Conjugate metamaterials (CMs), whose permittivity and permeability are complex conjugates in phase, realize simultaneous lasing and antilasing modes through a physical mechanism distinct from the conventional parity-time-symmetric framework yet limited to a special phase factor. Here, we propose a general scheme to achieve the coexistence of lasing and antilasing modes in multilayered CMs with arbitrary phase factors. By analyzing the scattering properties of cascaded CMs, the general conditions for coexistence singularities are revealed, arising from the combined effects of propagation phase resonance in each CM layer and impedance matching at the interfaces between adjacent CMs. Owing to the inherent requirement that the total accumulation of phase factors across the multilayer CMs equal odd multiples of $\pi /2$, the CM phase factor can be effectively tuned by adjusting the number of CM layers. A multilayer design consisting of a single CM and air is further proposed to realize the coexistence of lasing and antilasing modes. We design and numerically simulate the multilayer CM structure with non-Hermitian photonic crystals, successfully demonstrating controllable switching between lasing and antilasing modes. Our work provides a versatile platform for exploring non-Hermitian effects and designing multifunctional photonic devices.

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• Lasers
• Metamaterials
• Photonics
• Non-Hermitian systems