arXiv subjects

Chil-Min Kim

Publications and source records attributed to Chil-Min Kim.

At least 19 recordsLinked to original sources

arXiv2021

Impact of non-Hermitian Mode interaction on Inter-cavity Light transfer

Understanding inter-site mutual mode interaction in coupled physical systems is essential to comprehend large compound systems as this local interaction determines the successive multiple inter-site energy transfer efficiency. We demonstrate that only the non-Hermitian coupling can correctly account for the light transfer between two coupled optical cavities. We also reveal that the non-Hermitian coupling effect becomes much crucial as the system dimension gets smaller. Our results provide an important insight to deal with general coupled-devices in the quantum regime.

physics.optics↗

arXiv2012

Terahertz beat freuquency generation from two-mode lasing operation of coupled microdisk laser

We propose a coupled microdisk laser as a compact and tunable laser source for the generation of a coherent continuous wave THz radiation by photomixing. Using the Schrödinger-Bloch model including the nonlinear effect of active medium, we find single mode and two mode lasings depending on the pumping strength. We explain the transitions of lasing modes in terms of resonant modes which are the solutions of the Schrödinger-Bloch model without active medium and nonlinear interaction. In particular, a two mode lasing is shown to generate THz oscillating frequency originating from the light beating of two nearly degenerated resonant modes with different symmetries.

physics.optics↗

arXiv2011

Dynamics of Morphology-Dependent Resonances by Openness in Dielectric Disk for TE polarization

We have studied the dynamics of morphology-dependent resonances by openness in a dielectric microdisk for TE polarization. For the first time, we report that the dynamics exhibits avoided resonance crossings between inner and outer resonances even though the corresponding billiard is integrable. Due to the avoidance, inner and outer resonances can be exchanged and $Q$-factor of inner resonances is strongly affected. We analyze the diverse phenomena aroused from the dynamics including the avoided crossings.

physics.optics↗

arXiv2010

Outer Resonances and Effective Potential Analogy in Two-Dimensional Dielectric Cavities

Outer resonances are studied as one type of quasinormal modes in two-dimensional dielectric cavities with refractive index $n>1$. The outer resonances can be verified as the resonances which survive only outside the cavity in the small opening limit of the dielectric disk. We have confirmed that the outer resonances universally exist in deformed cavities irrespective of the geometry of cavity and they split into nearly degenerate states in slightly deformed cavity. Also we pointed out that the effective potential analogy is inapplicable to the description of outer resonances. Since most outer resonances in the dielectric cavities have quite high leakages, they would affect to the broad background in the density of states. Especially, for TE polarization case, relatively low-leaky outer resonances exist and it presents the possibility that they can interact with the inner resonances and affect lasing modes.

physics.optics↗

arXiv2009

An efficient finite element method applied to quantum billiard systems

An efficient finite element method (FEM) for calculating eigenvalues and eigenfunctions of quantum billiard systems is presented. We consider the FEM based on triangular $C_1$ continuity quartic interpolation. Various shapes of quantum billiards including an integrable unit circle are treated. The numerical results show that the applied method provides accurate set of eigenvalues exceeding a thousand levels for any shape of quantum billiards on a personal computer. Comparison with the results from the FEM based on well-known $C_0$ continuity quadratic interpolation proves the efficiency of the method.

nlin.CD↗

arXiv2008

Resonances in a circular dielectric cavity

We study resonance distributions in a circular dielectric cavity. It is shown that the decay-rate distribution has a peak structure and the details of the peak are consistent with the classical survival probability time distribution. We also investigate the behavior of the complex resonance positions at the small opening limit. At the large $n$ limit, the real part of complex resonance positions approaches the solutions with different $m$ of Dirichlet problem with a scale $n^{-2}$ and the imaginary part goes zero as $n^{-2m}$ for TM and $n^{-2(m+1)}$ for TE polarization, where $m$ is the order of the resonance.

physics.optics↗

arXiv2007

Multipartite Quantum Secret Sharing using Not-So-Weak Qubits

We propose a new quantum secret sharing scheme using a single non-entangled qubit. In the scheme, by transmitting a qubit to the next party sequentially, a sender can securely transmit a secret message to $N$ receivers who could only decode the message cooperatively after randomly shuffling the polarization of the qubit. We explain this quantum secret sharing scheme into the one between a sender and two receivers, and generalize the scheme between a sender and $N$ receivers. Since our scheme is capable of using a faint coherent pulse as a qubit, it is experimentally feasible within current technology.

quant-ph↗

arXiv2006

Transport control in deterministic ratchet system

We study the control of transport properties in a deterministic inertia ratchet system via the extended delay feedback method. A chaotic current of a deterministic inertia ratchet system is controlled to a regular current by stabilizing unstable periodic orbits embedded in a chaotic attractor of the unperturbed system. By selecting an unstable periodic orbit, which has a desired transport property, and stabilizing it via the extended delay feedback method, we can control transport properties of the deterministic inertia ratchet system. Also, we show that the extended delay feedback method can be utilized for separation of particles in the deterministic inertia ratchet system as a particle's initial condition varies.

nlin.CD↗

arXiv2006

Eavesdropping Attack with Hong-Ou-Mandel Interferometer and Random Basis Shuffling in Quantum Key Distribution

