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[IEEE 2018 IEEE International Power Electronics and Application Conference and Exposition (PEAC) - Shenzhen, China (2018.11.4-2018.11.7)] 2018 IEEE International Power Electronics and Application Conference and Exposition (PEAC) - Parity-time-symmetric Wireless Power Transfer System Using Switch-mode Nonlinear Gain Element
摘要： Parity-time (PT) symmetry, a concept ranging from quantum field theories and mathematical physics to classical optics, is generalized to a wireless power transfer (WPT) system in [7]. However, the already introduced system is based on an operational amplifier, limiting the power transfer efficiency of the whole system. In this paper, the concept of PT symmetry is generalized to a switch-mode WPT system. PT symmetry is achieved with a nonlinear gain element which is a single-phase bridge inverter, achieving robust wireless power transfer scheme. It is shown in simulation that the system could adjust the frequency within tens of switching period, providing attractive way of dynamic charging. The analysis of the whole system is based on coupled mode theory (CMT).
关键词： averaged model,switch-mode,Parity-time symmetry,coupled modes,wireless power transfer
更新于2025-09-23 15:22:29
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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - Optimal Switching Operation of PT-Symmetric Dimmers with Nonuniform Gain/Loss and Coupling Profiles
摘要： We assess through a variational optimization approach the optimal gain-loss profile for a non-uniform PT-symmetric coupler allowing the realization of a binary transfer function and minimizing the deviation of the total traveling light intensity as compared to that holding in a conservative system. We bring evidence that the gain-loss profile fulfilling this requirement corresponds to a non-conventional situation when light intensity is conserved in every point along the propagation distance in the PT-symmetric system. Furthermore, the optimal profile thus found corresponds to a practically important case of optical switching operation achieved with a minimal amount of amplification level. We show that switching architectures using such type of gain-loss profiles are very substantially advantageous as compared to conventional uniform PT-symmetric couplers. Furthermore, this type of optimal profile turns out to be robust with respect to fabrication imperfections. This opens new prospects for functional applications of PT-symmetric devices in photonics.
关键词： variational and optimization methods,parity-time symmetry,optical switches,waveguides and couplers
更新于2025-09-23 15:21:01
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Analytical analysis of PT and quasi-PT symmetry in thick diffraction gratings using coupled-wave theory
摘要： The concept of parity-time (PT) symmetry in optics could potentially provide emerging solutions to exploit the benefits of optical gain in optical processing. With this regard, PT and quasi-PT symmetry were studied in thick optical diffraction gratings by derivation of explicit analytical expressions using the coupled-wave theory and verified by numerical calculations. The conditions to observe PT and quasi-PT symmetry were discussed in terms of the gain-loss ratio and the refractive index modulation amplitudes for both reflective and transmissive gratings. The results show that the criterion to attain quasi-PT symmetry for the reflective and transmissive gratings is in reverse in terms of the ratio of the modulation amplitude of the imaginary to that of the real part of the refractive index (|Γ|). According to the model, a grating with fringes parallel to the surface experiences broken PT symmetry for a wide range of gain-loss ratios. Furthermore, by varying the gain-loss ratio or |Γ|, some extrema could be observed in the normalized transmission power of the diffraction orders, while operating in the quasi-PT symmetry regime. The analytical solutions could predict and justify the positions of those extrema which could be advantageous to the design purposes.
关键词： diffraction,grating,quasi-PT symmetry,Parity-time symmetry
更新于2025-09-23 15:19:57
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Chirality-enabled unidirectional light emission and nanoparticle detection in parity-time-symmetric microcavity
摘要： Achieving unidirectional emission and manipulating waves in a microcavity are crucial for information processing and data transmission in next-generation photonic circuits (PCs). Here we show how to impose twin microcavities with opposite chirality by incorporating parity-time (PT) symmetry to realize unidirectional emission. Our numerical calculation results show that the opposite chirality in microcavities stems from the asymmetric coupling of the clockwise (CW) and counterclockwise (CCW) components carried by the attached waveguide to the left- or right-sided microcavities, respectively. Notably, by engineering PT symmetry in the coupled system via the gain-loss control, the clockwise component of the lossy cavity could be selectively suppressed, which leads to the unidirectional emission with an extinction ratio of up to ?52 dB. Furthermore, the chirality and PT-symmetry breaking enabled unidirectional emission is extremely sensitive to external scatters, allowing the detection of nanoparticles with an ultrasmall radius of 5–50 nm by recording the extinction ratio change. The proposed system provides a simple yet general way to manipulate the standing waves in a microcavity and will be essential for advancing the potentials of the microcavity in PCs.
