Valerian Hongjie Hall-Chen

Valerian Hongjie Hall-Chen
Institute Of High Performance Computing · Electronics and Photonics

Doctor of Philosophy

About

14
Publications
2,649
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210
Citations
Introduction
I am coordinating and strategising A*STAR's entry into fusion research.
Additional affiliations
December 2021 - present
Institute Of High Performance Computing
Position
  • Researcher
Description
  • I am putting together a proposal to start a fusion research programme in A*STAR.
March 2016 - August 2016
Institute of Materials Science and Engineering
Position
  • Specialist I
July 2015 - February 2016
Institute Of High Performance Computing
Position
  • Engineer
Description
  • I worked on three projects: the losses in rough non-linear silicon waveguides; the use of genetic algorithms in designing metasurfaces with either broadband absorption or reflection; and the use of dielectric nanostructures for sensing.
Education
October 2016 - December 2021
University of Oxford
Field of study
  • Plasma Physics and Controlled Fusion
October 2012 - June 2015
University of Cambridge
Field of study
  • Natural Sciences (Physics)

Publications

Publications (14)
Article
Full-text available
The minimisation of birefringence, or polarisation mode dispersion, is vital for simplifying and miniaturising photonic components. In this work, we present a systematic study of the slot waveguide geometries required for having zero birefringence (ZB). We show that the rail widths required for ZB are more strongly dependent on the height of the wa...
Article
A gyroid structure is a distinct morphology that is triply periodic and consists of minimal isosurfaces containing no straight lines. We have designed and synthesized amorphous silicon (a-Si) mid-infrared gyroid photonic crystals that exhibit a complete bandgap in infrared spectroscopy measurements. Photonic crystals were synthesized by deposition...
Article
Full-text available
The optimal geometry of silicon-organic hybrid slot waveguides is investigated in the context of the efficiency of four-wave mixing (FWM), a χ(3) nonlinear optical process. We study the effect of slot and waveguide widths, as well as waveguide asymmetry on the two-photon absorption (TPA) figure of merit and the roughness scattering loss. The optima...
Article
Cobalt films with in-plane anisotropy were studied using two-axis magnetometry. Uniaxial anisotropy was induced in Co films by linear features on the substrate. These linear features were formed by various means: self-assembly of CaF2 grooves, nano-imprinting, and high energy atom flux or steps on vicinal surface of Si. From the analysis of compone...
Article
We use beam tracing --- implemented with a newly-written code, Scotty --- and the reciprocity theorem to derive a model for the linear backscattered power of the Doppler Backscattering (DBS) diagnostic. Our model works for both the O-mode and X-mode in tokamak geometry (and certain regimes of stellarators). We present the analytical derivation of o...
Preprint
Full-text available
A linear response, local model for the DBS amplitude applied to gyrokinetic simulations shows that radial correlation Doppler reflectometry measurements (RCDR, Schirmer et al., Plasma Phys. Control. Fusion 49 1019 (2007)) are not sensitive to the average turbulence radial correlation length, but to a correlation length that depends on the binormal...
Preprint
Full-text available
We use beam tracing -- implemented with a newly-written code, Scotty -- and the reciprocity theorem to derive a model for the linear backscattered power of the Doppler Backscattering (DBS) diagnostic. Our model works for both the O-mode and X-mode in tokamak geometry (and certain regimes of stellarators). We present the analytical derivation of our...
Article
Full-text available
The coloration of some butterflies, Pachyrhynchus weevils, and many chameleons are notable examples of natural organisms employing photonic crystals to produce colorful patterns. Despite advances in nanotechnology, we still lack the ability to print arbitrary colors and shapes in all three dimensions at this microscopic length scale. Here, we intro...
Article
The rings, spots and stripes found on some butterflies, Pachyrhynchus weevils, and many chameleons are notable examples of natural organisms employing photonic crystals to produce colorful patterns. Despite advances in nanotechnology, we still lack the ability to print arbitrary colors and shapes in all three dimensions at this microscopic length s...
Preprint
The rings, spots and stripes found on some butterflies, Pachyrhynchus weevils, and many chameleons are notable examples of natural organisms employing photonic crystals to produce colorful patterns. Despite advances in nanotechnology, we still lack the ability to print arbitrary colors and shapes in all three dimensions at this microscopic length s...
Article
Full-text available
We designed and simulated freestanding dielectric optical metasurfaces based on arrays of etched nanoholes in a silicon membrane. We showed 2π phase control and high forward transmission at mid-infrared (mid-IR) wavelengths around 4.2 μm by tuning the dimensions of the holes. We also identified the mechanisms responsible for high forward scattering...
Article
Cobalt films were grown by molecular beam epitaxy on CaF2 buffer layers on silicon. Due to unique properties of CaF2/Si(100) interface, the surface of CaF2 has grooves along [110] direction. Cobalt grown on it has in-plane uniaxial magnetic anisotropy with easy axis along the grooves. The dependence of remanence magnetisation and coercivity on azim...

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Projects

Project (1)
Project
Through analytical and computational effort, we seek to better interpret microwave fusion diagnostics. This enables better measurements of turbulence in fusion plasmas, which will hopefully contribute to the design of the next generation of machines.