing a linear network constructed from a number of identical reconfigurable modules. The modules are measured separately to produce an accurate model of the overall network. The cellular nature also allows the replacement of modules that are faulty or substandard. Each module comprises of an array of 10 Mach-Zhender interferometers. Forty thermo-optic phase shifters on each chip allows the control of both the amplitude and phase of the optical field within the devices. By cascading the modules any arbitrary NxN unitary network can be realised. The optical waveguides within the modules are fabricated by direct UV writing, where a scanning focused UV laser beam increases the local refractive index within a photosensitive germanosilicate glass layer. The resulting channel waveguides are engineered to have dimensions that are mode matched to standard optical fibre producing excellent coupling efficiency. Bragg gratings can also be simultaneously produced within the waveguides which greatly assists in the precise characterisation of the phase shifters, coupling ratios and optical losses within the modules. We will present our recent work in this area, demonstrating devices operating at telecom wavelengths for quantum information processing. We present a modular reconfigurable system for on-chip quantum optics experiments with excellent fibre compatibility and low propagation losses, implemented using direct-UV-written silica-on-silicon. The performance of fabricated devices in various configurations is reported.
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.
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