1,720,996 research outputs found
Non-Hermitian analysis of surface creeping waves in optical microcavities: Nature of external resonances
No full textUndiscovered properties of surface creeping wave states given by complex angular momentum poles, so-called Regge poles (RPs) in optical microcavity scattering, are transparently elucidated on the frameworks of non-Hermitian physics. In particular, we analytically show that the nature of external resonances (ERs) given by complex wave numbers is equivalent to surface creeping wave RPs. Moreover, by obtaining the full structural characteristics of RPs for different polarizations, it is found that notable nontrivial RPs in transverse-magnetic polarization arise owing to the classical Brewster angle. Finally, we explicitly demonstrate the emergence of non-Hermitian degeneracies incorporating different classes of RPs. © 2020 American Physical Society.1
Model for petahertz optical memory based on a manipulation of the optical-field-induced current in dielectrics
No full textA new physical insight into the ultrafast information communication can be gained from the reversible and robust petahertz (PHz, 10 15 Hz) current induced by a strong few-cycle optical waveform in large band-gap dielectrics. Weexplore an asymmetric conduction of the petahertz current using a heterojunction of low-hole-mass and low-electron-mass dielectrics and devise various functionalities enabling the petahertz signal processing, like diode, switch, and diode transistor. Wethen propose a model of one-bit optical nonvolatile random-access memory (RAM) by assembling those functionalities and demonstrate its petahertz operation. Further, we suggest the scalability up to a four-bit data manipulation based on the 2 x 2 array of four one-bitRAM elements.1
Hybridization of different types of exceptional points
No full textA large number of different types of second-order non-Hermitian degeneracies called exceptional points (EPs) were found in various physical systems depending on the mechanism of coupling between eigenstates. We show that these EPs can be hybridized to form higher-order EPs, which preserve the original properties of the initial EPs before hybridization. For a demonstration, we hybridize chiral and supermode second-order EPs, where the former and the latter are the results of intra-disk and inter-disk mode coupling in an optical system comprised of two Mie-scale microdisks and one Rayleigh-scale scatterer. The high sensitivity of the resulting third-order EP against external perturbations in our feasible system is emphasized. © 2019 Chinese Laser Press.1
Lasing of scarred mode near above threshold in a semiconductor microcavity laser
No full textWe study a lasing of mode groups in a fully chaotic rounded D-shape InGaAsP semiconductor microcavity laser when an electrode is smaller than a cavity (inward gap). Although there are numerous unstable periodic orbits supporting resonances, a mode group localized on period-5 unstable periodic orbit is more competitive than the others for our laser configuration of the inward gap. By means of theoretical and numerical analyses with ray and wave dynamics, we show that the analyses well agree with our experimental results. © 2020 Optical Society of America.1
Extremely high Q and unidirectional laser emission due to combination of the Kolmogorov-Arnold-Moser barrier and the chaotic sea in a dielectric microdisk
No full textEmission characteristics of an oval-shaped microcavity laser are studied. In experiments, modes localized on periodic orbits emit unidirectionally with a narrow in-plane divergence angle of about 12 deg. The origin of high directionality is elucidated by means of classical ray dynamics. Wave calculations show that the Q-factors of the resonances are higher than 108. We explain this extraordinary high Q-factor in relation with a dynamical barrier region where Kolmogorov–Arnold–Moser curves significantly obstruct leakages of resonances. © 2018 Optical Society of America.1
Unidirectional emission of high-Q scarred modes in a rounded D-shape microcavity
Get PDFWe propose a deformed microcavity laser, where a high-Q mode group emits unidirectionally. The cavity comprises three circular arcs and one linear section. To minimize diffraction effects from the boundary, three circular arcs and one linear section are tangentially connected. By adjusting the sizes and the positions of the two sub-circular arcs, unidirectionality is maximized. In an experiment with an InP based InGaAsP semiconductor microcavity laser, a lasing mode group localized on a period-7 unstable periodic orbit emits unidirectionally. In our resonance calculation, a high-Q factor is confirmed. © 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement1
