Abstract: A spectroscopic measuring apparatus for measuring a spectral response of a sample includes a probe light source device irradiating the sample with a probe light pulse of a defined duration, where interaction with the sample produces a free induction decay light field lasting longer than the probe pulse. An amplifier device amplifies this light field, and a detector device provides the spectral response by temporally resolved detection of the light field. The amplifier is an optical parametric amplification (OPA) device with a pump light source generating pump pulses shorter than the free induction decay duration, using an optically non-linear medium. The OPA scans the free induction decay light field with pump pulses at varying delays. The detector uses sampling light pulses shorter than the free induction decay duration for time-domain sampling, synchronized with the pump pulses. A corresponding spectroscopic measuring method is also described.

Abstract: Compact terahertz spectrometer. The spectrometer includes an optical beam both for generating terahertz radiation for interaction with the sample and for use in a detector. A DC heterodyne detector uses a DC field-induced second harmonic wave at a sensor plasma to serve as a local oscillator. The spectrometer has a bandwidth orders of magnitude larger than conventional THz spectrometers.