Terahertz radiation by optical rectification in a hydrogen-bonded   organic molecular ferroelectric crystal, 2-phenylmalondialdehyde
  Terahertz radiation by optical rectification has been observed at room temperature in a hydrogen-bonded organic molecular ferroelectric crystal, 2-phenyl malondialdehyde (PhMDA). The radiated electromagnetic wave consisted of a single-cycle terahertz pulse with a temporal width of $\sim$ 0.5 ps. The terahertz radiation amplitude divided by the sample thickness in PhMDA was nearly equivalent to that in a typical terahertz wave emitter ZnTe. This is attributable to a long coherence length in the range of 130 $\sim$ 800 $\mu$m for the terahertz radiation from PhMDA. We also discussed the possibility of PhMDA as a terahertz wave emitter in terms of the phase-matching condition. 
W. Guan, N. Kida, M. Sotome, Y. Kinoshita, R. Takeda, A. Inoue, S.   Horiuchi, and H. Okamoto
cond-mat.mtrl-sci physics.optics