Showing papers on "Saturable absorption published in 1991"
TL;DR: In this paper, the theory of additive pulse mode locking (APM) was developed in closed form under a linearization approximation, and the pulse parameters were determined in terms of the gain, the gain dispersion, the group-velocity dispersion and the self-phase modulation.
Abstract: The theory of additive pulse mode locking (APM) is developed in closed form under a linearization approximation. The pulse parameters are determined in terms of the gain, the gain dispersion, the group-velocity dispersion, and the self-phase modulation. Stability regimes are established. Various possible configurations of laser systems that can produce APM are presented. Some of them permit single-cavity realizations that may not require interferometric length stabilization circuits. In general, the results are applicable to a wide range of fast saturable absorber mode-locked systems.
534 citations
TL;DR: In this paper, the propagation of solitons in materials with saturable nonlinearity has been investigated with numerical and analytical methods, and it is demonstrated that bistable (or two-state) solITons exist that describe pulses with the same duration but different peak powers.
Abstract: The propagation of solitons in materials with saturable nonlinearity has been investigated with numerical and analytical methods. It is demonstrated that bistable (or two-state) solitons exist that describe pulses with the same duration but different peak powers. It is proved that both solution branches are stable. The minimum possible pulse duration of a fundamental soliton depending on the saturation parameter has been predicted. The influence of loss and the evolution of high-order solitons are studied.
195 citations
TL;DR: The generation of bandwidth-limited shoulder-free 125-fsec pulses by additive-pulse-compression mode locking of a neodymium glass laser is described, allowing stable pulse generation under the condition of large pulse shaping in the cavity.
Abstract: The generation of bandwidth-limited shoulder-free 125-fsec pulses by additive-pulse-compression mode locking of a neodymium glass laser is described. An all-fiber nonlinear amplifying loop mirror is employed as a fast saturable absorber and permits stable pulse generation under the condition of large pulse shaping in the cavity.
111 citations
TL;DR: In this paper, a two-contact InGaAsP semiconductor self-pulsating laser diode was used for all-optical clock extraction from 5 Gb/s RZ data.
Abstract: All-optical clock extraction from 5 Gb/s RZ data is demonstrated using a two-contact InGaAsP semiconductor self-pulsating laser diode. The saturable absorber region of the device was doped with zinc ions to reduce the carrier lifetime in this region such that strong self pulsations at frequencies up to 5.2 GHz were obtained. Injection of a 10- mu W optical data signal at a wavelength close to one of the Fabry-Perot wavelengths was sufficient to synchronize the self pulsations to the incoming data stream. The measured 3-dB RF electrical bandwidth of the synchronized optical clock signal was 10 Hz, approximately the same as that of the electrical transmitter clock. Initial bit-error-rate measurements for 2/sup 7/-1 5 Gb/s data result in a 0.5-dB receiver sensitivity penalty when using the optical clock signal compared to the transmitter clock. >
84 citations
TL;DR: In this article, Er-doped fiber laser pulses at 1557 nm were produced by passively mode locking an InGaAs/GaAs-on-GaAs superlattice as a fast saturable absorber.
Abstract: 1.2 ps transform-limited pulses at 1557 nm have been produced by passively mode locking an Er-doped fibre laser. An InGaAs/GaAs-on-GaAs superlattice was used as a fast saturable absorber. The all-fibre laser is designed to be in a ring configuration. The low pump power requirement allowed pumping by a semiconductor laser diode.
74 citations
TL;DR: The pedestal associated with a chirped-pulse-amplification (CPA) laser is studied in this article, where four components have been identified that contribute to the pedestal.
Abstract: The pedestal (prepulse and postpulse) associated with a chirped-pulse-amplification (CPA) laser is studied. Four components have been identified that contribute to the pedestal. Pulses are spectrally shaped by gain narrowing in a frequency-matched, regenerative amplifier, while self-phase modulation is avoided. The intensity contrast is further improved through the use of a saturable absorber, resulting in Gaussian pulses of ~0.9-ps duration with an intensity contrast exceeding 105:1. Both experimental and numerical descriptions of these processes are presented. This investigation makes possible the study of high-intensity ultrashort laser–plasma interactions with a fiber–grating CPA system.
