Deok Woo Kim

Currently at PhD student
Ultrafast lasers and Photonics Laboratory (ULPL), Lab homepage (URL)
Department of physics, KAIST
Supervisor: Fabian Rotermund
Contact
dwkim96@kaist.ac.kr / ys89827@hotmail.com
Personal instagram (URL)

Research Interests

Ultrafast Mode-Locked Laser Systems

Solid-state lasers have become indispensable tools across optical science, materials research, and industrial applications. Mode-locked lasers, in particular, represent the cutting edge of optical technology, offering unparalleled capabilities in precision timekeeping through optical atomic clocks, ultrafast dynamics investigation via pump-probe spectroscopy, and high-precision frequency comb metrology. Their exceptional properties—including equidistant frequency mode spacing, ultrashort pulse duration, and broad spectral bandwidth—make them essential for advancing our understanding of ultrafast phenomena.

My research focuses on the sophisticated transition from continuous wave to mode-locked pulsed operation, leveraging solid-state laser gain media within ultra-compact cavity architectures that push the boundaries of miniaturization without compromising performance.

Femtosecond Laser-Inscribed Waveguide Platforms

The emergence of femtosecond laser-inscribed waveguide platforms in crystalline optical media represents a paradigm shift toward enhanced laser efficiency and unprecedented cavity miniaturization. These innovative platforms, with dimensions scaling down to mere centimeters, offer remarkable potential for next-generation photonic devices.

I am particularly captivated by the dynamic operational regimes of these ultra-compact systems, exploring the rich spectrum of behaviors from Q-switched to mode-locked operations within waveguide architectures that enable extraordinary optical phenomena.

Quadratic/Cubic Nonlinear Optics

Since the 1990s, cascading nonlinear optical frequency conversion has emerged as a cornerstone of modern optical science, enabling wavelength-agile technologies that form the backbone of contemporary photonics. My research gravitates toward periodically poled lithium niobate (PPLN), an extraordinary quasi-phase matched ferroelectric crystal that exhibits an exceptionally high nonlinear optical coefficient (~30 pm/V)—significantly surpassing conventional crystals such as KTP, KDP, and BBO.

The elegance of PPLN lies in its tunability: precise frequency control achieved through systematic temperature modulation and poling period optimization, offering unprecedented flexibility in nonlinear optical applications.

Precision Dielectric Thin Film Characterization

High-precision measurement of dielectric thin film parameters—specifically refractive index and thickness in the nanometer to micrometer regime—represents both a fundamental necessity and a formidable challenge in modern optics. Accurate phase shift control in nonlinear optical processes demands exquisite knowledge of refractive index properties with extraordinary precision.

My expertise centers on ultra-precise measurement techniques utilizing prism coupler configurations in planar waveguide geometries, achieving remarkable precision levels of 0.0001 in refractive index determination and 10 nm resolution in thickness measurements. This is accomplished through sophisticated statistical analysis of excited waveguide modes and innovative interference fringe pattern analysis using advanced statistical methodologies.

Computation and Numerical Modeling

Complex experimental phenomena and intricate physical systems often transcend analytical solutions, necessitating sophisticated numerical approaches that bridge theory and observation. My computational toolkit encompasses:

Waveguide Mode Analysis: Statistical nonlinear least-squares methods for excited waveguide mode characterization, providing deep insights into modal behavior and propagation characteristics.

Ultrafast Pulse Dynamics: Numerical solutions to the nonlinear Schrödinger equation using split-step Fourier methods, enabling precise modeling of optical pulse propagation and evolution in complex media.

Eigenmode Analysis: Finite-difference methods for comprehensive optical eigenmode profile analysis in waveguide structures, revealing the fundamental physics governing light confinement and propagation.

Universal Differential Equation Solutions: Comprehensive approaches to solving diverse differential equations encountered across all domains of optical physics.

My computational framework is primarily built upon MATLAB.