Lipid imaging by conventional photoacoustic microscopy subjects to direct contact sensing with relatively low detection bandwidth and sensitivity, which induces superficial imaging depth and low signal-to-noise ratio (SNR) in practical imaging scenarios. Herein, we present a photoacoustic remote sensing microscopy for lipid distribution mapping in bio-tissue, featuring noncontact implementation, broad detection bandwidth, deep penetration depth, and high SNR. A tailored high-energy pulsed laser source with a spectrum centered at 1750 nm is used as the excitation beam, while a cofocused 1550 nm continuous-wave beam is used as the probe signal. The pump wavelength is selected to overlap the first overtone of the C-H bond in response to the intensive absorption of lipid molecules, which introduces a much-enhanced SNR (55 dB) onto photoacoustic remote sensing (PARS) signals. Meanwhile, the optical sensing scheme of the photoacoustic signals provides broadband detection compared to the acoustic transducer and refrains the bio-samples from direct contact operations by eliminating the ultrasonic coupling medium. Taking merits of the high detection sensitivity, deep penetration depth, broadband detection, and high resolution of the PARS system, high-quality tissue scale lipid imaging is demonstrated in a model organism and brain slice.

Soliton explosions, among the most exotic dynamics, have been extensively studied on parameter invariant stationary solitons. However, the explosion dynamics are still largely unexplored in breathing dissipative solitons as a dynamic solution to many nonlinear systems. Here, we report on the first observation of a breathing dissipative soliton explosion in a net-normal-dispersion bidirectional ultrafast fiber laser. The breathing soliton explosions could be stimulated by the soliton buildup process or alteration of polarization settings. Transient breathing soliton pairs with intensive repulsion that is sensitive to initial conditions can also be triggered by multiple soliton explosions in the soliton buildup process instead of being triggered by varying polarization settings. The high behavior similarity also exists in the breathing soliton buildup and explosion process owing to the common gain and loss modulation. In addition, dissipative rogue waves were detected in the breathing soliton explosion, and the collision of breathing soliton significantly enhanced the amplitude of rogue waves, which is characteristic of the breathing solitons in a bidirectional fiber laser. These results shed new insights into complex dissipative soliton dynamics.