关键词： unidirectional emission,nanoparticle detection,chirality,parity-time symmetry,microcavity
更新于2025-09-19 17:13:59
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Extraordinary transmission and reflection in ${PT}$-symmetric two-segment-connected triangular optical waveguide networks with perfect and broken integer waveguide length ratios
摘要： By adjusting the waveguide length ratio, we study the extraordinary characteristics of electromagnetic waves propagating in one-dimensional (1D) parity-time-symmetric (???? -symmetric) two-segment-connected triangular optical waveguide networks with perfect and broken integer waveguide length ratios respectively. It is found that the number and the corresponding frequencies of the extremum spontaneous ???? -symmetric breaking points are dependent on the waveguide length ratio. Near the extremum breaking points, ultrastrong extraordinary transmissions are created and the maximal can arrive at, respectively, 2.4079 × 1014 and 4.3555 × 1013 in both kinds of networks. However, bidirectional invisibility can only be produced by the networks with broken integer waveguide length ratio, whose mechanism is explained in detail from the perspective of photonic band structure. The findings of this work can be useful optical characteristic control in the fabrication of ???? -symmetric optical waveguide networks, which possesses great potential in designing optical amplifiers, optical energy saver devices, and special optical filters.
关键词： optical waveguide network,parity-time symmetry,integer broken ratios
更新于2025-09-19 17:13:59
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Parity–Time Symmetry in Bidirectionally Coupled Semiconductor Lasers
摘要： We report on the numerical analysis of intensity dynamics of a pair of mutually coupled, single-mode semiconductor lasers that are operated in a con?guration that leads to features reminiscent of parity–time symmetry. Starting from the rate equations for the intracavity electric ?elds of the two lasers and the rate equations for carrier inversions, we show how these equations reduce to a simple 2 × 2 effective Hamiltonian that is identical to that of a typical parity–time (PT)-symmetric dimer. After establishing that a pair of coupled semiconductor lasers could be PT-symmetric, we solve the full set of rate equations and show that despite complicating factors like gain saturation and nonlinearities, the rate equation model predicts intensity dynamics that are akin to those in a PT-symmetric system. The article describes some of the advantages of using semiconductor lasers to realize a PT-symmetric system and concludes with some possible directions for future work on this system.
关键词： parity–time symmetry,intensity dynamics,semiconductor laser
更新于2025-09-16 10:30:52
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Embedded waveguide band: New localized states from parity-time symmetric photonic crystal waveguide
摘要： Using conventional photonic crystal waveguides combined with the Parity-Time (PT) symmetry configuration, we study the evolution of the waveguide mode bands, and the mechanism of the band merging and the exceptional point forming. A special waveguide mode band occurs in the band evolution with a part of the band embedded in the bulky bands. The embedded band takes on a new localized state with its mode field is mainly localized in the waveguide. The frequency on the bottom of the embedded band excites a huge localized field. The exceptional point on the special band excites an asymmetric mode field in the waveguide and an amplified transmission.
