Introduction

Diamond defects has generated immense research interest due to their wide range of applications, including reliable identification of natural and synthetic diamonds, development of quantum computing technologies, creation of highly sensitive magnetic probes, medical diagnostics, and much more. To develop these cutting-edge technologies, the energy dynamics of the defects and their interaction with the diamond lattice must be fully understood.

I specialize in using ultrafast time-domain pump probe spectroscopy (TVAS) to explore the vibrational energy dynamics of diamond defects in nano- to femtosecond timescales (Fig. 1). Key outcomes of my research include the characterization of diamond defect vibrational energy structures (Fig. 2), quantification of vibrational state dephasing and population lifetimes, establishing methods for defect quantification, and characterizing defect-defect and defect-lattice interactions. Beyond diamond defects, I also investigate and develop novel techniques in pump-probe spectroscopy, such as using perturbed free induction decay to extract dephasing dynamics. These ultrafast spectroscopy techniques can be applied on a range of materials, such as other semiconductor defects (e.g. silicon, GaAs), perovskites, and molecular systems. Throughout my research, I also make use of various equilibrium spectroscopy techniques, including optical absorption spectroscopy (FTIR/UV-Vis) (Fig. 3), Raman spectroscopy, photoluminescence spectroscopy, and birefringence imaging. This project is jointly funded by The De Beers Group and the Diamond Science and Technology CDT. My PhD is jointly supervised by Prof James Lloyd-Hughes (Physics), Prof Mark Newton (Physics), and Prof Vas Stavros (Chemistry).

Fig. 1 Obtaining ground state bleach (GSB) and excited state absorption (ESA) signals using TVAS

Fig. 2 Vibrational energy structure of the N₃VH diamond defect based on TVAS measurements

Fig. 3 FTIR mapping of the N₃VH defect distribution in a diamond sample

Outside of my research I enjoy participating in a range of sports which includes basketball, bouldering, cycling, and weightlifting. I play the drums and guitar and also enjoy a good read in my spare time.

Research and Academic Background

MSci Physics, Imperial College London (2016-2020)

• 1st Class Honours
• Final year modules: Advanced Hydrodynamics, Entrepreneurship for Physicists, Information Theory, Laser Technology, Nanotechnology in Consumer Electronics, Optical Communications, Plasmonics and Metamaterials
• MSci project: Spectral Smoothing of Femtosecond Laser Pulses via Nonlinear Elliptical Polarisation Rotation (Supervised by Prof John W.G. Tisch)
• Third year project: Creating a Raspberry Pi Controlled 2D Deformable Mirror (Supervised by Prof Roland A Smith)

Undergraduate Research Opportunities Programme, Imperial College London (2018)

• An eight week summer research project supervised by Prof Ji-Seon Kim (Physics)

• Investigated organic photovoltaics using air-photoemission spectroscopy and conducted error analysis on the APS04 system developed by KPtechnologies

• Recipient of the BP UROP Award (co-funded by the Dean's Fund for the Faculty of Natural Sciences)

Summer Internship, City University of Hong Kong (2016)

• A six week summer internship supervised by Dr. Hau Ping Andy Chan
• Developed a multi-channel LiFi audio system which allows free-space data transfer for outreach purposes

Publications

• T. J. Keat, D. J. L. Coxon, R. J. Ruddace, V. G. Stavros, M. E. Newton, and J. Lloyd-Hughes The 3237 cm⁻¹ diamond defect: ultrafast vibrational dynamics, concentration calibration, and relationship to the N₃VH⁰ defect, Diamond and Related Materials, 141, 110661 (2024).
• T. J. Keat, D. J. L. Coxon, M. Staniforth, M. W Dale, V. G. Stavros, M. E. Newton, and J. Lloyd-Hughes Dephasing dynamics across different local vibrational modes and crystalline environments, Physical Review Letters, 129, 237401 (2022).

Conference Presentations

• (Poster presentation) "An Ultrafast Study on the N_s:H-C⁰ Diamond Defect" 2024 Spectroscopy and Dynamics Group Meeting
• (Oral and poster presentation) "Illuminating the Characteristics of Diamond Defects Using Transient Vibrational Absorption Spectroscopy" 33^rd International Conference on Diamond and Carbon Materials
• (Oral presentation) "Transient Vibrational Absorption Spectroscopy: An Ultrafast Route to Defect Energy Structure and Quantification" 2023 De Beers Diamond Research Conference
• (Oral presentation) "It's not that Hard: Unraveling Vibrational Dynamics and Interactions in Diamond Defects" Time Resolved Vibrational Spectroscopy 2023 Conference
• (Oral presentation) "A Flash Within Forever: Ultrafast Spectroscopy on Diamond Defects" 2023 Spectroscopy and Dynamics Group Meeting
• (Oral presentation) "Dephasing Dynamics of Local Vibrational Modes in Diamond Defects Detected Using Perturbed Free Induction Decay" 2022 MRS Fall Meeting
• (Poster presentation) "Ultrafast Pump-Probe Dynamics of the Unknown 3237cm^-1 Diamond Defect Absorption Feature" 2022 MRS Fall Meeting
• (Oral presentation) "Perturbed Free Induction Decay as a Method to Validate, Extract, and Predict Vibrational Energy Dynamics in Diamond Defects" 2022 De Beers Diamond Research Conference
• (Poster presentation) "Using Perturbed Free Induction Decay to Determine the Total Dephasing Lifetime of Diamond Defects" 2021 De Beers Diamond Research Conference

Awards

• 33rd International Conference on Diamond and Carbon Materials Silver Elsevier Young Scholar Award
• 2023 Spectroscopy and Dynamics Group Meeting Best Presentation Prize
• 2022 MRS Fall Meeting EQ07 Symposium Student Poster Prize
• 2022 De Beers Diamond Research Conference Best Student Presentation Prize
• 2021 De Beers Diamond Research Conference Best Student Poster Prize

Teaching

I am currently a 1st year tutorial demonstrator for PX149: Mathematics for Physicists