Topological antilaser

Abstract

Coherent perfect absorption (CPA)-the time-reversed operation of lasing at threshold-relies on finely tuned interference and is intrinsically fragile to disorder and structural imperfections. Whether absorption can be endowed with topological protection, by analogy to topological lasing, has remained an open question. Here, we experimentally demonstrate a topological antilaser: the time-reversed counterpart of a topological laser, in which chiral edge modes of a photonic lattice enable perfect light absorption protected by topology. Using a nonreciprocal microwave network with low intrinsic loss, we show that the topological antilaser preserves near-unity absorption under strong disorder, and, unlike conventional antilasers, remains functional for arbitrary placements of dissipation and input ports, even when the lattice is strongly perturbed. This robustness arises from the disorder-immune propagation and stable spatial profile of the topological edge modes. Our results establish topologically protected absorption as the missing counterpart of topological lasing, opening new directions for studying robust energy dissipation, wave control, and coherent-absorption-based detection technologies.

Figures (4)

• Figure 1: Scattering network model.a, Photograph of a fabricated scattering network, with an inset showing the details of a single circulator. b, The dispersion of the scattering network under a slab geometry with periodic boundary conditional along the $x$ direction and five unit cells along the $y$ direction. c, Experimentally measured edge transmission spectrum, with the shaded regions indicating the bulk bandgaps. The excitation (detection) port position is denoted as port 1(2) in the inset. d, Profiles of the modes highlighted by colored markers in (b). e-g, Measured (left) and calculated (right) field distributions under a single-port excitation for a chiral edge mode at 6.765 GHz (e), a bulk mode at 6.591 GHz (f), and a trivial mode at 6.927 GHz (g).
• Figure 2: Antilasing of the chiral edge mode.a, Schematic of the experimental setup with two input/output ports. b, Measured outputs from port 1 (blue dots) and port 2 (red dots), and the total output (yellow dots). An antilasing is achieved at 6.765 GHz, where the outputs from both ports simultaneously vanish. c-e, Measured total outputs in the $f-\phi$ (c), $f-q$ (d), $f-l$ (e) subspaces, with the antilasing clearly seen in each plot. The line plots on the vertical planes show selected cuts of the corresponding 2D plots. In (e), the position of the lossy antenna corresponding to the antilasing condition is defined as $l=0$ mm. f-h, Calculated total outputs corresponding to (c-e).
• Figure 3: Robustness of topological antilaser.a,b, Calculated and measured total outputs versus the disorder strength $W$ defined in the main text. The red, yellow, and blue colors respectively represent antilasers operating via chiral edge modes, bulk modes, and 1D trivial modes. The error bars denote the standard deviations from five repeated measurements and 1000 disorder realizations for experimental and numerical data, respectively. c,d, Measured total outputs in the $\phi-q$ subspace for antilasers using a bulk mode at 6.591 GHz (c), and a 1D trivial mode at 6.927 GHz (d). e, Calculated field distributions for the three cases at $W=0$ (upper panels) and at $W=1.5$ (lower panels). The disorder strength $W$ is evaluated at 7 GHz, and the disorder realization is the same as in the experiments. f, The Pearson correlation $\rho$ of the field distribution under CPA conditions as a function of disorder strength.
• Figure 4: Topological antilaser in strongly disordered systems.a, The minimum total output obtained by scanning the four-dimensional parameter space for all possible combinations ($C_{15}^{2}\times 24=2520$) of the port ($C_{15}^{2}$) and lossy site (24) positions in a strongly disordered sample. The red and blue dots represent numerical results for the topological case and the 1D trivial case, respectively. b, An example where antilasing is realized in a disordered topological sample. c, An example where antilasing is impossible in a disordered trivial sample. d-f, Experimental realization of antilasing in a strongly disordered topological sample for three distinct port/loss configurations. g-i, Experimentally achieved minimal total outputs in a strongly disordered hollowed sample under the same port/loss configurations.