Coherent Laser Source for High Frame-Rate Optical Time-Stretch Microscopy at 1.0 μm

We demonstrate a coherent picosecond pulsed fiber laser for the high frame-rate optical time-stretch microscopy at 1.0 μm. The spectrum of a picosecond pulsed laser is commonly broadened before the time-stretch imaging, which however will degrade its stability and coherence. As a result, it is required to enhance the degraded signal-To-noise ratio by averaging, which would compromise the frame rate on the other hand. Instead of pursuing such kind of spectrum-broadened picosecond pulsed laser sources, we propose a pulse train extracted directly from an all-normal dispersion mode-locked fiber laser with a rectangle-shaped optical spectrum. It delivers stable and coherent performance for the serial time-encoded amplified microscopy at 1.0 μm. With this robust picosecond pulsed laser, real-Time stain-free flow imaging with a frame rate of 26.25 MHz and a spatial resolution of < 2 μm is demonstrated. Featured with the compact configuration and good coherence property, it is a promising picosecond pulsed fiber laser source for the ultrafast interferometric time-stretch microscopy at 1.0 μm.