Browsing by Subject "ultrafast lasers"

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    Femtosecond optical parametric amplifiers based on beta-barium borate crystals
    (1996) Köprülü, Kahraman Güçlü
    In this thesis we describe our experiments to construct and evaluate nondegenerate and degenerate optical parametric amplifiers (OP.-\) based on betabarium borate (BBO) crystals. VVe used a mode-locked Titanium.Sapphire laser at a wavelength of 830 nm and a pulse duration of 140 fs. The Ti:Sapphire laser was frequency doubled with a type-I BBO crystal. The frequency doubled output of the laser was used to pump our OP.As. For 800 mVV’ of laser output, 300 mVV of maximum output power at the second harmonic was obtained, corresponding to a 38% conversion efficiency. Both type-I and type-II BBO crystals were used for parametric amplification. The type-II crystal resulted in a nondegenerate OPA due to the orthogonal polarizations of the signal and the idler beams. A degenerate OP.A was achieved with the type-I crystal. Phcise sensitive nature of the degenerate OPA, and phase insensitive nature of the nondegenerate OP.A were observed. The maximum gain of the degenerate OPA was measured to be 1.45, whereas the maximum gain of the nondegenerate OP.A was measured to be 1 .0 2 .
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    Femtosecond optical parametric oscillators based on potassium titanyl phosphate crystals
    (1996) Kartaloğlu, Tolga
    In this thesis, we describe our experiments to construct and characterize optical parametric oscillators (OPO) based on a potassium titanyl phosphate (KTP) crystals. The oscillator is synchronously pumped by a mode-locked Titanium:Sapphire laser at a wavelength of 745 nm, a pulse duration of 120 fs, and average power of 640 mW. The OPO converts the 745 nm pump beam to a signal beam at 1068 nm. The resonator is in the form of a ring cavity, with the KTP crystal positioned at the intracavity focus. The crystal is cut for type-II phase matching. We investigated the performance of the OPO with four different output coupler reflectivities. The 10% output coupler gives the best results with 170 mW of signal average power, corresponding to 27% conversion efficiency. The signal beam has an autocorrelation pulse width of 650 fs. In addition, we demonstrate phase-matched intracavity frequency doubling of the signal beam with the same KTP crystal, by placing a waveplate inside the resonator. The waveplate is used to rotate the polarization for type-II phase matching.