Showing papers on "Saturable absorption published in 2011"
TL;DR: In this article, a wideband-tunable Q-switched fiber laser exploiting a graphene saturable absorber was demonstrated, with 2μs pulses, tunable between 1522 and 1555 nm.
Abstract: We demonstrate a wideband-tunable Q-switched fiber laser exploiting a graphene saturable absorber. We get ∼2 μs pulses, tunable between 1522 and 1555 nm with up to ∼40 nJ energy. This is a simple and low-cost light source for metrology, environmental sensing, and biomedical diagnostics.
436 citations
TL;DR: In this article, the authors show that dispersed functionalized graphene can exhibit broadband nonlinear optical absorption at fluences well below the damage threshold and obtain an optical energy-limiting onset benchmark of 10 mJ cm−2 at a linear transmittance of 70% for nanosecond visible and near-infrared pulses.
Abstract: Researchers show that dispersed functionalized graphene can exhibit broadband nonlinear optical absorption at fluences well below the damage threshold. An optical energy-limiting onset benchmark of 10 mJ cm−2 at a linear transmittance of 70% was obtained for nanosecond visible and near-infrared pulses. The findings shed light on the formation of practical thin films with broadband optical limiting characteristics.
426 citations
TL;DR: In this article, the intrinsic properties of monolayer graphene allow it to act as a more effective saturable absorber for mode-locking fiber lasers when compared to multilayer graphene.
Abstract: We demonstrate that the intrinsic properties of monolayer graphene allow it to act as a more effective saturable absorber for mode-locking fiber lasers when compared to multilayer graphene. The absorption of monolayer graphene can be saturated at lower excitation intensity compared to multilayer graphene, graphene with wrinkle-like defects, or functionalized graphene. Monolayer graphene has a remarkably large modulation depth of 65.9%, whereas the modulation depth of multilayer graphene is greatly reduced due to nonsaturable absorption and scattering loss. Picosecond ultrafast laser pulses (1.23 ps) can be generated using monolayer graphene as a saturable absorber. Due to the ultrafast relaxation time, larger modulation depth and lower scattering loss of monolayer graphene, it performs better than multilayer graphene in terms of pulse shaping ability, pulse stability, and output energy.
406 citations
TL;DR: A dual-wavelength passively mode-locked soliton fiber laser based on the single-wall carbon nanotube saturable absorber that is able to simultaneously generate sub-picosecond pulses at both ~1532 and 1557 nm wavelength is demonstrated.
Abstract: We demonstrate a dual-wavelength passively mode-locked soliton fiber laser based on the single-wall carbon nanotube saturable absorber. By using a simple scheme of adjusting the intracavity loss, the gain profile of the erbium-doped fiber laser is effectively controlled. Besides operating at a single wavelength, the laser is able to simultaneously generate sub-picosecond pulses at both ~1532 and 1557 nm wavelength. The mode-locking wavelength can also be quickly switched from one wavelength to the other by changing the intracavity loss with a tunable attenuator.
222 citations
TL;DR: In this paper, a simple method for the in-situ monitoring of the deposition of few-layers graphene in an optical fiber end by mechanical exfoliation is presented.
Abstract: Graphene exhibits wavelength-independent, saturable optical absorption with fast response time, and large modulation depth. Thus, it is an attractive material for the saturable absorption of fiber lasers. In this paper, we report a simple method for the in-situ monitoring of the deposition of few-layers graphene in an optical fiber end by mechanical exfoliation. Saturable absorbers with different number of graphene layers (from 4 layers of graphene to few 10 s of layers) are prepared and low threshold, self-starting passive mode-locked operation of a fiber laser with sub-picosecond pulse duration is demonstrated.
221 citations
TL;DR: To the best of the knowledge, this is the first report for passively Q-switched sub-100-ns pulse operation of a graphene-based saturable absorber in a Yb-doped fiber laser.
Abstract: We demonstrate stable 70 ns pulse generation from a Yb-doped fiber laser passively Q-switched by a graphene-based saturable absorber mirror in a short linear cavity. The maximum output power was 12 mW and the highest single pulse energy was 46 nJ. The repetition rate of the fiber laser can be widely tuned from 140 to 257 kHz along with the increase of the pump power. To the best of our knowledge, this is the first report for passively Q-switched sub-100-ns pulse operation of a graphene-based saturable absorber in a Yb-doped fiber laser.
