Showing papers on "Saturable absorption published in 2005"
TL;DR: In this paper, a model describing passive mode locking, a set of differential equations with time delay, was derived and analyzed in a parameter range typical of semiconductor lasers and the limit of a slow saturable absorber was analyzed analytically.
Abstract: We derive and study a model describing passive mode locking---a set of differential equations with time delay. Unlike classical mode locking models based on the Haus master equation, this model does not assume small gain and loss per cavity round trip. Therefore, it is valid in a parameter range typical of semiconductor lasers. The limit of a slow saturable absorber is analyzed analytically. Bifurcations responsible for the appearance and breakup of the mode locking regime are studied numerically.
284 citations
TL;DR: The optical nonlinear absorption of the aqueous solution of platinum nanospheres protected by poly (N -vinyl-2-pyrrolidone) was investigated using open aperture Z-scan method with nanosecond pulse laser at the wavelength of 532 nm.
242 citations
TL;DR: In this article, the authors demonstrate passive mode locking of solid-state lasers by saturable absorbers based on carbon nanotubes (CNTs), which are fabricated by spin-coating a polymer doped with CNTs onto commercial dielectric laser-mirrors.
Abstract: We demonstrate passive mode locking of solid-state lasers by saturable absorbers based on carbon nanotubes (CNT). These novel absorbers are fabricated by spin-coating a polymer doped with CNTs onto commercial dielectric laser-mirrors. We obtain broadband artificial saturable absorber mirrors with ultrafast recovery times without the use of epitaxial growth techniques and the well-established spin-coating process allows the fabrication of devices based on a large variety of substrate materials. First results on passive mode locking of Nd:glass and Er/Yb:glass lasers are discussed. In the case of Er/Yb:glass we report the to our knowledge shortest pulse generated in a self-starting configuration based on Er/Yb:bulk-glass: 68 fs (45 fs Fourier-limit) at 1570 nm wavelength at a pulse-repetition rate of 85 MHz.
205 citations
TL;DR: In this article, the authors presented two novel semiconductor saturable absorber mirror (SESAM) designs which can exhibit more than ten times lower saturation fluence than classical SESAM devices.
Abstract: We present two novel semiconductor saturable absorber mirror (SESAM) designs which can exhibit more than ten times lower saturation fluence than classical SESAM devices. Design considerations and characterization data are presented. These devices are particularly suited for passively mode-locked lasers with ultra-high repetition rates.
138 citations
TL;DR: The generation of self-similar pulses from an self-starting saturable absorber mirror (SAM) based environmentally stable fiber laser comprising only polarization maintaining (PM) fibers is reported.
Abstract: We report on the generation of self-similar pulses from an self-starting saturable absorber mirror (SAM) based environmentally stable fiber laser comprising only polarization maintaining (PM) fibers. Pulse energies of 1 nJ at a repetition rate of 17 MHz were obtained, which could be externally compressed to an autocorrelation width of 280 fs.
120 citations
TL;DR: In this paper, the authors show that the measured rollover is consistent with two-photon absorption only for short (femtosecond) pulses, while a stronger (yet unidentified) kind of nonlinear absorption is dominant for longer (picosecond), and discuss strategies to enhance or reduce this induced absorption.
Abstract: The reflectivity of a semiconductor saturable absorber mirror (SESAM) is generally expected to increase with increasing pulse energy. However, for higher pulse energies the reflectivity can decrease again; we call this a ‘roll-over’ of the nonlinear reflectivity curve caused by inverse saturable absorption. We show for several SESAMs that the measured roll-over is consistent with two-photon absorption only for short (femtosecond) pulses, while a stronger (yet unidentified) kind of nonlinear absorption is dominant for longer (picosecond) pulses. These inverse saturable absorption effects have important technological consequences, e.g. for the Q-switching dynamics of passively mode-locked lasers. A simple equation using only measurable SESAM parameters and including inverse saturable absorption is derived for the Q-switched mode-locking threshold. We present various data and discuss the sometimes detrimental effects of this roll-over for femtosecond high repetition rate lasers, as well as the potentially very useful consequences for passively mode-locked multi-GHz lasers. We also discuss strategies to enhance or reduce this induced absorption by using different SESAM designs or semiconductor materials.
