Showing papers on "Saturable absorption published in 2009"
TL;DR: In this paper, the use of atomic layer graphene as saturable absorber in a mode-locked fiber laser for the generation of ultrashort soliton pulses (756 fs) at the telecommunication band is demonstrated.
Abstract: The optical conductance of monolayer graphene is defined solely by the fine structure constant, α = (where e is the electron charge, is Dirac's constant and c is the speed of light). The absorbance has been predicted to be independent of frequency. In principle, the interband optical absorption in zero-gap graphene could be saturated readily under strong excitation due to Pauli blocking. Here, use of atomic layer graphene as saturable absorber in a mode-locked fiber laser for the generation of ultrashort soliton pulses (756 fs) at the telecommunication band is demonstrated. The modulation depth can be tuned in a wide range from 66.5% to 6.2% by varying the graphene thickness. These results suggest that ultrathin graphene films are potentially useful as optical elements in fiber lasers. Graphene as a laser mode locker can have many merits such as lower saturation intensity, ultrafast recovery time, tunable modulation depth, and wideband tunability.
2,217 citations
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TL;DR: In this paper, the authors demonstrate the use of atomic layer graphene as saturable absorber in a mode-locked fiber laser for the generation of ultrashort soliton pulses (756 fs) at the telecommunication band.
Abstract: The optical conductance of monolayer graphene is defined solely by the fine structure constant. The absorbance has been predicted to be independent of frequency. In principle, the interband optical absorption in zero-gap graphene could be saturated readily under strong excitation due to Pauli blocking. Here, we demonstrate the use of atomic layer graphene as saturable absorber in a mode-locked fiber laser for the generation of ultrashort soliton pulses (756 fs) at the telecommunication band. The modulation depth can be tuned in a wide range from 66.5% to 6.2% by varying the thickness of graphene. Our results suggest that ultrathin graphene films are potentially useful as optical elements in fiber lasers. Graphene as a laser mode locker can have many merits such as lower saturation intensity, ultrafast recovery time, tunable modulation depth and wideband tuneability.
2,039 citations
TL;DR: Results show that atomic layer graphene could be a promising saturable absorber for large energy mode locking and stable mode locked pulses with single pulse energy up to 7.3 nJ and pulse width of 415 fs have been directly generated from the laser.
Abstract: We report on large energy pulse generation in an erbium-doped fiber laser passively mode-locked with atomic layer graphene. Stable mode locked pulses with single pulse energy up to 7.3 nJ and pulse width of 415 fs have been directly generated from the laser. Our results show that atomic layer graphene could be a promising saturable absorber for large energy mode locking.
491 citations
TL;DR: In this article, a graphene-polymer nanocomposite membrane was fabricated and first used to mode lock a fiber laser, and stable mode-locked solitons with 3 nJ pulse energy, 700 fs pulse width at the 1590 nm wavelength have been directly generated from the laser.
Abstract: Due to its unique electronic property and the Pauli blocking principle, atomic layer graphene possesses wavelength-independent ultrafast saturable absorption, which can be exploited for the ultrafast photonics application. Through chemical functionalization, a graphene-polymer nanocomposite membrane was fabricated and first used to mode lock a fiber laser. Stable mode locked solitons with 3 nJ pulse energy, 700 fs pulse width at the 1590 nm wavelength have been directly generated from the laser. We show that graphene-polymer nanocomposites could be an attractive saturable absorber for high power fiber laser mode locking.
477 citations
TL;DR: In this article, an erbium-doped fiber laser passively mode-locked with atomic layer graphene was used to generate large energy pulses with single pulse energy up to 7.3 nJ and pulse width of 415 fs.
Abstract: We report on large energy pulse generation in an erbium-doped fiber laser passively mode-locked with atomic layer graphene. Stable mode locked pulses with single pulse energy up to 7.3 nJ and pulse width of 415 fs have been directly generated from the laser. Our results show that atomic layer graphene could be a promising saturable absorber for large energy mode locking.
452 citations
TL;DR: The first experimental demonstration of saturable absorption in core-electron transitions in aluminium paves the way for investigating warm dense matter, which potentially has an important role in planetary science and the realization of inertial confinement fusion.
Abstract: The first experimental demonstration of saturable absorption in core-electron transitions in aluminium paves the way for investigating warm dense matter, which potentially has an important role in planetary science and the realization of inertial confinement fusion.
239 citations
TL;DR: The novel fabrication method of the polymer-free absorber and device parameters determined using nonlinear reflectivity measurement are described in detail and the observed operation bandwidth of approximately 1 microm is the broadest reported to date for a single carbon nanotube-based saturable absorber.
