Wave emission and absorption at spectral singularities

Wang, P.; Jin, Lin; Zhang, G.; Song, Z.

doi:10.1103/physreva.94.053834

Cited by 35 publications

(29 citation statements)

References 72 publications

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“…The concept of rotation-time symmetry was previously introduced only in fermionic systems 43 – 45 . However, bosonic systems are currently a topic of intense research 24 , 39 , 46 – 52 due to being a promising platform for gain and loss engineering in physical experiments 3 . We demonstrate that invariance allows a given system to have a real energy spectrum, which becomes singular, as a result of a symmetry phase transition.…”

Section: Introductionmentioning

confidence: 99%

Rotation-time symmetry in bosonic systems and the existence of exceptional points in the absence of $${\mathscr{PT}}$$ symmetry

Lange

Chimczak

Kowalewska-Kudłaszyk

et al. 2020

Sci Rep

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We study symmetries of open bosonic systems in the presence of laser pumping. Non-Hermitian Hamiltonians describing these systems can be parity-time ($${{\mathscr{PT}}}$$ PT ) symmetric in special cases only. Systems exhibiting this symmetry are characterised by real-valued energy spectra and can display exceptional points, where a symmetry-breaking transition occurs. We demonstrate that there is a more general type of symmetry, i.e., rotation-time ($${\mathscr{RT}}$$ RT ) symmetry. We observe that $${\mathscr{RT}}$$ RT -symmetric non-Hermitian Hamiltonians exhibit real-valued energy spectra which can be made singular by symmetry breaking. To calculate the spectra of the studied bosonic non-diagonalisable Hamiltonians we apply diagonalisation methods based on bosonic algebra. Finally, we list a versatile set rules allowing to immediately identifying or constructing $${\mathscr{RT}}$$ RT -symmetric Hamiltonians. We believe that our results on the $${\mathscr{RT}}$$ RT -symmetric class of bosonic systems and their spectral singularities can lead to new applications inspired by those of the $${{\mathscr{PT}}}$$ PT -symmetric systems.

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Section: Introductionmentioning

confidence: 99%

Rotation-time symmetry in bosonic systems and the existence of exceptional points in the absence of $${\mathscr{PT}}$$ symmetry

Lange

Chimczak

Kowalewska-Kudłaszyk

et al. 2020

Sci Rep

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“…The physics of two states are clear, representing self-sustained emission and complete absorption of two oppositely propagating waves [23,66]. The intriguing feature of the spectral singularity is that two degenerate states for the incidences from the left and right merge into one state.…”

Section: The Effect Of Couplingmentioning

confidence: 99%

Coupling-induced nonunitary and unitary scattering in anti- PT -symmetric non-Hermitian systems

Jin

2021

Phys. Rev. A

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We investigate the properties of two anti-parity-time (anti-PT )-symmetric four-site scattering centers. The anti-PT -symmetric scattering center may have imaginary couplings, real couplings, and real on-site potentials. The only difference between the two scattering centers is the coupling between two central sites of the scattering center, which plays a crucial role in determining the parity of anti-PT symmetry and significantly affects the scattering properties. For the imaginary coupling, the even-parity anti-PT -symmetric scattering center possesses nonunitary scattering and the difference between the reflection and transmission is unity; for the real coupling, the odd-parity anti-PT -symmetric scattering center possesses unitary scattering and the sum of the reflection and transmission is unity. The coupling-induced different scattering behaviors are verified in the numerical simulations. Our findings reveal that a significant difference in the dynamics can be caused by a slight difference between two similar anti-PT -symmetric non-Hermitian scattering centers.

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“…2(c) and 2(d). A Gaussian wave packet excites the wave emission, characterized by a Gaussian error function and its intensity increases linearly [98]. At V 0 ¼ 2i sin k, lasing is bidirectional when V α;β ≠ −e ik ; the wave emission is symmetric if V α;β is real, but asymmetric if complex V α ≠ V β .…”

Section: −1=2mentioning

confidence: 99%

Incident Direction Independent Wave Propagation and Unidirectional Lasing

2018

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We propose an incident direction independent wave propagation generated by properly assembling different unidirectional destructive interferences (UDIs), which is a consequence of the appropriate match between synthetic magnetic fluxes and the incident wave vector. Single-direction lasing at spectral singularity is feasible without introducing nonlinearity. UDI allows unidirectional lasing and unidirectional perfect absorption; when they are combined in a parity-time-symmetric manner, the spectral singularities vanish with bounded reflections and transmissions. Furthermore, the simultaneous unidirectional lasing and perfect absorption for incidences from opposite directions is created. Our findings provide insights into light control and may shed light on the explorations of desirable functionality in fundamental research and practical applications. DOI: 10.1103/PhysRevLett.121.073901 Introduction.-Parity-time (PT ) symmetry has been theoretically and experimentally investigated in a variety of non-Hermitian systems ; non-Hermiticity controls the exact and broken PT -symmetric phases [18][19][20][21][22]. The phase transition points are exceptional points [23][24][25][26][27] utilized for sensing enhancement [28][29][30][31][32]. The topologies of exceptional points are distinct [33][34][35][36][37]. Spectral singularities (SSs) in scattering systems belong to another type of non-Hermitian singularities, at which eigenstate completeness is spoiled [38,39]; incident waves from opposite directions at an appropriate phase match are perfectly absorbed in a coherent perfect absorber [40][41][42][43][44][45][46][47][48].Non-Hermitian character causes unidirectionality [49][50][51][52][53][54], the fundamental mechanism of which differs from that created by chiral light-matter interaction [55][56][57][58][59]. Typical phenomena include unidirectional reflectionlessness [49,50] and unidirectional spectral singularity that allows unidirectional perfect absorption (UPA) and unidirectional lasing (UL) [51,52]; however, the transmissions there protected by symmetry are reciprocal [60][61][62][63]. Nonreciprocal transmission is indispensable for optical information processing. Nonreciprocity, implemented via magneto-optic effect [64] and optical nonlinearity [65], has been created based on various strategies in linear and magnetic-free devices [66,67], in singlephoton level [68,69], and even in acoustics [70]. Benefited from synthetic magnetic flux realized for photons [71][72][73][74][75][76][77][78][79] and progress in non-Hermitian physics [22], non-Hermiticity associated with synthetic magnetic flux

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Wave emission and absorption at spectral singularities

Cited by 35 publications

References 72 publications

Rotation-time symmetry in bosonic systems and the existence of exceptional points in the absence of $${\mathscr{PT}}$$ symmetry

Rotation-time symmetry in bosonic systems and the existence of exceptional points in the absence of $${\mathscr{PT}}$$ symmetry

Coupling-induced nonunitary and unitary scattering in anti- PT -symmetric non-Hermitian systems

Incident Direction Independent Wave Propagation and Unidirectional Lasing

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