Investigation of nonlinear photoacoustic microscopy using a low-cost infrared lamp.

Nonlinear photoacoustic microscopy (PAM) is a novel approach to enhance contrast and resolution. In this study, a low-cost infrared (IR) lamp as a simple approach for nonlinear PAM is demonstrated. Numerical simulations are first performed to verify the nonlinear photoacoustic effect under steady heating for two cases: (a) Differentiation of absorbers with different Grüneisen coefficients; (b) enhancement of photoacoustic amplitude. Then, sets of experiments are conducted to experimentally demonstrate our proposed approach: (a) Longitudinal monitoring of photoacoustic A-line signals from two samples, porcine tissue ex vivo and hemoglobin and indocyanine green (ICG) solutions in tubes in vitro for demonstrating the above-mentioned two cases; (b) PAM imaging of hemoglobin and ICG solutions in tubes before and after IR lamp heating. Different signal change and amplitude enhancement are observed in different demonstrations, showing the efficacy of the proposed approach. By virtue of cost-effectiveness and decent performance, our work facilitates nonlinear PAM studies.