Abstract: Mode-locked sub-picosecond operation of Yb-, Er- and Tm:Hodoped fiber lasers operating at 1.05 microm, 1.56 microm and 1.99 microm, respectively, is demonstrated using the same sample carbon nanotube-based saturable absorber mirror. A mesh of single-walled carbon nanotubes was deposited on an Ag-mirror using a one-step dry-transfer contact press method to combine broadband saturable absorption and high reflectance properties. The novel fabrication method of the polymer-free absorber and device parameters determined using nonlinear reflectivity measurement are described in detail. To our knowledge the observed operation bandwidth of approximately 1 microm is the broadest reported to date for a single carbon nanotube-based saturable absorber.
234 citations
TL;DR: In this paper, the authors review the recent developments of the carbon nanotube and its composites for nonlinear optical applications, and two research hot spots are discussed: optical limiting for laser protection and the saturable absorber as a mode-locking component for ultra-short pulsed lasers.
Abstract: Carbon nanotubes possess not only outstanding mechanical, electrical and thermal properties but also unique nonlinear optical properties. In this Feature Article, we review the recent developments of the carbon nanotube and its composites for nonlinear optical applications. Two research hot spots are discussed: optical limiting for laser protection and the saturable absorber as a mode-locking component for ultra-short pulsed lasers. The physical mechanism, materials and devices are intensively introduced for each application. All of the investigations indicate that the carbon nanotube is one of the main competitive candidates for next generation of photonic components.
214 citations
TL;DR: In this paper, a 60-fs source was demonstrated, based on a semiconductor laser that is mode-locked using a saturable absorber mirror in an external cavity, and the source was shown to be a compact source of 60fs pulses.
Abstract: A compact source of 60-fs pulses is demonstrated, based on a semiconductor laser that is mode-locked using a saturable absorber mirror in an external cavity.
197 citations
TL;DR: Stabilization of a thulium-holmium codoped fiber soliton laser with a saturable absorber based on carbon nanotubes with transform-limited 750-fs pulses with 0.5-nJ energy is reported.
Abstract: We report stabilization of a thulium-holmium codoped fiber soliton laser with a saturable absorber based on carbon nanotubes. The laser generates transform-limited 750-fs pulses with 0.5-nJ energy.
195 citations
TL;DR: In this paper, nonlinear optical properties and carrier relaxation dynamics in graphene, suspended in three different solvents, were investigated using femtosecond (80 fs pulses) Z-scan and degenerate pump-probe spectroscopy at 790 nm.
Abstract: Nonlinear optical properties and carrier relaxation dynamics in graphene, suspended in three different solvents, are investigated using femtosecond (80 fs pulses) Z-scan and degenerate pump-probe spectroscopy at 790 nm. The results demonstrate saturable absorption property of graphene with a nonlinear absorption coefficient, beta of (similar to 2-9) x 10(-8) cm/W. Two distinct time scales associated with the relaxation of photoexcited carriers, a fast one in the range of 130-330 fs (related to carrier-carrier scattering) followed by it slower one in 3.5-4.9 ps range (associated with carrier-phonon scattering) are observed. (C) 2009 American Institute of Physics.
TL;DR: This is the first demonstration of mode-locked 2 mum fiber laser using shorter than 1-m-long active fiber, which paves the way for the demonstration ofmode-locked fiber laser at 2 mum with gigahertz fundamental repetition rate.
Abstract: We report self-starting passively mode-locked fiber lasers with a saturable absorber mirror using a piece of 30-cm-long newly developed highly thulium (Tm)-doped silicate glass fibers. The mode-locked pulses operate at 1980 nm with duration of 1.5 ps and energy of 0.76 nJ. This newly developed Tm-doped silicate fiber exhibits a slope efficiency of 68.3%, an amplified spontaneous emission spectrum bandwidth (FWHM) of 92 nm, and a gain per unit length of greater than 2 dB/cm. To the best of our knowledge, it is the first demonstration of mode-locked 2 μm fiber laser using shorter than 1-m-long active fiber, which paves the way for the demonstration of mode-locked fiber laser at 2 μm with gigahertz fundamental repetition rate.
TL;DR: Stable and self-starting mode-locking of a Tm:KLu(WO(4))(2) crystal laser is demonstrated using a transmission-type single-walled carbon nanotube (SWCNT) based saturable absorber (SA) using the E11 transition of the SWCNTs for nonlinear saturable absorption.
