1,721,091 research outputs found
Optical switches and modulators in deep freeze
No full textThe integration of silicon-based waveguides with barium titanate thin films enables the realization of efficient electro-optic switches and modulators operating at cryogenic temperatures, offering promising opportunities for quantum technologies
News and Views. Electronics and photonics united
No full textA method for integrating photonic devices with state-of-the-art nanoelectronics overcomes previous limitations. The approach shows promise for realizing high-speed, low-power optoelectronic technology
Predictions of free-carrier electroabsorption and electrorefraction in germanium
No full textGermanium is becoming an important material for mid-infrared photonics, but the modulation mechanisms in Ge are not yet well understood. In this paper, we estimate the size of free-carrier electroabsorption and electrorefraction effects in germanium across the 2 to 16 µm wavelength range at 300 K. The predictions are based as much as possible upon experimental absorption data from the literature and are supported by extrapolations from experimental data using first-principle quantum theoretical modeling. We find that free-carrier absorption is substantially stronger in Ge than in Si
Towards Mid-IR Germanium Defect Detector
No full textThe feasibility of room temperature defect mediated Mid-IR Germanium detectors will be investigated. We will implant Germanium detectors with various ion species, doses and post annealing temperatures to optimize the detector response in the Mid-IR. Here, we report on the detectors design and fabrication process.</p
Design of integrated silicon waveguides for Raman-enhanced four-wave mixing in the telecom band
No full textSilicon planar waveguides are designed to maximize the wavelength conversion efficiency via the use of Raman-enhanced four-wave mixing in the telecom band. By investigating the dispersion properties of various rib waveguide structures, the optimum etch depth and width are selected to obtain efficient phase-matching for a continuous-wave pump at 1545 nm. The design benefits from good fabrication tolerance in the structural parameters, which are well within the precision of standard lithography and etching processes. Using the optimized waveguides, simulations show that it is possible to reach conversion efficiencies as high as ∼ 45 dB for waveguide lengths as short as 4.6 cm, with a pump power of only 130 mW. This enhancement in the conversion efficiency is about 50 dB higher than conventional values for FWM in integrated silicon photonic systems, highlighting the benefits of exploiting the coupling between the two nonlinear processes
Free-carrier electro-refraction and electro-absorption modulation predictions for silicon over the 1-14µm infrared wavelength range
No full textWe present relationships for the free-carrier-induced electrorefraction and electroabsorption in crystalline silicon over the 1-14 µm wavelength range. Electroabsorption modulation is calculated from impurity-doping spectra taken from the literature, and a Kramers-Kronig analysis of these spectra is used to predict electrorefraction modulation. More recent experimental results for terahertz absorption of silicon are also used to improve the commonly used 1.3 and 1.55 µm equations. We examine the wavelength dependence of electrorefraction and electroabsorption, finding that the predictions suggest longer wave modulator designs will, in many cases, be different from those used in the telecom range
Education and training of silicon photonics engineers and technicians
No full textAt the University of Southampton, we have established an educational photonics pathway in which we teach our undergraduate and postgraduate students the fundamentals of silicon photonics. We have designed silicon photonics laboratories, for both simulation and characterization, where our students have opportunities to design their chips and characterize them. Our assessment strategy aims to improve students’ self-assessment and feedback skills. The material we have developed is also being used for training our technicians and PhD students
High throughput physical vapor deposition growth of Pb(Zr<sub>x</sub>Ti<sub>1-x</sub>)O<sub>3 </sub>perovskite thin films growth on silicon substrates
No full textThe integration of lead zirconate titanate (Pb(ZrxTi1-x)O3) (PZT) compounds on Si substrates with a smooth surface would provide a key technology for silicon photonic devices. The quality of the deposited thin film is critical in order to integrate Pb(ZrxTi1-x)O3 on Si substrates for applications such as pyroelectric mid-infrared detectors or optical modulators. Here, we have applied physical vapour deposition technique using a modified molecular beam epitaxy tool to deposit perovskite Pb(ZrxTi1-x)O3 on Si and Pt substrates. We have developed a method to grow crack-free PZT films on Si substrates. The fabrication procedure entailed the use of TiO2 as a buffer layer and post annealing of the PZT/TiO2/Si films under oxygen atmosphere. Cross section Scanning Electron Microscopy images enabled the identification of two distinct layers: PZT and TiO2, which was also confirmed by Spectroscopic Ellipsometry. X-Ray Diffraction patterns indicated the transition from the rhombohedral to the tetragonal phase and the formation of the perovskite phase of Pb(Zr0.44Ti0.56)O3
Third order Bragg grating filters in small SOI waveguides
No full textThird order grating filters fabricated in small Silicon-on-Insulator rib waveguides are demonstrated. Variations in grating etch depth and duty cycle are considered, and a maximum experimental reflection of 42% is demonstrated for gratings of 1500 µm in length, with a grating period of approximately 689nm and an etch depth of 200nm. Agreement with modeling is shown to be good
Hot-wire chemical vapour deposition for silicon nitride waveguides
No full textIn this work, we demonstrate the use of HWCVD as an alternative technique to grow SiN layers for photonic waveguides at temperatures <400ºC. In particular, the effect of the ammonia flow and the filament temperature on the material structure, optical properties and propagation losses of the deposited films was investigated. SiN layers with good thickness uniformity, roughness as low as 0.61nm and H concentration as low as 10.4×1021 atoms/cm3 were obtained. Waveguides fabricated on the studied materials exhibited losses as low as 7.1 and 12.3 dB/cm at 1310 and 1550nm respectively
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