<p>This study presents a biosensor based on cleaved graphene, compared witha graphene-gold nanoparticle structure, for detecting carcinoembryonic antigen(CEA), leveraging graphene’s tunable resonance frequency and the structure’spolarization-independent performance. This sensor consists of three layers: a goldsubstrate with a conductivity of 4.7 × 10⁷, a silicondioxide (SiO₂) dielectric layer with a permeability of 3.9,and a graphene layer with strategic cuts to increase absorption. The performance ofthe proposed structure has been measured by measuring its absorption around the 8.9terahertz frequency band, which has reached absorption values ​​above 99.4–99.9% forthe first structure and absorption above 99.6–100% for the second structure, whichincludes graphene plus gold nanoparticles, respectively. These high absorption ratesmake the sensor an excellent candidate for biosensing applications, especially forthe detection of CEA in clinical samples. By testing the sensor with analytescontaining CEA in concentrations of 1, 2, 3, 4, and 5 ng/ml, the refractive indexvalues ​​were 1.3337, 1.33374, 1.3448, and 1.3485, respectively. When the analytelayer is placed on the three-band absorber structure, the peak shift is absorbed andallows the detection of the desired analyte. The second proposed structure showedsignificant sensitivity and achieved 4.3 THz / RIU at 1.3411 refractive index and8.8483 THz frequency, LOD = 0.001 and FOM = 26. This high sensitivity is especiallyuseful for detecting low concentrations of analyte. Such a sensor has a highpotential to increase the detection of biomarkers. These findings highlight thepotential of the sensor for CEA detection with high sensitivity.</p>