Abstract: Stable and self-starting mode-locking of a Tm:KLu(WO4)2 crystal laser is demonstrated using a transmission-type single-walled carbon nanotube (SWCNT) based saturable absorber (SA). These experiments in the 2 µm regime utilize the E11 transition of the SWCNTs for nonlinear saturable absorption. The recovery time of the SWCNT-SA is measured by pump-probe measurements as ~1.2 ps. The mode-locked laser delivers ~10-ps pulses near 1.95 µm with a maximum output power of up to 240 mW at 126 MHz repetition rate.
TL;DR: In this article, the authors demonstrate that mode-locking of ytterbium fiber lasers with a carbon nanotube saturable absorber can produce pulses ranging from 20 ps to 2 ns at repetition rates between 21 MHz and 177 kHz, depending on cavity length.
Abstract: We demonstrate that mode-locking of ytterbium fiber lasers with a carbon nanotube saturable absorber can produce pulses ranging from 20 ps to 2 ns at repetition rates between 21 MHz and 177 kHz, respectively, depending on cavity length. Nonlinear polarization evolution is not responsible for mode-locking. Even in the nanosecond regime, clean single pulses are observed and the pulse train exhibits low jitter. Combined with extremely large chirp, these properties are suited for chirped-pulse amplification systems.
TL;DR: In this article, the existence of dissipative soliton bound state solutions (soliton molecules) in a mode-locked fiber laser with an instantaneous saturable absorber in the normal dispersion domain is numerically demonstrated.
Abstract: We numerically demonstrate the existence of a discrete family of robust dissipative soliton bound state solutions (soliton molecules) in a mode-locked fiber laser with an instantaneous saturable absorber in the normal dispersion domain. For a certain domain of the small-signal gain, we obtain a robust first-level bound state with almost constant separation where the phase of the two pulses evolves independently. Moreover, their phase difference can evolve either periodically or chaotically depending on the small-signal gain. Interestingly, higher level bound states exhibit a fundamentally different dynamics. They represent oscillating solutions with a phase difference alternating between zero and $\ensuremath{\pi}$. We identify the crucial role of the linear gain saturation for the existence of these robust molecules independently of their level.
TL;DR: Comparison with analytical mode-locking theory shows a good quantitative agreement with the master equation mode- locking model for nanosecond pulse spectrogram shape and chirp.
Abstract: We evaluate the shape and chirp of nanosecond pulses from a fiber laser passively mode locked with a nanotube-based saturable absorber by using a synchronously scanning streak camera and a monochromator to directly measure the pulse spectrogram. We show that the stable sech2 output pulse possesses a predominantly linear chirp, with a residual quartic phase and low noise. Comparison with analytical mode-locking theory shows a good quantitative agreement with the master equation mode-locking model.
TL;DR: In this article, two types of gold nanoparticles, nanocubes and nano-octahedra, were prepared and their nonlinear absorption properties were investigated by using femtosecond open aperture Z-scan experiments.
Abstract: Two types of gold nanoparticles, nanocubes and nano-octahedra were prepared and their nonlinear absorption properties were investigated by using femtosecond open aperture Z-scan experiments. Both nanocubes and nano-octahedra exhibited a shift from saturable absorption (SA) to reverse saturable absorption (RSA) at higher excitation intensities. The SA behavior was ascribed to ground state plasmon band bleaching and RSA was ascribed to excited state absorption and two-photon absorption of these materials. The competition of different processes is responsible for the observed switching behavior.
TL;DR: Transmission- and reflection-type single-walled carbon nanotube saturable absorbers were designed and fabricated for passive mode-locking of bulk lasers in the 1 microm spectral range, and nearly identical performance indicates that well-optimized SWCNT-SAs can substitute SESAMs even in the1 microm region.
Abstract: Transmission- and reflection-type single-walled carbon nanotube saturable absorbers (SWCNT-SAs) were designed and fabricated for passive mode-locking of bulk lasers in the 1 microm spectral range. Mode-locked laser operation based on a diffusion-bonded Yb:KYW/KYW crystal was demonstrated, and pulses as short as 83 fs and 140 fs were achieved applying reflection-type and transmission-type SWCNT-SA, respectively. The nonlinear parameters of the absorbers were measured to be in close vicinity to those of a semiconductor saturable absorber mirror for the same wavelength range. Mode-locking performance with SWCNT-SAs and the SESAM was compared utilizing the same cavity, with the SESAM resulting in only slightly shorter pulses of 66 fs duration. The nearly identical performance indicates that well-optimized SWCNT-SAs can substitute SESAMs even in the 1 microm region.
TL;DR: Numerical simulations accurately reflect the experimental results and show that pulse-shaping in this laser could be interpreted as producing 'dissipative solitons'.
