Showing papers on "Saturable absorption published in 2008"
TL;DR: In principle, different diameters and chiralities of nanotubes could be combined to enable compact, mode-locked fibre lasers that are tuneable over a much broader range of wavelengths than other systems.
Abstract: Ultrashort-pulse lasers with spectral tuning capability have widespread applications in fields such as spectroscopy, biomedical research and telecommunications1–3. Mode-locked fibre lasers are convenient and powerful sources of ultrashort pulses4, and the inclusion of a broadband saturable absorber as a passive optical switch inside the laser cavity may offer tuneability over a range of wavelengths5. Semiconductor saturable absorber mirrors are widely used in fibre lasers4–6, but their operating range is typically limited to a few tens of nanometres7,8, and their fabrication can be challenging in the 1.3–1.5 mm wavelength region used for optical communications9,10. Single-walled carbon nanotubes are excellent saturable absorbers because of their subpicosecond recovery time, low saturation intensity, polarization insensitivity, and mechanical and environmental robustness11–16. Here, we engineer a nanotube–polycarbonate film with a wide bandwidth (>300 nm) around 1.55 mm, and then use it to demonstrate a 2.4 ps Er31-doped fibre laser that is tuneable from 1,518 to 1,558 nm. In principle, different diameters and chiralities of nanotubes could be combined to enable compact, mode-locked fibre lasers that are tuneable over a much broader range of wavelengths than other systems.
616 citations
TL;DR: In this paper, a theoretical and experimental study of multimode operation regimes in quantum cascade laser (QCLs) is presented and a model that can account for coherent phenomena, a saturable absorber, and SHB is developed and studied in detail both analytically and numerically.
Abstract: A theoretical and experimental study of multimode operation regimes in quantum cascade lasers (QCLs) is presented. It is shown that the fast gain recovery of QCLs promotes two multimode regimes: One is spatial hole burning (SHB) and the other one is related to the Risken-Nummedal-Graham-Haken instability predicted in the 1960s. A model that can account for coherent phenomena, a saturable absorber, and SHB is developed and studied in detail both analytically and numerically. A wide variety of experimental data on multimode regimes is presented. Lasers with a narrow active region and/or with metal coating on the sides tend to develop a splitting in the spectrum, approximately equal to twice the Rabi frequency. It is proposed that this behavior stems from the presence of a saturable absorber, which can result from a Kerr lensing effect in the cavity. Lasers with a wide active region, which have a weaker saturable absorber, do not exhibit a Rabi splitting and their multimode regime is governed by SHB. This experimental phenomenology is well-explained by our theoretical model. The temperature dependence of the multimode regime is also presented.
210 citations
TL;DR: A high-brightness diode end-pumped Nd:YAG microchip laser, passively Q-switched by a Cr(4+):YAG saturable absorber (SA), has been developed and the dependences of pulse energy and width were investigated based on theoretical verification to enhance the peak power.
Abstract: A high-brightness diode end-pumped Nd:YAG microchip laser, passively Q-switched by a Cr(4+):YAG saturable absorber (SA), has been developed. The dependences of pulse energy and width were investigated based on theoretical verification to enhance the peak power. As a result, the peak power exceeded 1.2 MW with M(2) = 1.04 and spectrum width Delta lambda < 5.1 pm at a repetition rate of 100 Hz. Brightness of 98 TW/sr x cm(2) was obtained with a supplied average electrical power of 2.3 W. The peak power increased up to 2.1 MW with M(2) = 1.36. Peak power of 1.7 MW was obtained from a 2-cm-diameter x 5-cm-long monolithic laser head.
177 citations
TL;DR: Mode locking of an Yb-doped bulk laser in the 1 microm spectral range using a single-walled carbon nanotube saturable absorber (SWCNT-SA) is demonstrated for the first time, to the authors' knowledge.
Abstract: Mode locking of an Yb-doped bulk laser in the 1 μm spectral range using a single-walled carbon nanotube saturable absorber (SWCNT-SA) is demonstrated for the first time, to our knowledge. Passive mode locking of an Yb:KLuW laser resulted in nearly transform-limited pulses as short as 115 fs at 1048 nm. In addition, the nonlinear response of the SWCNT-SA was measured, yielding a modulation depth of 0.25% and a relaxation time of 750 fs.
170 citations
04 May 2008
TL;DR: In this article, a passively modelocked VECSEL with both gain and saturable absorber integrated into a single semiconductor structure is proposed, referred to as the modelocked integrated external-cavity surface emitting laser (MIXSEL).
