Accurate spectral shaping was achieved by operating a
closed loop between the voltage patterns driving the SLMs and
a spectrometer measuring the output spectrum of the simulator.
Because of nonlinearities in the response of our optical system,
an iterative approach was used to obtain the optimum voltage
patterns which minimized the difference between the target
and measured spectra.
An off-axis parabolic mirror with a 152 mm focal length was
used to concentrate the light from the simulator, generating a
focused beam of broadband light with a measured diameter of
1.0 mm. The ease with which the output of the simulator was
concentrated was a direct result of the spatial coherence of the
super-continuum laser. Propagation through the step-index
multimode fiber resulted in a focused spot of light with an
approximate square-top intensity profile