Abstract: We report on a passively mode-locked erbium-doped fiber laser, using a high nonlinear modulation depth saturable absorber mirror, in a Fabry-Perot cavity. A segment of dispersion compensation fiber is added inside the cavity in order to build a high-positive dispersion regime. The setup produced highly chirped pulses with an energy of 1.8 nJ at a repetition rate of 33.5 MHz. Numerical simulations accurately reflect our experimental results and show that pulse-shaping in this laser could be interpreted as producing ‘dissipative solitons’.
TL;DR: The passively mode-locked fiber laser is demonstrated including the SWCNT-filled HOF where the spectral bandwidth and the pulse duration of the laser output are 5.5 nm and 490 fs, respectively, with a repetition rate of 18.5 MHz.
Abstract: We propose a novel in-line saturable absorber incorporating a hollow optical fiber (HOF) filled with single-walled carbon nanotube (SWCNT) dispersion. The evanescent field of the propagating light in the ring core interacts with the SWCNT/polymer composite distributed over the whole length of the HOF. The proposed saturable absorber with all-fiber format offers the robust and long nonlinear interaction along the waveguide direction expecting the increase of the threshold for optical and thermal damages with simple fabrication process. Low concentration SWCNT/polymer composite exhibiting very broadband resonant absorption around 1.5 microm with low scattering loss is prepared and based on this, we successfully demonstrate the passively mode-locked fiber laser including the SWCNT-filled HOF where the spectral bandwidth and the pulse duration of the laser output are 5.5 nm and 490 fs, respectively, with a repetition rate of 18.5 MHz.
TL;DR: For the first time, a passive Q-switched Yb-doped fiber laser with a saturable absorber based on Ho-Doped fiber was realized as mentioned in this paper.
Abstract: For the first time we have suggested and realized passive Q-switched Yb-doped fiber laser with a saturable absorber based on Ho-doped fiber laser. The pulse duration was of 250 ns, the pulse energy – 70 μJ, the peak power – 300 W. The laser is perspective for technology processes. Possible ways of laser characteristics improving are discussed.
TL;DR: For steady state operation of a passively Q-switched laser (PRF=10 Hz), the pulse-to-pulse timing jitter showed approximately 12X reduction in standard deviation, from 241 nsec for free running operation to 20 nsec with optical triggering.
Abstract: A method for optical triggering of a Q-switched Nd:YAG laser by direct bleaching of a Cr:YAG saturable absorber is described. This method involves the bleaching of a thin sheet of the saturable absorber from a direction orthogonal to the lasing axis using a single laser diode bar, where the Cr:YAG transmission increased from a non-bleached value of 47% to a bleached value of 63%. For steady state operation of a passively Q-switched laser (PRF=10Hz), the pulse-to-pulse timing jitter showed ~12X reduction in standard deviation, from 241 nsec for free running operation to 20 nsec with optical triggering.
TL;DR: In this paper, an organic chromophore, Amido Black 10B, embedded in a vinyl polymer, polyvinyl alcohol, and comprising a uniform distribution of aggregated nanoclusters was studied using the standard Z-scan technique under low intensity continuous wave laser light excitation at 632?nm, while increasing the concentration of the dye content.
Abstract: We report an observed transition from a saturable absorption type of behaviour to a reverse saturable absorption one for solid films of a guest?host system constituted by an organic chromophore, Amido Black 10B, embedded in a vinyl polymer, polyvinyl alcohol, and comprising a uniform distribution of aggregated nanoclusters, as studied using the standard Z-scan technique under low intensity continuous wave laser light excitation at 632?nm, while increasing the concentration of the dye content. This is attributed to the presence of higher aggregates of the dye molecules in the sample. Besides this, the samples also displayed complex nonlinear refraction behaviour, yielding a net negative nonlinearity, explained on the basis of a possible, simultaneous occurrence of refractive nonlinearities of different origin, in addition to the obvious effect of absorption. The estimated values of the effective coefficients of nonlinear absorption, nonlinear refraction and third-order nonlinear susceptibility, |?(3)|, compared to those reported for continuous wave laser light excitation, measure up to the highest among them. These nonlinear effects could be the basis for possible applications of this new reverse saturable absorption material, sensitive even to low power excitation, as an efficient material for use in nonlinear optical devices.
TL;DR: The generation of 99 fs pulses is demonstrated by a mode-locked laser oscillator built around a Yb:CaF(2) crystal and the limits of the stabilization process are investigated.
Abstract: We demonstrate the generation of 99 fs pulses by a mode-locked laser oscillator built around a Yb:CaF2 crystal. An average power of 380 mW for a 13 nm bandwidth spectrum centered at 1053 nm is obtained. The short-pulse operation is achieved thanks to a saturable absorber mirror and is stabilized by the Kerr lens effect. We investigated the limits of the stabilization process and observed a regime slowly oscillating between mode locking and Q switching.
