Dual picosecond fast tunable optical parametric amplifier laser system for wide-field nonlinear optical microscopy

In the last decades, nonlinear optical microscopy techniques, such as two-Photon Excited Fluorescence (2PEF), Sum Frequency Generation (SFG), and Hyperspectral Coherent Anti-Stokes Raman Scattering (H-CARS) microscopy, emerged as powerful tools to image biological samples in a label-free, fast, and non-destructive way. Traditionally, these techniques are performed with single point-scanning acquisition schemes featuring a limited field of view and often leading to sample damage when high laser power is used to increase the acquisition speed. Wide-field illumination and camera-based detection schemes offer a solution to these issues, enabling fast imaging over a large field view. However, current laser sources used for nonlinear microscopy operating at several MHz repetition rates are not able to induce nonlinear effects over areas larger than 100 x 100 mu m(2). Here, we present a powerful 200 kHz repetition rate laser source based on an Ytterbium fiber laser pumping two picosecond optical parametric amplifiers tunable in the 700-900 nm spectral range and rapidly tunable (up to 100 KHz) within a 20 nm sub-range. We exemplify the possibilities of this laser system to perform rapid CARS spectroscopy (2 ms/spectrum) and nonlinear wide-field imaging, up to 3.3 frames/s for 2PEF and SFG and 0.3 hypercubes/s for H-CARS, over a field of view >300 x 300 mu m(2).