Browsing by Subject "Pulse repetition rate"
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Item Open Access 50-W, 1.6-GHz pulse repetition rate from a burst-mode Yb-doped fiber laser(IEEE, 2017) Elahi, Parviz; Ertek, A. C.; Eken, K.; İlday, Fatih ÖmerWe report a 50-W average power Yb-doped fiber laser amplifier system. The laser system produces bursts at a minimum rate of 200 kHz, with 1.6 GHz intraburst repetition rate. The total energy delivers in a burst is 250 μJ and the individual pulse energy is about 0.4 μJ. The output pulses are compressed to 270 fs by using two compressor gratings.Item Open Access All-fiber laser systems that can operate in burst mode(OSA, 2016) Kesim, Denizhan Koray; Kalaycıoğlu, Hamit; Akçaalan, Önder; İlday, Fatih ÖmerFiber lasers which operate in burst-mode where densely spaced pulses occur inside bursts repeated at much lower repetition rates can be valuable tool for sensing and imaging. We introduce such lasers and propose possible applications.Item Open Access Burst-mode thulium all-fiber laser delivering femtosecond pulses at a 1 GHz intra-burst repetition rate(Optical Society of America, 2017) Elahı, P.; Kalaycıoğlu, H.; Akçaalan, Ö.; Şenel, Ç.; Ilday, F. Ö.We report on the development of, to the best of our knowledge, the first ultrafast burst-mode laser system operating at a central wavelength of approximately 2 μm, where water absorption and, consequently, the absorption of most biological tissue is very high. The laser comprises a harmonically mode-locked 1-GHz oscillator, which, in turn, seeds a fiber amplifier chain. The amplifier produces 500 ns long bursts containing 500 pulses with 1 GHz intra-burst and 50 kHz inter-burst repetition rates, respectively, at an average power of 1 W, corresponding to 40 nJ pulse and 20 μJ burst energies, respectively. The entire system is built in an all-fiber architecture and implements dispersion management such that output pulses are delivered directly from a single-mode fiber with a duration of 340 fs without requiring any external compression. This gigahertz-repetition-rate system is intended for ablation-cooled laser material removal in the 2 μm wavelength region, which is interesting for laser surgery due to the exceptionally high tissue absorption at this wavelength.Item Open Access Femtosecond laser written waveguides deep inside silicon(Optical Society of America, 2017) Pavlov, I.; Tokel, O.; Pavlova, S.; Kadan, V.; Makey, G.; Turnalı, A.; Yavuz, Ö.; Ilday, F. Ö.Photonic devices that can guide, transfer, or modulate light are highly desired in electronics and integrated silicon (Si) photonics. Here, we demonstrate for the first time, to the best of our knowledge, the creation of optical waveguides deep inside Si using femtosecond pulses at a central wavelength of 1.5 μm. To this end, we use 350 fs long, 2 μJ pulses with a repetition rate of 250 kHz from an Er-doped fiber laser, which we focused inside Si to create permanent modifications of the crystal. The position of the beam is accurately controlled with pump-probe imaging during fabrication. Waveguides that were 5.5 mm in length and 20 μm in diameter were created by scanning the focal position along the beam propagation axis. The fabricated waveguides were characterized with a continuous-wave laser operating at 1.5 μm. The refractive index change inside the waveguide was measured with optical shadowgraphy, yielding a value of 6 × 10−4, and by direct light coupling and far-field imaging, yielding a value of 3.5 × 10−4. The formation mechanism of the modification is discussed.Item Open Access Femtosecond laser-induced TiO2 nano structures on titanium(Optical Society of America, 2010) Öktem, Bülent; Kalaycıoğlu, Hamit; İlday, F. ÖmerWe report formation of polarization-dependent nanostructures (nanolines, nanocircles) by high repetition-rate femtosecond laser pulses on titanium surface through a novel mechanism, converting Ti to TiO2. Arbitrarily large-area patterns are created by self-stitching of these patterns. © 2010 Optical Society of America.Item Open Access Femtosecond pulse generation from a Ti3+: Sapphire laser near 800 nm with voltage reconfigurable graphene saturable absorbers(OSA - The Optical Society, 2017) Baylam, Işınsu; Özharar, Sarper; Kakenov, Nurbek; Kocabaş, Coşkun; Sennaroglu, AlphanWe experimentally show that a voltage-controlled graphene-gold supercapacitor saturable absorber (VCG-gold-SA) can be operated as a fast saturable absorber with adjustable linear absorption at wavelengths as low as 795 nm. This was made possible by the use of a novel supercapacitor architecture, consisting of a high-dielectric electrolyte sandwiched between a graphene and a gold electrode. The high-dielectric electrolyte allowed continuous, reversible