Showing papers on "Saturable absorption published in 1977"
TL;DR: In this article, it was shown that resonance absorption together with ponderomotive force effects such as filamentation and density profile steepening strongly influence the laser light absorption, while inverse bremsstrahlung absorption is not the dominant absorption mechanism.
Abstract: High-intensity (1013–1017 W/cm2) 1.06 μm laser light absorption experiments with spherical and planar targets suggest that inverse bremsstrahlung absorption is not the dominant absorption mechanism. Evidence is presented that resonance absorption together with ponderomotive force effects such as filamentation and density profile steepening strongly influence the laser light absorption.
49 citations
TL;DR: Simultaneous picosecond and sub-picosecond pulses are generated in a cw double mode-locked dye laser as mentioned in this paper, with pulse durations of around 1 psec.
Abstract: Simultaneous picosecond and subpicosecond pulses are generated in a cw double mode‐locked dye laser. The rhodamine 6G dye pulses are of the order of 0.5 psec long, while the saturable absorber cresyl violet lases simultaneously with pulse durations of around 1 psec.
35 citations
TL;DR: In this paper, a nonlinear device termed the optical Kerr effect modulator (OKEM) is used to passively switch and mode lock high-power lasers, and the mode-locking threshold dependence upon the parameters of the OKEM transmission function is definitively established.
Abstract: A detailed analytical investigation is presented of a nonlinear device termed the optical Kerr effect modulator (OKEM) which is used to passively Q switch and mode lock high-power lasers. Experimentally, an OKEM employing two standard quarter-wave plates is used to passively mode lock the Nd:glass laser. The mode-locking threshold dependence upon the parameters of the OKEM transmission function is definitively established. Pulsewidths and spectral measurements are given for the train of ultrashort pulses from the glass laser mode locked with the OKEM using two different Kerr liquids. The analytical and experimental results together indicate that the OKEM technique is a versatile and viable alternative and in addition overcomes most of the shortcomings intrinsic to the saturable absorber technique. The non-resonant nature of the OKEM suggests that it should find immediate application as a passive Q -switching and mode-locking element for a Variety of lasers, including dye lasers, UV lasers, the CO 2 laser, and, notably, the high-power iodine laser.
35 citations
TL;DR: In this article, a quantitative investigation of HITC dissolved in methanol has been made using the method of ultrafast absorption spectroscopy with a streak camera, where samples were excited by picosecond pulses of a mode-locked ruby laser.
Abstract: A quantitative investigation of HITC dissolved in methanol has been made using the method of ultrafast absorption spectroscopy with a streak camera. Samples were excited by picosecond pulses of a mode-locked ruby laser. Analysis of time-resolved spectra yielded non-exponential decay kinetics consisting of a fast (τ variable) and a slow (τ=1.13±0.08 ns) component. The excited state absorption spectrum has its maximum at 493 nm and shoulders at 415 and 540 nm. The excited state absorption cross section was determined by simulataneous measurement of the bleaching of ground state absorption taking polarization of excitation and probe light and excited state absorption at the laser wavelength into account. A value of σ1 (493 nm)=1.0·10−16 cm2 was found.
20 citations
TL;DR: In this article, active mode locking of a flashlamp-pumped dye laser by bleaching the saturable absorber contained in its resonator with picosecond lightpulses from a master oscillator was proposed.
17 citations
TL;DR: In this article, an absorption cell for the 1.315 mu m iodine laser wavelength has been constructed using thermal dissociation of molecular iodine vapour to produce ground-state iodine atoms, and measurements of the small-signal absorption coefficient for iodine pressures up to 5 Torr and temperatures up to 750 degrees C have been compared with the predictions of a simple thermodynamic model of the iodine dissociation equilibrium.
Abstract: An absorption cell for the 1.315 mu m iodine laser wavelength has been constructed using thermal dissociation of molecular iodine vapour to produce ground-state iodine atoms. Measurements of the small-signal absorption coefficient for iodine pressures up to 5 Torr and temperatures up to 750 degrees C have been compared with the predictions of a simple thermodynamic model of the iodine dissociation equilibrium, and satisfactory agreement obtained. The model readily allows calculation of operating conditions required for the use of the iodine absorber as a saturable absorber, for free-induction decay pulse generation and for coherent pulse propagation experiments.
14 citations
TL;DR: In this article, a solution of Fluorol 7GA in methanol as active medium and DQOCI (1,3'-diethyl 4,2'-quinolyloxadicarbocyanineiodide) as saturable absorber was achieved in a flashlamp-pumped system.
13 citations
TL;DR: In this article, a metal-oxyde-metal whisker detector was used to detect 1.5μs wide pulses at 118, 373, and 496 μm wavelength.
