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

Abstract

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 × 100 µm2. 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 × 300 µm2.