Abstract: We discuss a passively modelocked VECSEL with both gain and saturable absorber integrated into a single semiconductor structure. We refer to this new kind of laser as the modelocked integrated external-cavity surface emitting laser (MIXSEL).
157 citations
TL;DR: A novel all-fiber bidirectional passively mode-locked ring laser using an erbium-doped fiber chosen as the active element in a ring cavity arrangement that will find important applications in precision rotation sensing.
Abstract: We report the design and operation of a novel all-fiber bidirectional passively mode-locked ring laser. An erbium-doped fiber was chosen as the active element in a ring cavity arrangement. A short segment of a fiber taper embedded in carbon nanotubes/polymer composite, acting as a saturable absorber, was used to enable bidirectional mode locking. The laser generates two stable femtosecond pulse trains in opposite directions. A beat note of about 2 MHz, having a bandwidth of less than 2 kHz, is measured when the pulses propagating in opposite directions are (temporally) overlapped at a photodetector. We believe this device will find important applications in precision rotation sensing.
152 citations
TL;DR: An all-polarization-maintaining Er-doped ultrashort-pulse fiber laser using a single-wall carbon nanotube polyimide nanocomposite saturable absorber is presented and it is confirmed that the noise figure is as low as that of a solid-state laser.
Abstract: We present an all-polarization-maintaining Er-doped ultrashortpulse fiber laser using a single-wall carbon nanotube polyimide nanocomposite saturable absorber. The maximum average power for single-pulse operation is 4.8 mW, and the repetition frequency is 41.3 MHz. Self-start and stable mode-locking operation is achieved. The RF amplitude noise is also examined and it is confirmed that the noise figure is as low as that of a solid-state laser. Using a polarization-maintaining anomalous dispersive fiber, a 314 fs output pulse is compressed to 107 fs via higher-order soliton compression. The peak power of the compressed pulse is up to 1.1 kW.
142 citations
TL;DR: Experimental observation of localized structures in two mutually coupled broad-area semiconductor resonators, one of which acts as a saturable absorber, which have the same properties as cavity solitons without requiring the presence of a driving beam into the system.
Abstract: We report on experimental observation of localized structures in two mutually coupled broad-area semiconductor resonators, one of which acts as a saturable absorber. These structures coexist with a dark homogeneous background and they have the same properties as cavity solitons without requiring the presence of a driving beam into the system. They can be switched individually on and off by means of a local addressing beam.
136 citations
TL;DR: Saturable absorption and reverse saturable absorption (RSA) at 532 nm were observed in Ag nanodots prepared by pulsed laser deposition as discussed by the authors, and the recovery time of these nonlinear processes was measured by a degenerate pump-probe experiment.
Abstract: Saturable absorption (SA) and reverse saturable absorption (RSA) at 532 nm were observed in Ag nanodots prepared by pulsed laser deposition. The real [Re χ(3)] and imaginary [Im χ(3)] parts of the third order nonlinearity of these films were measured using the Z-scan technique. At low input irradiances, the decrease in absorption near the focal point results from a negative Im χ(3) and yields SA. At higher input irradiance, RSA becomes dominant. The transition from SA to RSA suggests that there is a threshold irradiance at which additional nonlinear process(es) is (are) involved and become dominant. The recovery time of these nonlinear processes was measured by a degenerate pump-probe experiment. The effects are explained in terms of the electron dynamics in the excited states.
119 citations
TL;DR: In this article, a nanotube-polyvinyl alcohol saturable absorber with a broad absorption at 1.6μm was used as a mode locker for a pulsed fiber laser.
Abstract: We fabricate a nanotube-polyvinyl alcohol saturable absorber with a broad absorption at 1.6 μm. We demonstrate a pulsed fiber laser working in the telecommunication L band by using this composite as a mode locker. This gives ∼498±16 fs pulses at 1601 nm with a 26.7 MHz repetition rate.
112 citations
TL;DR: In this paper, a single-walled carbon nanotubes (CN) is used to reflect ultrafast saturable absorbers for stable mode locking of bulk solid-state lasers operating near 1μm.
Abstract: Transmitting and reflecting ultrafast saturable absorbers based on single-walled carbon nanotubes are developed that are applicable for stable mode locking of bulk solid-state lasers operating near 1μm. For fabrication of these saturable absorbers, relatively simple spin coating and spray methods are employed. Parameters important for stable mode locking, such as transient nonlinear absorption, saturation fluence, and recovery time, are investigated by nonlinear transmission and time-resolved pump-probe measurements near 1μm. Typical modulation depths and recovery times amount to ∼0.21%–0.25% and <1ps, respectively.
