Browsing by Subject "Normal dispersion"
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Item Open Access 83 W, 3.1 MHz, square-shaped, 1 ns-pulsed all-fiber-integrated laser for micromachining(Optical Society of America, 2011-08-29) Özgören, Kıvanç; Öktem, Bülent; Yılmaz, Sinem; İlday, F. Ömer; Eken, K.We demonstrate an all-fiber-integrated laser based on off-the-shelf components producing square-shaped, 1 ns-long pulses at 1.03 mu m wavelength with 3.1 MHz repetition rate and 83 W of average power. The master-oscillator power-amplifier system is seeded by a fiber oscillator utilizing a nonlinear optical loop mirror and producing incompressible pulses. A simple technique is employed to demonstrate that the pulses indeed have a random chirp. We propose that the long pulse duration should result in more efficient material removal relative to picosecond pulses, while being short enough to minimize heat effects, relative to nanosecond pulses commonly used in micromachining. Micromachining of Ti surfaces using 0.1 ns, 1 ns and 100 ns pulses supports these expectations. (C) 2011 Optical Society of AmericaItem Open Access All-fiber all-normal dispersion laser with a fiber-based Lyot filter(Optical Society of America, 2010-04-15) Özgören, K.; Ilday, F. Ö.We propose the use of a short section of polarization-maintaining fiber as a birefringent medium to construct an all-fiber Lyot filter inside the cavity of a fiber laser. This allows mode-locked operation of an all-fiber all-normal dispersion Yb-fiber oscillator without the use of a bulk bandpass filter and using standard components. Moreover, filter bandwidth and modulation depth is easily controlled by changing the length and splice angle of the polarization-maintaining-fiber section, leading to an adjustable filter. At mode-locked operation, the 30% output fiber port delivers 1nJ pulses that are dechirped to 230 fs duration.Item Open Access All-fiber all-normal dispersion laser with an in-fiber Lyot filter(Optical Society of America, 2010) Özgören, Kıvanç; İlday, F. ÖmerWe propose use of a short PM-fiber section as birefringent medium to construct an all-fiber Lyot filter, with bandwidth adjustable through the PM-fiber length. An all-fiber all-normaldispersion laser is demonstrated using standard components only. © 2009 Optical Society of America.Item Open Access All-fiber nonlinearity-and dispersion-managed dissipative soliton nanotube mode-locked laser(American Institute of Physics, 2015) Zhang Z.; Popa, D.; Wittwer, V. J.; Milana, S.; Hasan, T.; Jiang, Z.; Ferrari, A. C.; Ilday F. Ö.We report dissipative soliton generation from an Yb-doped all-fiber nonlinearity- and dispersion-managed nanotube mode-locked laser. A simple all-fiber ring cavity exploits a photonic crystal fiber for both nonlinearity enhancement and dispersion compensation. The laser generates stable dissipative solitons with large linear chirp in the net normal dispersion regime. Pulses that are 8.7 ps long are externally compressed to 118 fs, outperforming current nanotube-based Yb-doped fiber laser designs.Item Open Access All-fiber-integrated soliton-similariton laser with in-line fiber filter(Optical Society of America, 2012-08-16) Zhang, Z.; Öktem, B.; Ilday, F. Ö.We demonstrate an all-fiber-integrated Er-doped fiber laser operating in the soliton-similariton mode-locking regime. In the similariton part of the cavity, a self-similarly evolving parabolic pulse with highly linear chirp propagates in the presence of normal dispersion. Following an in-line fiber-based birefringent filter, the pulse evolves into a soliton in the part of the cavity with anomalous dispersion. The similariton and the soliton pulses are dechirped to 75.5 and 167.2 fs, respectively, outside of the cavity. Mode-locked operation is very robust, owing to the influence of the two similariton and soliton attractors that predominate each half of the laser cavity. The experimental results are supported with numerical simulations, which provide good agreement.Item Open Access Filterless all-normal dispersion fiber laser(IEEE, 2009) Özgören, Kıvanç; İlday, F. ÖmerWe demonstrate mode-locked operation of an allnormal dispersion Yb-fiber oscillator without the use of bulk bandpass filter. A section of PM-fiber incorporated into the cavity acts as a filter, paving the way towards an all-fiber oscillator based on off-the-shelf components. © 2009 IEEE.Item Open Access Generation of dissipative solitons in normal-dispersion Raman fiber laser(IEEE, 2016) Teğin, Uğur; Elahi, Parviz; Şenel, Ç.; Ergeçen, E.; İlday, Fatih ÖmerDissipative soliton pulses in a synchronously pumped all-normal-dispersion Raman fiber laser is presented theoretically and experimentally. The laser generates 7.1 nJ intra-cavity pulses at 1.12 μm and is compressed to 136 fs.Item Open Access Geometric parametric instability of femtosecond pulses in graded-index multimode fiber(Optical Society of America, 2017) Teğin, Ugur; Ortaç, BülendWe numerically and experimentally study the spatio-temporal femtosecond pulse evolution in graded-index multimode fiber at normal dispersion regime. We report the first demonstration of geometric parametric instability sidebands generation with ultrashort pulses in the literature.