Topological modes in a laser cavity through exceptional state transfer

Abstract

Shaping the light emission characteristics of laser systems is of great importance in various areas of science and technology. In a typical lasing arrangement, the transverse spatial profile of a laser mode tends to remain self-similar throughout the entire cavity. Going beyond this paradigm, we demonstrate here how to shape a spatially evolving mode such that it faithfully settles into a pair of bi-orthogonal states at the two opposing facets of a laser cavity. This was achieved by purposely designing a structure that allows the lasing mode to encircle a non-Hermitian exceptional point while deliberately avoiding non-adiabatic jumps. The resulting state transfer reflects the unique topology of the associated Riemann surfaces associated with this singularity. Our approach provides a route to developing versatile mode-selective active devices and sheds light on the interesting topological features of exceptional points.

Tunable Topological Lasing of Circularly Polarized Light in a Soft‐Matter‐Based Superlattice

“…[21][22][23][24][25][26][27][28] Robust lasing has been demonstrated also by employing one-dimensional chiral edge states and two-dimensional valley-Hall edge states in various photonic settings, [29][30][31][32][33][34][35][36][37] or by use of the topological features of non-Hermitian exceptional points. [38] Overall, it has been proven that optical modes with topological protection can significantly improve the laser performance and immune to disorder and defect in the processing process. However, whereas this characteristic also makes it difficult to tune the lasing wavelength flexibly.…”

Proximity‐Encirclement of Multiple Exceptional Points in Non‐Hermitian Photonic Waveguides

“…The study of non-Hermitian systems breaks the conventional scope of Hermitian Hamiltonians in closed systems, and also enriches the understanding about the quantum realm. [1] Once the gain or loss is introduced, exceptional points (EPs) are ubiquitous in non-Hermitian systems, such as those in optical microresonators, [2,3] coupled optical waveguides or cavities, [4][5][6] and fiber-based systems. [7,8] EPs are singularities where eigenvalues and the corresponding eigenvectors simultaneously coalesce, [9] and as one of the quintessential features in non-Hermitian physics, exhibit many topological properties that are not analogous to Hermitian systems.…”

“…[11] The applications of EPs under the  phase transition are also considerable in optics, such as coherent perfect absorption, [12,13] unidirectional invisibility, [14,15] induced transparency, [16][17][18] and single-mode laser. [6,19,20] One of the most appealing phenomena is the state conversion when dynamically encircling an EP in a parameter space, exhibiting a chiral behavior. [21] This unique phenomenon has been demonstrated in myriad experiments of waveguides, [4,5,23,[25][26][27][28][29][30] evidencing the robustness to system perturbations including the form of the encircling loop and the device length.…”

“…[ 11 ] The applications of EPs under the $$\mathcal{P}\mathcal{T}$$ phase transition are also considerable in optics, such as coherent perfect absorption, [ 12,13 ] unidirectional invisibility, [ 14,15 ] induced transparency, [ 16–18 ] and single‐mode laser. [ 6,19,20 ]…”

Topological Interface-state Lasing in a Polymer-Cholesteric Liquid Crystal Superlattice

“…Along with recently discovered higher-order topological insulators [9][10][11], nontrivial topological phases can be utilized to implement a variety of topological photonic devices such as broadband unidirectional propagating waveguides, optical isolators, optical splitters and robust optical delay lines [12][13][14][15][16], and, in particular, the topological resonators and lasers [17][18][19][20][21][22][23][24][25]. Robust lasing has been demonstrated also by employing one-dimensional chiral edge states and two-dimensional valley-Hall edge states in various photonic settings [26][27][28][29][30][31][32][33][34], or by use of the topological features of non-Hermitian exceptional points [35].…”