adjustment of the Fermi level and, hence, the optical loss of the VCG-gold-SA up to the visible wavelengths at low bias voltages of the order of a few volts (0-2 V). The fast saturable absorber action of the VCG-gold-SA and the bias-dependent reduction of its loss were successfully demonstrated inside a femtosecond Ti3+:sapphire laser operating near 800 nm. Dispersion compensation was employed by using dispersion control mirrors and a prism pair. At a bias voltage of 1.2 V, the laser operated with improved power performance in comparison with that at zero bias, and the VCG-gold-SA initiated the generation of nearly transform-limited pulses as short as 48 fs at a pulse repetition rate of 131.7 MHz near 830 nm. To the best of our knowledge, this represents the shortest wavelength where a VCG-gold-SA has been employed as a mode locker with adjustable loss. © 2017 Optical Society of America.Item Open Access Fiber amplification of pulse bursts at low repetition rates via synchronous pulsed pumping(Optical Society of America, 2011) Kalaycıoğlu,Hamit; Yavaş, Seydi; İlday, F. Ömer; Eken, KorayWe report, for the first time, amplification of pulse-bursts in Yb-doped fiber at repetition rates as low as 200 Hz for applications to accelerators and material processing. Synchronous pulsed pumping allows suppression of ASE generation. © 2011 Optical Society of America.Item Open Access Fiber amplification of pulse bursts up to 20 μj pulse energy at 1 kHz repetition rate(Optical of Society of America, 2011-08-23) Kalaycıoğlu, Hamit; Eken, K.; İlday, F. ÖmerWe demonstrate burst-mode operation of a polarization-maintaining Yb-doped fiber amplifier. Groups of pulses with a temporal spacing of 10 ns and 1 kHz overall repetition rate are amplified to an average pulse energy of ∼20 μJ and total burst energy of 0:25 mJ. The pulses are externally compressed to ∼400 fs. The amplifier is synchronously pulsed-pumped to minimize amplified spontaneous emission between the bursts. We characterize the influence of pump pulse duration, pump-to-signal delay, and signal burst length.Item Open Access Generation of Sub-20-fs Pulses From a Graphene Mode-Locked Laser(OSA - The Optical Society, 2017) Canbaz, F.; Kakenov, N.; Kocabas, C.; Demirbas, U.; Sennaroglu, A.We demonstrate, what is to our knowledge, the shortest pulses directly generated to date from a solid-state laser, mode locked with a graphene saturable absorber (GSA). In the experiments, a low-threshold diode-pumped Cr3+:LiSAF laser was used near 850 nm. At a pump power of 275 mW provided by two pump diodes, the Cr3+:LiSAF laser produced nearly transform-limited, 19-fs pulses with an average output power of 8.5 mW. The repetition rate was around 107 MHz, corresponding to a pulse energy and peak power of 79 pJ and 4.2 kW, respectively. Once mode locking was initiated with the GSA, stable, uninterrupted femtosecond pulse generation could be obtained. In addition, the femtosecond output of the laser could be tuned from 836 nm to 897 nm with pulse durations in the range of 80-190 fs. We further performed detailed mode locking initiation tests across the full cavity stability range of the laser to verify that pulse generation was indeed started by the GSA and not by Kerr lens mode locking. � 2017 Optical Society of America.Item Open Access Graphene mode-locked Cr:LiSAF laser at 850 nm(OSA - The Optical Society, 2015) Canbaz F.; Kakenov, N.; Kocabas, C.; Demirbas, U.; Sennaroglu, A.We report, for the first time to our knowledge, a mode-locked femtosecond Cr:LiSAF laser initiated with a high-quality monolayer graphene saturable absorber (GSA), synthesized by chemical-vapor deposition. The tight-focusing resonator architecture made it possible to operate the Cr:LiSAF laser with only two 135 mW, 660 nm low-cost single-mode diode lasers. At a pump power of 270 mW, the laser produced nearly transform-limited 68 fs pulses with an average power of 11.5 mW at 850 nm. The repetition rate was around 132 MHz, corresponding to a pulse energy and peak power of 86 pJ and 1.26 kW, respectively. Once mode locking was initiated with the GSA, stable, uninterrupted femtosecond pulse generation could be sustained for hours. The saturation fluence and the modulation depth of the GSA were further determined to be 28 μJ/cm2 and 0.62%, respectively. 