The main amplifiers of the 2-µm CPA system are based on Ho:YLF crystals and consist of a highly stable regenerative amplifier and two booster amplifiers. All of them are operated at room temperature and pumped by continuous-wave Tm:fiber lasers with a total power of 270 W. Starting from a 2-µm supercontinuum source the seed pulses are stretched and pre-amplified and subsequently fed into the Ho:YLF amplifier chain.The re-compressed pulse energy of the Ho:YLF CPA amounts to 52.5 mJ and reveals an excellent pulse-to-pulse stability of <0.23% rms. The long-term pulse stability together with the beam quality, measured to be better than a M² of 1.2. The emitted spectrum centered at 2050 nm with a bandwidth of 3.5 nm (FWHM) supports a ~1.7 ps Fourier-transform limited pulse duration. After amplification the pulses are re-compressed in a Treacy-type grating arrangement with an efficiency >93%. The recorded autocorrelation trace exhibits a FWHM of 4.1 ps. This corresponds to a duration of the main pulse of 2.4 ps (FWHM) with an estimated energy content of 85%, translating into 17 GW peak power. The latter and the pulse energy of >50 mJ represent the highest values ever achieved for few-ps pulses at 2 µm wavelength yet.

This source is currently being applied as pump in a system for the generation of few-cycle pulses around 5-µm with multi-millijoule energies. Applications in nonlinear optics, spectroscopy and materials processing are underway.

Story Source:

Materials provided by Forschungsverbund Berlin. Note: Content may be edited for style and length.

Journal Reference:

1. Lorenz von Grafenstein, Martin Bock, Dennis Ueberschaer, Azize Koç, Uwe Griebner, Thomas Elsaesser. 205  µm chirped pulse amplification system at a 1  kHz repetition rate—24  ps pulses with 17  GW peak power. Optics Letters, 2020; 45 (14): 3836 DOI: 10.1364/OL.395496