Browsing by Subject "Oscillators, Crystal."

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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.
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    Laser wavelength upconversion with optical parametric oscillators using simultaneously phase-matched crystals
    (2002) Kartaloğlu, Tolga
    In this thesis, we present our work on optical parametric oscillators that employ a single nonlinear crystal that is simultaneously-phase-matched for second-harmonic or sum-frequency generation in order to obtain frequency upconversion of laser radiation. We achieved simultaneous phase matching of optical parametric amplification together with second harmonic generation or sum frequency generation in bulk KT10P04 and KTi0 As04 crystals, and in an aperiodically-poled LiNbOs crystal. We demonstrated very efficient frequency conversion of pulsed and continuous-wave lasers to higher frequencies with power conversion efficiencies reaching 40%. In addition, we present our work on an intracavity-doubled optical parametric oscillator that employs a periodicallypoled KT10P 04 crystal for optical parametric amplification and an intracavity (3- Ba2B04 crystal for second harmonic generation. In this thesis, we also introduce a method for designing aperiodic grating structures for simultaneous phase matching in poled nonlinear crystals. In contrast to periodic grating structures, a grating structure designed using our method allows one to achieve simultaneous quasi-phase matching of two arbitrarily chosen nonlinear interactions with freely adjustable coupling coefficients.
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    Plane-wave dynamics of single crystal upconversion optical parametric oscillators
    (1999) Akgün, Gülbin
    This thesis presents our investigation of the dynamics of single crystal up- conversion optical parametric oscillators (OPO’s). In these devices, parametric generation and sum frequency generation or second harmonic generation processes are simultaneously phase matched in a single crystal for the same direction of propagation. These devices can be categorized depending on the polarization geometries of the interacting fields leading to simultaneous phase matching of the two processes. The dynamics of these OPO’s are analyzed using a discrete dynamical system representation. The dependence of the dynamics of the system on various parameters is investigated by forming bifurcation diagrams. Regions of stable steady state, multistable, periodic and chaotic operation are identified on these diagrams.