Development of Line Scan Confocal Raman Microscopy using a Spectrometer with Improved Diffraction Efficienc

Abstract

Confocal Raman microscopy is widely used in various fields of research since it allows for label-free sample investigation. However, the slow data acquisition speed of Raman microscopy limits the applications for imaging large area samples. I developed a line-scan confocal Raman microscope for high-speed data acquisition and proposed a dual mirror scan method to improve the diffraction efficiency of the spectrometer. I used a Powell lens for the line illumination and demonstrated that it can provide a more uniform intensity distribution than a cylindrical lens. A volume phase holographic grating was used in the spectrometer due to it can provide higher diffraction efficiency than the surface-relief grating. The proposed dual mirror scan method can provide a high-resolution Raman spectrum at high efficiency over a wide spectral range. By combining the system with a high sensitivity EMCCD camera, the maximum spectral rate can reach to 25,000 spectra/s. I demonstrated the performance by imaging a custom-designed large area sample and arterial tissue sections. With the parallel detection by the line excitation and the improved diffraction efficiency, I expect the proposed system can be used in a variety of applications that require a high spectral rate.