Figure 8: Fast Fourier transform of images from Figs 3, 4 and 5 at 2 ns delay illustrating the spatial frequency spectrum of the images.
From: Enabling time resolved microscopy with random Raman lasing
The narrow spike in the fluorescence spectrum is the result of the lack of sharp details in the image, and the broad spectral noise background in the laser image is the result of background noise due to the formation of laser speckle. In contrast the random Raman laser image demonstrates a broad range of spatial frequencies, allowing for the resolution of fine details, while maintaining a much smaller background due to speckle formation.
