Browsing by Subject "Nonlinear frequency conversion"

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    Femtosecond self-doubling optical parametric oscillator based on KTiOAsO4
    (IEEE, 2003) Kartaloğlu, T.; Aytür, O.
    We report a femtosecond intracavity-frequency-doubled optical parametric oscillator that employs a single KTiOAsO4 crystal for both parametric generation and frequency doubling. This device generates a yellow output beam at 575 nm with 39.4% power conversion efficiency when synchronously pumped by a femtosecond Ti:sapphire laser at a wavelength of 796 nm. An intracavity retarder is employed to alleviate temporal pulse overlap problems associated with group velocity mismatch inside the KTiOAsO4 crystal.
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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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    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.
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    Plane-wave theory of self-doubling optical parametric oscillators
    (Institute of Electrical and Electronics Engineers, 1998-03) Aytür, O.; Dikmelik, Y.
    This paper presents a theoretical analysis of self-doubling optical parametric oscillators (OPO's) where a single nonlinear crystal is used for both parametric generation and frequency doubling. In these devices, the parametric generation and frequency-doubling processes are both phase matched for the same direction of propagation inside the crystal. Different polarization geometries for which this simultaneous phase-matching condition can potentially be satisfied are identified and categorized. Plane-wave coupled-mode equations are presented for each of these categories. Numerical solutions of these coupled-mode equations and calculation of the single-pass saturated signal gain are outlined. Intracavity signal photon flux calculations iased on these numerical solutions are presented. The dependence of performance measures such as the photon conversion efficiency on various design parameters are investigated.
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    Plane-wave theory of single-crystal upconversion optical parametric oscillators
    (1998) Dikmelik, Yamaç
    'rhis thesis pi'('s('nts a theoi'etical analysis of single-crystal upconversion optical parametric oscillators (OPO’s) where a single nonlinear crystal is used for both the OPO and sum-frequency generation (SPG) or second-harmonic generation (SHG). In these devices, the OPO and SFG/SHG processes are both phase matched for the same direction of propagation inside the crystal. Different polarization geometries for which this simultaneous phase matching condition can potentially be satisfied are identified and categorized, for both biréfringent. a.nd quasi-phcise matching methods. This categorization results in four classes of sumfrequency generating OPO’s (SF-OPO’s) and three classes of self-doubling OPO’s (SD-OPO’s). Plane-wa.ve coupled mode equations a.re presented for each of these seven classes. Solutions of these coupled mode equations, and calculation of the single-pass saturated signal gain are outlined. The dependence of the photon conversion efficiency on various design parameters are investigated. .Λ pulsed plane-wave model that takes into account the temporal profiles of the fields and the group velocity mismatch between pulses is constructed. This model is in good qualitative agreement with experimental measurements of a class-G SF-OPO.