Browsing by Subject "Amplification"
Now showing 1 - 11 of 11
Results Per Page
Sort Options
Item 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 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. ÖmerThere 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.Item Open Access Demonstration of cavity-enhanced optical parametric chirped-pulse amplification system at high repetition rate(OSA, 2010) Siddiqui, A.; Hong, K. H.; Moses, J.; Chen, J.; İlday, Fatih Ömer; Kartner, F. X.First experimental demonstration of cavity-enhanced OPCPA at 78 MHz with <1 W of pump power is presented. For comparison, we demonstrated saturated gain in a single-pass experiment from 6-W Yb-fiber pump and Er-fiber signal sources.Item Open Access Design considerations for MMIC distributed amplifiers(IEEE, 1994) Ergun, Şanlı; Atalar, AbdullahThe bandwidth of the input artificial line in a distributed amplifier is the main band limiting factor. By choosing this impedance properly the bandwidth of a distributed amplifier can be maximized. A four section GaAs MESFET distributed amplifier is designed using this strategy. The fabricated MMIC amplifier gives satisfactory performance. By adding proper length of series transmission lines in the drain side, the gain and the gain flatness of the amplifier can be further improved. This fact is presented via simulation results. The superior gain potential of cascode connected FETs is also demonstrated.Item Open Access Femtosecond response of J aggregates adsorbed onto silver colloid surfaces(2003) Yaǧlioǧlu G.; Dorsinville, R.; Özçelik, S.The observation of stimulated emission from J aggregates adsorbed onto silver colloid surfaces using femtosecond excitation was reported. The stimulated emission was inferred from the excitation intensity and wavelength dependence of the emission band. The stimulated emission originated from the amplification of the one-exciton state emission by an induced transition from the two-exciton state to the one-exciton state.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 Generation of picosecond pulses directly from a 100 W, burst-mode, doping-managed Yb-doped fiber amplifier(Optical Society of America, 2014) Elahi, P.; Yilmaz, S.; Eldeniz, Y. B.; Ilday, F. O.Burst-mode laser systems offer increased effectiveness in material processing while requiring lower individual pulse energies. Fiber amplifiers operating in this regime generate low powers in the order of 1 W. We present a Yb-doped fiber amplifier, utilizing doping management, that scales the average power up to 100 W. The laser system produces bursts at 1 MHz, where each burst comprises 10 pulses with 10 mu J energy per pulse and is separated in time by 10 ns. The high-burst repetition rate allows substantial simplification of the setup over previous demonstrations of burst-mode operation in fiber lasers. The total energy in each burst is 100 mu J and the average power achieved within the burst is 1 kW. The pulse evolution in the final stage of amplification is initiated as self-similar amplification, which is quickly altered as the pulse spectrum exceeds the gain bandwidth. By prechirping the pulses launched into the amplifier, 17 ps long pulses are generated without using external pulse compression. The peak power of the pulses is similar to 0.6 MW. (C) 2014 Optical Society of AmericaItem Open Access High-power-high-repetition-rate-single-mode Er-Yb-doped fiber laser system(Optical Society of America, 2012) Pavlov, I.; Ilbey, E.; Dulgergil, E.; Bayri, A.; Ilday, F. O.We demonstrate an all-fiber-integrated, high-power chirped-pulse-amplification system operating at 1550 nm. The seed source is a soliton fiber laser with 156 MHz repetition rate. Two-stage single mode amplifier provides an amplification of more than 40 dB without significant spontaneous amplified emission. The power amplifier is based on cladding-pumped 10 mu m-core Er-Yb co-doped fiber, the output of which was spliced into standard singlemode fiber. We obtain 10 W average power in a strictly singlemode operation. After dechirping with a grating compressor, near transform-limited, 450 fs-long pulses are obtained. The laser source exhibits excellent short and long-term intensity stability, with relative intensity noise measurements characterizing the short-term stability. (C) 2012 Optical Society of AmericaItem Open Access Influence of modulation of pump and seed signals on fiber amplification of broadband pulses(OSA, 2011) Gürel, Kutan; Elahi, Parviz; Budunoğlu, İbrahim Levent; Şenel, Çağrı; Paltani, Punya Prasanna; İlday, Fatih ÖmerWe report on characterization of the transfer of pump and seed signal modulations, including noise, during fiber amplification. We demonstrate experimentally and theoretically that pump (signal) modulations are transferred only below (above) a cut-off frequency.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 Time-and position-dependent modeling of high-power low-repetition-rate Er-Yb-fiber amplifier(IEEE, 2013) Pavlov, Ihor; Dülgergil, E.; Elahi, Parviz; İlday, F. ÖmerThere is rapid progress in the development of high-power fiber lasers due to their robust operation, low cost, high beam quality at high powers. There are various applications, such as laser sensing, LIDAR applications, processing of specific materials, which require robust and high-power pulsed laser sources at 1550 nm with high beam quality. Achievement of high peak power with low repetition rate is challenging due to well-known problems of strong nonlinear effects and amplified spontaneous emission (ASE) build-up between pulses. In order to reach highest efficiency, the design of each stage of amplification should be carefully optimized. Numerical modeling can be a great tool due to the large number of parameters involved [1]. To date, most modeling efforts of fiber amplification have assumed either a lumped gain model for pulse propagation or a distributed, position-dependent gain model for CW signal for computational simplicity. Here, we investigate both time- and position-dependent gain dynamics numerically, which are used to optimize experimental results. © 2013 IEEE.