Browsing by Subject "Ytterbium"

Now showing 1 - 20 of 24

Open Access
1 mJ pulse bursts from a Yb-doped fiber amplifier
(Optical Society of America, 2012-07-01) Kalaycıoğlu, Hamit; Eldeniz, Y. B.; Akçalan, Önder; Yavaş, Seydi; Efe, M.; İlday, Fatih Ömer
We demonstrate burst-mode operation of a polarization-maintaining Yb-doped fiber amplifier capable of generating 60 μJ pulses within bursts of 11 pulses with extremely uniform energy distribution facilitated by a novel feedback mechanism shaping the seed of the burst-mode amplifier. The burst energy can be scaled up to 1 mJ, comprising 25 pulses with 40 μJ average individual energy. The amplifier is synchronously pulse pumped to minimize amplified spontaneous emission between the bursts. Pulse propagation is entirely in fiber and fiber-integrated components until the grating compressor, which allows for highly robust operation. The burst repetition rate is set to 1 kHz and spacing between individual pulses is 10 ns. The 40 μJ pulses are externally compressible to a full width at half-maximum of 600 fs. However, due to the substantial pedestal of the compressed pulses, the effective pulse duration is longer, estimated to be 1.2 ps.
Open Access
1018 nm Yb-doped high-power fiber laser pumped by broadband pump sources around 915 nm with output power above 100 W
(OSA - The Optical Society, 2017) Midilli, Y.; Efunbajo, O. B.; Şimşek, B.; Ortaç, B.
We demonstrate a 1018 nm ytterbium-doped all-fiber laser pumped by tunable pump sources operating in the broad absorption spectrum around 915 nm. In the experiment, two different pump diodes were tested to pump over a wide spectrum ranging from 904 to 924 nm by altering the cooling temperature of the pump diodes. Across this so-called pump wavelength regime having a 20 nm wavelength span, the amplified stimulated emission (ASE) suppression of the resulting laser was generally around 35 dB, showing good suppression ratio. Comparisons to the conventional 976 nm-pumped 1018 nm ytterbium-doped fiber laser were also addressed in this study. Finally, we have tested this system for high power experimentation and obtained 67% maximum optical-to-optical efficiency at an approximately 110 W output power level. To the best of our knowledge, this is the first 1018 nm ytterbium-doped all-fiber laser pumped by tunable pump sources around 915 nm reported in detail.
Open Access
20-fs 1.6-mJ pulses from a cw-diode-pumped single-stage 1-kHz Yb amplifier
(OSA, 2010) Andriukaitis, G.; Kartashov, D.; Pugzlys, A.; Lorenc, D.; Baltuska, A.; Giniunas, L.; Danielius, R.; İlday, Ömer Fatih
200-fs 2.5-mJ pulses from a fiber-oscillator-seeded DPSS Yb:CaF2 MOPA are spectrally broadened in Ar and recompressed to 20 fs using a pair of LAK14 prisms. Multi-millijoule 12-fs pulses are feasible upon higher-order spectral phase correction.
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 Ömer
We 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.
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.
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.
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. Ömer
Single-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.
Open Access
Balancing gain narrowing with self phase modulation: 100-fs, 800-nJ from an all-fiber-integrated Yb amplifier
(IEEE, 2013) Pavlov, Ihor; Rybak, A.; Cenel, C.; İlday, F. Ömer
There is much progress in Yb-fiber oscillator-amplifier systems, which enable generation of high-repetition-rate, microjoule energies and sub-picosecond pulse widths [1,2]. Given the extremely large total gain factors to reach microjoules starting from nanojoules, which is often in the range of 40-60 dB, due to losses, and the impact of mismatched high-order dispersion as temporal stretching and compression of pulses by large factors (30-40 dB) need to be employed. As a result of these challenges, most of the Yb-fiber amplifiers have resulted in pulse durations of several 100 fs or longer. While pulse durations in this range are suited for some applications, there are many cases where 100-fs or shorter pulses in microjoule range are required. Gain narrowing can be effectively countered by self-phase modulation (SPM) [3] by limiting amplification factor in each stage of amplification and through careful optimization of SPM and inversion level along the gain fiber. The conceptual template is readily present in the evolution of the pulse inside the oscillator cavity, where gain factors are often in the 10-50 range per roundtrip. To the extend that the B-integral and the gain distribution along the amplifier can be kept identical to the oscillator by proper scaling of the chirped pulse width and fiber mode area, the original oscillator can be preserved in arbitrary number of amplification stages. Here, we demonstrate a highly fiber-integrated master-oscillator power-amplifier (MOPA) system, from which - 1 μJ pulses are extracted and externally compressed to 100 fs by arranging amplification in each stage as close as possible to the intra-cavity evolution. To our knowledge, these results are the shortest demonstrated from all-fiber-integrated amplifier at the microjoule level. © 2013 IEEE.
Open Access
Burst-mode Yb fiber amplifier producing 30 μJ individual pulse energy
(Optical Society of America, 2012) Kalaycıoğlu, Hamit; Burak Eldeniz, Y.; İlday, F. Ömer; Eken, K.
