Browsing by Subject "Parametric devices."

Now showing 1 - 4 of 4

Open Access
Analysis of Gaussian-beam pumped optical parametric amplifiers for the generation of squeezed states of light
(2002) Köprülü, Kahraman Güçlü
Open Access
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.
Open Access
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.
Open Access
Nanosecond upconversion optical parametric oscillators
(2005) Figen, Ziya Gürkan
In this thesis, we demonstrate a technique for highly efficient red beam generation using nanosecond upconversion optical parametric oscillators based on KTiOAsO4 crystals that are simultaneously phase matched for optical parametric generation and sum-frequency generation. Pumped at a wavelength of 1064 nm by a Qswitched Nd:YAG laser, these devices produce red output beams at 627 nm with 1064-nm-to-627-nm energy conversion efficiencies reaching 20% for the singlepass pumping and 30% for the double-pass pumping. Our devices are simpler in architecture compared to other devices converting nanosecond Nd:YAG laser radiation into red wavelengths. A typical nanosecond upconversion optical parametric oscillator is comprised of three cavity mirrors which are all high reflectors at the signal wavelength (1525 nm), a 2-cm-long KTiOAsO4 crystal, and an intracavity retarder plate for rotating the polarization of the signal beam. The total cavity length is under 5 cm. With its small size, the device can be shaped into a module to be placed in front of Nd:YAG lasers for highly efficient red beam generation. The single-pass sum-frequency generating optical parametric oscillator is the first demonstration of a nanosecond optical parametric oscillator using simultaneous phase matching. We have fully characterized these devices in terms of their energy output as functions of polarization rotation angle and input pump energy, time profiles, spatial beam profiles, and spectra of the output. In this thesis, we also present our work on modelling continuous-wave intracavity optical parametric oscillators.