  The JILA Multidimensional Optical Nonlinear SpecTRometer (JILA-MONSTR) is a
robust, ultra-stable platform consisting nested and folded Michelson
interferometers that can be actively phase stabilized. This platform generates
a square of identical laser pulses that can be adjusted to have arbitrary time
delay between them, while maintaining phase stability. The JILA-MONSTR provides
output pulses for nonlinear excitation of materials and phase-stabilized
reference pulses for heterodyne detection of the induced signal. This
arrangement is ideal for performing coherent optical experiments, such as
multidimensional Fourier-transform spectroscopy, which records the phase of the
nonlinear signal as a function of the time delay between several of the
excitation pulses. The resulting multidimensional spectrum is obtained from a
Fourier transform. This spectrum can resolve, separate and isolate coherent
contributions to the light-matter interactions associated with electronic
excitation at optical frequencies. To show the versatility of the JILA-MONSTR,
several demonstrations of two-dimensional Fourier-transform spectroscopy are
presented, including an example of a phase-cycling scheme that reduces noise.
