  High-frequency gravitational waves can be detected by observing the frequency
modulation they impart on photons. We discuss fundamental limitations to this
method related to the fact that it is impossible to construct a perfectly rigid
detector. We then propose several novel methods to search for O(MHz-GHz)
gravitational waves based on the frequency modulation induced in the spectrum
of an intense laser beam, by applying optical frequency demodulation
techniques, or by using optical atomic clock technology. We find promising
sensitivities across a broad frequency range.
