Fig. 1.

Dual Wavelength Photothermal (DWP)-OCT. A tunable Ti:Al₂O₃ laser was utilized as an excitation source (765 and 800 nm). Excitation laser light was intensity modulated at 42 Hz with a mechanical chopper and delivered to the blood sample through a multimode 50 µm core-diameter fiber (NA = 0.22). Relative intensity of excitation laser light on the blood sample was calibrated with a 4% partial reflector. Probe OCT light (1328 nm) emitted from a single mode fiber was focused on the blood sample from the topside with a GRIN lens. A reference reflector (5%) provides the OCT reference optical signal. Inset in the upper right corner shows absorption spectra of oxy- and deoxy-hemoglobin. Dashed lines indicate laser excitation wavelengths (765 nm and 800 nm) utilized in the reported experiments.