SNR Improvement in Differential Reflection Method for Weak Absorption Measurement

Differential reflection measurement is widely utilized as an effective method for characterizing optical absorption and gain in thin and small-scale materials. However, a significant challenge arises due to the low signal-to-noise ratio (SNR) encountered when measuring weak absorption or gain. In this study, we delved into the impact of the dielectric environment on SNR within the differential reflection method. To investigate this phenomenon, we employed a two-dimensional (2D) rare earth material as a model. By comparing its behavior on a transparent substrate to that when encapsulated in both metal and high-refractive-index (HRI) materials, we observed a remarkable improvement in SNR, reaching an order of magnitude enhancement in simulation. The reflective contrast exceeded 0.3, even at a quite small absorption coefficient of approximately 200 $\text{cm}^{-1}$ . These findings present an outstanding and practical solution to address the challenges of weak absorption or gain measurements within the differential reflection method.