TL;DR: The maximum average output power of 202 mW obtained with a 5% output coupler at a repetition rate of 79.1 MHz represents, to the best of the knowledge, the highest power level ever reported for SWCNT-SA mode locking of solid-state lasers.
Abstract: We report what we believe to be the first passive mode-locking of Cr:forsterite laser using a single-walled carbon nanotube saturable absorber (SWCNT-SA). The dispersion-compensated Cr:forsterite laser in a self-starting configuration produces nearly Fourier transform-limited pulses as short as 120 fs near 1.25 microm. The maximum average output power of 202 mW obtained with a 5% output coupler at a repetition rate of 79.1 MHz represents, to the best of our knowledge, the highest power level ever reported for SWCNT-SA mode locking of solid-state lasers.
Patent•
31 Mar 2008TL;DR: In this paper, a monolithic passively Q switched microlaser includes an optically transparent heat conductive element bonded to a gain medium, which is in turn coupled to a saturable absorber.
Abstract: A monolithic passively Q switched microlaser includes an optically transparent heat conductive element bonded to a gain medium, which is in turn bonded to a saturable absorber, which may also be bonded to a second optically transparent heat conductive element. Only the gain medium and saturable absorber are disposed within the laser resonator.
TL;DR: In this article, a mode-locked soliton erbium-doped fiber laser was demonstrated with a saturable absorber made of a high-optical quality film based on cellulose derivative with dispersed carbon single-wall nanotubes.
Abstract: A mode-locked soliton erbium-doped fiber laser generating 177fs pulses is demonstrated. The laser pumped by a 85mW, 980nm laser diode emits 7mW at 1.56μm at a pulse repetition rate of 50MHz. Passive mode locking is achieved with a saturable absorber made of a high-optical quality film based on cellulose derivative with dispersed carbon single-wall nanotubes. The film is prepared with the original technique by using carbon nanotubes synthesized by the arc-discharge method.
TL;DR: In this paper, the optical and nonlinear optical properties of the glasses were investigated and it was found that thermal annealing up to the glass softening temperature makes the samples behave like saturable absorbers, while annaling at higher temperatures makes them behave like optical limiters.
TL;DR: A novel device consisting of an optofluidic device filled with a dispersion of CNT, which is compactness and robustness against optical, mechanical and thermal damage and demonstrated with an output power of 13.5 dBm is proposed and implemented.
Abstract: Fueled by their high third-order nonlinearity and nonlinear saturable absorption, carbon nanotubes (CNT) are expected to become an integral part of next-generation photonic devices such as all-optical switches and passive mode-locked lasers. However, in order to fulfill this expectation it is necessary to identify a suitable platform that allows the efficient use of the optical properties of CNT. In this paper, we propose and implement a novel device consisting of an optofluidic device filled with a dispersion of CNT. By fabricating a microchannel through the core of a conventional fiber and filling it with a homogeneous solution of CNTs on Dimethylformamide (DMF), a compact, all-fiber saturable absorber is realized. The fabrication of the micro-fluidic channel is a two-step process that involves femtosecond laser micro-fabrication and chemical etching of the laser-modified regions. All-fiber high-energy, passive mode-locked lasing is demonstrated with an output power of 13.5 dBm. The key characteristics of the device are compactness and robustness against optical, mechanical and thermal damage.
TL;DR: In this article, the dependences of pulse width, pulse repetition rate on incident pump power at different small-signal transmissions of Cr4+:YAG are measured for the green-light pulses.
Abstract: A laser-diode-pumped passively-Q-switched intracavity-frequency-doubled Nd:YVO4/YVO4 green laser with a MgO-PPLN and Cr4+:YAG is realized. The dependences of pulse width, pulse repetition rate on incident pump power at different small-signal transmissions of Cr4+:YAG are measured for the green-light pulses. The corresponding pulse energy and peak power are also been obtained.
TL;DR: In this article, the authors present the experimental study of the nonlinear absorption of gold nanospheres and nanorods in aqueous suspension, using picosecond white-light supercontinuum open-aperture Z-scan.
Abstract: In this work, we present the experimental study of the nonlinear absorption of gold nanospheres and nanorods in aqueous suspension, using picosecond white-light supercontinuum open-aperture Z-scan. We demonstrate a saturable absorption effect in all particle suspensions at low-pulse energy. In the high-pulse energy regime, the apparent reverse-saturable absorption, observed in gold nanorods, was determined to be induced by photodegradation. Using the Lorentzian deconvolution method for the absorption spectra, we explain the variations on nonlinear optical effects and prove that saturable absorption only occurs within the plasmonic bands.
TL;DR: In this article, the nonlinear optical absorption, refraction and optical limiting behavior of an organic dye, neutral red, were investigated under excitation with nanosecond laser pulses at 532nm.
