| Abstract [eng] |
Laser radiation has a very wide range of applications – pump-probe spectroscopy, optical communication, femtosecond micromachining, attosecond pulse generation. It is necessary to be able to operate and characterize it for a successful application. Laser radiation power, energy, wavelength are measured by standard methods, however, temporal and spatiotemporal ultrashort light pulses parameters' characterization is only possible with optical correlation methods. Modern optoelectronics methods are not adequate because the temporal resolution is too low. Generally, the optical methods schemes are complex, the experiments demand a considerable time input and that is why alternative optical correlation methods, which would allow to simplify the temporal and spatiotemporal ultrashort light impulses parameters' characterization experiments, are being sought for. The objective of this work was to design, assemble and optimize the single-shot transverse second harmonic autocorrelator optical scheme, to demonstrate the possibilieties to characterize „Pharos“ (Yb:KGW) and „Libra-USP-HE“ (Ti:Sapphire) ultrashort light pulses temporal and spatiotemporal parameters. At the time of this work the single-shot transverse second harmonic autocorrelator, which operation is based on transverse second-harmonic generation in strontium barium niobate crystal (SBN:61), was designed, assembled and optimized. The assembled scheme's geometry allows to measure the light pulses' autocorrelation functions and pulse front tilt angle of laser systems „Pharos“ and „Libra-USP-HE“ without thermal or angular SBN:61 crystal tuning. It has been shown that this device can register „Pharos“ light pulses' duration with an accuracy of <8 % at ~200-400 fs diapason, compared with the multiple-shot FROG autocorrelator experimental results. Measured pulse front tilt magnitude of both laser systems is in the noise level of this method (dozens of arcseconds). Also, this autoccorelator is suitable to tune prism compressor, which is made of two prisms, with precision of ~9'. We have also demonstrated that using 5 mm length SBN:61 crystal precise measurements of „Libra-USP-HE“ light pulses (59 fs) are not viable because of material dispersion. Although, dispersion spreading effects were eliminated by performing compression of „Libra-USP-HE“ light pulses in the SBN:61 crystal to theoretical 71 fs duration, it has been shown that autocorrelator imaging system point spread function limits the performance of autocorrelator. Theoretically, because of point spread function influence, >180 fs duration of 800 nm light pulses could be measured by less than 5 % error. |
