Browsing by Subject "Yb-doped fiber lasers"
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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-fiber Yb-doped laser mode-locked by nanotubes(IEEE, 2013) Zhang, Zewang; Popa, D.; Sun, Z.; Hasan, T.; Ferrari, A.C.; İlday, F. ÖmerSingle-wall carbon nanotubes (SWNTs) and graphene have emerged as promising saturable absorbers (SAs), due to their broad operation bandwidth and fast recovery times [1-3]. However, Yb-doped fiber lasers mode-locked using CNT and graphene SAs have generated relatively long pulses. All-fiber cavity designs are highly favored for their environmental robustness. Here, we demonstrate an all-fiber Yb-doped laser based on a SWNT saturable absorber, which allows generation of 8.7 ps-long pulses, externally compressed to 118 fs. To the best of our knowledge, these are the shortest pulses obtained with SWNT SAs from a Yb-doped fiber laser. © 2013 IEEE.Item Open Access Femtosecond Yb-doped fiber laser system at 1 μm of wavelength with 100-nm bandwidth and variable pulse structure for accelerator diagnostics(2007-05) Winter, A.; İlday, F. Ömer; Steffen, B.Laser-based diagnostic systems play an increasingly important role in accelerator diagnostics in, for instance, electron bunch length measurements. To date, the laser system of choice for electro-optic experiments has been the Ti:sapphire laser, providing several nanojoules of pulse energies at fixed a repetition rate, which is not well suited to the bunch structure of accelerator facilities such as FLASH. Limited long-term stability and operability of Ti:sapphire systems are significant drawbacks for a continuously running measurement system requiring minimal maintenance and maximum uptime. We propose fiber lasers as a promising alternative with significant advantages. Gating of the pulse train to match the bunch profile is simple with fibercoupled modulators, in contrast to bulk modulators needed for Ti:sapphire lasers. An in-line fiber amplifier can boost the power, such that a constant pulse energy is maintained regardless of the chosen pulse pattern. Significantly, these lasers offer excellent robustness at a fraction of the cost of a Ti:sapphire laser and occupy a fraction of the optical table space.Item Open Access Sub-50 fs all-fiber Yb-doped laser with anomalous-dispersion photonic crystal fiber(IEEE, 2013) Zhang, Zewang; Cenel, C.; Hamid, R.; İlday, F. ÖmerAn intense research effort has been channelled into improving mode-locked Yb-fiber oscillators in recent years. Despite efforts in all-normal dispersion oscillators, dispersion management is evidently necessary to reach pulse durations below 50 fs. This is implemented most commonly with bulk optical components in Yb-doped fiber lasers. Increased robustness remains a valuable trait, for which all-fiber-integration is highly desirable. Photonic crystal fibers (PCF) with anomalous dispersion have small mode field diameters, enhancing nonlinear effects and usually are birefringent. The first mode-locked laser to incorporate a PCF was reported in 2002 [1]. However, mode-locking was not self-starting owing to the residual birefringence of the PCF Since then, a number of dispersion-managed Yb-doped fiber lasers using PCFs and all-fiber-integrated lasers have been reported. After 10 years, no all-fiber-integrated Yb-fiber laser has been demonstrated to support pulses below 60 fs [2]. © 2013 IEEE.Item Open Access Sub-50 fs Yb-doped laser with anomalous-dispersion photonic crystal fiber(Optical Society of America, 2013) Zhang, Z.; Şenel, Ç.; Hamid, R.; Ilday, F. Ö.We report on the generation of 42 fs pulses at 1 μm in a completely fiber-integrated format, which are, to the best of our knowledge, the shortest from all-fiber-integrated Yb-doped fiber lasers to date. The ring fiber cavity incorporates anomalous-dispersion, solid-core photonic crystal fiber with low birefringence, which acts as a broadband, in-fiber Lyot filter to facilitate mode locking. The oscillator operates in the stretched-pulse regime under slight normal net cavity dispersion. The cavity generates 4.7 ps long pulses with a spectral bandwidth of 58.2 nm, which are dechirped to 42 fs via a grating pair compressor outside of the cavity. Relative intensity noise (RIN) of the laser is characterized, with the integrated RIN found to be 0.026% in the 3 Hz-250 kHz frequency range.Item Open Access Texturing of titanium (Ti6Al4V) medical implant surfaces with MHz-repetition-rate femtosecond and picosecond Yb-doped fiber lasers(Optical Society of American (OSA), 2011) Erdoǧan, M.; Öktem, B.; Kalaycioǧlu H.; Yavaş, S.; Mukhopadhyay P.K.; Eken, K.; Özgören, K.; Aykaç, Y.; Tazebay, U.H.; Ilday F.O.We propose and demonstrate the use of short pulsed fiber lasers in surface texturing using MHz-repetition-rate, microjoule- and sub-microjoule-energy pulses. Texturing of titanium-based (Ti6Al4V) dental implant surfaces is achieved using femtosecond, picosecond and (for comparison) nanosecond pulses with the aim of controlling attachment of human cells onto the surface. Femtosecond and picosecond pulses yield similar results in the creation of micron-scale textures with greatly reduced or no thermal heat effects, whereas nanosecond pulses result in strong thermal effects. Various surface textures are created with excellent uniformity and repeatability on a desired portion of the surface. The effects of the surface texturing on the attachment and proliferation of cells are characterized under cell culture conditions. Our data indicate that picosecond-pulsed laser modification can be utilized effectively in low-cost laser surface engineering of medical implants, where different areas on the surface can be made cell-attachment friendly or hostile through the use of different patterns. © 2011 Optical Society of America.