66 citations
TL;DR: In this article, the propagation of ultrashort light pulses in fibers with saturable nonlinearity and positive group-velocity dispersion was investigated using a variational approach, frequency chirp and the other main characteristics of pulse evolution were studied.
Abstract: The propagation of ultrashort light pulses in fibers with saturable nonlinearity and positive group-velocity dispersion has been investigated. Using a variational approach, frequency chirp and the other main characteristics of pulse evolution are studied. The minimum duration of the output-pulse of a fiber-grating compressor is calculated.
65 citations
TL;DR: An analysis of passive mode locking with the intracavity self-focusing effect is presented, and the self-starting issue is addressed and the initial pulse-shortening force of this mechanism is too weak to start the mode locking from mode beating or noise.
Abstract: An analysis of passive mode locking with the intracavity self-focusing effect is presented, and the self-starting issue is addressed. The analysis shows that the initial pulse-shortening force of this mechanism is too weak to start the mode locking from mode beating or noise and how it can be greatly enhanced with a dilute dye saturable absorber in the cavity. This analysis also shows how the pulse-width evolution is related to the pulse-shortening force in cw mode-locking lasers.
59 citations
TL;DR: In this article, the authors examined the effect of self-pulsation on ultra-high-frequency mode locking, and concluded that lasers with high reflectivity coatings can most reliably achieve mode locking without being adversely affected by self pulsation.
Abstract: The inclusion of an intracavity saturable absorber for ultrahigh‐frequency passive mode locking of semiconductor lasers also produces intensity self‐pulsation in many instances. We examined experimentally and theoretically the deleterious effect of self‐pulsation on ultrahigh‐frequency mode locking, and arrived at the conclusion that lasers with high reflectivity coatings can most reliably achieve mode locking without being adversely affected by self‐pulsation.
57 citations
TL;DR: In this article, the output coupling and the coupling of the external nonlinear cavity along the gain medium of the main cavity were derived for a pulse envelope propagating through a coupled-cavity laser.
Abstract: By distributing the output coupling and the coupling of the external nonlinear cavity along the gain medium of the main cavity, I derive a nonlinear differential equation for a pulse envelope propagating through a coupled-cavity laser. For a phase-mismatch angle of π/2 between the two cavities, a stable hyperbolic-secant short pulse is a solution of the differential equation for negative dispersion (of the soliton into the fiber) as well as for positive dispersion of the nonlinear external medium. The width of the predicted pulse is a function of the coupling factor and the intensity traveling through the optical fiber. The operation of the coupled-cavity laser for this stable regime is shown to be completely similar to passive mode locking by a fast saturable absorber.
53 citations
TL;DR: In this paper, the authors measured the 355-nm transient absorption of polyimide thin films following excitation with subablative, 24-ps long, 355nm laser pulses, and fitted a three-level rate equation model incorporating the temperature dependence of the ground state absorption coefficient.
Abstract: The 355-nm transient absorption of polyimide thin films has been measured following excitation withsubablative, 24-ps long, 355-nm laser pulses. The 355-nm absorption increases by 25% following 355-nm, 20 mJ/cm2 excitation and recovers with a fast time constant ≈34 ps, and a slow time constant which is much longer than 6 ns. The data are fitted by a three-level rate equation model incorporating the temperature dependence of the ground state absorption coefficient. The fast component is attributed to the decay ofS
1 and the slow component results from increased ground state absorption caused by a laser-induced temperature rise. The nonlinear intensity dependence is attributed to excited state (S
1) absorption. These results indicate the importance of considering the dynamic absorption in modelling ablation.
TL;DR: In this paper, checks of homoclinic chaos made with nonlinear analysis techniques have been performed on the signals coming from a CO2 laser containing CH3I as a saturable absorber.
Abstract: Checks of homoclinic chaos made with nonlinear analysis techniques have been performed on the signals coming from a CO2 laser containing CH3I as a saturable absorber. The one-dimensional return maps of the regimes appearing inside the alternating periodic chaotic sequence are typical of homoclinic chaos. Numerical simulations give results in good agreement with the experimental observations. In the case of a fast absorber, a homoclinic tangency to a cycle created in a suberitical Hopf bifurcation is seen to be responsible for the homo-clinic behavior observed in the model.