Abstract: The nonlinear optical absorption, refraction and optical limiting behaviour of an organic dye, neutral red, were investigated under excitation with nanosecond laser pulses at 532 nm. The nonlinear optical responses of the material were studied both in solution and solid film, made in methanol and polyvinyl alcohol, respectively, using single-beam Z-scan technique. The open aperture Z-scans of the solution samples displayed a switch over from saturable absorption to enhanced absorption with increase in input intensity. Theoretical fit to the experimental data indicated that the dominant mechanism of nonlinear absorption is two-photon absorption. The closed aperture Z-scans of both the samples denoted positive nonlinearity, which was three orders larger in magnitude in solid film, compared with that in solution. The results of optical limiting experiments revealed that neutral red exhibited strong optical limiting of nanosecond laser pulses with a threshold lower than that of C60 in toluene.
TL;DR: In this article, the authors report the third order nonlinear optical properties of ZnO thin films deposited using self assembly, sol gel process as well as pulsed laser ablation by z scan technique.
TL;DR: In this paper, a new saturable absorber V3+:YAG, a flash-lamp-pumped passively Q-switched Nd:GdVO4 laser at 1.34 μm has been realized.
Abstract: By using a new saturable absorber V3+:YAG, a flash-lamp-pumped passively Q-switched Nd:GdVO4 laser at 1.34 μm has been realized. Both a-cut and c-cut Nd:GdVO4 crystals are used. The output single-pulse energy and the pulse width versus the pump energy for different initial transmissions of V3+:YAG saturable absorbers are measured. The experimental results show that, c-cut Nd:GdVO4 laser can generate the shorter pulse width and higher energy in comparison to a-cut one.
TL;DR: A survey of results on use of semiconductor-doped glass saturable absorbers for near-infrared passively mode-locked and Q-switched solid-state lasers is presented in this article.
Abstract: A survey of results on use of semiconductor-doped glass saturable absorbers for near-infrared passively mode-locked and Q-switched solid-state lasers is presented. Nanosized semiconductor particles (quantum dots) belong to quantum confined systems where motion of an electron and a hole is defined by the finite size of the nanoparticle. Dependence of the excitonic transition energy on the QDs size provides the possibility to tune the absorption of the glasses embedded with such particles to wavelength of specific light source. IV-VI semiconductor QDs (PbS, PbSe) are of interest for IR application due to their narrow band gap and large exciton Bohr radii. These allow for exciton absorption band at the wavelength through 1–3μm. Nonlinear optical properties of PbS, PbSe, and CuxSe nanoparticles embedded in glass matrices necessary for saturable absorber applications are analyzed. It is shown that these materials can be efficiently used for passive mode locking and Q switching of solid-state lasers based on Nd3+, Yb3+, Cr4+, Tm3+, and Ho3+ ions emitting through 1–2.1μm spectral range.
TL;DR: In this article, the continuous wave (CW) and passive Q-switching performance of a high-power diode-pumped Nd:GGG laser was reported, achieving a CW output power of 7.20 W under an absorbed pump power of 14.97 W, which gives a slop efficiency of 52.7%.
Abstract: We report on the continuous wave (CW) and passive Q-switching performance of a high-power diode-pumped Nd:GGG laser. A CW output power of 7.20 W was obtained under an absorbed pump power of 14.97 W, which gives a slop efficiency of 52.7%. With a Cr4+ doped yttrium aluminum garnet crystal as the saturable absorber, the shortest passively Q-switched pulse width, largest pulse energy, and highest peak power achieved were 7.7 ns, 126.25 μJ, and 15.5 kW, respectively.
TL;DR: The 20 ns pulses are the shortest Q-switched pulses from a fiber laser operating beyond 1850 nm and were produced at a repetition rate of 57 kHz and pulse energy of 15 microJ using a short-length cavity.
Abstract: We demonstrate a compact core-pumped 2 microm Tm(3+), Ho(3+)- doped all-fiber laser passively Q-switched with an antimony-based saturable absorber. The 20 ns pulses are the shortest Q-switched pulses from a fiber laser operating beyond 1850 nm and were produced at a repetition rate of 57 kHz and pulse energy of 15 microJ using a short-length (4 ns) cavity. The large absorber modulation depth of approximately 70% together with transient gain compression is shown to provide an efficient mechanism for Q-switched pulse shortening.
TL;DR: In this paper, a diode-pumped passively Q-switched and mode-locked Nd:GdVO(4)/V(3+):YAG laser at 1.34 microm is realized.
