arXiv subjects

Byunggi Kim

Publications and source records attributed to Byunggi Kim.

8 recordsLinked to original sources

arXiv2026

Gigahertz-frequency Lamb wave resonator cavities on suspended lithium niobate for quantum acoustics

Phononic nanodevices offer a promising route toward quantum technologies, as phonons combine strong confinement within matter with broad coupling capabilities to various quantum systems. In particular, the piezoelectric response of materials such as lithium niobate enables coupling between superconducting qubits and gigahertz-frequency phonons. However, bulk lithium niobate phononic devices typically rely on surface acoustic waves and are therefore inherently subject to leakage from the surface into the bulk substrate. Here, we explore the acoustic behavior of resonator cavities supporting GHz-frequency Lamb waves in a 200 nm-thick suspended lithium niobate layer. We characterize the acoustic response at both room and millikelvin temperatures. We find that our resonator cavities with strong confinement reach intrinsic quality factors of approximately 6000 at the single phonon level. We use the measured parameters of the resonators to model their coupling to a superconducting transmon qubit, allowing us to evaluate their potential as quantum acoustic devices.

cond-mat.mes-hall↗

arXiv2025

Ultra-High-Temperature Vacuum Prober for Electrical and Thermal Measurements

We develop an ultra-high-temperature vacuum probe station (UHT-VPS) featuring a sample holder heated by thermal radiation from a silicon carbide heater. This contactless configuration electrically isolates the sample from the high-power heating source through a vacuum gap, ensuring reliable measurements under extreme conditions. The capability of this UHT-VPS to measure electrical signals from 30 nV upward on bulk sapphire is demonstrated using the 3w/2w method. Measurements are continuously operated from 300 to 1150 K, under high vacuum, for a total of about 66 hours without readjusting the contact. They yield the linear and quadratic temperature coefficients of resistance of chromium/platinum micro-resistances, as well as the sapphire's thermal conductivity and thermal diffusivity. By recording the heater and sensor temperature signals up to 30 kHz and fitting them with theoretical models that account for the quadratic TCR of Cr/Pt microwires, we obtain values in agreement with literature data obtained by optical methods. In this temperature range, we also measure thermal conductivity, which cannot be directly accessed by optical techniques. Our system thus provides an effective solution for simultaneously retrieving the electrical and thermal properties of materials using a single set of 3w/2w data up to unprecedented temperature levels.

physics.ins-det↗

arXiv2025

Hypersonic acoustic wave control via hyperuniform phononic nanostructures

Controlling hypersonic surface acoustic waves is crucial for advanced phononic devices such as high-frequency filters, sensors, and quantum computing components. While periodic phononic crystals enable precise bandgap engineering, their ability to suppress acoustic waves is limited to specific frequency ranges. Here, we experimentally demonstrate the control of surface acoustic waves using a hyperuniform arrangement of gold nanopillars on a lithium niobate layer. The hyperuniform structure exhibits characteristics of both random and ordered systems, leading to an overall reduction in acoustic transmission and the formation of bandgap-like regions where phonon propagation is strongly suppressed. We further demonstrate effective waveguiding by incorporating linear and S-shaped waveguides into the hyperuniform pattern. Both simulations and experiments confirm high transmission through the waveguides at frequencies within the bandgaps, demonstrating the flexibility of hyperuniform structures to support waveguides of complex shapes. These findings provide a novel approach to overcoming the limitations of traditional phononic crystals and advancing acoustic technologies in applications such as mechanical quantum computing and smartphone filters.

cond-mat.mes-hall↗

arXiv2024

Piezoelectrically driven diamond phononic nanocavity by phonon-matching scheme for quantum applications

Efficiently exciting and controlling phonons in diamond nanoresonators represents a fundamental challenge for quantum applications. Here, we theoretically demonstrate the possibility to excite mechanical modes within a double-hybrid-cavity (DHC), formed by adjoining to a diamond cavity a second cavity, made of aluminum nitride. The latter is piezoelectric and serves as a microwave-to-phonon transducer, activating mechanical modes in the entire DHC. We show the process to match the cavities phononic properties, making them work coordinately in the DHC and obtaining a well confined mode. In the diamond part of the cavity, this mode replicates the fundamental mode of the individual diamond cavity, showing that the piezoelectric transducer doesn't alter the diamond individual fundamental mode. In the piezoelectric part, the strong confinement of stress and electric field results in a high piezoelectric coupling rate, demonstrating the effectiveness of a phononic cavity as a transducer. The study is contextualized in the framework of a quantum networking application, where the DHC serves as a spin qubit, exploiting the spin-mechanical coupling within diamond color centers.

