Конструкции блокирующих слоев для подавления паразитной рекомбинации в мощных диодных лазерах с GaAs волноводом

Using numerical simulation, a search is carried out for designs of asymmetric barrier layers (ABLs) for a laser diode having GaAs waveguide and emitting at the wavelength λ = 980 nm. A pair of ABLs, adjoining the active region on both sides, blocks undesired charge carrier flows and suppresses parasitic spontaneous recombination in the waveguide layers. Optimal designs of ABLs based on AlGaAsSb and GaInP for blocking electrons and holes, respectively, are proposed that make it possible to reduce the parasitic recombination current down to less than 1% of the initial value. To suppress electron transport, an alternative structure based on three identical AlInAs barriers is also proposed. The GaAsP spacers separating these barriers from each other have different thicknesses. Due to this, its own set of quasi-bound (resonant) states is formed in each spacer that is different from the neighbor spacer set of states. As a result of this, the resonant tunneling channels are blocked: the parasitic electron flow is reduced by several tens of times in comparison with the case of spacers of equal thickness.

Calculation of discrete and resonant states of Coulomb acceptor in HgCdTe alloys

The energies and wavefunctions of both localized and resonant states are calculated for Coulomb acceptor in narrow-gap HgCdTe alloys with cadmium mole fraction from 0 to 30%. The simulation is performed with scattering matrix method within a spherically-symmetric three-band Kane model that takes into account the conduction band and two valence bands. The energies of both localized and resonant states are determined using the localization rate magnitude, introduced in this work.

Investigation of directivity of the nanoantenna by its inherent resonant states

We present a quasinormal mode (QNM) approach for modeling the nanoantenna and describe the response of localized dielectric cylinder resonators. The inherent resonant states of the dielectric cylinder nanocavity are investigated for modified and reduced geometrical symmetry. We find some modes contributing mainly to the directivity and have a high-quality factor. The variation of the eigenmodes with cylinder height and substrate refractive index has also been investigated.

High-Q states in acoustic apple-shaped resonators

Apples play a significant role in our culture in various points of human history: starting from Adam and Eve, going on with Judgement of Paris, it also touches such great minds as Sir Isaac Newton and Alan Turing. Beyond that apples are still extremely relevant today due to Steve Jobs. In this work we study high quality (high-Q) resonant states of apple-shaped resonators. We have found that quasi bound states in continuum (quasi-BICs) are possible in the linear acoustic domain. We show that quasi-BICs are of Friedrich-Wintgen type, i.e. accompanied with avoided crossings while elongating or shrinking the apple-shaped resonator. Finally, we build a concise theory based on the group theory approach utilizing Wigner’s theorem. We illustrate that only the resonator symmetry plays major role, but not particular resonator’s shape.

The explanation of some exotic states in the $$cs{\bar{c}}{\bar{s}}$$ tetraquark system

Inspired by the recent observation of $$\chi _{c0}(3930)$$ χ c 0 ( 3930 ) , X(4685) and X(4630) by the LHCb Collaboration and some exotic resonances such as X(4350), X(4500), etc. by several experiment collaborations, the $$cs{\bar{c}}{\bar{s}}$$ c s c ¯ s ¯ tetraquark systems with $$J^{PC}=0^{++}$$ J PC = 0 + + , $$1^{++}$$ 1 + + , $$1^{+-}$$ 1 + - and $$2^{++}$$ 2 + + are systematically investigated in the framework of the quark delocalization color screening model(QDCSM). Two structures, the meson–meson and diquark–antidiquark structures, as well as the channel-coupling of all channels of these two configurations are considered in this work. The numerical results indicate that the molecular bound state $$D^{-}_{s}D_{s}^{+}$$ D s - D s + with $$J^{PC}=00^{++}$$ J PC = 00 + + can be supposed to explain the $$\chi _{c0}(3930)$$ χ c 0 ( 3930 ) . Besides, by using the stabilization method, several resonant states are obtained. Among these states, X(4350), X(4500) and X(4700) can be explained as the compact tetraquark states with $$J^{PC}=00^{++}$$ J PC = 00 + + , and the X(4274) is possible to be a candidate of the compact tetraquark state with $$J^{PC}=1^{++}$$ J PC = 1 + + . Apart from that, the $$J^{PC}=0^{++}$$ J PC = 0 + + resonance state with energy range 4028–4033 MeV, the two $$J^{PC}=2^{++}$$ J PC = 2 + + resonance states with energy range of 4394–4448 MeV and 4526–4536 MeV are possible to be new exotic states, which are indeed worthy of attention. More experimental tests are expected to check the existence of all these possible resonance states.