Fourier plane analysis of up-converted images in the visible region under different bandwidth IR illumination sources

Nonlinear wavelength up-conversion from the infrared (IR) to the visible spectrum appears as an interesting alternative for imaging applications. Since early demonstrations [1], work is being done to improve significantly features of up-converted images in terms of the efficiency by intra-cavity continuous wave up-conversion [2] and resolution and field-of-view by incoherent illumination [3]. Direct comparison of up-converted images according to a standardized pattern in the image plane is not always possible or appropriate to draw clear differences or conclusions. This is particularly the case when resolution of up-converted images is evaluated depending on features of the illumination source used: brightness, spectral bandwidth, coherence… For this reason, a complementary tool is needed to make comparative studies in imaging up-conversion when illuminating with different kind of sources. To date, there are no studies based on the Fourier plane analysis of up-converted images providing additional information to those based on observation of standardized patterns. This work aims for the comparison of up-converted images in the Fourier plane when illuminating with laser and amplified spontaneous emission (ASE) while keeping all the parameters of the up-conversion system identical.