Performance of a MOPA laser system for photocathode research

A Nd:YLF laser system with frequency doubled output is described. Several aspects concerning energy and stability of the pulses will be discussed. The system consists of a CW mode locked Nd:YLF oscillator and two double pass amplifiers having a total small signal gain of about a million which means care must be taken to prevent self-oscillations. Due to saturation effects the energy per micropulse is limited to 20 µJ, resulting in 8 µJ at the second harmonic frequency (526.5 nm). For the frequency conversion KTP type II is used. The short term timing stability was measured using a spectrum analyser and found to be less than 200 fs with a width of 450 Hz. The amplitude fluctuations over the 15 ¿s macropulse are determined by the saturation behaviour of the amplifiers and the shot to shot stability of the amplifiers. Third and fourth harmonic generation is under study

On the jitter of mode-locked pulses introduced by an optical fibre

Measurements on the jitter of mode-locked pulses of a Nd:YLF laser after travelling through an optical fibre are presented. For low powers self phase modulation occurs which leaves the jitter unaltered. For powers higher than the threshold of stimulated Raman scattering the jitter increases due to the exponential growth of the Stokes field

Status of the "TEU-FEL" project

The free-electron laser of the TEU-FEL project will be realized in two phases. In phase I the FEL will be driven by a 6 MeV photoelectric linac. In phase II the linac will be used as an injector for a 25 MeV race-track microtron. Information is presented on some technical details and the status of the different subsystems

The "TEU-FEL" project

The free-electron laser of the TEU-FEL project will be based on a 6 MeV photo-cathode linac as injector, a 25 MeV race-track microtron as main accelerator and a hybrid, 25 mm period undulator. The project will be carried out in two phases. In phase one only the 6 MeV linac will be used, The FEL will then produce tunable radiation around 200 µm. In phase two the linac will be used as an injector for the microtron. The FEL will then produce tunable radiation around 10 µm. Technical information will be presented on the different subsystems

Measurement of the ambipolar carrier capture time in a gallium arsenide/aluminum gallium arsenide separate confinement heterostructure quantum well

The carrier capture in a separate confinement heterostructure quantum well has been studied both experimentally and theoretically. Our calculations show that the electron and hole capture time vary strongly as a function of the excess energy. At an excess energy of 40 meV, both capture times are equal resulting in an ambipolar capture process which allows a direct comparison between theory and experiment. We carried out subpicosecond luminescence spectroscopy experiments and deduce an ambipolar overall capture time of 20 ps, a number which for the first time is in agreement with theoretical predictions. The quantum mechanical overall capture time of 20 ps gives rise to a classical local capture time of 3 ps which is determined from a diffusion model