  We propose a method for simulating an Unruh-DeWitt detector, coupled to a
1+1-dimensional massless scalar field, with a suitably-engineered $\chi^{(2)}$
nonlinear interaction. In this simulation, the parameter playing the role of
the detector acceleration is played by the relative inverse-group-velocity
gradient inside the nonlinear material. We identify experimental parameters
that tune the detector energy gap, acceleration, and switching function. This
system can simulate time-dependent acceleration, time-dependent detector energy
gaps, and non-vacuum initial detector-field states. Furthermore, for very short
materials, the system can simulate the weak anti-Unruh effect, in which the
response of the detector decreases with acceleration. While some Unruh-related
phenomena have been investigated in nonlinear optics, this is the first
proposal for simulating an Unruh-DeWitt detector in these systems.