115 citations
Abstract: We fabricated single-wall carbon nanotube (SWNT)/poly(vinylalcohol) (PVA) nanocomposite freestanding films and examined their application in devices in which the saturable absorption of SWNTs at near-infrared optical telecommunication wavelengths can be utilized. In a passively mode-locked fiber laser, we integrated a 30-µm-thick SWNT/PVA film into a fiber connection adaptor with the film sandwiched by a pair of fiber ferrules. A ring fiber laser with a SWNT/PVA saturable absorber was operated very easily in the mode-locked short-pulse mode with a pulse width of about 500 fs. Reproducible stable device performance was confirmed. In examining noise suppression for optical amplifiers, mixed light of semiconductor amplified spontaneous emission (ASE) source and 370 fs laser pulses was passed through a 100-µm-thick SWNT/PVA film. The transmission loss of the femtosecond pulse light was smaller than that of the ASE light. This proved that the SWNT/PVA film has the ability to suppress ASE noise.
98 citations
TL;DR: In this paper, a broad-area vertical cavity surface emitting laser (VCSEL) with a saturable absorber was studied and the presence of cavity solitons was shown numerically.
Abstract: We study theoretically a broad-area vertical cavity surface emitting laser (VCSEL) with a saturable absorber. We show numerically the presence of cavity solitons in the system: they exist as solitary structures formed through a modulationally unstable homogeneous lasing state that coexists with a background with zero intensity. Such a peculiar scenario endows the solitons with unique properties compared to cavity solitons in most previously studied optical systems. In particular, these solitons do not as such rely on a proper phase of the addressing pulses to be either created or deleted. We show that exciting and deleting the solitons depend crucially on whether a threshold in the soliton peak has been reached.
88 citations
TL;DR: In this paper, the authors demonstrate passive mode-locking of a short-cavity fiber Fabry-Pe/spl acute/rot laser by incorporating a carbon-nanotube-based saturable absorber.
Abstract: We demonstrate passive mode-locking of a short-cavity (/spl sim/2 cm) fiber Fabry-Pe/spl acute/rot laser by incorporating a carbon-nanotube-based saturable absorber. Stable pulses are generated with a pulsewidth as short as 0.68 ps at a repetition rate as high as 5.18 GHz. This is the smallest femtosecond fiber pulsed laser ever demonstrated to date.
84 citations
TL;DR: In this article, the authors report on the generation and measurement of a > 108 contrast ratio between main pulse and amplified spontaneous emission (ASE) from a relativistic kHz chirped-pulse amplified laser.
Abstract: We report on the generation and measurement of a > 108 contrast ratio between main pulse and amplified spontaneous emission (ASE) from a relativistic kHz chirped-pulse amplified laser. We have enhanced the ASE contrast ratio as much as > 400 times by employing a pulse cleaner composed of a μJ preamplifier and a saturable absorber. A third-order cross-correlator with a dynamic range of > 109 and a scanning range of up to 4 ns has been developed for the contrast measurement. Detailed analysis of the cross-correlation trace shows that the random noise of spectral phase generates 20-ps pedestal structure starting from 10−6 level of the main pulse.
83 citations
TL;DR: In this article, the authors performed absorption measurements and generated absorption cross sections as a function of wavelength for the laser material YAG doped with ytterbium at 300, 175, and 75 K.
Abstract: We have performed absorption measurements and generated absorption cross sections as a function of wavelength for the laser material YAG doped with ytterbium at 300, 175, and 75 K. This data was generated to enable a direct comparison of the absorption intensity and linewidths at room and cryogenic temperatures, and in particular near the temperature of liquid nitrogen at 77 K. The data have been used to compute universal absorption contour plots that display absorption as a function of the incident light center wavelength and optical thickness (doping density times penetration depth) for a number of bandwidths, and assuming that the spectrum of the incident light can be described as a Gaussian. Curves are presented for both 300 and 75 K, and may be used to optimize the absorption and laser efficiency.
TL;DR: In this article, self-pulsation at 45 GHz repetition frequency has been demonstrated in 1.5µm single-section quantum dot Fabry-Perot semiconductor lasers without saturable absorber.
Abstract: Self-pulsation at 45 GHz repetition frequency has been demonstrated in 1.5 µm monolithic single-section quantum dot Fabry-Perot semiconductor lasers without saturable absorber. The mode-beating exhibits a narrow linewidth below 100 kHz, demonstrating high phase correlation between these modes. Such modelocked lasers open ways to low timing-jitter components for clock recovery or millimetre-wave generation in wireless transmission applications.
TL;DR: Efficient cw and passively Q-switched operation with self-stimulated Raman scattering conversion was demonstrated in a compact diode-pumped Yb:KLu(WO4)2 laser.
