Multifocal 1064 nm Raman imaging of carbon nanotubes

We show that multifocal 1064 nm Raman microscopy based on Hadamard-coded multifocal arrays is useful for imaging carbon nanotubes (CNTs) that would otherwise be damaged if a conventional single focus microscope design is used. The damage threshold for CNTs, dependent on laser power density and exposure time, limits the spectral detection sensitivity of single focus Raman imaging. With multifocal detection, the signal-to-noise ratio of the Raman spectra were improved by more than a factor of three, allowing for the G and D Raman bands of CNTs to be detected while avoiding specimen damage. These results lay the foundation for developing multifocal 1064 nm Raman microscopy as a tool for in situ imaging of CNTs in plant material. (C) 2020 Optical Society of America