  The generation of shaped laser beams, or structured light, is of interest in
a wide range of fields, from microscopy to fundamental physics. There are
several ways to make shaped beams, most commonly using spatial light modulators
comprised of pixels of liquid crystals. These methods have limitations on the
wavelength, pulse duration, and average power that can be used. Here we present
a method to generate shaped light that can be used at any wavelength from the
UV to IR, on ultrafast pulses, and a large range of optical powers. By
exploiting the frequency difference between higher order modes, a result of the
Gouy phase, and cavity mode matching, we can selectively couple into a variety
of pure and composite higher order modes. Optical cavities are used as a
spatial filter and then combined with sum frequency generation in a nonlinear
crystal as the output coupler to the cavity to create ultrafast, frequency comb
structured light.