TL;DR: In this article, the authors investigated the third-order nonlinear optical properties of two polythiophene composite films investigated using the Z-scan technique and found that the composite films exhibit self-defocusing nonlinearity.
Abstract: We report here the studies on third-order nonlinear optical properties of two novel polythiophene composite films investigated using the Z-scan technique. The measurements were carried out using a Q-switched, frequency doubled Nd:YAG laser producing 7 nanosecond laser pulses at 532 nm. Z-scan results reveal that the composite films exhibit self-defocusing nonlinearity. The real and imaginary parts of the third-order nonlinear optical susceptibility were of the order 10−12 esu. The effective excited-state absorption cross section was found to be larger than the ground state absorption cross section, indicating that the operating nonlinear mechanism is reverse saturable absorption (RSA). The polythiophene composite films also exhibit good optical power limiting of the nanosecond laser pulses. The nonlinear optical parameters are found to increase on increasing the strength of the electron-donor group, indicating the dependence of χ
(3) on the electron-donor/acceptor units of polythiophenes.
TL;DR: Pulse shaping was different from the soliton-like mode-locking process known from lasers using dielectric gain media; passive amplitude modulation provided by a fast saturable absorber was essential.
Abstract: Almost chirp-free pulses with a duration of 190 fs were achieved from a mode-locked semiconductor disk laser (SDL) emitting at ≈1045 nm. Pulse shaping was different from the soliton-like mode-locking process known from lasers using dielectric gain media; passive amplitude modulation provided by a fast saturable absorber was essential. The spectrum of the absorber had to be matched to the gain spectrum within a few nm. A tapered diode amplifier was demonstrated to be a device for both picking and amplifying SDL pulses. The pulse repetition rate of the SDL output was reduced from 3 GHz to 47 MHz.
TL;DR: In this paper, a diode-pumped passively mode-locked YVO4/Nd:YVO4 composite crystal green laser with a semiconductor saturable absorber mirror (SESAM) and a intracavity frequency-doubling KTP crystal was realized.
Abstract: A diode-pumped passively mode-locked YVO4/ Nd:YVO4 composite crystal green laser with a semiconductor saturable absorber mirror (SESAM) and a intracavity frequency-doubling KTP crystal was realized. The maximum average output power of 2.06 W at 532 nm with a repetition rate of 100 MHz was obtained at a pump power of 15 W, corresponding to optical slop efficiency 17.2%. The 532 nm mode-locked pulse width was estimated to be approximately 18-ps.
TL;DR: In this paper, a coupled-cavity model of a laser with frequency-selective feedback is presented, and the existence of stationary and dynamic spatial solitons in the device is analyzed and explained.
Abstract: We present a coupled-cavity model of a laser with frequency-selective feedback, and use it to analyze and explain the existence of stationary and dynamic spatial solitons in the device. Particular features of soliton addressing in this system are discussed. We demonstrate the advantages of our model with respect to the common Lang-Kobayashi approximation.
TL;DR: In this paper, a diode-end-pumped passively Q-switched mode-locked Nd:GdVO4 laser operating at 1.34 μm was demonstrated in a Z-type cavity.
Abstract: A diode-end-pumped passively Q-switched mode-locked Nd:GdVO4 laser operating at 1.34 μm by using the Co2+:LaMgAl11O19 (Co2+:LMA) as the saturable absorber in a Z-type cavity has been demonstrated in our experiment for the first time. The repetition rate of the Q-switched pulse envelop increases from 4.2 kHz to 17 kHz as the pump power increases from 3.8 W to 8.9 W, and a maximum Q-switched and mode-locked fundamental mode average output power of 126 mW is obtained. The mode-locked pulse inside the Q-switched pulse has a repetition rate of 114 MHz, and its average pulse width is estimated to be about 280 ps.
TL;DR: The design has been numerically and experimentally demonstrated using Er(3+)-doped fiber at the emission wavelength of 1550 nm and a set of location-dependent rate equations is established for Q-switching modeling.
Abstract: We propose a simple design of a saturable absorber Q-switched all-fiber ring laser. By locating a saturable absorber fiber in the intensity-enhanced section of a ring resonator, the laser is passively Q-switched. A set of location-dependent rate equations is established for Q-switching modeling. The design has been numerically and experimentally demonstrated using Er3+ -doped fiber at the emission wavelength of 1550 nm. A single-mode Q-switched pulse with pulse energy of 0.37 μJ and pulse duration of 218 ns was achieved with 980-nm pump power near 7 mW.