TL;DR: Trapping powers of trapped light in a saturable nonlinear medium can depend sensitively on the effective propagation constant of the trapped modes and the maximum allowed intensity-induced refractive-index change.
Abstract: Light trapping in homogeneous media with saturable nonlinearity is examined. Trapping of light is found to be possible in any saturable nonlinear material so long as its maximum allowed refractive-index change is positive. However, quite different from Kerr nonlinearity, trapping powers of trapped light in a saturable nonlinear medium can depend sensitively on the effective propagation constant of the trapped modes and the maximum allowed intensity-induced refractive-index change.
TL;DR: A new nonlinear intracavity device called a microdot mirror mode locker is demonstrated for ultrashort-pulse generation in solid-state lasers and produces fast saturable absorber action by using self-focusing.
Abstract: A new nonlinear intracavity device called a microdot mirror mode locker is demonstrated for ultrashort-pulse generation in solid-state lasers. The microdot mirror produces fast saturable absorber action by using self-focusing. Pulse durations of 190 fs are achieved in a Ti:Al2O3 laser. The microdot mirror mode locker is modular, preserves wavelength tunability, and can be extended to a wide range of solid-state lasers.
Patent•
24 Oct 1991
TL;DR: In this paper, a reverse saturable absorber comprising one or a class of organic compounds known as buckminsterfullerene, such as C₆₀, is proposed.
Abstract: Optically sensitive materials (18) such as sensors or the human eye are passively protected against overexposure to high intensity light (20) in the visible region using a reverse saturable absorber (14) comprising one or a class of organic compounds known as buckminsterfullerene, such as C₆₀. As the intensity of incident light increases, the intensity of transmitted light also increases up to a saturation level, but above the saturation level, the transmitted light intensity remains substantially constant even with increasing intensity of incident light. C₆₀ has an unexpectedly low threshold for optical limiting action, is thermally stable, and is easily manufacturable into devices.
01 Jul 1991
TL;DR: In this article, a linear relationship between χ( 3 ) and α is found for thin films of poly(3-decyl-thiophene), poly(p-phenylene vinylene) and Rhodamine 6G.
Abstract: Wavelength dispersed degenerate four wave mixing (DFWM) experiments were performed with thin films of poly(3-decyl-thiophene), poly ( p -phenylene vinylene) and Rhodamine 6G. At the low energy side of the main absorption bands the resonant χ( 3 ) (-ω; ω, ω, -ω) values scale differently with the absorption coefficient α. In Rhodamine 6G, χ( 3 ) is proportional to α 2 due to saturable absorption in a two level system. In the case of polymers with a conjugated one-dimensional π-electron system a linear relationship between χ( 3 ) and α is found. This is attributed to phase-space filling effects by one-dimensional excitons.
TL;DR: In this paper, the saturable absorption dynamics of a femtosecond dye laser was studied theoretically and the Nisomer and P-isomer photoisomerization dynamics were included.
Abstract: The saturable absorption dynamics of DODCI in a femtosecond dye laser is studied theoretically. The N-isomer and P-isomer photoisomerization dynamics is included. The wavelength region between 570 nm and 650 nm is considered where the N-isomer and P-isomer absorption dynamics changes from short-wavelength to long-wavelength s0-s1 excitation. The slow saturable absorber DODCI shortens a circulating pulse in a laser oscillator down to femtosecond duration if the gain medium compensates the absorber losses. Fast local relaxation in the S1 -state in the case of short-wavelength excitation and fast level refilling in the S0 -state in the case of long-wavelength excitation facilitate the pulse shortening and the background signal suppression.
TL;DR: Pump-resonant excitation, in which a weakly absorbing gain medium is placed inside an optical cavity that is resonant at both the pump and laser wavelengths, is shown to reduce significantly the losses due to saturable absorption in a quasi-three-level, diode-pumped laser.
Abstract: Pump-resonant excitation, in which a weakly absorbing gain medium is placed inside an optical cavity that is resonant at both the pump and laser wavelengths, is shown to reduce significantly the losses due to saturable absorption in a quasi-three-level, diode-pumped laser. Initial experiments, in which this technique is applied to the 946-nm Nd:YAG laser, have yielded incident threshold power levels below 1.3 mW and optical slope efficiencies exceeding 25%.