210 citations
TL;DR: In this article, the first observation of the synchronous oscillation of electromagnetic modes in a cavity in a random laser has been made, known as mode-locking in random lasers.
Abstract: Researchers report the first observation of the synchronous oscillation of electromagnetic modes in a cavity — known as mode-locking — in random lasers.
206 citations
TL;DR: This paper reports all-fiber laser operation with fundamental repetition rates of 4.24 GHz, 9.63 GHz and 19.45 GHz, which is, to date and to the best of the authors' knowledge, the highest fundamental repetition rate reported for an all-Fiber laser.
Abstract: There is an increasing demand for all-fiber passively mode-locked lasers with pulse repetition rates in the order of gigahertz for their potential applications in fields such as telecommunications and metrology. However, conventional mode-locked fiber lasers typically operate at fundamental repetition rates of only a few megahertz. In this paper, we report all-fiber laser operation with fundamental repetition rates of 4.24 GHz, 9.63GHz and 19.45GHz. This is, to date and to the best of our knowledge, the highest fundamental repetition rate reported for an all-fiber laser. The laser operation is based on the passive modelocking of a miniature all-fiber Fabry-Perot laser (FFPL) by a carbon nanotube (CNT) saturable absorber. The key components for such device are a very high-gain Er:Yb phosphosilicate fiber and a fiber compatible saturable absorber with very small foot print and very low losses. The laser output of the three lasers was close to transform-limited with a pulsewidth of approximately 1ps and low noise. As a demonstration of potential future applications for this laser, we also demonstrated supercontinuum generation with a longitudinal mode-spacing of 0.08nm by launching the laser operating at 9.63GHz into 30m of a highly nonlinear dispersion shifted fiber.
200 citations
TL;DR: In this paper, the ultrafast relaxation dynamics and nonlinear optical response in single and few-layered graphene oxide (GO) were studied by ultrafast optical differential transmission spectroscopy and Z-scan technique using various pump intensities.
Abstract: The ultrafast relaxation dynamics and nonlinear optical response in single- and few-layered graphene oxide (GO) were studied by ultrafast optical differential transmission spectroscopy and Z-scan technique using various pump intensities. It was found that charge carriers with subpicosecond-to-picosecond dynamics from sp2-hybridized domains dominate the ultrafast response at low pump intensities, like graphene. Surprisingly, the influence of two-photon absorption from sp3-hybridized domains on the transient absorption signal becomes increasingly strong with pump intensities. On the basis of heterogeneous ultrafast dynamics of GO with saturable absorption in sp2 domains and two-photon absorption in sp3 domains, the nonlinear optical response can be tailored by manipulation of the degree and location of oxidation on GO sheets; this unravels the important role of sp3 domains in graphene optics and will facilitate the potential applications of GO in optoelectronics.
168 citations
TL;DR: High-quality graphene sheets with lateral size over 20 μm have been obtained by bath sonicating after subjecting the wormlike graphite marginally to mixed oxidizer and are the largest graphene sheets prepared by exfoliation in the liquid phase.
Abstract: High-quality graphene sheets with lateral size over 20 μm have been obtained by bath sonicating after subjecting the wormlike graphite marginally to mixed oxidizer. To date, to our knowledge, they are the largest graphene sheets prepared by exfoliation in the liquid phase. A saturable absorber mirror was fabricated based on these sheets. We exploited it to realize mode-locking operation in a diode-pumped Nd:GdVO(4) laser. A pulse duration of 16 ps was produced with an average power of 360 mW and a highest pulse energy of 8.4 nJ for a graphene mode-locked laser.
161 citations
TL;DR: In this paper, the ultrafast carrier dynamics and saturable absorption of few-layered graphene oxide, well-dispersed in organic solvent, were studied using femtosecond pump-probe and Z-scan techniques.
