  Detection and identification of lipids are highly coveted for the
interrogation of chronic diseases such as atherosclerosis and myocardial
infarction. Intravascular photoacoustic imaging (IVPA) and deep tissue imaging
are modern techniques, which rely on complex near infrared (NIR) optical
parametric oscillators (OPOs) and other high-power solid-state laser systems
for the diagnosis, which in turn make the systems bulky and expensive. In this
work, we propose a cost-effective directly modulated high pulse energy
supercontinuum source (operating in kHz regime) based on a standard optical
fiber with pulse energy density as high as ~ 26 nJ/nm. We demonstrate how such
supercontinuum source combined with a tunable filter can be highly suitable for
vibration-based photoacoustic imaging and spectroscopy of lipids in the
molecular overtone band of lipids (1650-1850 nm). We show the successful
discrimination of two different lipids (cholesterol and lipid in adipose
tissue) and the photoacoustic cross-sectional scan of lipid-rich adipose tissue
at three different locations. The proposed high pulse energy supercontinuum
laser paves a new direction towards compact, broadband and cost-effective
source for multi-spectral spectroscopic photoacoustic imaging.