We report 30-μJ individual pulse energy for 150-ns long amplified bursts of 0.4 mJ total energy from a 1-kHz Yb-fiber amplifier. Non-uniformity of pulse energy distribution inside amplified bursts is significantly reduced. ©2012 Optical Society of America.
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. Ömer
Transfer 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.
Open Access
Development and investigation of high power ytterbium-doped fiber lasers operating At 1018 nm
(2017-07) Efunbajo, Oyewole Benjamin
The development of ytterbium-doped ber lasers (YDFL) operating around 1018 nm with two major pumping schemes are reported. The study on the developed all ber lasers were characterized based on parameters such as pump source, active ber type and output-coupling ber bragg gratings. Diode lasers operating at around 915 nm, and 976 nm were used as primary pump sources for the experiments. While several works had reported 1018 nm YDFLs using 976 nm pump sources, up until now, there were no reports of the use of 915 nm for 1018 nm YDFLs in the literature. Active ber types, based on length and doping concentration of ytterbium ions were also considered. The choice of output-coupling (OC) ber bragg gratings (FBG) were made based on laser model simulation and manufacturing feasibility. Simulations were also carried out for every tested set of implemented parameters so as to minimize undesired optical e ects such as ampli ed stimulated emission (ASE) and inadequate pump absorption. For both pump sources, high power ytterbium-doped all- ber lasers operating in the 1018 nm region with good e ciency and ampli ed stimulated emission (ASE) suppression were established. In addition, the broad absorption crosssection of ytterbium-doped glasses around 915 nm was exploited as tunable pump sources for the ber laser systems demonstrated.
Open Access
Doping management for high-power fiber lasers: 100 W, few-picosecond pulse generation from an all-fiber-integrated amplifier
(Optical Society of America, 2012-07-16) Elahi, P.; Yilmaz, S.; Akçaalan, Ö.; Kalaycioğlu, H.; Öktem, B.; Şenel, Ç.; Ilday, F. Ö.; Eken, K.
Thermal effects, which limit the average power, can be minimized by using low-doped, longer gain fibers, whereas the presence of nonlinear effects requires use of high-doped, shorter fibers to maximize the peak power. We propose the use of varying doping levels along the gain fiber to circumvent these opposing requirements. By analogy to dispersion management and nonlinearity management, we refer to this scheme as doping management. As a practical first implementation, we report on the development of a fiber laser-amplifier system, the last stage of which has a hybrid gain fiber composed of high-doped and low-doped Yb fibers. The amplifier generates 100 W at 100 MHz with pulse energy of 1 μJ. The seed source is a passively mode-locked fiber oscillator operating in the all-normaldispersion regime. The amplifier comprises three stages, which are all-fiber-integrated, delivering 13 ps pulses at full power. By optionally placing a grating compressor after the first stage amplifier, chirp of the seed pulses can be controlled, which allows an extra degree of freedom in the interplay between dispersion and self-phase modulation. This way, the laser delivers 4.5 ps pulses with ∼200 kW peak power directly from fiber, without using external pulse compression.
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. Ömer
We 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.
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.
Open Access
Filterless all-normal dispersion fiber laser
(IEEE, 2009) Özgören, Kıvanç; İlday, F. Ömer
We 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.
Open Access
Gold catalysts supported on ceria doped by rare earth metals for water gas shift reaction: influence of the preparation method
(2009) Andreeva, D.; Ivanov, I.; Ilieva, L.; Abrashev, M. V.; Zanella, R.; Sobczak, J. W.; Lisowski, W.; Kantcheva, M.; Avdeev, G.; Petrov, K.
Gold catalysts based on ceria, doped by various RE metals (La, Sm, Gd, Yb, Y) were studied. The influence of the preparation methods on structure, properties and catalytic activity in the WGS reaction was investigated. The catalysts' supports were prepared using two different methods: co-precipitation (CP) and mechanochemical activation (MA). The catalysts were tested in a wide temperature interval without and after reactivation. All samples were characterized using a combination of X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), Raman spectroscopy (RS) and X-ray photoelectron spectroscopy (XPS) and TPR. It was found that the catalytic activity of MA catalysts is higher than CP ones. The gold catalysts based on ceria doped by Yb and Sm exhibited the highest activity. After reactivation in air the MA samples almost kept the WGS activity same, while the CP catalysts increased it. The catalysts of a single- and double-phase structure are formed as a result of CP and MA preparation, respectively. There are no big differences in the gold particles size (2-3 nm) depending on dopants and on the preparation techniques. The RS spectra analysis indicates that most probably the oxygen vacancies are adjacent to Me3+ dopant and the ceria structure seems to be better ordered than in the case of alumina as a dopant. There is no distinct correlation between reducibility and WGS activity. The XPS analysis disclose positively charged gold particles in addition to metallic gold within a surface region of fresh samples and only metallic gold on the samples after catalytic processing. There is no simple correlation between the concentration of Ce3+ in the samples and their WGS activity.
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.
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.
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.
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.