Browsing by Subject "Second harmonic generation"
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Item Open Access 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.Item Open Access Laser wavelength upconversion with optical parametric oscillators using simultaneously phase-matched crystals(2002) Kartaloğlu, TolgaIn 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.Item Open Access Nanosecond sum-frequency generating optical parametric oscillator using simultaneous phase matching(Optical Society of American (OSA), 2005) Figen, Z.G.; Aytür O.We report a nanosecond sum-frequency generating optical parametric oscillator based on a single KTiOAsO4 crystal that is simultaneously phase matched for optical parametric generation and sum-frequency generation. Pumped at a wavelength of 1064 nm by a Q-switched Nd:YAG laser, this device produces 10.4-ns-long 8.3 mJ red pulses at a wavelength of 627 nm with 21% energy conversion efficiency. This device provides a simple and efficient method for converting high energy Nd:YAG lasers to a red wavelength. © 2005 Optical Society of America.Item Open Access Nonlinear optical properties of CVD-synthesized CuS crystals(AIP Publishing LLC, 2024-12-27) Suleiman, Abdulsalam Aji; Rahighi, Reza; Parsi, Amir; Kasırga, Talip SerkanCopper sulfide (CuS) is a material of growing interest due to its distinctive electronic, optical, and catalytic properties. In this study, we successfully synthesized ultrathin CuS crystals, with thicknesses as low as 14 nm and lateral dimensions reaching 60 μm, using a single-step chemical vapor deposition process. Detailed structural, compositional, and morphological analyses revealed intrinsic lattice defects, including stacking faults and domain misorientations. These defects disrupt the centrosymmetry of the CuS lattice and are responsible for an unexpected second harmonic generation response, an uncommon behavior in centrosymmetric materials. In addition, we measured the first-order temperature coefficients of Raman shifts, providing insights into the thermal dynamics of the CuS crystal structure. These findings position CuS as a potential material for nonlinear optical applications, while reinforcing its established roles in catalysis and electronics.Item Open Access Phase-matched self-doubling optical parametric oscillator(Optical Society of America, 1997-03-01) Kartaloğlu, T.; Köprülü, K. G.; Aytür, O.We report a synchronously pumped intracavity frequency-doubled optical parametric oscillator that employs a single KTiOPO4 crystal for both parametric generation and frequency doubling. Both nonlinear processes are phase matched for the same direction of propagation in the crystal. The parametric oscillator, pumped by a femtosecond Ti:sapphire laser at a wavelength of 745 nm, generates a green output beam at 540 nm with a 29% power conversion efficiency. Angle tuning in conjunction with pump wavelength tuning provides output tunability in the 530-585-nm range.Item Open Access Phase-matched self-doubling optical parametric oscillator(IEEE, 1996) Kartaloğlu, Tolga; Köprülü, Kahraman G.; Aytür, OrhanA new self-doubling optical parametric oscillator (OPO) uses a single nonlinear crystal for both parametric generation and frequency doubling. It is based on a KTiOPO4 (KTP) crystal pumped by a Ti:Sapphire laser operating at a wavelength of 739 nm. The crystal is cut such that the signal wavelength of the OPO is at 1064 nm, corresponding to an idler wavelength of 2420 nm. The OPO cavity resonates only the signal wavelength. The signal beam is also phase-matched for second harmonic generation (SHG) at the same crystal orientation. With proper polarization rotation, an output beam at a wavelength of 532 nm can be obtained.Item Open Access Plane-wave dynamics of single crystal upconversion optical parametric oscillators(1999) Akgün, GülbinThis 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.Item Open Access 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.Item Open Access Second harmonic generation in generalized ferroelectric superlattices(Taylor & Francis, 2021-12-01) Ozer, Z.; Palaz, S.; Mamedov, Amirullah M.; Ozbay, EkmelThe goal of the work presented in this investigation is to achieve the efficient parametric interaction of narrow beams (in particular second harmonic generation) using a nonlinear (ferroelectric-LiTaO3) photonic crystal tuned to self-collimation (nondiffractive) regimes. A numerical study of second harmonic generation (SHG) in one-dimensional nonlinear photonic crystals based on a full nonlinear system of equations, implemented by a combination of the method of finite elements and fixed-point iterations, is reported. This model is derived from a nonlinear system of Maxwell’s equations that partly overcomes the known shortcoming of some existing models that rely on the undepleted pump approximation. We derive a general solution of SHG in one-dimensional nonlinear photonic crystals structures. Numerical simulations also show that the conversion efficiency of SHG can be significantly enhanced when the frequencies of the fundamental wave are located at the photonic band edges or are assigned to the designed defect states.Item Open Access A self-doubling optical parametric oscillator based on aperiodically-poled lithium niobate(IEEE, 2001) Kartaloǧlu, Tolga; Figen, Ziya Gürkan; Aytür, OrhanA self-doubling optical parametric oscillator (SDOPO) having one-dimensional aperiodic grating structure based on a LiNbO3 crystal was constructed. The structure was designed to quasi-phase-match both second harmonic generation (SHG) and optical parametric oscillation (OPO) processes. The grating structure contained in the LiNbO3 crystal was based on the construction of a function by summing up two cosine functions with arbitrary phase and amplitude.Item Open Access Simultaneous phase matching of optical parametric oscillation and second-harmonic generation in aperiodically poled lithium niobate(Optical Society of American (OSA), 2003) Kartaloğlu, T.; Figen, Z. G.; Aytür, O.We report a simple ad hoc method for designing an aperiodic grating structure to quasi-phase match two arbitrary second-order nonlinear processes simultaneously within the same electric-field-poled crystal. This method also allows the relative strength of the two processes to be adjusted freely, thereby enabling maximization of the overall conversion efficiency. We also report an experiment that is based on an aperiodically poled lithium niobate crystal that was designed by use of our method. In this crystal, parametric oscillation and second-harmonic generation are simultaneously phase matched for upconversion of a femtosecond Ti:sapphire laser to 570 nm. This self-doubling optical parametric oscillator provides an experimental verification of our design method. © 2003 Optical Society of America.Item Open Access Wafer bonded capacitive micromachined underwater transducers(IEEE, 2009-09) Olcum, Selim; Oǧuz, Kaan; Şenlik, Muhammed N.; Yamaner F. Y.; Bozkurt, A.; Atalar, Abdullah; Köymen, HayrettinIn this work we have designed, fabricated and tested CMUTs as underwater transducers. Single CMUT membranes with three different radii and 380 microns of thickness are fabricated for the demonstration of an underwater CMUT element. The active area of the transducer is fabricated on top of a 3″ silicon wafer. The silicon wafer is bonded to a gold electrode coated glass substrate wafer 10 cm in diameter. Thermally grown silicon oxide layer is used as the insulation layer between membrane and substrate electrodes. Electrical contacts and insulation are made by epoxy layers. Single CMUT elements are tested in air and in water. Approximately 40% bandwidth is achieved around 25 KHz with a single underwater CMUT cell. Radiated pressure field due to second harmonic generation when the CMUTs are driven with high sinusoidal voltages is measured. ©2009 IEEE.