Lock-in infrared illumination for high-resolution microscopic thermal imaging

Infrared (IR) thermal imaging at ambient temperature using conventional IR cameras often faces challenges such as reduced image contrast and elevated noise levels, restricting its application in high-resolution microscopic imaging. In this Letter, we report an in-situ lock-in infrared illumination approach to enhance the IR image quality. By combining mid-wave IR (MWIR) illumination with lock-in synchronization, the proposed method improves image contrast, enhances resolving capability, and suppresses noise in the image effectively, important for microscopic thermal imaging. The method is validated through the demonstration of defect localization in GaAs nano-ridge lasers, highlighting its practical application. This in-situ non-contact approach offers several advantages over the contrast enhancement methods reported in the literature and can be readily integrated into existing thermal imaging systems.