Contrasting Spectral Signatures and Sensitivities of CPA-Lasing in a $\mathcal{P}\mathcal{T}$-Symmetric Periodic Structure

Abstract

The CPA-laser is a coexisting state of coherent perfect absorption and lasing that was proposed in parity-time ($\mathcal{P}\mathcal{T}$) symmetric photonic systems. In this work we show that the spectral signature of a CPA-laser displayed by the singular value spectrum of the scattering matrix ($S$) can be orders of magnitude wider than that displayed by the eigenvalue spectrum of $S$. Since the former reflects how strongly light can be absorbed or amplified and the latter announces the spontaneous symmetry breaking of $S$, these contrasting spectral signatures indicate that near perfect absorption and extremely strong amplification can be achieved even in the $\mathcal{P}\mathcal{T}$-symmetric phase of $S$, which is known for and defined by its flux-conserving eigenstates. We also show that these contrasting spectral signatures are accompanied by strikingly different sensitivities to disorder and imperfection, suggesting that the eigenvalue spectrum is potentially suitable for sensing and the singular value spectrum for robust switching.

9 pages, 7 figures

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• Emitter and absorber assembly for multiple self-dual operation and directional transparency
• Study on Asymmetric Diffraction of Acoustic Parity-Time-Symmetric Gratings Using Rigorous Coupled-Wave Analysis
• Robust incoherent perfect absorption
• Universal Large-order asymptotic behavior of the Strong-coupling and High-Temperature series expansions
• Effective size of a parity-time symmetric dimer