The signal-to-noise ratio of pulsed, coherent lidar signals is, under typical conditions, of order unity and independent of signal strength. The decorrelation of a pair of signals as a function of optical frequency, or as a function of the spatial separation of detectors, potentially offers a route to improvement of the signaltonoise ratio. Professor Ward is currently conducting experiments on these decorrelations. Optical harmonic generation in gases has allowed Professor Ward's group to measure nonlinear polarizabilities for small molecules. His group has measured experimental values that differ from ab initio computations by more than 30%, even for a molecule as small as hydrogen fluoride. This is the case even for the best computations, which typically take several hours of supercomputer time. To resolve this discrepancy, it would be useful to remove one source of calculational difficulty: the inclusion of optical frequency effects. The group's initial experiments have demonstrated second harmonic generation of 60 Hz fundamental in an ammonium dihydrogen phosphate crystal as a precursor to the more difficult problem of detecting low frequency nonlinear effects in a molecular gas.