Abstract: Using V:YAG as the saturable absorber, a diode-pumped passively Q-switched and mode-locked Nd:GdVO(4) laser at 1.34 microm is realized. Nearly 100% modulation depth of mode-locking has been achieved. The width of the mode-locked pulse is estimated to be less than 460 ps with 125 MHz repetition rate within an about 1 micros-long Q-switched pulse envelope. A maximum output power of 220 mW and Q-switched pulse energy of 10.5 microJ is obtained. Using the hyperbolic secant function methods, a fluctuation rate equation model considering the Gaussian distribution of the intracavity photon density and the population inversion in the gain medium as well as the ground-state population intensity of the saturable absorber has been proposed to describe the mode-locking process of diode-pumped Nd:GdVO(4)/V(3+):YAG laser. With the space-dependent rate equations solved numerically, the theoretical calculations reproduce the laser characteristics well.
TL;DR: A soliton fiber laser based on an anomalously dispersive erbium-doped fiber butt-coupled to a saturable absorber mirror for passive mode locking is demonstrated.
Abstract: We demonstrate a soliton fiber laser based on an anomalously dispersive erbium-doped fiber butt-coupled to a saturable absorber mirror for passive mode locking. The laser generates 180 fs pulses at a repetition rate of 491 MHz and exhibits a timing jitter as low as 20 fs over the frequency range 1 kHz-10 MHz.
TL;DR: A high-performance AlGaInAs quantum-well saturable absorber is developed for passively Q-switched Er-Yb double-clad fiber lasers at 1560 nm with maximum peak power greater than 500 W.
Abstract: A high-performance AlGaInAs quantum-well saturable absorber is developed for passively Q-switched Er-Yb double-clad fiber lasers at 1560 nm. With an incident pump power of 13.5 W, an average output power of 1.26 W with a pulse repetition rate of 12 kHz is obtained. The maximum peak power is greater than 500 W.
TL;DR: In this paper, a Q-switching operation was performed by self-Qswitching of a mode-locked oscillator with appropriate cavity design, pump power and output coupling and the total energy of the pulses within the Q-switch envelope was 42 μJ.
Abstract: This paper reports on a passively mode-locked and Q-switched Nd:YVO4 laser generating picosecond pulses with an average output power exceeding 7 W. In a first step Q-switch mode-locking was obtained by self Q-switching of a mode-locked oscillator with appropriate cavity design, pump power and output coupling. In a second system the Q-switching was actively controlled and stabilized by modulating the resonator internal losses with an acousto-optic modulator. In the Q-switch mode-locking operation the laser provided 12.8 ps long mode-locked pulses with a repetition rate of 80 MHz. The repetition rate of the Q-switch envelope was 185 kHz. The maximum pulse energy of a single ps pulse was 0.55 μJ which is 5.5 times the pulse energy measured for cw mode locking. The total energy of the pulses within the Q-switch envelope was 42 μJ.
TL;DR: The primary excited state absorption processes relating to the I65→I75 3μm laser transition in singly Ho3+-doped fluoride glass have been investigated in detail using time-resolved fluorescence spectroscopy as mentioned in this paper.
Abstract: The primary excited state absorption processes relating to the I65→I75 3μm laser transition in singly Ho3+-doped fluoride glass have been investigated in detail using time-resolved fluorescence spectroscopy. Selective laser excitation of the I65 and I75 energy levels established the occurrence of two excited state absorption transitions from these energy levels that compete with previously described energy transfer upconversion processes. The I75→I45 excited state absorption transition has peak cross sections at 1216nm (σesa=2.8×10−21cm2), 1174nm (σesa=1×10−21cm2), and 1134nm (σesa=7.4×10−22cm2) which have a strong overlap with the I85→I65 ground state absorption. On the other hand, it was established that the excited state absorption transition I65→S25 had a weak overlap with ground state absorption. Using numerical solution of the rate equations, we show that Ho3+-doped fluoride fiber lasers employing pumping at 1100nm rely on excited state absorption from the lowest excited state of Ho3+ to maintain a population inversion and that energy transfer upconversion processes compete detrimentally with the excited state absorption processes in concentrated Ho3+-doped fluoride glass.
TL;DR: Transform-limited pulses as short as 290 fs at 1036 nm are generated by a diode-pumped semiconductor disk laser that employs a graded-gap-barrier design in the gain section.
Abstract: Transform-limited pulses as short as 290 fs at 1036 nm are generated by a diode-pumped semiconductor disk laser. The all-semiconductor laser employs a graded-gap-barrier design in the gain section. A fast saturable absorber mirror serves as a passive mode-locker. No further elements for internal or external dispersion control are required.