Browsing by Subject "Pulse generators"
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Item 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.Item Open Access Femtosecond pulse generation from an extended cavity Cr4+: Forsterite laser using graphene on YAG(Optical Society of America, 2013) Baylam I.; Ozharar, S.; Natali Cizmeciyan, M.; Balcı, Osman; Pince, Erçağ; Kocabaş, Coşkun; Sennaroglu, A.A room temperature, multipass-cavity, femtosecond Cr4+:forsterite laser was modelocked with a single-layer graphene saturable absorber on a YAG substrate. The resonator produced nearly transform-limited 92 fs pulses near 1250 nm with 53 kW of peak power. © OSA 2013.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 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 Graphene supercapacitor as a voltage controlled saturable absorber for femtosecond pulse generation(OSA, 2014) Baylam, I.; Çizmeciyan, M. N.; Özharar, S.; Polat, Emre Ozan; Kocabaş, Coşkun; Sennaroğlu, A.For the first time to our knowledge, we employed a graphene supercapacitor as a voltage controlled saturable absorber at bias voltages of 0.5-1V to generate 84-fs pulses from a solid-state laser near 1255 nm.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 Graphene-gold supercapacitor as a voltage-controlled saturable absorber for femtosecond pulse generation(OSA, 2015) Baylam, I.; Balcı, Osman; Kakenov, Nurbek; Kocabaş, Coşkun; Sennaroğlu, A.We report, for the first time to our knowledge, a voltage-controlled graphene-gold supercapacitor saturable absorber, as a modulator with adjustable insertion loss for low-gain mode-locked lasers. Nearly transform-limited, 80-fs pulses were generated near 1240 nm.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 Sub-50 fs Yb-doped laser with anomalous-dispersion photonic crystal fiber(Optical Society of America, 2013) Zhang, Z.; Şenel, Ç.; Hamid, R.; Ilday, F. Ö.We report on the generation of 42 fs pulses at 1 μm in a completely fiber-integrated format, which are, to the best of our knowledge, the shortest from all-fiber-integrated Yb-doped fiber lasers to date. The ring fiber cavity incorporates anomalous-dispersion, solid-core photonic crystal fiber with low birefringence, which acts as a broadband, in-fiber Lyot filter to facilitate mode locking. The oscillator operates in the stretched-pulse regime under slight normal net cavity dispersion. The cavity generates 4.7 ps long pulses with a spectral bandwidth of 58.2 nm, which are dechirped to 42 fs via a grating pair compressor outside of the cavity. Relative intensity noise (RIN) of the laser is characterized, with the integrated RIN found to be 0.026% in the 3 Hz-250 kHz frequency range.Item Open Access Sub-80 fe dissipative soliton large-mode-area fiber laser(2010) Baumgartl, M.; Ortaç, B.; Lecaplain, C.; Hideur, A.; Limpert J.; Tünnermann, A.We report on high-energy ultrashort pulse generation from an all-normal-dispersion large-mode-area fiber laser by exploiting an efficient combination of nonlinear polarization evolution (NPE) and a semiconductor-based saturable absorber mode-locking mechanism. The watt-level laser directly emits chirped pulses with a duration of 1 ps and 163 nJ of pulse energy. These can be compressed to 77 fs, generating megawatt-level peak power. Intracavity dynamics are discussed by numerical simulation, and the intracavity pulse evolution reveals that NPE plays a key role in pulse shaping. © 2010 Optical Society of America.