Abstract: Ultrafast carrier dynamics and saturable absorption of few-layered graphene oxide, well-dispersed in organic solvent, are studied using femtosecond pump-probe and Z-scan techniques. The results demonstrate that few-layered graphene oxide has a fast energy relaxation of hot carriers and strong saturable absorption, which is comparable with that of reduced graphene oxide. Fast carrier relaxation combined with well solution processing capability arises from the large fraction of sp2 carbon atom inside the few-layered graphene oxide sheet together with oxidation mainly existing at the edge areas. This superiority of few-layered graphene oxide will facilitate potential applications of graphene for ultrafast photonics.
TL;DR: High-quality monolayer graphene as large as 1.2×1.2 cm2 was synthesized by chemical vapor deposition and used as a transmitting saturable absorber for efficient passive mode-locking of a femtosecond bulk solid-state laser.
Abstract: High-quality monolayer graphene as large as 1.2×1.2 cm2 was synthesized by chemical vapor deposition and used as a transmitting saturable absorber for efficient passive mode-locking of a femtosecond bulk solid-state laser. The monolayer graphene mode-locked Cr:forsterite laser was tunable around 1.25 μm and delivered sub-100 fs pulses with output powers up to 230 mW. The nonlinear optical characteristics of the monolayer graphene saturable absorber and the mode-locked operation were then compared with the case of the bilayer graphene saturable absorber.
TL;DR: It is shown that a monolithic and compact vertical cavity laser with intracavity saturable absorber can emit short excitable pulses that can be excited as a response to an input perturbation whose amplitude is above a certain threshold.
Abstract: We show that a monolithic and compact vertical cavity laser with intracavity saturable absorber can emit short excitable pulses. These calibrated optical pulses can be excited as a response to an input perturbation whose amplitude is above a certain threshold. Subnanosecond excitable response is promising for applications to novel all-optical devices for information processing or logical gates.
TL;DR: By brushing and scribing an ultra-thin polymer polyvinyl alcohol (PVA) film on one end face of a FC/APC connector in erbium-doped fiber laser (EDFL), the intra-cavity graphite nano-particle based saturable absorber can be formed to induce passive mode-locking effect in the EDFL.
Abstract: By directly brushing and scribing an ultra-thin (< 5-μm thick) polymer polyvinyl alcohol (PVA) film on one end-face of a FC/APC connector in erbium-doped fiber laser (EDFL), and then imprinting it with the graphite nano-particles exfoliated from a graphite foil, the intra-cavity graphite nano-particle based saturable absorber can be formed to induce passive mode-locking effect in the EDFL. Such a novel approach greatly suppresses the film-thickness induced laser-beam divergent loss to 3.4%, thus enhancing the intra-cavity circulating power to promote the shortening on mode-locking pulsewidth. The saturable absorber with area coverage ratio of graphite nano-particles is detuned from 70 to 25% to provide the modulation depth enhancing from 11 to 20% and the saturated transmittance from 27 to 60%. Optimizing the coverage ratio reduces the non-saturable loss to 40% and enhances the modulation depth to 21%, such that the sub-ps soliton mode-locking can be initiated to provide a chirped pulsewidth of 482 fs and a linewidth of 2.87 nm.
TL;DR: It is demonstrated that the graphene could be used as an effective saturable absorber for Q-switched solid-state lasers and has slope efficiency as high as 37% approximating to 40% of the continue-wave laser, indicating a low intrinsic loss of the graphene.
Abstract: We demonstrated that the graphene could be used as an effective saturable absorber for Q-switched solid-state lasers. A graphene saturable absorber mirror was fabricated with large and high-quality graphene sheets deprived from the liquid phase exfoliation. Using this mirror, 105-ns pulses and 2.3-W average output power are obtained from a passively Q-switched Nd:GdVO(4) laser. The maximum pulse energy is 3.2 μJ. The slope efficiency is as high as 37% approximating to 40% of the continue-wave laser, indicating a low intrinsic loss of the graphene.
TL;DR: In this article, a tunable and switchable multiwavelength passively mode-locked fiber laser by using a semiconductor saturable absorber mirror (SESAM) and an inline birefringence fiber filter is proposed and demonstrated.