Abstract: Pulsed operation of submillimeter gas lasers was achieved with the laser gas inside the resonator of the CO2 pump laser acting as a saturable absorber for passive Q switching the CO2 laser. With a metal‐oxyde‐metal whisker detector 1–5‐μs‐wide pulses could be detected at 118, 373, and 496 μm wavelength.
13 citations
TL;DR: In this paper, the authors show that mode-locking of Rhodamine 6G and Rhodamine B dye lasers can be achieved using methanol, DMSO or glycerol solutions.
10 citations
TL;DR: In this paper, a neodymium-phosphate glass oscillator mode locked using the saturable absorber dye No. 3955 in a plastic host has been shown to give completely modulated outputs.
Abstract: A neodymium‐phosphate glass oscillator mode locked using the saturable absorber dye No. 3955 in a plastic host has been shown to give completely modulated outputs. Single pulses of duration ∼5 psec with the low background have been obtained, when operating close to threshold. The aperature time of the dye in the plastic host was measured to be 130±25 psec.
TL;DR: In this paper, the effect of the bleaching property of a saturable absorber and the optical loss in a corrugated waveguide on bistability was analyzed by using the coupledmode theory.
Abstract: The effect of the bleaching property of a saturable absorber and the optical loss in a corrugated waveguide on bistability is analyzed by using the coupled-mode theory. Hysteresis and nonlinear properties are given as a function of the quantities characterizing the saturable absorber (the absorption coefficient Γ0, and the length of saturable absorber l) and the propagation characteristics of the corrugated waveguide (the coupling coefficient k and the optical loss in waveguide Γ). It is clear, by selecting the optimum values of these parameters., that the saturable optical resonator has a bistable property which is useful as an optical gate, an optical amplifier, and an optical memory in integrated optical circuits.
TL;DR: In this article, the authors analyzed the growth of intensity fluctuations inside the cavity and the corresponding development of a train of output pulses in passively mode-locked solid-state lasers and particularly concerned with the problem of pulse compression and broadening.
Abstract: This is the second in a series of papers analysing the generation of picosecond pulses in passively mode-locked solid-state lasers. The growth of intensity fluctuations inside the cavity and the corresponding development of a train of output pulses are carefully considered. This paper is particularly concerned with the problem of pulse compression and broadening. The wave-like character of radiation inside n laser easily is first considered ; it is then shown that the radiation intensity function I = I(t, x) can be mathematically represented by a wave growing or decaying with distance. Simple mathematical expressions arc derived for a gradual change of such properties of the wave as its slope and curvature at a given point. The concept of width of a radiation peak is then introduced and its variation on passage through a non-linear medium, such as a saturable absorber, is carefully analysed. Pulse compression in ring and conventional cavities is discussed, including the effect of excited state absorption,...
TL;DR: In this paper, a model for time delay and Q-switching effects in semiconductor lasers is described, incorporating saturable absorption and loss of optical confinement, and the model has been extended to include the high current limit on the Q -switching region and also the wavelength dependence of threshold current.
Abstract: Detailed calculations have been carried out of time delay and Q -switching effects in semiconductor lasers using a model described previously, incorporating saturable absorption and loss of optical confinement. The model has been extended to include the high-current limit on the Q -switching region and also the wavelength dependence of threshold current in grating-controlled lasers. In addition, the full rate equations for the electron concentrations in the lasing and absorbing states and for the photon concentration in the lasing mode have been solved by integration in the time domain using a Runge-Kutta numerical procedure. The results illustrate in a relatively simple form the complicated processes occurring during long time delays, abnormal time delays, and Q -switching.
TL;DR: In this article, the correlation function of the intensity fluctuation and the field amplitude in a dye laser and a laser with a saturable absorber were investigated by solving the Fokker-Planck equation.
Abstract: The correlation function of the intensity fluctuation and the correlation function of the field amplitude in a dye laser and a laser with a saturable absorber are investigated by solving the Fokker-Planck equation. It is found that in the threshold region the intensity fluctuation has a sharp maximum. The noise spectrum is nearly Lorentzian in the center of the threshold region being highly non Lorentzian in the remaining parts of this region. Outside the threshold region the spectrum is Lorentzian. The line spectrum deviates from the Lorentzian profile slightly below the threshold.
TL;DR: In this paper, a review of the theory of the stimulated resonance Raman scattering (SRRS) is given, and the gains for the SRRS with the ground level and an excited one are compared.
Abstract: A review of the theory of the stimulated resonance Raman scattering (SRRS) is given.
The calculation of the gains for the SRRS with the ground level (SRRS I) or an excited one (SRRS II) as initial states shows that there are some restrictions for their appearance. Due to the strong resonance absorption of the pumping wave and the disturbing influence of stimulated fluorescence the SRRS I is not observable in a Franck-Condon excitation and in an absorption of Lorentzian line shape.