TL;DR: In this paper, general analytic expressions concerning optical stability, mode spot size in the gain and saturable absorber jets, and misalignment sensitivity of femtosecond dye laser resonators are derived by using the one-way ABCD ray matrix technique.
TL;DR: In this paper, a multistripe, single quantum well GaAs laser diode is passively mode-locked without an external cavity, and an intracavity saturable absorber is formed by ion implantation of the diode's facet.
Abstract: A multistripe, single quantum well GaAs laser diode is passively mode locked without an external cavity. The intracavity saturable absorber is formed by ion implantation of the laser diode’s facet. The dose and energy of implanted ions were adjusted to achieve mode locking. This monolithically integrated laser diode and saturable absorber generates 40 GHz optical pulses with a pulse width of 5 ps.
TL;DR: Stable, self-starting operation of a coupled-cavity mode-locked KCl:T1(0)(1) color-center laser has been achieved by incorporating a semiconductor diode optical amplifier into the control cavity by adjusting the amplifier drive current.
Abstract: Stable, self-starting operation of a coupled-cavity mode-locked KCl:T1(0)(1) color-center laser has been achieved by incorporating a semiconductor diode optical amplifier into the control cavity. By adjustment of the amplifier drive current, nonlinearity in the regimes of either saturable gain or saturable absorption has been exploited to generate subpicosecond pulses. Under conditions of saturable gain, pulse durations as short as 280 fs were obtained. Self-starting has also been demonstrated for a coupled-cavity mode-locked NaCl:OH(-) color-center laser by using the same technique.
Journal Article•
TL;DR: In this paper, a detailed review of the theoretical studies of these processes is presented, and current efforts to find RSAs at desired wavelength for testing these theoretical predictions are also discussed.
Abstract: A variety of applications exist for reverse saturable absorbers (RSAs) in the area of optical pulse processing and computing. An RSA can be used as power limiter/pulse smoother and energy limiter/pulse shortner of laser pulses. A combination of RSA and saturable absorber (SA) can be used for mode locking and pulse shaping between high power laser amplifiers in oscillator amplifier chain. Also, an RSA can be used for the construction of a molecular spatial light modulator (SLM) which acts as an input/output device in optical computers. A detailed review of the theoretical studies of these processes is presented. Current efforts to find RSAs at desired wavelength for testing these theoretical predictions are also discussed.
TL;DR: Polarization switching and hysteresis are observed in a semiconductor laser with a two-armed polarization-sensitive external cavity as discussed by the authors, where an intracavity polarization-dependent saturable absorber is placed asymmetrically in one of the two arms of the external cavity so that one polarization mode is saturated more strongly than the other.
Abstract: Polarization switching and hysteresis are observed in a semiconductor laser with a two‐armed polarization‐sensitive external cavity. An intracavity polarization‐dependent saturable absorber is placed asymmetrically in one of the two arms of the external cavity so that one polarization mode is saturated more strongly than the other. The observed phenomena can be explained by the complementary processes of competition in the gain region and the polarization‐dependent saturable loss in the external cavity. This mechanism is potentially useful as the basis of a two‐mode switchable and bistable diode laser for applications as high‐speed optical memories and logic gates.
TL;DR: In this paper, voltage, temperature, and intensity dependence of saturable absorption in InGaAs/InP multiple quantum wells are investigated and related to the lasing characteristics of intracavity loss modulated InGAAs/inP quantum well lasers.
Abstract: Voltage, temperature, and intensity dependence of saturable absorption in InGaAs/InP multiple quantum wells are investigated and related to the lasing characteristics of intracavity loss modulated InGaAs/InP quantum well lasers. Bistability in the static laser light output/absorber voltage characteristic arises from the shape of the measured absorption/voltage/intensity surface of the quantum well absorber. This surface is little changed in the temperature range 0–100 °C. A consequence of this fact is that an intracavity absorber modulates laser threshold more efficiently at higher substrate temperatures.
TL;DR: Good agreement between theory and experiment indicates that the origin of the complicated behavior of a laser with a saturable absorber is a saddle cycle, which is also present in maps of time of flight between planes in phase space.