Abstract: A tunable and switchable multiwavelength passively mode-locked fiber laser by using a semiconductor saturable absorber mirror (SESAM) and an inline birefringence fiber filter is proposed and demonstrated. By properly rotating the polarization controllers (PCs), up to 7-wavelength mode-locked pulses in 3-dB bandwidth with 3.65-nm channel spacing are obtained. The wavelength switchable operation is determined by the characteristics of the comb filter used in the experiment. Taking advantage of an intensity-dependent loss mechanism caused by the nonlinear polarization rotation (NPR) effect, the mode competition is efficiently suppressed. In addition, the lasing locations of multiwavelength mode-locked pulses can be flexibly tuned via the wavelength-dependent loss mechanism.
TL;DR: It is demonstrated that graphene oxide material could be used as a highly efficient saturable absorber for the Q-switched Nd:GdVO4 laser.
Abstract: We demonstrated that graphene oxide material could be used as a highly efficient saturable absorber for the Q-switched Nd:GdVO4 laser. A novel and low-cost graphene oxide (GO) absorber was fabricated by a vertical evaporation technique and high viscosity of polyvinyl alcohol (PVA) aqueous solution. A piece of GO/PVA absorber, a piece of round quartz, and an output coupler mirror were combined to be a sandwich structure passive component. Using such a structure, 104 ns pulses and 1.22 W average output power were obtained with the maximum pulse energy at 2 µJ and a slope efficiency of 17%.
TL;DR: In this paper, the authors consider the relatively new design of the pulsed fiber lasers, namely lasers with the fiber saturable absorber (FSA), and show that such lasers can be based on the different types of the fiber absorber and operate in different spectral ranges.
Abstract: In this brief review we consider the relatively new design of the pulsed fiber lasers, namely lasers with the fiber saturable absorber (FSA). Main advantage of this design consists in a possibility to realize a simple all-fiber scheme of Q-switched laser. We show that such lasers can be based on the different types of the fiber absorber and operate in the different spectral ranges. Up to now a set of the pulsed lasers were build. Pulse energy from several μJ to several hundred μJ was demonstrated. Pear power was changed from tens W to several kW with the pulse duration from 50 ns to 1 μs. We show that described principles of Q-switching can be applied for other types of the fiber lasers. Also, new fiber absorbers are suggested.
TL;DR: In this article, the E22 electronic transition of a sample of single-walled carbon nanotubes and use it to mode-lock an erbium fiber ring laser.
Abstract: We characterize the saturable absorption of the second (E22) electronic transition of a sample of single-walled carbon nanotubes and use it to mode-lock an ytterbium fiber ring laser. The modulation depth of ~ 15% was found to be similar to the corresponding E11 transition (~ 13%), but the saturation intensity (~ 220 MW cm-2) about an order of magnitude larger (~ 10 MW cm-2). We achieved a 15 MHz mode-locked pulse train with an output pulse duration of 6.5 ps. For comparison we also demonstrate stable mode-locking on the E11 transition, of the same nanotubes, with an erbium fiber ring laser, producing 1.1 ps pulses. Using the E22 transition should enable the use of carbon nanotube saturable absorbers at shorter wavelengths than currently possible with the E11 transition, which are limited by the smallest achievable nanotube dimensions.
TL;DR: In this article, the authors showed that graphene within fiber laser cavities can generate four-wave-mixing (FWM) by observing the laser spectral broadening and the transition from the single longitudinal mode oscillation to multiple-longitudinal mode one.
Abstract: We experimentally confirm that graphene within fiber laser cavities can generate four-wave-mixing (FWM) by observing the laser spectral broadening and the transition from the single-longitudinal-mode oscillation to multiple-longitudinal-mode one. Then, by simultaneously exploiting the graphene-induced nonlinear FWM and its super-broadband saturable absorption, we further achieve for the first time to the best of our knowledge, multiwavelength Q-switched Yb3+- or Er3+-doped fiber lasers at 1 μm and 1.5 μm wavebands, respectively. Simultaneous 23-wavelength Q-switching oscillation with a wavelength spacing of 0.2 nm is stably generated at 1.5 μm waveband. The multiwavelength Q-switched pulses have the minimum pulse duration of 2.5 μs, the maximum pulse energy of 72.5 nJ and a wide range of pulse-repetition-rate (PRR) from 2.8 to 63.0 kHz. At 1 μm waveband, we also obtain five-wavelength simultaneous lasing in Q-switching regime with the pulse duration of ~ 3 μs, pulse energy of 10.3 nJ and PRR between 39.8 and 56.2 kHz.
