We report what we believe to be the first demonstration of an all-semiconductor room-temperature terahertz time domain spectrometer. An optical Stark mode-locked vertical-external-cavity surface-emitting laser with $480\mathrm{fs}$ pulses at $1044\mathrm{nm}$ was used to illuminate low-temperature-grown photoconductive antennae with $5\mu \mathrm{m}$ -gap bow-tie-shaped electrodes. The coherently detected spectrum has a bandwidth close to $1\mathrm{THz}$ , in which water absorption lines at 0.555 and $0.751\mathrm{THz}$ can be resolved.