532/1176 nm all-crystal laser for dual-contrast photoacoustic imaging of blood and lipids

Photoacoustic microscopy (PAM) is a label-free and noninvasive imaging tool for monitoring blood vessels and lipids in vivo. However, simultaneously imaging both indicators has been challenging with a single laser source. Here, we report a compact all-crystal passively Q-switched solid-state laser that simultaneously generates 532 nm and ~1.2 μm wavelengths for blood and lipid contrasts in PAM. The laser leverages both second-harmonic generation (SHG) and stimulated Raman scattering (SRS) in nonlinear crystals. It produces ~2 ns pulses at ~16 kHz repetition rate, satisfying high-performance PAM requirements. We demonstrate dual-wavelength PAM imaging of a USAF1951 test target, blood (hemoglobin), butter, and mouse mesenteric fat. This 532/1176 nm source provides a new, to the best of our knowledge, option for multi-contrast PAM, with potential utility in clinical applications.