The SRRS II has a sufficiently large gain on the condition τel ≪vib (τel, τvib – transversal relaxation time of the electronic or vibronic transition). In case of a strong deviation of the wings of the absorption profile from the Lorentzian shape, however, the SRRS I is favoured rather than the two other processes.
Another possibility to avoid the resonance absorption of the pumping wave exists for the transversal excitation of the SRRS. Thereby the limit of application of the SRRS may be extended to other substances which are no saturable absorbers.
Apart from the saturable absorption and the transversal excitation the self-induced transparency is the third possibility to generate SRRS of ultrashort light pulses.
TL;DR: In this article, a pair of diffraction gratings were used to produce temporal squaring effects on 30 ps duration 1.06 μm pulses that were negatively self phase modulated in cesium vapor.
TL;DR: In this article, the photodynamic interactions operative during the dual pulse irradiation of a saturable absorbing dye are treated by a rate equation approach which allows the temporal changes in the gain and attenuation conditions of the absorber to be predicted.
Abstract: The ultrafast modification of molecular electronic state populations by picosecond duration laser pulses is discussed. The photodynamic interactions operative during the dual pulse irradiation of a saturable absorbing dye are treated by a rate equation approach which allows the temporal changes in the gain and attenuation conditions of the absorber to be predicted. The treatment relies on a knowledge of the molecular absorption and stimulated emission profiles and the existence of homogeneously broadened electronic states of the molecule. The approach is applied to a description of the passive mode‐locking capability of certain saturable absorbing dyes at wavelengths substantially different from their absorption maxima.
TL;DR: In this paper, the authors investigated the possibility of generating picosecond pulses in flashlamp-pumped organic dye lasers under conditions of induced reduction in the relaxation time of a saturable absorber by exciting laser action in this absorber.
Abstract: An investigation was made of the possibility of generation of picosecond pulses in flashlamp-pumped organic dye lasers under conditions of induced reduction in the relaxation time of a saturable absorber by exciting laser action in this absorber. Under these conditions it was possible to generate pulses of minimum attainable duration after the least number of passes.
TL;DR: An experimental study of the saturable absorption of SF(6) at high pressure (up to 500 Torr) with high laser irradiance is presented and the decrease of transmittance is shown to be due to vibrational excitation, whereas bleaching is caused by rotational hole burning.
Abstract: An experimental study of the saturable absorption of SF6 at high pressure (up to 500 Torr) with high laser irradiance is presented. Experiments carried out at the P(28) line of the CO2 laser show a decrease of transmittance with increasing laser irradiance before bleaching sets in. This is explained by a theoretical model using a single rate equation. The decrease of transmittance is shown to be due to vibrational excitation, whereas bleaching is caused by rotational hole burning. Previous results on saturation behavior of SF6 at the P(16) line of CO2 reported by Armstrong and Gaddy are given a new interpretation using the present model.
TL;DR: In this article, a single isolated saturated absorption feature in 127I2 using the optically pumped 5461nm Hg laser has been observed with low (∼6 MHz) resolution.
Abstract: A single isolated saturated‐absorption feature in 127I2 using the optically pumped 5461‐nm Hg laser has been observed with low (∼6 MHz) resolution The 3S1→3P2 Hg laser transition can be centered exactly on this feature by varying the N2 buffer gas pressure using the measured pressure tuning rate of −94 MHz/Torr This may provide an attractive laser system for absolute wavelength stabilization
TL;DR: A saturable absorber is irradiated by a step of radiation from a CO(2) laser, and the step response of the medium is observed, and a set of rate equations is developed for a simplified model of two energy levels.
Abstract: A saturable absorber (SF6) is irradiated by a step of radiation from a CO2 laser, and the step response of the medium is observed. Since the characteristic times of rotational, vibrational, and thermal excitation are different, it is possible to observe each process separately. A set of rate equations is developed for a simplified model of two energy levels. This set includes only one differential equation and qualitatively describes the effects of rotational hole burning and vibrational relaxation. Heat effects are accounted for separately.
TL;DR: In this paper, a HeNe laser with an intracavity saturable Ne absorber has been subjected to a periodic modulation of the passive cavity loss near the regime of single-mode hysteresis.
TL;DR: In this paper, a pair of diffraction gratings on 30 psecduration 1.06 micrometer pulses that were negatively self phase modulated in cesium vapor were used to produce temporal squaring effects.
Abstract: : Temporal squaring effects are produced using a pair of diffraction gratings on 30 psecduration 1.06 micrometer pulses that were negatively self phase modulated in cesium vapor. The results are in good agreement with the theory, which is discussed in detail. Further enhancement of the squaring by a saturable absorber is also discussed.
