Non-isothermal phase-field simulations of laser-written in-plane SiGe heterostructures for photonic applications

Advanced solid-state devices, including lasers and modulators, require semiconductor heterostructures for nanoscale engineering of the electronic bandgap and refractive index. However, existing epitaxial growth methods are limited to fabrication of vertical heterostructures grown layer by layer. Here, we report the use of finite-element-method-based phase-field modelling with thermocapillary convection to investigate laser inscription of in-plane heterostructures within silicon-germanium films. The modelling is supported by experimental work using epitaxially-grown Si0.5Ge0.5 layers. The phase-field simulations reveal that various in-plane heterostructures with single or periodic interfaces can be fabricated by controlling phase segregation through modulation of the scan speed, power, and beam position. Optical simulations are used to demonstrate the potential for two devices: graded-index waveguides with Ge-rich (>70%) cores, and waveguide Bragg gratings with nanoscale periods (100–500 nm). Periodic heterostructure formation via sub-millisecond modulation of the laser parameters opens a route for post-growth fabrication of in-plane quantum wells and superlattices in semiconductor alloy films

Laser Thermal Processing of Group IV Semiconductors for Integrated Photonic Systems

In the quest to expand the functionality and capacity of group IV semiconductor photonic systems, new materials and production methods are constantly being explored. In particular, flexible fabrication and postprocessing approaches that are compatible with different materials and allow for tuning of the components and systems are of great interest. Within this research area, laser thermal processing has emerged as an indispensable tool that can be applied to enhance and/or modify the material, structural, electrical and optical properties of group IV elemental and compound semiconductors at various stages of the production process. Herein, the recent progress made in the application of laser processing techniques to develop integrated semiconductor systems in both fiber- and planar-based platforms is evaluated. Laser processing has allowed for the production of semiconductor waveguides with high crystallinity in the core and low optical losses, as well as postfabrication trimming of device characteristics and direct writing of tunable strain and composition profiles for bandgap engineering and optical waveguiding. For each platform, the current challenges and opportunities for the future development of laser-processed integrated semiconductor photonic systems are presented

Critical phenomena in dynamical Ising-typed thin films by effective-field theory

The stationary state solutions of the Ising-typed thin films with different layers in the presence of an external oscillatory field are examined within the effective-field theory. The study focuses on the effects of external field frequency and amplitude on the overall behavior. Particular attention is paid on evolution of the special point with dynamic field frequency corresponding to critical temperature of the three-dimensional infinite bulk system where the surface and modified exchange parameters are of no importance. Some findings such as surface enhancement phenomenon and effect of thickness on the dynamic process are introduced together with some other well known characteristics. An attempt is made to explain the relations between the competing time scales (intrinsic microscopic relaxation time of the system and the time period of the external oscillatory field) and frequency dispersion of the critical temperature coordinate of the special point. (C) 2014 Elsevier B.V. All rights reserved

Dataset for Tapered silicon core fibers with nano-spikes for optical coupling via spliced silica fibers

Reported here is the fabrication of tapered silicon core fibers possessing a nano-spike input that facilitates their seamless splicing to conventional single mode fibers. A proof-of-concept 30 &micro;m cladding diameter fiber device is demonstrated with nano-spike coupling and propagation losses below 4 dB and 2 dB/cm, respectively. Finite-element-method-based simulations show that the nano-spike coupling losses could be reduced to below 1 dB by decreasing the cladding diameters down to 10 &micro;m. Such efficient and robust integration of the silicon core fibers with standard fiber devices will help to overcome significant barriers for all-fiber nonlinear photonics and optoelectronics.</span

Popliteal Lymph Node Metastasis After Excision of the Malign Melanoma of the Heel

Generally, melanoma of the distal leg and the foot metastasize to the lymph nodes of the groin. Sometimes the first site of nodal disease may be the popliteal fossa. A 50-year-old woman presented with pigmented macular lesion on the left heel. Pathology report was positive for malign melanoma, 6.63 mm thickness and Clark's level V, following excision. There was no evidence for systemic metastasis; additional surgical intervention was not performed because of the thickness of the lesion and the patient was monitored. After 21 months, we noticed a 3 x 2 cm palpable inguinal lymph node on the same side and popliteal lymphatic metastasis was determined by pre-operative lymphoscintigraphy. Pathologic report was positive for only popliteal sentinel lymph node. We performed both popliteal and grion lymph node dissections simultaneously. We suggest that groin and popliteal lymphatic dissection must be per-formed together for popliteal lymph node positive malign melanoma cases

Dataset for Non-Isothermal Phase-Field Simulation of Laser-Written In-Plane SiGe Heterostructures for Photonic Applications

DATASET for Non-Isothermal Phase-Field Simulation of Laser-Written In-Plane SiGe Heterostructures for Photonic Applications in Communications Physics.</span

Data supporting Southampton Doctoral Thesis &quot;Direct laser writing in semiconductors for photonics applications&quot;

This dataset supports the thesis entitled Direct Laser Writing in Semiconductors for Photonics Applications AWARDED BY: Univeristy of Southampton DATE OF AWARD: 2022 This dataset contains: Transmission loss measurement data, detailing waveguide length, input power and output power. Raman spectroscopy data collected using a Renishaw Invia Raman spectrometer. Nonlinear transmission data detailing measurement wavelength and transmitted power. Complete details of data collection processess are available in the associated thesis. Data for: - Linear and nonlinear transmission losses in laser-fabricated polysilicon waveguides, - Linear loss measurements in laser-defined hydrogenated amorphous silicon waveguides, - Raman spectroscopy measurements on both polysilicon and hydrogenated amorphous silicon waveguides.</span