Daniel Ho

Dr

Accepting PhD Students

PhD projects

I. 3D Nanophotonics in artificially structured materials: 3D photonic crystal materials with a full photonic bandgap hold much promise for guiding, storing and controlling light but such structures are not routinely researched because of the difficulty of fabrication of arbitrary structures at the wavelength scale. In this project, we aim to fabricate wavelength-scale 3D structures blocking light propagation and orientation in all directions and polarizations in the 0.5 -1.6 µm region, and deliver the significant impact of emerging technologies (e.g., novel sensors, biomimetic structures, nano-lasers, and quantum light sources). To this end, the three objectives of the proposed work are: 1. Fabricating structures for controlling light trapping and propagation in the wavelength range of 0.5 - 1.6 µm; 2. Creating full photonic bandgap materials by backfilling the low index contrast polymer templates with high index chalcogenide materials using CVD/ALD techniques; 3. Investigating the application of 3D photonic structures in novel sensors, biomimetic structures, nano-lasers and quantum light sources. ------------------------------------------------------------------------------------------------------------------------- II. Single-photons on-demand: Planck's assumption of electromagnetic energy quantization and Einstein's hypothesis of light quanta (or photons) introduced the wave-particle duality of light and led to the quantum effects, such as quantum vacuum fluctuations and quantum entanglement; novel technologies now make it possible for us to create and detect single photons on demand. In this project, we will characterize experimentally the single-photon emission from quantum dots, colour centre in diamond, and 2D materials, measuring second-order autocorrelation functions using single-photon counting in a confocal fluorescent microscope. We will do this by engineering the defects, cavities, and waveguides at the wavelength scale to create devices with optimized structures for maximal photon emission and collection efficiency into useful modes. --------------------------------------------------------- III. Micro-Nanostructure-Stabilized Liquid-Crystalline Blue-Phase: Currently, the remaining grand challenge LCDs face in the display market is response time (a few milliseconds), which is ~ 100 times slower than that of an OLEDs (~ 0.1 ms); to achieve sub-millisecond response time for suppressing the colour breakup issue, blue phase liquid crystal (BPLC) is emerging as a strong candidate for reaching this goal. In recent works, my group has demonstrated that a polymeric microwell template can dramatically improve the stable temperature range up to 20oC (typically 1 − 5 °C) of the BPLC while enhancing reflectivity, and stability of the reflection peak wavelength. In this project, we will extend the temperature range and ideal single-crystals of blue phase liquid crystal, which can be used to significantly increase the refresh rate of LCD displays to 50°C by an approach based on the combination of organised microstructures and nano-patterned planar surface substrates.

  • Source: Scopus
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Personal profile

Biography

Dr. Ying-Lung Daniel Ho received his BSc degree in Electrical Engineering from the National Taipei University of Technology in Taiwan and the Ph.D. degree in Quantum Photonics from the University of Bristol. His doctoral dissertation, supervised by Prof. John Rarity, FRS, investigated the method of designing efficient single-photon sources for quantum information applications. He also built the confocal microscope for characterization of a single-photon source and was awarded a commendation for this work at the 16th International Conference on Quantum Electronics and Photonics and Photon 04. Subsequently, he was employed as a Postdoctoral Researcher and then a Research Fellow there. His work as a Research Fellow (Researcher Co-Investigator and Co-Investigator) under the EPSRC Programme Grants (EP/M009033/1 and EP/P034446/1) has led research in direct laser writing using two-photon polymerisation in the Quantum Engineering Technology Labs, and he is also a Visiting Lecturer at the Department of Electrical and Electronic Engineering in Bristol.

In September 2019, he started a position as a Vice-Chancellor's Senior Fellow in Physics and Electrical Engineering, after a career in Quantum Photonics research at the University of Bristol. Recently, he has received an EPSRC grant (EP/V040030/1) of £379,763 (80% FEC) to develop and conduct Nanophotonics research, which focuses on a comprehensive investigation into the fundamentals and applications of 3D nanophotonics in artificially structured materials. The project is in collaboration with research partners (QET Labs, University of Bristol and ORC, University of Southampton) and industrial partner (Oxford Instruments Plasma Technology) to develop novel sensors, biomimetic structures, nano-lasers, and ultrafast optical switches and devices for quantum technology.

Research interests

Daniel's research is concerned with both the theory and application of artificially structured electromagnetic materials for photonic engineering and quantum technologies.

(i) Nanofabrication Techniques: The realization of full 3D confinement of photons in photonic crystals (PhCs) has proven to be quite challenging. I designed and fabricated an inverse crystal using two-photon lithography followed by CVD backfilling. Backfilling used a low-temperature CVD process demonstrating a single-inversion technique; this provides reliable fabrication of full photonic bandgap materials confining light in 3D leading to a wide range of future photonic applications such as sensors, biomimetic structures, nano-lasers, and quantum light sources.

(ii) Optical Characterisation: Another aspect of my research concerns the angle-resolved light scattering characterisation technique using Fourier image spectroscopy (FIS) which measures the spectra across an image formed at the back focal plane of the objective lens, capturing the scattering pattern of the device under study. I have characterised structures in transmission and reflection modes using an in-house built FIS to visualise the photonic band structure.

(iii) Numerical Modelling: Modelling based on the electromagnetic simulation software (Finite-Difference Time-Domain, FDTD and plane-wave expansion, PWE) can assist in the design of devices compared with angle-resolved light scattering characterisation, which enables an estimation of device quality at each fabrication step. I have successfully demonstrated design and simulation of light confinement in diamond lattice structures based on removing or adding materials to create low-index or high-index cavities. Additionally, the complete PBGs of inverse RCDs formed in low refractive index contrast (1.9:1) via chalcogenide materials, were experimentally measured with results compared with numerical simulations. These results demonstrated that, the threshold of the lowest refractive index contrast can support a complete PBG, thus validating predicted data using the topology optimization approach.

Education/Academic qualification

Electrical and Electronic Engineering, PhD, University of Bristol

… → 14 Feb 2007

Award Date: 20 Jun 2007

Electrical Engineering, BSc, National Taipei University of Technology

… → 30 Jun 1999

Award Date: 30 Jun 1999

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