TL;DR: The potential of this laser for Two-Photon Excited Fluorescence (TPEF) imaging of in vivo Caenorhabditis elegans expressing Green Fluorescent Protein (GFP) in a set of neuronal processes and cell bodies is demonstrated.
Abstract: We present a portable ultrafast Semiconductor Disk Laser (SDL) (or vertical extended cavity surface emitting laser—VECSELs), to be used for nonlinear microscopy. The SDL is modelocked using a quantum-dot semiconductor saturable absorber mirror (SESAM), delivering an average output power of 287 mW, with 1.5 ps pulses at 500 MHz and a central wavelength of 965 nm. Specifically, despite the fact of having long pulses and high repetition rates, we demonstrate the potential of this laser for Two-Photon Excited Fluorescence (TPEF) imaging of in vivo Caenorhabditis elegans (C. elegans) expressing Green Fluorescent Protein (GFP) in a set of neuronal processes and cell bodies. Efficient TPEF imaging is achieved due to the fact that this wavelength matches the peak of the two-photon action cross section of this widely used fluorescent marker. The SDL extended versatility is shown by presenting Second Harmonic Generation images of pharynx, uterus, body wall muscles and its potential to be used to excite other different commercial dyes. Importantly this non-expensive, turn-key, compact laser system could be used as a platform to develop portable nonlinear bio-imaging devices.
TL;DR: In this paper, bound states of solitons with various pulse separations are obtained in an erbium-doped fiber laser passively mode-locked by the carbon nanotube saturable absorber.
TL;DR: In this paper, a Ti:sapphire laser employing a single-walled carbon nanotube saturable absorber (SWCNT-SA) was designed and fabricated for wavelengths near 800 nm.
Abstract: We report on passive mode-locking of a Ti:sapphire laser employing a single-walled carbon nanotube saturable absorber (SWCNT-SA) specially designed and fabricated for wavelengths near 800 nm. Mode-locked pulses as short as 62 fs were generated at a repetition rate of 99.4 MHz. We achieved output powers from the SWCNT-SA mode-locked laser as high as 600 mW with a slope efficiency of 26%. The characteristics of SWCNT-SA-assisted mode-locking were compared with those of Kerr-lens mode-locking without SWCNT-SA.
TL;DR: In this paper, the authors demonstrate passive mode-locking of a Raman fiber laser using a nanotube-based saturable absorber coupled to a net normal dispersion cavity.
Abstract: We demonstrate passive mode-locking of a Raman fiber laser using a nanotube-based saturable absorber coupled to a net normal dispersion cavity. This generates highly chirped 500 ps pulses. These are then compressed down to 2 ps, with 1.4 kW peak power, making it a simple wavelength-versatile source for various applications.
TL;DR: The SWCNT-SA film is fabricated without the polymer material by using a vertical evaporation technique, and then used in the passive mode-locking of Nd:GdVO4 laser at 1-µm, obtaining the highest output power to the authors' knowledge.
Abstract: We use a new (to our knowledge) fabrication method of a single-walled carbon nanotube (SWCNT) absorber without polymer to sustain high-power illumination. Using a series of saturable absorbers (SAs) incorporating different amounts of SWCNTs, we demonstrate mode-locking for a Nd:GdVO4 laser in the 1 μm spectral range. Continuous-wave mode-locking (CWML) pulses with a maximum output power of 3.6 W at 1063 nm and high noise extinction of 61 dB has been achieved to give the highest pulse peak power of 3.6 kW and pulse energy of 30 nJ under 15 Wpumping. To our knowledge, this is the highest CWML output power with SWCNT-SAs reported. The measured nonlinear absorption of the SWCNT-SAs shows a modulation depth of ∼3% with subpicosecond recovery time.