cond-mat.mes-hall↗

arXiv2023

Diamond optomechanical cavity with a color center for microwave-to-optical quantum interfaces

Quantum transduction between microwave and optical photons plays a key role in quantum communication among remote qubits. Although the quantum transduction schemes generating communication photons have been successfully demonstrated by using optomechanical interfaces, the low conversion efficiency remains an obstacle to the implementation of a quantum network consisting of multiple qubits. Here, we present an efficient quantum transduction scheme using a one-dimensional diamond optomechanical crystal cavity tuned at a color-center emission without optomechanical coupling. The optomechanical crystal cavity incorporates a thin aluminum nitride (AlN) pad piezoelectric coupler near the concentrator cavity region, while retaining ultrasmall mechanical and optical mode volumes of about 1.5 \times 10^{-4} and ~0.2(λ/n)^3, respectively. The energy level of a coherent color-center electron is manipulated by a strong mechanical-mode-color-center electron-coupling rate up to 16.4MHz. In our system, we theoretically predict that the population-conversion efficiency from a single microwave photon into an optical photon can reach 15% combined with current technologies. The coherent conversion efficiency is over 10% with a reasonably pure decay time of T^2_{*} > 10 ns. Our results imply that an atomic color center strongly coupled to the optomechanical crystal cavity will offer a highly efficient quantum transduction platform.

quant-ph↗

arXiv2023

Polaritonic Waveguide Emits Super-Planckian Thermal Radiation

Classical Planck's theory of thermal radiation predicts an upper limit of the heat transfer between two bodies separated by a distance longer than the dominant radiation wavelength (far-field regime). This limit can be overcome when the dimensions of the absorbent bodies are smaller than the dominant wavelength due to hybrid electromagnetic waves, known as surface phonon-polaritons (SPhPs). Here, we experimentally demonstrate that the far-field radiative heat transfer between two non-absorbent bodies can also overcome Planck's limit, by coating them with an absorbent material to form a polaritonic waveguide. This super-Planckian far-field thermal radiation is confirmed by measuring the radiative thermal conductance between two silicon plates coated with silicon dioxide nanolayers. The observed conductance is twice higher than Planck's limit and agrees with the predictions of our model for the SPhP waveguide modes. Our findings could be applied to thermal management in microelectronics and silicon photonics.

physics.optics↗

arXiv2021

Optics-less beam control of EUV high harmonics generated from solids

High harmonics generation (HHG) of coherent extreme ultraviolet (EUV) radiation enables ultrafast pump-probe spectroscopy with attosecond-scale timing resolutions. Yet beam control of generated EUV radiation remains a major challenge for handy implementation of ultrafast spectroscopy particularly for nano-micro samples. Here, we demonstrate a solid-based HHG scheme that incorporates non-collinear illumination to perform the propagation control of EUV harmonics by wavefront phase manipulation via a spatial light modulator. Further, our solid-based non-collinear HHG scheme converts EUV harmonics to Bessel beams without extra optics for beam focusing, offering a useful tool for diverse EUV applications of metrology and fabrication.

physics.optics↗

arXiv2020

Selective laser ablation of metal thin films using ultrashort pulses

Selective thin-film removal is needed in many microfabrication processes such as 3-D patterning of optoelectronic devices and localized repairing of integrated circuits. Various wet or dry etching methods are available, but laser machining is a tool of green manufacturing as it can remove thin films by ablation without use of toxic chemicals. However, laser ablation causes thermal damage on neighboring patterns and underneath substrates, hindering its extensive use with high precision and integrity. Here, using ultrashort laser pulses of sub-picosecond duration, we demonstrate an ultrafast mechanism of laser ablation that leads to selective removal of a thin metal film with minimal damage on the substrate. The ultrafast laser ablation is accomplished with the insertion of a transition metal interlayer that offers high electron-phonon coupling to trigger vaporization in a picosecond timescale. This contained form of heat transfer permits lifting off the metal thin-film layer while blocking heat conduction to the substrate. Our ultrafast scheme of selective thin film removal is analytically validated using a two-temperature model of heat transfer between electrons and phonons in material. Further, experimental verification is made using 0.2 ps laser pulses by micropatterning metal films for various applications.

physics.app-ph↗