Abstract
We investigate the coherent perfect absorption laser points (CPA-LPs) in anti-parity–time-symmetric photonic crystals. CPA-LPs, which correspond to the poles of reflection and transmission, can be found in the parameter space composed of gain–loss factor and angular frequency. Discrete exceptional points (EPs) split as the gain–loss factor increases. The CPA-LPs sandwiched between the EPs are proved to be defective modes. The localization of light field and the bulk effect of gain/loss in materials induce a sharp change in phase of the reflection coefficient near the CPA-LPs. Consequently, a large spatial Goos–Hänchen shift, which is proportional to the slope of phase, can be achieved around the CPA-LPs. The study may find great applications in highly sensitive sensors.
Highlights
In photonic crystals (PCs), one can manipulate photons in the same way as electrons in semiconductors.By modulating the refractive indices of dielectric materials, it forms periodic distribution in space and obtains special optical properties
We show that coherent perfect absorption laser points (CPA-LPs) arise in the parameter space composed of gain–loss factor, and angular frequency
We have studied the CPA-LPs in one-dimensional anti-PT-symmetric PCs
Summary
In photonic crystals (PCs), one can manipulate photons in the same way as electrons in semiconductors. In a non-Hermitian optical system, by simultaneously modulating the real part and the imaginary part of the refractive index of the material, single-mode laser [28], loss-induced transparency [29], and optical field localization [30] can be achieved. The work presented belongs to a set of explorations of non-Hermitian symmetries beyond PT, a vast and promising field that is just beginning to develop It will surely provide many important results and applications [44]. Studies on non-Hermitian photonics have shown that loss and gain, satisfied with PT symmetry, provide a new degree of freedom for the system, which can effectively control photons and generate new optical effects, such as unidirectional reflectionless resonance, which can be used to prepare chip-level semiconductor lasers [48]. We illustrate the application of the singular phase near the CPA-LPs, and induce large spatial Goos–Hänchen (GH) shift, which can be utilized for highly sensitive sensing
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