Abstract: Efficient cw and passively Q-switched operation with self-stimulated Raman scattering conversion was demonstrated in a compact diode-pumped Yb:KLu(WO4)2 laser. A cw output power of 3.28?W was obtained with an optical efficiency of 48.2% and a slope efficiency of 78.2% with respect to the incident pump power. Stable Q-switched operation was achieved with a Cr4+:YAG saturable absorber, generating 32.4??J fundamental pulses with a duration of 1.41?ns at 1030.6?nm and 14.4??J Raman pulses with a duration of 0.71?ns at 1137.6?nm. At an incident pump power of 7.0?W, the average output power reached 0.9 and 0.4?W for fundamental and Raman radiation, with slope efficiencies of 32.1% and 14.1%, respectively.
TL;DR: In this article, single-wall carbon nanotubes (SWNTs) were dispersed in polyvinyl alcohol (PVA) film mostly with nanoscale uniformity and mechanically stretched it.
TL;DR: In this paper, a Q-switched microchip laser emitting radiation at wavelength 1338 nm was designed and constructed based on a monolith crystal which combines in one piece a cooling undoped part (undoped YAG crystal), an active laser part (Nd3+:YAG, T0=85%), and a saturable absorber.
Abstract: Q-switched microchip laser emitting radiation at wavelength 1338 nm was designed and constructed. This laser was based on a monolith crystal which combines in one piece a cooling undoped part (undoped YAG crystal), an active laser part (Nd3+:YAG), and a saturable absorber (V3+:YAG, T0=85%). The microchip resonator consists of dielectric mirrors directly deposited on the monolith surfaces. The output coupler with reflection 90% was placed on the V3+-doped part. Q-switched microchip laser was tested under pulsed, and CW diode pumping. The pulse length was the same for all regimes and it equals to 6.2 ns. The wavelength of linearly polarized laser emission was 1338 nm. For pulsed pumping the output pulse energy was stable up to mean pump power 1 W and it was equal to 131 μJ, which corresponds to peak power 21 kW. In CW regime for pumping up to 14 W the pulse energy was 37 μJ.
TL;DR: In this article, the authors demonstrate a novel passively mode-locked fiber laser operating at 1300 nm using purified single-walled carbon nanotubes (CNTs) as a saturable absorber.
Abstract: For the first time, we demonstrate a novel passively mode-locked fiber laser operating at 1300 nm using purified single-walled carbon nanotubes (CNTs) as a saturable absorber. The saturable absorber incorporates diameter-controlled CNTs with peak absorption /spl sim/1300 nm, guaranteeing mode-locking over the same wavelength region. The ring laser uses praseodymium-doped fiber as a gain medium. The pulse repetition rate is 3.18 MHz, and the spectral half-width is 0.15 nm. Dual-wavelength mode-locking is also demonstrated with a channel spacing of 1.1 nm.
TL;DR: The nonlinear optical transmission of the axially substituted tetrapyrazinotetraazaporphyrinato complex Pyz(4)TAPInCl and the excited states involved in the nonlinear absorption have been determined at the frequency of the second harmonic generation of a Nd:YAG laser in the nanosecond time regime.
Abstract: The multiphoton absorption properties of the axially substituted tetrapyrazinotetraazaporphyrinato complex Pyz4TAPInCl (1) are reported and interpreted. In particular, the nonlinear optical transmi...
TL;DR: In this paper, the authors developed a novel description of electrically driven vertical-external-cavity surface-emitting semiconductor lasers (VECSELs) mode-locked by saturable absorber mirrors.
Abstract: We develop a novel description of electrically driven vertical-external-cavity surface-emitting semiconductor lasers (VECSELs) mode-locked by saturable absorber mirrors. Our approach is based on an analytical solution of the bidirectional traveling-wave equations for fundamental transverse mode operation. The resulting time-domain equations describe the evolution of the electric fields and carrier-densities at the quantum-well layers of the emitter and absorber structures which are coupled through delayed boundary conditions. For the design considered, we obtain stable mode-locked pulses of few tens of picoseconds at 15-GHz repetition rate in agreement with recently reported experimental results.
TL;DR: In this paper, the authors demonstrate the bistability and mode switching of a photonic molecule consisting of twin microdisks with an effective pump power of <100μW and showed that the operation was based on saturable absorption and gain switching, which depended on the nonuniformity, disk diameter detuning and Q factors of coupled modes.