20 Oct 1977
TL;DR: In this article, the authors consider several types of devices which can perform all these functions with sub-nanosecond response times, however, the emphasis in this paper is on the limiting function, which can be designed for use with a wide range of laser wave lengths.
Abstract: In a variety of laser applications there are requirements for devices which shorten laser pulses, emphasize the peaks, or act as a limiter to suppress peaks in the intensity. In this paper we consider several types of devices which can perform all these functions with subnanosecond response times. The emphasis in this paper is on the limiting function, however. All the devices are based on the concept of a dual-beam interferometer with a nonlinear element in one or both beams. The nonlinear component can be either a saturable absorber or a medium exhibiting the optical Kerr effect. In the former case, the transmission of the absorber increases with increasing incident intensity; in the latter case, a phase shift is introduced as the intensity increases. By combining both beams at the out-put port of the interferometer with an appropriate static phase difference, these nonlinear effects can be made to produce either pulse peaking or limiting. In the same way, using two orthogonal polarizations and one beam, rather than two physically separated beams, one can construct a nonlinear polarization interferometer with the same characteristics but with reduced sensitivity to vibration and temperature changes. Theoretical and experimentally determined characteristics of several nonlinear interferometers are presented here. Of particular interest is a simple, inexpensive limiter with excellent shaping characteristics which we have demonstrated using a Nd:YAG laser at 1064 nm. This device operates for days without adjustment and can be designed for use with a wide range of laser wave lengths.© (1977) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: In this article, an analysis of the conditions for obtaining high contrast power resonances in a weakly saturable absorber is presented. Butler et al. used an optical delay line as an internal absorption cell for the purpose of increasing the effective absorption length.
Abstract: An analysis is made of the conditions for obtaining high-contrast resonances in a weakly saturable absorber. A description is given of an experiment in which high-contrast power resonances were established in an He–Ne/127I2 laser. An optical delay line is used as an internal absorption cell for the purpose of increasing the effective absorption length. An analysis is made of the spectrum of the hyperfine structure of the absorption in iodine in this laser. The stability of the laser when locked to one of these resonances is determined.
TL;DR: In this paper, two distinctly different mechanisms of transverse mode formation are illustrated: anomalous interaction of spectral modes where their formations take place within a few nanoseconds of each other and is characterized by spectral separation of a few tenths of a nanometer with the eventual domination by the long wavelength mode/s.
Abstract: Spatial, spectral, and temporal (SST) resolved measurements are carried out on homostructure junction lasers at room temperature. Two distinctly different mechanisms of transverse-mode formation are illustrated. One is attributed to anomalous interaction of spectral modes where their formations take place within a few nanoseconds of each other and is characterized by spectral separation of a few tenths of a nanometer with the eventual domination by the long wavelength mode/s. In the other, a second mode at shorter wavelength appears only above a current I 0 . The delay of this second mode is well-fitted by the equation t_{d2} = \tau \ln I_{1}/(I - I_{0}) with τ of the order of 27 ns. The separation of the two spectral modes increases during the pulse and finally settles to a magnitude an order higher than the first case. It is experimentally observed that a cavity-width reduction mechanism is present as the laser emission evolves during a pulse. Evidence of a non-linear gain versus injected carrier concentration due to the switching of power from one mode to another is discussed. The results have been explained in terms of changes in the cavity brought about by refractive index variation, gain distribution, or saturable absorption.
01 Jan 1977
TL;DR: In this paper, the spatial, spectral, and temporal details of the laser output have been determined to give the opportunity of eliciting a more detailed picture of the internal mechanisms of a laser, and the role played by effects such as refractive index distribution, gain distribution, saturable absorption, and temperature changes.
Abstract: across the active region of the heterostructure. An attempt to correlate the results of these calculations with the output of injection lasers would, however, require detailed measurements of the spectra and modes together with their temporal dependence in the laser output. Previous measurements have indicated the spectral output during Q-switching [6] and associated with long time delays [7] and although the results included time effects they were not sufficient in general to indicate the detailed mode structures involved. Long time delays were associated with two separate wavelength families which were attributed to lasing from the band tails and from the continuous band of the laser. The longer wavelength family was dominant at temperatures below T,, the critical temperature for long time delays, while the shorter wavelength family was dominant at temperatures above T,. In this paper we shall describe a system which has been developed to determine the spatial, spectral, and temporal details of the laser output to give us the opportunity of eliciting a more detailed picture of the internal mechanisms of the laser. Although we shall report results for a homostructure, nonfdamenting laser, it will be clear that it will be possible to identify the roles played by effects such as refractive-index distribution, gain distribution, saturable absorption, and temperature changes. The spatial, spectral, and temporal (SST) information obtained in each case provides indications of the changes in the electromagnetic field distribution which in turn affect the far-field patterns of the various wavelength emissions as the output evolves during a current pulse.