Projects

Optical parametric chirped pulse amplifiers (OPCPA) are often used to generate high-energy, ultra-short laser pulses with a pulse duration of a few femtoseconds and pulse energy of several millijoules. With this amplification principle, the low-energy, time-stretched seed laser pulse is superposed with a high-energy pump laser pulse in an optical crystal. Due to the non-linear interaction between the two pulses, energy is transferred from the pump pulse to the seed pulse. For an effective and stable energy transfer, the two laser pulses must have a pulse length that is as similar as possible (typically in the range of a few picoseconds) and be in the optical crystal at the same time at the location of the superposition.

In practice, there are time shifts between the pulses due to temperature-related length changes or vibrations in the mechanical components or due to changes in air temperature/pressure or humidity, which results in fluctuations in the amplification efficiency.

As part of this project, an arrangement to compensate for the temporal fluctuations was implemented. A suitable PSD detector for determining the position of ultra-short laser pulses was developed, as well as an FPGA-SoC based control electronics.

The system is characterized by the ability to detect single pulses in a wide pulse frequency range up to several 100 kHz and a high signal-to-noise ratio for the time deviation of approx. 80 dB. In an exemplary application, the temporal drift between pump and seed pulse could be compensated for hours with this system, with a remaining jitter of about 3 fs.