Fig. 5: Experimental observation of the evanescent wave laser-absorber mode.
From: Observation of parity-time symmetry for evanescent waves
a Logarithmic plot of the eigenvalues \({\alpha }_{\pm }\) (red and blue solid lines) of the generalized \(S\left({\hat{\omega }}_{0}\right)\) matrix versus the damping \(\gamma\), showcasing the evanescent wave laser-absorber mode indicated in Fig. 4. The blue and red dashed lines correspond to the experimental scenarios [see Fig. 4], while the vertical dashed lines indicate the critical damping values \({\gamma }_{{PZ}}=0\), \({\gamma }_{P}/2{{{\rm{\pi }}}}=-0.17 \, {{{\rm{Hz}}}}\), \({\gamma }_{Z}/2{{{\rm{\pi }}}}=1.17 \, {{{\rm{Hz}}}}\), and \({\gamma }_{\exp }/2{{{\rm{\pi }}}}=1 \, {{{\rm{Hz}}}}\) discussed in the main text. b Theoretical (curves) and experimental (circles) results for the overall output coefficient \(\Theta\) versus excitation frequency, considering left (red), right (orange) incident evanescent waves, and bilateral excitation fulfilling \(\left|{\alpha }_{-}\right\rangle\) (blue), under the same experimental scenarios as in (a) with the dimer defect’s damping coefficient set to \(\gamma ={\gamma }_{\exp }\). Logarithmic representation of measured and simulated acoustic pressure profiles for (c) left incidence and (d) bilateral excitation fulfilling \(\left|{\alpha }_{-}\right\rangle\), associated with \(\Theta\) extremes of 17.2 dB and \(-\)36.4 dB, respectively, at frequency \(1.633\,{{{\rm{kHz}}}}\) in (b). The arrows mark the locations of excitation sources, while the shaded areas highlight the scattering regions containing cavities \({-}\) and \(+\). Other unspecified system parameters are the same as in Fig. 4.