We introduce new sophisticated attacks with a Hong-Ou-Mandel interferometer against quantum key distribution (QKD) and propose a new QKD protocol grafted with random basis shuffling to block up those attacks. When the polarization basis is randomly and independently shuffled by sender and receiver, the new protocol can overcome the attacks even for not-so-weak coherent pulses. We estimate the number of photons to guarantee the security of the protocol.

quant-ph↗

arXiv2005

Directional interacting whispering gallery modes in coupled dielectric microdisks

We study the optical interaction in a coupled dielectric microdisks by investigating the splitting of resonance positions of interacting whispering gallery modes (WGMs) and their pattern change, depending on the distance between the microdisks. It is shown that the interaction between the WGMs with odd parity about y-axis becomes appreciable at a distance less than a wavelength and causes directional emissions of the resulting interacting WGMs. The directionality of the interacting WGMs can be understood in terms of an effective boundary deformation in ray dynamical analysis. We also discuss about the oscillation of the splitting when the distance is greater than a wavelength.

physics.optics↗

arXiv2005

Survival probability time distribution in dielectric cavities

We study the survival probability time distribution (SPTD) in dielectric cavities. In a circular dielectric cavity the SPTD has an algebraic long time behavior, $\sim t^{-2}$ in both TM and TE cases, but shows different short time behaviors due to the existence of the Brewster angle in TE case where the short time behavior is exponential. The SPTD for a stadium-shaped cavity decays exponentially, and the exponent shows a relation of $γ\sim n^{-2}$, $n$ is the refractive index, and the proportional coefficient is obtained from a simple model of the steady probability distribution. We also discuss about the SPTD for a quadrupolar deformed cavity and show that the long time behavior can be algebraic or exponential depending on the location of islands.

nlin.CD↗

arXiv2005

Scarred Resonances and Steady Probability Distribution in a Chaotic Microcavity

We investigate scarred resonances of a stadium-shaped chaotic microcavity. It is shown that two components with different chirality of the scarring pattern are slightly rotated in opposite ways from the underlying unstable periodic orbit, when the incident angles of the scarring pattern are close to the critical angle for total internal reflection. In addition, the correspondence of emission pattern with the scarring pattern disappears when the incident angles are much larger than the critical angle. The steady probability distribution gives a consistent explanation about these interesting phenomena and makes it possible to expect the emission pattern in the latter case.

nlin.CD↗

arXiv2005

Quantum Key Distribution with Blind Polarization Bases

We propose a new quantum key distribution scheme that uses the blind polarization basis. In our scheme the sender and the receiver share key information by exchanging qubits with arbitrary polarization angles without basis reconciliation. As only random polarizations are transmitted, our protocol is secure even when a key is embedded in a not-so-weak coherent-state pulse. We show its security against the photon number splitting attack and the impersonation attack.

quant-ph↗

arXiv2005

Chaos Synchronization of delayed systems in the presence of delay time modulation

We investigate synchronization in the presence of delay time modulation for application to communication. We have observed that the robust synchronization is established by a common delay signal and its threshold is presented using Lyapunov exponents analysis. The influence of the delay time modulation in chaotic oscillators is also discussed.

nlin.CD↗

arXiv2005

Hiding message in Delay Time: Encryption with Synchronized time-delayed systems

We propose a new communication scheme that uses time-delayed chaotic systems with delay time modulation. In this method, the transmitter encodes a message as an additional modulation of the delay timeand then the receiver decodes the message by tracking the delay time.We demonstrate our communication scheme in a system of coupled logistic maps.Also we discuss the error of the transferred message due to an external noiseand present its correction method.

nlin.CD↗

arXiv2004

Periodic Phase Synchronization in coupled chaotic oscillators

We investigate the characteristics of temporal phase locking states observed in the route to phase synchronization. It is found that before phase synchronization there is a periodic phase synchronization state characterized by periodic appearance of temporal phase locking state and that the state leads to local negativeness in one of the vanishing Lyapunov exponents. By taking a statistical measure, we present the evidences of the phenomenon in unidirectionally and mutually coupled chaotic oscillators, respectively. And it is qualitatively discussed that the phenomenon is described by a nonuniform oscillator model in the presence of noise.

nlin.CD↗

arXiv2004

Resonance Patterns in a Stadium-shaped Microcavity

We investigate resonance patterns in a stadium-shaped microcavity around $n_ck R \simeq 10$, where $n_c$ is the refractive index, $k$ the vacuum wavenumber, and $R$ the radius of the circular part of the cavity. We find that the patterns of high $Q$ resonances can be classified, even though the classical dynamics of the stadium system is chaotic. The patterns of the high $Q$ resonances are consistent with the ray dynamical consideration, and appears as the stationary lasing modes with low pumping rate in the nonlinear dynamical model. All resonance patterns are presented in a finite range of $kR$.

nlin.CD↗

arXiv2004

Quasi-Scarred Resonances in a Spiral-Shaped Microcavity

We study resonance patterns of a spiral-shaped dielectric microcavity with chaotic ray dynamics. Many resonance patterns of this microcavity, with refractive indices $n=2$ and 3, exhibit strong localization of simple geometric shape, and we call them {\em quasi-scarred resonances} in the sense that there is, unlike the conventional scarring, no underlying periodic orbits. It is shown that the formation of quasi-scarred pattern can be understood in ter ms of ray dynamical probability distributions and wave properties like uncertainty and interference.

nlin.CD↗