Stretchable and colorless freestanding microwire arrays for transparent solar cells with flexibility
Get PDFTransparent solar cells (TSCs) are emerging devices that combine the advantages of visible transparency and light-to-electricity conversion. Currently, existing TSCs are based predominantly on organics, dyes, and perovskites; however, the rigidity and color-tinted transparent nature of those devices strongly limit the utility of the resulting TSCs for real-world applications. Here, we demonstrate a flexible, color-neutral, and high-efficiency TSC based on a freestanding form of n-silicon microwires (SiMWs). Flat-tip SiMWs with controllable spacing are fabricated via deep-reactive ion etching and embedded in a freestanding transparent polymer matrix. The light transmittance can be tuned from ~10 to 55% by adjusting the spacing between the microwires. For TSCs, a heterojunction is formed with a p-type polymer in the top portion of the n-type flat-tip SiMWs. Ohmic contact with an indium-doped ZnO film occurs at the bottom, and the side surface has an Al2O3 passivation layer. Furthermore, slanted-tip SiMWs are developed by a novel solvent-assisted wet etching method to manipulate light absorption. Finite-difference time-domain simulation revealed that the reflected light from slanted-tip SiMWs helps light-matter interactions in adjacent microwires. The TSC based on the slanted-tip SiMWs demonstrates 8% efficiency at a visible transparency of 10% with flexibility. This efficiency is the highest among Si-based TSCs and comparable with that of state-of-the-art neutral-color TSCs based on organic???inorganic hybrid perovskite and organics. Moreover, unlike others, the stretchable and transparent platform in this study is promising for future TSCs
Rayleigh scatterer-induced steady exceptional points of stable-island modes in a deformed optical microdisk
No full text© 2021 Optical Society of America. A formation of second-order non-Hermitian degeneracies, called exceptional points (EPs), in a chaotic oval-shaped dielectric microdisk is studied. Different symmetric optical modes localized on a stable period-3 orbit coalesce to form chiral EPs. Unlike a circular microdisk perturbed by two scatterers (CTS), our proposed system requires only one scatterer to build chiral EPs. The scatterer positions for counterpropagating EP modes are far distant from one another and almost steady against varying scatterer sizes in contrast to the CTS case. Our results can contribute to establishing a more solid platform for EP-based-device applications with flexibility and easy feasibility in obtaining EPs.11Nsciescopu
Lowest threshold lasing modes localized on marginally unstable periodic orbits in a semiconductor microcavity laser
Get PDFThe lowest threshold lasing mode in a rounded D-shape microcavity is theoretically analyzed and experimentally demonstrated. To identify the lowest threshold lasing mode, we investigate threshold conditions of different periodic orbits by considering the linear gain condition due to the effective pumping region and total loss consisting of internal and scattering losses in ray dynamics. We compare the ray dynamical result with resonance mode analysis, including gain and loss. We find that the resonance modes localized on the pentagonal marginally unstable periodic orbit have the lowest threshold in our fabrication configuration. Our findings are verified by obtaining the path lengths and far-field patterns of lasing modes. © 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.1
Avoided level crossings in an elliptic billiard
No full textIn an elliptic billiard, we find avoided level crossings taking place over wide ranges, which are of a Demkov type for generations of eigenfunctions localized on an islands chain and its pair unstable periodic orbit. For a proof of the existence of avoided level crossings, first, we show that the quantized eigenvalue of the unstable periodic orbit, obtained by the Einstein-Brillouin-Keller quantization rule, passes the eigenvalues of bouncing-ball modes localized on the unstable periodic orbit after Demkov type avoided level crossings so that pairs of bouncing-ball modes are sequentially generated. Next, by using a perturbed Hamiltonian, we show that off-diagonal elements in Hamiltonian are nonzero, which give rise to an interaction between two eigenfunctions. Last, we verify that the observed phenomenon is Fermi resonance: that is, the quantum number difference of two normal modes equals the periodic orbits, where eigenfunctions are localized after an avoided level crossing.1
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