The research introduces a novel L-shaped plasmonic refractive index (RI) sensor, integrated with a straight metal-insulator-metal (MIM) waveguide configuration. The sensor's performance is optimized through numerical analysis using the finite element method (FEM), achieving a maximum sensitivity of 1638 nm/RIU. This high sensitivity allows for the detection of minute changes in molecular quantities, making it highly effective in molecular detection applications. The sensor's utility is further extended by evaluating its performance in detecting various types of alcohol. The study highlights the significant advancements in plasmonics, particularly in the development of MIM waveguides, which offer robust light confinement, low loss, and compactness, making them ideal for a wide range of applications, including biomedical diagnostics, environmental monitoring, and telecommunications. The research also emphasizes the potential of plasmonic sensors in achieving high sensitivity and performance through strategic modifications to the topological structure of the MIM waveguide cavity.The research introduces a novel L-shaped plasmonic refractive index (RI) sensor, integrated with a straight metal-insulator-metal (MIM) waveguide configuration. The sensor's performance is optimized through numerical analysis using the finite element method (FEM), achieving a maximum sensitivity of 1638 nm/RIU. This high sensitivity allows for the detection of minute changes in molecular quantities, making it highly effective in molecular detection applications. The sensor's utility is further extended by evaluating its performance in detecting various types of alcohol. The study highlights the significant advancements in plasmonics, particularly in the development of MIM waveguides, which offer robust light confinement, low loss, and compactness, making them ideal for a wide range of applications, including biomedical diagnostics, environmental monitoring, and telecommunications. The research also emphasizes the potential of plasmonic sensors in achieving high sensitivity and performance through strategic modifications to the topological structure of the MIM waveguide cavity.