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 Observation of soliton molecules with independently evolving phase in a mode-locked fiber laser(2010) Ortaç, B.; Zaviyalov, A.; Nielsen, C.K.; Egorov O.; Iliew, R.; Limpert J.; Lederer F.; Tünnermann, A.We report the experimental generation of two-soliton molecules in an all-polarization-maintaining ytterbium-doped fiber laser operating in the normal dispersion regime. These molecules exhibit an independently evolving phase and are characterized by a regular spectral modulation pattern with a modulation depth of 80% measured as an averaged value. Moreover, the numerical modeling confirms that the limited modulation depth of the spectrum is caused by the evolution of the phase difference between the pulses. © 2010 Optical Society of America.Item Open Access Properties of a microjoule-class fiber oscillator mode-locked with a SESAM(IEEE, 2011) Lecaplain, C.; Ortac, Bülend; MacHinet G.; Boullet J.; Baumgartl, M.; Schreiber, T.; Cormier, E.; Hideur, A.Energy scaling of ultrafast Yb-doped fiber oscillators has experienced rapid progress largely driven by many applications that require high average power femtosecond pulses. The fundamental challenge for ultrafast fiber lasers relies on the control of excessive nonlinearity, which limits pulse energy. The development of all-normal dispersion laser cavities based on large-mode-area photonic crystal fibers (PCFs) has enabled significant energy scaling [1-3]. In particular, up to microjoule energy levels have been achieved from rod-type fiber-based oscillators [2-3]. In such lasers, pulse shaping is dominated by the strength of the mode-locking mechanism which determines the pulse properties. In this contribution, we report the generation of high-energy sub-picosecond pulses from a highly normal dispersion fiber laser featuring an Yb-doped rod-type PCF and a large-mode-area PCF [Fig.1(a)]. Passive mode-locking is achieved using saturable absorber mirrors (SAMs). We study the influence of the SAM parameters on performances obtained in this new class of fiber oscillators. The structures exhibit 20 % modulation depths and 500 fs relaxation time with resonant and antiresonant designs. The antiresonant SAM structures ensure absorption bandwidths 45 nm while the resonant structures exhibit 20 nm bandwidths. Stable mode locking with average powers as high as 15 μW at 15 MHz repetition rate, corresponding to microjoule energy level are obtained with all the structures. However, pulse properties and pulse shaping mechanism distinguish between resonant and antiresonant designs. Using a broadband antiresonant SAM leads to generation of highly-chirped pulses with 30 ps duration and 10 nm spectral width [Fig.1(b)]. The output pulses are extra-cavity dechirped down to 550 fs duration. By increasing the strength of the mode-locking mechanism through the combination of the SAM with the NPE process, we obtain shorter pulses with slightly boarder spectra. Indeed, the output pulse duration is decreased from 30 ps to 13 ps by adjusting the wave-plates settings. The dechirped pulse duration is then shortened to 450 fs. We note that the current laser performances are limited to 1 J by the available pump power. Using a resonant SAM structure, the output pulse duration is decreased to 7 ps [Fig.1(b)]. This pulse shortening results from the spectral filtering induced by the limited SAM bandwidth. All these results are in good agreement with numerical simulations which will be discussed in this communication. © 2011 IEEE.Item Open Access Spatiotemporal instability of femtosecond pulses in graded-index multimode fibers(Institute of Electrical and Electronics Engineers Inc., 2017) Teǧin, U.; Ortaç, B.We study the spatiotemporal instability generated by a universal unstable attractor in normal dispersion graded-index multimode fiber for femtosecond pulses for the first time. Experimentally observed spatiotemporal instability sidebands are 91-THz detuned from the pump wavelength of 800 nm. Detailed analysis carried out numerically by employing coupled-mode pulse propagation model. Numerically obtained results are well-aligned with experimental observations. Spatial evolution of the total field and spatiotemporal instability sidebands is calculated numerically, and for the input pulses of 200-fs duration, formation and evolution of spatiotemporal instability are shown in both spatial and temporal domains. Our results present the unique features of spatiotemporal instability, such as remarkable frequency shift with inherited beam shape of instability sidebands.