Widely-tunable synchronisation-free picosecond laser source for multimodal CARS, SHG and two-photon microscopy

Xu, Duanyang, Price, Jonathan, Xu, Lin and Richardson, David (2020) Widely-tunable synchronisation-free picosecond laser source for multimodal CARS, SHG and two-photon microscopy. Biomedical Optics Express. (doi:10.1364/BOE.411620). (In Press)

Abstract

We demonstrate a continuous wave (CW) seeded synchronization-free optical parametric amplifier (OPA) pumped by a picosecond, 1 μm laser and show its performance when used as a simple yet powerful source for label-free Coherent anti-Stokes Raman scattering (CARS) and concurrent Second Harmonic Generation (SHG) and two-photon fluorescence microscopy in an epi-detection geometry. The average power level of above 175 mW, spectral resolution of 8 cm−1, and 2 ps pulse duration are well optimized for CARS microscopy in bio-science and bio-medical imaging systems. Our OPA is a much simpler setup than either the ‘gold-standard’ laser and optical parametric oscillator (OPO) combination traditionally used for CARS imaging, or the more recently developed OPA systems pumped with femtosecond pulses [1]. Rapid and accurate tuning between resonances was achieved by changing the poled channels and temperature of the periodically-poled lithium niobate (PPLN) OPA crystal together with the OPA seed wavelength. The Pump-Stokes frequency detuning range fully covered the C-H stretching band used for the imaging of lipids. By enabling three multiphoton techniques using a compact, synchronization free laser source, our work paves the way for the translation of label-free multi-photon microscopy imaging from biomedical research to an imaging based diagnostic tool for use in the healthcare arena.

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Contributors

Author: Duanyang Xu

Author: Jonathan Price

Author: Lin Xu

Author: David Richardson

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