Browsing by Subject "Mode-locked fiber lasers"
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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 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 Characterization of coupling of pump fluctuations to laser in mode-locked Yb-doped and Er-doped fiber oscillators(Optical Society of America, 2010) Budunoğlu, İbrahim Levent; Gürel, Kutan; İlday, F. ÖmerTransfer of fluctuations of pump power to laser power is characterized for mode-locked fiber oscillators. Contribution of pump noise to laser noise is estimated. Limits to pump modulation bandwidth for carrier-envelopephase stabilization are briefly discussed. © 2010 Optical Society of America.Item Open Access Femtosecond microjoule-Class ytterbium fiber lasers(Optical Society of America, 2011) Lecaplain, C.; Ortaç, Bülend; Machinet G.; Boullet J.; Baumgartl, M.; Schreiber, T.; Cormier, E.; Hideur, A.We report the generation of 830 nJ energy from a mode-locked all-normal dispersion fiber laser featuring large-mode-area photonic crystal fibers. After external compression, 550 fs pulses with 1.2 MW peak power are demonstrated. © 2011 OSA.Item Open Access Fiber laser-microscope system for femtosecond photodisruption of biological samples(Optical Society of America, 2012-02-22) Yavaş, Seydi; Erdoğan, Mutlu; Gürel, Kutan; İlday, F. Ömer; Eldeniz, Y. B.; Tazebay, Uygar H.We report on the development of a ultrafast fiber lasermicroscope system for femtosecond photodisruption of biological targets. A mode-locked Yb-fiber laser oscillator generates few-nJ pulses at 32.7 MHz repetition rate, amplified up to ~125 nJ at 1030 nm. Following dechirping in a grating compressor, ~240 fs-long pulses are delivered to the sample through a diffraction-limited microscope, which allows real-time imaging and control. The laser can generate arbitrary pulse patterns, formed by two acousto-optic modulators (AOM) controlled by a custom-developed fieldprogrammable gate array (FPGA) controller. This capability opens the route to fine optimization of the ablation processes and management of thermal effects. Sample position, exposure time and imaging are all computerized. The capability of the system to perform femtosecond photodisruption is demonstrated through experiments on tissue and individual cells.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 mode-locked femtosecond Cr: LiSAF laser(Optical Society of America (OSA), 2015) Canbaz F.; Kakenov, N.; Kocabas, C.; Demirbas, U.; Sennaroglu, A.We report the first demonstration of femtosecond pulse generation from a Cr:LiSAF laser mode-locked with a monolayer graphene saturable absorber. Nearly transform-limited 72-fs pulses were generated at 850 nm with only two 135-mW pump diodes.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 Nonlinearity engineering of mode-locked fiber lasers: Similariton and soliton-similariton lasers(IEEE, 2011) İlday F. Ömer; Öktem, Bülent; Ülgüdür, CoşkunFiber lasers are attractive with their simplicity, high powers and low cost. However, propagation of short pulses in optical fiber leads to nonlinear effects, which limit the technical performance. These effects drive rich dynamics, which is interesting from a fundamental perspective. The nonlinear waves community has unraveled the fascinating world of solitons and similaritons through experiments in fibers. This paper overviews the recent development of the soliton-similariton laser. The original similariton laser was the first to work with nonlinear effects, rather than minimizing or compensating them. In the soliton-similariton laser, the propagation is strongly nonlinear everywhere. © 2011 IEEE.Item Open Access A novel fiber laser development for photoacoustic microscopy(SPIE, 2013) Yavaş, Seydi; Aytac-Kipergil, E.; Arabul, M.U.; Erkol H.; Akçaalan, Önder; Eldeniz, Y.B.; İlday, F. Ömer; Unlu, M.B.Photoacoustic microscopy, as an imaging modality, has shown promising results in imaging angiogenesis and cutaneous malignancies like melanoma, revealing systemic diseases including diabetes, hypertension, tracing drug efficiency and assessment of therapy, monitoring healing processes such as wound cicatrization, brain imaging and mapping. Clinically, photoacoustic microscopy is emerging as a capable diagnostic tool. Parameters of lasers used in photoacoustic microscopy, particularly, pulse duration, energy, pulse repetition frequency, and pulse-to-pulse stability affect signal amplitude and quality, data acquisition speed and indirectly, spatial resolution. Lasers used in photoacoustic microscopy are typically Q-switched lasers, low-power laser diodes, and recently, fiber lasers. Significantly, the key parameters cannot be adjusted independently of each other, whereas microvasculature and cellular imaging, e.g., have different requirements. Here, we report an integrated fiber laser system producing nanosecond pulses, covering the spectrum from 600 nm to 1100 nm, developed specifically for photoacoustic excitation. The system comprises of Yb-doped fiber oscillator and amplifier, an acousto-optic modulator and a photonic-crystal fiber to generate supercontinuum. Complete control over the pulse train, including generation of non-uniform pulse trains, is achieved via the AOM through custom-developed field-programmable gate-array electronics. The system is unique in that all the important parameters are adjustable: pulse duration in the range of 1-3 ns, pulse energy up to 10 μJ, repetition rate from 50 kHz to 3 MHz. Different photocoustic imaging probes can be excited with the ultrabroad spectrum. The entire system is fiber-integrated; guided-beam-propagation rendersit misalignment free and largely immune to mechanical perturbations. The laser is robust, low-cost and built using readily available components. © 2013 Copyright SPIE.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 Soliton-similariton fibre laser(Macmillan Publishers, 2010-03-21) Öktem, Bülent; Ülgüdür, Coşkun; İlday, F. ÖmerRapid progress in passively mode-locked fibre lasers is currently driven by the recent discovery of new mode-locking mechanisms, namely, the self-similarly evolving pulse (similariton) and the all-normal-dispersion (dissipative soliton) regimes. These are fundamentally different from the previously known soliton and dispersion-managed soliton (stretched-pulse) regimes. Here, we report a fibre laser in which the mode-locked pulse evolves as a similariton in the gain segment and transforms into a regular soliton in the rest of the cavity. To our knowledge, this is the first observation of similaritons in the presence of gain, that is, amplifier similaritons, within a laser cavity. The existence of solutions in a dissipative nonlinear cavity comprising a periodic combination of two distinct nonlinear waves is novel and likely to be applicable to various other nonlinear systems. For very large filter bandwidths, our laser approaches the working regime of dispersion-managed soliton lasers; for very small anomalous-dispersion segment lengths it approaches dissipative soliton lasers. .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-picosecond microjoule-class fiber lasers(Optical Society of America, 2011) Lecaplain, C.; Ortaç, Bülend; MacHinet G.; Boullet J.; Baumgartl, M.; Schreiber, T.; Cormier, E.; Hideur, A.We study the impact of the mode-locking mechanism on the performances of a microjoule-class all-normal dispersion fiber laser featuring large-mode-area photonic crystal fibers. © 2011 OSA.Item Open Access Ultrashort pulse formation and evolution in mode-locked fiber lasers(2011) Baumgartl, M.; Ortaç, B.; Schreiber, T.; Limpert J.; Tünnermann, A.Passive mode-locking in fiber lasers is investigated by numerical and experimental means. A non-distributed scalar model solving the nonlinear Schrödinger equation is implemented to study the starting behavior and intra-cavity dynamics numerically. Several operation regimes at positive net-cavity dispersion are experimentally accessed and studied in different environmentally stable, linear laser configurations. In particular, pulse formation and evolution in the chirped-pulse regime at highly positive cavity dispersion is discussed. Based on the experimental results a route to highly energetic pulse solutions is shown in numerical simulations. © 2011 Springer-Verlag.