关键词： Localized state,Exceptional point,Parity-time symmetry,Photonic crystal waveguides
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Different Lasing Regimes of Parity-Time Symmetric Fiber Ring Laser
摘要： The concept of parity-time (PT) symmetry in optics attracts great deal of attention. Recently, a parity-time symmetry-breaking laser consisted of two coupled microrings has been experimentally demonstrated [1, 2]. A single-mode operation in an initially multimode system was achieved through stronger mode discrimination close to a PT-symmetry breaking transition. Further on, a single transverse mode operation in a system of coupled microring lasers was demonstrated near the exceptional point [3]. A possible route to a PT symmetry-based mode-locking has been theoretically discussed in paper [4]. This work develops a recently proposed concept of PT-symmetric fiber laser [5]. The laser layout [5] comprises two fiber loops of the same length cross-coupled via a set of two fiber 50:50 couplers with incorporated adjustable phase shifts ((cid:77)1, (cid:77)2) between them. Changing phase shift difference one can control coupling ratio between two fiber loops and get either PT-symmetric or PT-broken lasing regime [5]. Using exhaustive numerical modeling based on generalized nonlinear Schr?dinger equation we investigated into spectral and spatio-temporal dynamics [6] of this PT-symmetric fiber Raman laser. In particular we demonstrate that such laser is capable to operate in a variety of lasing regimes, including turbulent [7] (stochastic quasi-stationary), laminar (coherent quasi-stationary) lasing, as well as generation of a single pulse or multiple pulses per cavity round-trip, see Fig. 1. We analyze PT-symmetry of laser radiation in each regime and show how the laser can switch between these lasing regimes by means of adjustment of pump power and phase shift between fiber loops. In particular, when (cid:77)1 ≈ (cid:77)2 the gain and loss fiber loops are almost uncoupled, the radiation is almost completely concentrated in the gain loop, so that the laser operates in PT-broken turbulent regime irrespective to pump power. In the opposite limiting case (cid:77)1 - (cid:77)2 ≈ (cid:83), two fiber loops are fully coupled. Once the pump power is above the threshold and (cid:77)1 - (cid:77)2 ≈ (cid:83), the laser always operates in PT-symmetric regime thus having equal powers in the middle of gain and loss segments. The laser produces highly coherent narrow-bandwidth radiation (laminar regime [7]) near the lasing threshold and stochastic (turbulent) radiation with broad optical spectrum and low coherence well above the threshold. We show that at intermediate phase shift 0 < (cid:77)1 - (cid:77)2 < (cid:83) where PT-transition takes place, the laser may operate in pulsed regimes with “partial” (local) symmetry, i.e. temporal areas of PT-symmetric and PT-broken radiation interleave. The laser pulses correspond to areas of PT-broken regime with power concentrated mainly inside gain loop, whereas between adjacent pulses there’s a PT-symmetric laminar background with equal extremely low-level powers at the middle of gain and loss loops.
关键词： laminar,turbulent,parity-time symmetry,fiber laser,PT-broken,PT-symmetric,pulsed,lasing regimes
更新于2025-09-12 10:27:22
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Parity-Time Symmetry in Laterally Coupled Bragg Waveguides
摘要： We investigate theoretically, in the frame of Coupled-Mode Theory (CMT), a system made of two laterally coupled, index-coupled Bragg waveguides, the modal gain of the amplifying one compensating exactly the modal losses of the other. Reverting to the supermode eigenbasis of the underlying “naked” (non-periodic) Parity-Time Symmetric (PTS) directional coupler, we derive analytically the scattering parameters of the whole structure. We also consider a system made of two purely gain-coupled Bragg waveguides, either in phase or in anti-phase. In each case, we comment upon the gain requirement for achieving a laser oscillation.
关键词： Parity-Time Symmetry (PTS),Coupled-Mode Theory (CMT),Distributed Feedback (DFB),Distributed Bragg Reflector (DBR)
更新于2025-09-12 10:27:22
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PT-symmetric transverse mode splitting in coupled quantum cascade lasers
摘要： Separation of transverse modes in waveguides typically achieved by manipulating mode effective indices is of current interest in integrated optics and various designs have been proposed. Recently, implementation of non-Hermitian optics under parity time (PT) symmetry has led to an alternate class of devices employing gain and loss media with far reaching results. Introduction of PT symmetry to non-Hermitian systems results in real solutions while symmetry breaking results in imaginary eigenvalues. However, applications of PT symmetry in the infrared devices is quite limited. In this work, we demonstrate a mode splitter that can separate transverse modes in coupled PT symmetric in realistic quantum cascade lasers (QC lasers). We study the effects of gain and loss for coupled PT symmetric QC laser waveguides and show that TE0 and TE1 modes can be separated with proper choice of gain and loss values.
关键词： quantum cascade lasers,parity-time symmetry,photonic devices,optical waveguide,optical systems,Mode splitter
更新于2025-09-12 10:27:22