Coherent perfect absorption (CPA) is the time-reversed process of laser emission, enabling complete light capture via the destructive interference of coherent light waves. Its tunable characteristics open avenues for next-generation optical modulators. However, the existing research predominantly focuses on isotropic materials, leaving a significant gap in theoretical studies addressing anisotropic systems. To fill this gap, this study investigates the CPA effect in composite media composed of anisotropic substrates combined with metallic nanoparticles as fillers. Employing effective medium theory, we calculate the effective permittivity and permeability of the composite, and derive the reflection and transmission coefficients for the resulting effective medium. The CPA condition is quantitatively characterized by the logarithm of scattered light intensity. By strategically coordinating the parameters such as nanoparticle size, anisotropic substrate permittivity, and composite layer thickness, while accounting for the inherent nonlocal effect, we achieve precise control over CPA properties. Notably, two distinct CPA variation trends are observed when tuning the substrate permittivity. Furthermore, through careful parameter optimization, we identify and demonstrate that the composite medium can achieve CPA in two separate wavelength bands under identical volume fractions. This dual-band CPA phenomenon represents a capability in anisotropic composite systems. This work provides a foundational theoretical framework for developing advanced nanocomposite-based optical absorbers utilizing anisotropic media, opening the possibilities for tunable optical device design.

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• Light propagation, transmission & absorption
• Metamaterials
• Optical coherence
• Composite materials
• Electromagnetic wave theory