Beam-Scanning for Rapid Coherent Raman Hyperspectral Imaging
Seungwan Ryu, Charles H. Camp, Ying Jin, Marcus T. Cicerone, Young J. Lee
Coherent Raman imaging requires high peak power laser pulses to maximize the nonlinear multiphoton signal generation, but accompanying photo-induced sample damage often poses a challenge to microscopic imaging studies. We demonstrate that a beam-scanning by a resonant mirror in a broadband coherent anti-Stokes Raman scattering (BCARS) imaging system can reduce photo-induced damages without compromising the signal intensity. Reflective mirrors in a beam scanning assembly are employed to minimize chromatic aberration and temporal dispersion. Hyperspectral data for a line area are acquired as a two-dimensional image by a CCD with a single exposure. The beam-scanning approach is compared with the sample-scanning mode in terms of spatial resolution, photo-induced damage, and imaging speed at the maximum laser power below a sample damage threshold. We show that the beam-scanning BCARS imaging method can reduce photodamage probability in biological cells and tissues, thus the imaging speed can be improved by using higher excitation laser power.