On the strong and narrow absorption signature in lactose at 0.53 THz

The authors report on the room-temperature characterization of a narrow absorption signature in an organic molecular solid (alpha-lactose monohydrate) centered around 530 GHz and having a full width at half maximum as small as 23 GHz. Three different spectrometric techniques were applied, two of them (tunable photomixing and tunable frequency multiplication) having a high enough resolution (< 100 MHz) to accurately curve fit the signature and determine that it is much better described by a Lorentzian than a Gaussian function. The Lorentzian model provides an estimate of 14 ps for the damping time associated with this signature.