Single shot high resolution THz upconversion spectrometer

We have designed an upconversion spectrometer that has been used to measure the frequency of individual pulses from the UCSB free electron lasers (FEL). The FEL THz radiation is mixed with NIR radiation in a non-linear optical crystal to generate sum and difference frequency radiation. The FEL frequency is obtained by measuring the frequency difference between the fundamental radiation and the sum or difference frequency sideband, which is accomplished using a 1 m focal length Czerny-Turner spectrometer. Single shot sum and difference frequency generation of NIR and THz radiation is demonstrated with accuracy up to 0.1 cm^-1 and with signal to noise ratios of greater than 100:1.