Near-field verification for a 10mkm water droplet - create test case

[kostyfisik]

Create test data with mpmath and set GTest for the test case described below (see #42 for more context)

I'm considering 10 μm water drops (uncoated spheres with n≈1.33, no absorption) in a vacuum, illuminated by a pulse of light containing several semiperiods of oscillation, with wavelength of 650 nm. This is done via Fourier transform, which spans wavelengths from about 100 nm to about 1.3 mm (for a single semiperiod), which implies size parameters from 0.05 to 600.

This is a similar simulation to the one here, but for near field (spanning about 10 sphere radii) instead of the far field.