Abstract: We demonstrate the bistable lasing in a photonic molecule consisting of twin microdisks. When the photonic molecule was nonuniformly photopumped, the bistability and/or mode switching were observed with an effective pump power of <100μW. The rate equation analysis indicated that the operation was based on saturable absorption and gain switching, which depended on the nonuniformity, disk diameter detuning, and Q factors of coupled modes. Such a bistable laser, particularly showing the mode switching, will be applied for ultrasmall high-speed optical memories, flip-flops, and so on.
TL;DR: In this paper, the authors reported the efficient continuous-wave (CW) and Q-switched laser operation of a diode-pumped Yb:YVO4 laser.
Abstract: We report the efficient continuous-wave (CW) and Q-switched laser operation of a diode-pumped Yb:YVO4 laser. A CW output power of 1 W with a slope efficiency of 59% with respect to absorbed pump power was demonstrated. Passively Q-switched with a Cr4+:YAG saturable absorber, a Yb:YVO4 laser with Raman conversion was demonstrated. Q-switched 18.7-μ J pulses with a pulse duration of 17 ns and a peak power up to 1 kW were obtained at 1018-nm fundamental wavelength and 3.6-μ J pulses with a pulse duration of 6 ns and a peak power of about 0.6 kW were obtained at 1119.5-nm first-Stokes wavelength.
TL;DR: In this article, a single-pass configuration of Raman crystal was investigated for frequency down-shift in a Nd:YAG mode-locked laser system, and the maximum energy and conversion efficiency were 1.6 mJ and 25%, respectively.
Abstract: Stimulated Raman scattering process in Nd:SrWO4 crystal was employed to frequency down-shift the fundamental frequency of a Nd:YAG mode-locked laser system. A single-pass configuration of Raman crystal was investigated for this purpose. After that Nd:SrWO4 laser was built and coherent pumping by alexandrite laser radiation was used. The simultaneous generation of stimulated Raman scattering was proofed for the case of Q-switching and mode-locking of Nd:SrWO4 Raman cavity. For Nd:YAG 50 ps long (1064 nm) pulsed pumping a single-pass first Stokes maximum energy and conversion efficiency were 1.6 mJ and 25% , respectively. With the free-running Nd:SrWO4 laser the maximum energy of 90 mJ at wavelength 1057 nm was obtained. Q-switching with the LiF:F-2 saturable absorber gave up to 1.3 mJ energy at the first Stokes frequency (1170 nm) in the pulse length of 3 ns. In mode-locking regime (with saturable absorber ML51 in dichlorethan or 3955 in ethanol), the total generated energy was 1.8 mJ and 2.4 mJ for ML51 and 3955 dyes, respectively. The SRS output at 1170 nm was approximately 20% of those values.
TL;DR: The absorption spectra of the 0.5 at.% and 1at.% Co:LMA crystals show that the Co: LMA crystals have two absorption bands, and the absorption band located at 1030-1660 nm can be used for a passive saturable absorber Q switch of 1.3-1.6mum laser.
Abstract: The absorption spectra of the 0.5at.% and 1at.% Co: LaMgAl11O19 (LaMg1-xCoxAl11O19, x=0.005 and 0.01, abbreviated as Co:LMA) crystals were measured at room temperature, and the results show that the Co: LMA crystals have two absorption bands, and the absorption band located at 1030–1660 nm can be used for a passive saturable absorber Q switch of 1.3–1.6µm laser. The passive pulsed laser output of LD-end-pumped Nd:GdVO4 1.34µm laser was demonstrated for the first time by using the 0.5 at.% Co:LMA crystal as a saturable absorber Q switch. The maximum average output power of 500 mW was obtained under the pumping power of 25 W. The shortest pulse width, the largest pulse energy and the highest peak power were obtained to be 160 ns, 25.5µJ and 150 W, respectively.
TL;DR: It is found that both effects of saturable absorption and reverse saturation absorption are obtained with a solution of subphthalocyanine at 532 nm depending on the intensity of 9 ns laser pulses.
TL;DR: In this article, a single-clad Tm-silica fiber laser operating at 1.9μm is demonstrated using a Cr 2+ :ZnSe saturable absorber crystal.
TL;DR: With a Nd:YAG laser setup, well controlled and extremely stable Q-switched operation in the degenerate Laguerre-Gaussian TEM04, TEM14, T EM24, Tem34, and TEM44 modes was obtained.
