Abstract
Recently, interdisciplinary science researches have been paid much attention, and biophotonics is a popular topic. This thesis focuses on the development of wavelength-tunable visible pulse generation for hemoglobin oxygen saturation (SO2) estimation and optical resolution photoacoustic microscopy (OR-PAM). SO2 estimation requires a tunable laser possessing two wavelengths which include an isosbestic point, narrow linewidths (1-2 nm), enough pulse energy (100 nJ), and stable transverse mode (TEM00) . Therefore, our laser light source uses a cascaded nonlinear wavelength conversion; second harmonic generation(SHG), optical parametric oscillator(OPO), sum frequency generation SFG) with single mode fiber (SMF) coupling. Moreover, we are able to convert wavelengths fast with the aid of a fan-out periodically poled lithium niobate (PPLN) crystal and thermoelectric cooler (TEC). In photoacoustic experiments, the pulse laser at 545 nm (an isosbestic point) and 552 nm is sent into a phantom, respectively. Variation of concentration in a phantom is obtained through photoacoustic (PA) signals from different wavelengths. Experimental results shows that errors of SO2 estimation in a phantom are below 8%, and the spatial resolution is around 5 um.