Theoretical Analysis for Sensitivity Enhancement in Broad-Band Thermal Lens Microscope

Abstract

Thermal lens microscope (TLM) coupled to lab-on-chip chemistry in microfluidic systems is a powerful tool for analyzing a variety of compounds. However, the limited range of emission lines of laser-based TLM severely restricted the specificity of this technique and therefore limited the use of such TLM systems for practical applications. Here, a broad-band incoherent light source was introduced into the TLM to improve the specificity. A three-layer theoretical model was built. Through numerical simulation, it was found that at usual sample length of 100 μm in micro-volumes, the sensitivity can be increased by approximately one order of magnitude at low frequencies when the top and bottom layers are organic solvents. The sensitivity is even higher than that in laser excitation case.