PROFESSIONAL SKILLS

Optical Characterization and Metrology

I have 8+ years of experience in measuring with light spanning from low-energy infrared/terahertz to X-ray spectral ranges. Below is a brief description of the experiments I've performed so far to investigate the physical properties of quantum materials with various single crystalline and thin-film samples.

TERAHERTZ

  • Terahertz generation through optical rectification with non-linear crystals

  • Terahertz detection through electro-optic sampling method

  • Time-domain terahertz spectroscopy

INFRARED | VISIBLE

  • Time-domain optical reflectivity/transmittance spectroscopy

  • High-harmonics generation with femtosecond pulses

  • Fourier transform infrared spectroscopy (FTIR)

  • Ellipsometry

X-RAY

  • X-ray absorption spectroscopy (XAS)

  • X-ray magnetic circular/linear dichroism (XMCD/XMLD)

  • X-ray photoemission spectroscopy (XPS)

  • X-ray diffraction (XRD), X-ray scattering

  • Time- and angle-resolved photoemission spectroscopy (time-resolved ARPES)

Ultrafast spectroscopy set-up at IBS-CCES

I've also built up a home lab of ultrafast spectroscopy at the Center for Correlated Electron Systems, Institute for Basic Science (IBS-CCES) in South Korea (link here). Currently, I'm working at the team at the Laboratory for Ultrafast Materials and Optical Science (LUMOS) in Los Alamos National Laboratory (link here), operating the ultrafast spectroscopic equipment. The spectroscopic systems at these laboratories are for time-resolved optical measurements with light sources of infrared, visible, and terahertz light sources in reflection and transmission geometries. Below is the specification of the laser and equipment that I've installed and operated so far.

FEMTOSECOND LASER

  • Ti:Sapphire oscillator: Vitara-T, Coherent Co. | Tsunami, Spectra-Physics

  • Ti:Sapphire regenerative amplifier:
    RegA9040, RegA9000 (250 kHz), Coherent Co. | Spitfire ACE (1 kHz), Spectra-Physics

  • Optical Parametric Amplifier (OPA):  OPA9450 (wavelength: 480-700 / 933-2300 nm), Coherent Co.

CRYOGENIC SYSTEMS

  • Superconducting magnetic cryostat (Oxford)

  • Optical cryostat (Oxford, Janis)

Data Analysis and Simulation

I have 8+ years of experience in programming for scientific data analysis and simulation of optical and structural properties of condensed matters. I've been dealing with large data set over a few TB volumes of optical spectroscopic measurements by using programming codes written in Python and MATLAB languages. One other task for my programming has been to control and operate the experimental devices, and I've used LABVIEW for this job. Below is a brief description of some of my programming works below, and the code can be found on my Github page here.

X-RAY DIFFRACTION (XRD) GEOMETRY SIMULATION
FOR PUMP-PROBE EXPERIMENT

When you're doing X-ray diffraction/scattering, it's usually tricky to figure out the exact geometry conditions for X-ray alignments, especially for pump-probe experiments. I made a code for simulation for X-ray diffraction (XRD) geometric conditions of a 4-circle (4C) diffractometer system with a fixed grazing angle condition, as well as pump beam geometry considering its angle of incidence and polarization. From the code, you can find the following results from this simulation:

  • visualization of diffraction + pump-probe geometry

  • omega, two-theta, chi, phi angles 4C alignment for X-ray beam

  • incidence grazing angle, polarization angle for optical beam

The code for this simulation can be found on my Github page here.

PROGRAMMING LANGUAGES & SOFTWARES

  • Python (Numpy, Pandas, Tensorflow) 

  • Jupyter Notebooks

  • MATLAB

  • Origin

  • Igor

  • Mathematica

  • Adobe Photoshop | Ilustrator | Premiere

  • Microsoft Office

  • LabVIEW

  • VESTA

  • Demeter

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