A tunable autocorrelator for pulse measurements at IR FEL-oscillator facilities

Abstract Radiation characteristics of a Free-Electron Laser (FEL) such as pulse length, time structure, intensity, bandwidth, wavelength, power, frequency, etc., which were measured on a diagnostics table, are thoroughly discussed. In this respect, pulse length measurements of an Infrared FEL (IR-FEL) beam are evaluated through an intensity autocorrelator, designed and installed as a diagnostics tool at the “Helmholtz-Zentrum Dresden-Rossendorf (HZDR)-Radiation Source ELBE” of Germany. In addition, the autocorrelator was designed as a unique, cost-effective, and in-house setup. It operates within the wavelength range of 3–35 microns, using Cadmium-Telluride (CdTe) crystals in the Second Harmonic Generation (SHG) medium. The intensity autocorrelation curves were obtained for the FEL beam with the wavelength of 26.2 microns, indicating an FWHM pulse duration ranging between 3.29–8.03 ps with different optical cavity detuning values. Furthermore, the pulse duration of Ti: sapphire laser beam is measured between 1–3 ps through the designed autocorrelator at the ELBE light source. On the other hand, the setup may pave the way for pulse length measurements of the Turkish infrared FEL-oscillator facility (TARLA) as well, which is currently under the hardware installation phase. Finally, it is elaborated in section 3 that the unique autocorrelator design fully meets all requirements for pulse length measurements of an infrared FEL source.