Abstract: An intra-cavity phase element, combined with a passive Q-switch saturable absorber and a suitable intra-cavity aperture, can provide extremely high mode discrimination, so as to obtain laser operation with single, pure, very high order Laguerre-Gaussian mode. With a Nd:YAG laser setup, well controlled and extremely stable Q-switched operation in the degenerate Laguerre-Gaussian TEM04, TEM14, TEM24, TEM34, and TEM44 modes was obtained. The measured output energy per pulse for each of these modes was 5.2mJ, 7.5mJ, 10mJ, 12.5mJ, and 13.7mJ respectively, compared to 2.5mJ for the Gaussian mode without the phase element (more than a five fold increase in output energy). Correcting the phase for these modes, so that all transverse lobes have uniform phase, results in a very bright and narrow central lobe in the far field intensity distribution that can theoretically contain more than 90% of the output energy.
TL;DR: In this paper, a continuously pumped, passively Q-switched, 1617 nm Er:yttrium-aluminum-garnet (YAG) laser oscillator with a pulse width of just under 7 ns, a pulse repetition frequency of about 4 kHz, and an output power of 0.9 W was demonstrated.
Abstract: We have demonstrated a continuously pumped, passively Q-switched, 1617 nm Er:yttrium-aluminum-garnet (YAG) laser oscillator with a pulse width of just under 7 ns, a pulse repetition frequency of about 4 kHz, and an output power of 0.9 W. The oscillator was pumped using an Er:fiber laser at 1534 nm, and Q switched using a Cr2+:ZnSe saturable absorber. The Er:YAG laser is useful either stand-alone, or as the master oscillator in a master-oscillator-power-amplifier architecture.
TL;DR: In this article, the role of the laser pulsewidth in effecting the nonlinear optical transmission in noble metal clusters excited near the surface plasmon resonance was investigated, and it was shown that thermal effects contribute to nonlinearity in the picosecond excitation domain.
TL;DR: A rate equation model is introduced to theoretically analyze the results obtained in the experiment, in which the spatial distributions of the intracavity photon density, the pump beam and the population-inversion density are taken into account.
Abstract: Using both acoustic-optic (AO) Q-switcher and GaAs saturable absorber, a diode-pumped doubly Q-switched Nd:YVO4/KTP green laser is realized for the first time to our knowledge This laser can generate a symmetric and shorter pulse when compared with purely AO and passive Qswitching A rate equation model is introduced to theoretically analyze the results obtained in the experiment, in which the spatial distributions of the intracavity photon density, the pump beam and the population-inversion density are taken into account The numerical solutions of the rate equations are in good agreement with the experimental results
01 Jan 2005
TL;DR: In this paper, the authors show that the measured rollover is consistent with two-photon absorption only for short (femtosecond) pulses, while a stronger (yet unidentified) kind of nonlinear absorption is dominant for longer (picosec-ond) pulses.
Abstract: The reflectivity of a semiconductor saturable ab- sorber mirror (SESAM) is generally expected to increase with increasing pulse energy. However, for higher pulse energies the reflectivity can decrease again; we call this a 'roll-over' of the nonlinear reflectivity curve caused by inverse saturable absorption. We show for several SESAMs that the measured roll-over is consistent with two-photon absorption only for short (femtosecond) pulses, while a stronger (yet unidentified) kind of nonlinear absorption is dominant for longer (picosec- ond) pulses. These inverse saturable absorption effects have important technological consequences, e.g. for the Q-switching dynamics of passively mode-locked lasers. A simple equation using only measurable SESAM parameters and including in- verse saturable absorption is derived for the Q-switched mode- locking threshold. We present various data and discuss the sometimes detrimental effects of this roll-over for femtosecond high repetition rate lasers, as well as the potentially very use- ful consequences for passively mode-locked multi-GHz lasers. We also discuss strategies to enhance or reduce this induced ab- sorption by using different SESAM designs or semiconductor materials.
TL;DR: In this paper, the authors modified the multimode rate equations by including the spatial hole-burning effect in the active medium and the nonlinear absorption of the saturable absorber, and the numerical simulations of the mode-competition dynamics of two-mode laser are in good agreement with the experimental data.
Abstract: Stable single-longitudinal-mode laser pulses and instability of two-longitudinal-mode oscillation due to the spatial hole-burning effect were observed experimentally in a laser-diode pumped microchip Cr4+,Nd3+:Y3Al5O12 self-Q-switched laser. We modified the multimode rate equations by including the spatial hole-burning effect in the active medium and the nonlinear absorption of the saturable absorber. The numerical simulations of the mode-competition dynamics of two-mode laser are in good agreement with the experimental data. Instability induced by the mode-competition dynamics was investigated by the evolution of the inversion population and the bleaching and recovery of the inversion population of the saturable absorber.