Browsing by Author "Kara, O."
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Item Open Access 33-fs Yb-fiber laser comb locked to Cs-atomic clock(IEEE, 2013) Şenel, Çağrı; Hamid, R.; Erdoğan, C.; Çelik, M.; Kara, O.; İlday, Fatih ÖmerDespite the prevalence of fiber frequency combs around 1.5 μm, few fully stabilized frequency combs have been demonstrated around 1.0 μm, despite the generally superior performance of Yb-fiber lasers compared to Er-fiber lasers. Short pulses are to generate coherent supercontinuum using anomalous dispersion regime of microstructured fibers. Near-zero cavity dispersion is highly desirable for low-noise frequency comb performance. Here, we report a Yb-doped fiber laser that operates at net-zero group-velocity dispersion and produces pulses that can be compressed externally to 33-fs. The frequency comb generated by this system is repetition-and carrier-envelope-phase-locked to Cs atomic clocks. The laser oscillator design is based on a novel algorithmic methodology, which allows us to design cavities to meet specific requirements; in this case, there was the need to generate as short pulses as possible, while having several nJ of pulse energy and the cavity at strictly zero total dispersion.Item Open Access All-normal-dispersion fiber lasers for frequency metrology(Optical Society of America, 2011) Şenel, Çağrı; İlday, F. Ömer; Kara, O.; Birlikseven, C.; Erdoǧan, C.; Hamid, R.Development of an all-normal-dispersion Yb-doped fiber laser-based frequency comb is reported. Repetition-frequency stabilization to the cesium standard, amplitude and phase noise measurements indicate low-noise performance. ©2011 Optical Society of America.Item Open Access Singularities of the modular curve(Academic Press, 2001) Klyachko, A.; Kara, O.Let X0 (l) be the modular curve, parameterizing cyclic isogenies of degree l, and Z0 (l) be its plane model, given by the classical modular equation 'l (X,>)"0. We prove that all singularities of Z0 (l), except two cusps, are intersections of smooth branches, and evaluate the order of contact of these branches.