TL;DR: The synchronization of two all-fiber mode-locked lasers, operating at 1.0 μm and 1.54 μm, coupled through the use of a shared single-wall carbon nanotube absorber are presented, achieving a synchronized repetition rate of 13.08 MHz.
Abstract: We present the synchronization of two all-fiber mode-locked lasers, operating at 1.0 μm and 1.54 μm, coupled through the use of a shared single-wall carbon nanotube absorber. Both lasers operate in the soliton-regime, achieving a synchronized repetition rate of 13.08 MHz. The broadband absorption range of the single-wall carbon nanotubes allows the stable mode-locking behavior at 1 μm and 1.5 μm. The nonlinear coupling effects between two energy states of the carbon nanotube absorber result in stable synchronized pulses for hours of operation, with a large cavity mismatch of 1400 μm.
TL;DR: A simple way to clean the pulse after the first amplification stage is proposed by introducing a solid state saturable absorber which results in a LPCR improvement to better than 10(10) with only a 30% energy loss at a 10 Hz repetition rate.
Abstract: Laser matter interaction at relativistic intensities using 100 TW class laser systems or higher is becoming more and more widespread. One of the critical issues of such laser systems is to let the laser pulse interact at high intensity with the solid target and avoid any pre-plasma. Thus, a high Laser Pulse Contrast Ratio (LPCR) parameter is of prime importance. We present the LPCR characterization of a high repetition 100 TW class laser system. We demonstrate that the generated Amplified Spontaneous Emission (ASE) degrades the overall LPCR performance. We propose a simple way to clean the pulse after the first amplification stage by introducing a solid state saturable absorber which results in a LPCR improvement to better than 10(10) with only a 30% energy loss at a 10 Hz repetition rate. We finally correlated this cleaning method with experimental results.
TL;DR: Passive harmonic mode-locking in soliton fiber laser is presented with excellent noise characteristics by employing a single-walled carbon nanotubes saturable absorber designed to interact with evanescent wave of the laser field.
Abstract: Passive harmonic mode-locking in soliton fiber laser is presented with excellent noise characteristics by employing a single-walled carbon nanotubes saturable absorber designed to interact with evanescent wave of the laser field. The 34th harmonic mode-locking pulses at 943.16 MHz repetition rate were stably generated with 18 mW output power, >50 dB side-mode suppression and −140 dB/Hz relative intensity noise. Soliton energy control with polarization controller further increased the harmonic order to 61st, 1.692 GHz, but with compromised performance. Scaling to higher-order harmonic mode-locking is discussed for practical application in optical communication system.
TL;DR: In this paper, a gallium-antimonide-based semiconductor disk laser was passively modelocked to produce near transform-limited 384 fs pulses at a wavelength of 1960 nm.
Abstract: A gallium-antimonide-based semiconductor disk laser was passively modelocked to produce near transform-limited 384 fs pulses at a wavelength of 1960 nm. A fast semiconductor saturable absorber mirror was used as a modelocking element in the laser. Both the gain structure and the saturable absorber incorporated multiple InGaSb/GaSb quantum wells, providing necessary gain and absorption.
TL;DR: In this paper, a diode-pumped passively Q-switched Nd:Lu0.33Y0.37Gd0.3VO4 (NdLuYGdVO4) laser at 1.06 μm with a single-walled carbon nanotube saturable absorber is demonstrated.
Abstract: A diode-pumped passively Q-switched Nd:Lu0.33Y0.37Gd0.3VO4 (Nd:LuYGdVO4) laser at 1.06 μm with a single-walled carbon nanotube saturable absorber is demonstrated. At the incident pump power 9.1 W, the minimum pulse width of 52 ns and the maximum peak power 66.5 W can be obtained. In order to compare different gain media, the passively Q-switched Nd:LuVO4 and Nd:Lu0.15Y0.85VO4 (Nd:LuYVO4) lasers under the same laser cavity are also investigated. The experimental results show that Nd:LuYGdVO4 crystal is more suitable for passively Q-switched laser with single-walled carbon nanotube saturable absorber than Nd:LuVO4 or Nd:LuYVO4 crystals.