2015 Optical Society of America.Item Open Access Graphene-gold supercapacitor as a voltage controlled saturable absorber for femtosecond pulse generation(Optical Society of America, 2016-02) Baylam, I.; Balci, O.; Kakenov, N.; Kocabas, C.; Sennaroglu, A.We report, for the first time to the best of our knowledge, use of a graphene-gold supercapacitor as a voltage controlled fast saturable absorber for femtosecond pulse generation. The unique design involving only one graphene electrode lowers the insertion loss of the device, in comparison with capacitor designs with two graphene electrodes. Furthermore, use of the high-dielectric electrolyte allows reversible, adjustable control of the absorption level up to the visible region with low bias voltages of only a few volts (0-2 V). The fast saturable absorber action of the graphene-gold supercapacitor was demonstrated inside a multipass-cavity Cr:forsterite laser to generate nearly transform-limited, sub-100 fs pulses at a pulse repetition rate of 4.51 MHz at 1.24 μm.Item Open Access High average and peak power femtosecond large-pitch photonic-crystal-fiber laser(2011) Baumgartl, M.; Jansen F.; Stutzki F.; Jauregui, C.; Ortaç, B.; Limpert J.; Tünnermann, A.We report on the generation of high-average-power and high-peak-power ultrashort pulses from a mode-locked fiber laser operating in the all-normal-dispersion regime. As gain medium, a large-mode-area ytterbium-doped large-pitch photonic-crystal fiber is used. The self-starting fiber laser delivers 27 W of average power at 50:57 MHz repetition rate, resulting in 534 nJ of pulse energy. The laser produces positively chirped 2 ps output pulses, which are compressed down to sub-100 fs, leading to pulse peak powers as high as 3:2 MW. © 2011 Optical Society of America.Item Open Access High-energy femtosecond photonic crystal fiber laser(2010) Lecaplain, C.; Ortaç, B.; MacHinet G.; Boullet J.; Baumgart, M.; Schreiber, T.; Cormier, E.; Hideur, A.We report the generation of high-energy high-peak power pulses in an all-normal dispersion fiber laser featuring large-mode-area photonic crystal fibers. The self-starting chirped-pulse fiber oscillator delivers 11 W of average power at 15:5 MHz repetition rate, resulting in 710 nJ of pulse energy. The output pulses are dechirped outside the cavity from 7 ps to nearly transform-limited duration of 300 fs, leading to pulse peak powers as high as 1:9 MW. Numerical simulations reveal that pulse shaping is dominated by the amplitude modulation and spectral filtering provided by a resonant semiconductor saturable absorber. © 2010 Optical Society of America.Item Open Access Microjoule-energy, 1 MHz repetition rate pulses from all-fiber-integrated nonlinear chirped-pulse amplifier(Optical Society of America, 2010-03-23) Kalaycioglu, H.; Oktem, B.; Şenel, Ç.; Paltani, P. P.; Ilday, F. Ö.We demonstrate generation of pulses with up to 4 μJ energy at 1 MHz repetition rate through nonlinear chirped-pulse amplification in an entirely fiber-integrated amplifier, seeded by a fiber oscillator. The peak power and the estimated nonlinear phase shift of the amplified pulses are as much as 57 kW and 22π, respectively. The shortest compressed pulse duration of 140 fs is obtained for 3.1 μJ of uncompressed amplifier output energy at 18 π of nonlinear phase shift. At 4 μJ of energy, the nonlinear phase shift is 22 π and compression leads to 170-fs-long pulses. Numerical simulations are utilized to model the experiments and identify the limitations. Amplification is ultimately limited by the onset of Raman amplification of the longer edge of the spectrum with an uncompressible phase profile.Item Open Access Micromachining with square-Shaped 1 ns-Long pulses from an all-Fiber Yb-Doped laser-Amplifier system(Optical Society of America, 2011) Özgören, Kıvanç; Öktem, Bülent; İlday, F. Ömer; Pasin, Ece; Eken, K.We demonstrate micromachining with 1ns-long pulses from an all-fiber laser. Fiber lasers generating uncompressible long pulses have been ignored as undesired operational modes, however their robust, low-repetition-rate operation is well suited to micromachining. © 2011 Optical Society of America.Item Open Access Pulse fidelity control in a 20-μJ sub-200-fs monolithic Yb-fiber amplifier(Pleiades Publishing, 2011-06-04) Fernández, A.; Zhu, L.; Verhoef, A. J.; Sidorov-Biryukov, D.; Pugzlys, A.; Galvanauskas, A.; Ilday, F. Ö.; Baltuška, A.We discuss nonlinearity management versus energy scalability and compressibility in a three-stage monolithic 100-kHz repetition rate Yb-fiber amplifier designed as a driver source for the generation and tunable parametric amplification of a carrier-envelope phase stable white-light supercontinuum.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.Item Open Access Ultrafast micromachining of Cu and Si at ultra-high repetition rates with pulse bursts(IEEE, 2016) Kerse, Can; Kalaycıoğlu, Hamit; Elahi, Parviz; Yavuz, Koray; Mirza I.; Bulgakova N.M.; İlday, F. ÖmerWe report a novel ultrafast burst mode fiber laser system, which can deliver pulses at ultra-high repetition rates in order to systematically investigate micromachining efficiency on copper and silicon samples. © 2015 IEEE.