Abstract: Intensity maps from an experiment on a laser with a saturable absorber, in the case of strong dissipation, are compared with theoretical one-dimensional (1D) maps. These 1D maps are derived in the limit of infinite dissipation, starting from 2D maps for a dissipative saddle cycle with stable and unstable manifolds approaching a quadratic tangency and giving rise to a structurally unstable homoclinic orbit. They are multibranched, each branch corresponding to a particular number of turns around the saddle cycle. The good agreement between theory and experiment indicates that the origin of the complicated behavior of a laser with a saturable absorber is a saddle cycle. A multibranched structure is also present in maps of time of flight between planes in phase space. Depending on the choice of these planes, it is possible to obtain time-of-flight maps that give the same symbolic dynamics of the intensity maps.
TL;DR: In this article, a novel approach to clock extraction for non-return-to-zero (NRZ) formatted data is demonstrated using two contact semiconductor nonlinear optical amplifiers (NLOAs).
Abstract: A novel approach to clock extraction for non-return-to-zero (NRZ) formatted data is demonstrated using two contact semiconductor nonlinear optical amplifiers (NLOAs). The NLOA amplifies the transmitted data (fiber-fiber approximately 5 dB) and due to the absorptive nonlinearity, induced by bleaching a region of saturable absorption within the NLOA, an electrical clock component is generated at the absorber electrical contact. Narrow bandpass electrical filtering of the absorber contact electrical RF spectrum is all that is required in order to extract a stable clock signal. Bit-error-rate measurements at 155.6 Mb/s showed no receiver sensitivity penalty when using the NLOA extracted clock compared to the transmitter clock. Using quantum well material strong clock component generation has been achieved at modulation rates from >
TL;DR: By analyzing the experimental data based on the glassy polymer dye model, it can be confirmed that the nonlinearity is induced by the transition of excited on-site pi electrons.
Abstract: A new kind of organic polymer doped with natural active chlorophyll is made, and self-focusing and saturable absorption are observed on it under the excited laser light at 532 nm with a pulse width of 20 ns. The nonlinear refractive indices n2, estimated to be ~10−7 cm2/W, measured by two methods were consistent with each other. By analyzing the experimental data based on the glassy polymer dye model, it can be confirmed that the nonlinearity is induced by the transition of excited on-site π electrons.
TL;DR: A pharmacokinetic model incorporating saturable rate of absorption of the Michaelis-Menten type is proposed in which a time constraint, Δt, is added to the MM model and is able to summarize the nonlinearity observed in both rate and extent of absorption.
Abstract: A pharmacokinetic model incorporating saturable rate of absorption of the Michaelis-Menten type was recently developed to fit cefatrizine (CFZ) plasma concentrations with time following oral administration of 500-mg capsules to humans. This model (MM) was statistically superior to models incorporating either first-order or zero-order absorption. However, the MM model does not predict the reduction in extent of absorption with dose observedin vivo. In this study, a model is proposed in which a time constraint, Δt, is added to the MM model. This new model (MM-Δt) is tested with data following doses of 250, 500, and 1000 mg of CFZ. When Δt is set to 1.5 hr, the predicted relative changes with dose in bioavailability,F, peak plasma concentration,Cmax, the time at which the peak concentration occurs,tmax, and the mean absorption time,MAT, are generally in good agreement with the experimental data. The time interval of 1.5 hr is compatible with passage by a limited region within the small intestine where drug is absorbed by a facilitated transport mechanism. Influence of each absorption model parameter (Vmax,Km, and Δt) on total area under the concentration versus time curve (AUC),F,Cmax, andtmax, is assessed by simulation. The MM-Δt model is able to summarize the nonlinearity observed in both rate and extent of absorption.
TL;DR: In this paper, a weak CW laser beam was injected into a Q-switched AlGaAs laser diode with a fast saturable absorber to produce powerful single-mode picosecond pulses at 082μm.
Abstract: Injection of a weak CW laser beam in a Q-switched AlGaAs laser diode with a fast saturable absorber is shown to produce powerful single-mode picosecond pulses at 082μm The saturable absorber regions are obtained by deep implantation of heavy ions through the diode facets Single-mode operation is achieved with CW injection powers as low as 50μW Peak powers exceeding 15W are detected at the laser output A time-resolved spectroscopy of the laser pulses reveals an overall downchirp of 15nm