Showing papers on "Saturable absorption published in 1973"
TL;DR: In this paper, the authors used a streak-camera to measure 1 mJ pulses at the beginning of the pulse train of a mode-locked Nd: glass laser, with self-phase modulation frequency broadening at the end of the train.
52 citations
TL;DR: In this paper, a theoretical model for mode locking induced by saturable absorbers is presented, employing an unidirectional ring laser cavity, where both the gain and loss media are assumed to be homogeneously broadened two-level systems, on-resonance with the radiation field.
Abstract: A theoretical model for mode locking induced by saturable absorbers is presented, employing an unidirectional ring laser cavity. Both the gain and loss media are assumed to be homogeneously broadened two‐level systems, on‐resonance with the radiation field. The loss of the cavity is treated as discrete and is supposed to occur at an equivalent mirror. Laser coupled equations are then derived, employing the density matrix formalism together with Maxwell's equations, using the rotating wave and slowly varying envelope approximations. Time‐invariant solutions of the coupled equations are deduced exactly and mode‐locking regions are predicted by a perturbation method. It is found that a suitable absorber can produce mode locking if the laser parameters are appropriately chosen. Generation of the steady‐state pulses (SSP) by the finite‐difference method shows that relatively short intense pulses can be obtained from a mode‐locked laser. In addition, the theoretical model is extended to account for the possibil...
48 citations
TL;DR: In this paper, a quantum efficiency of ≈ 0.01 for the generation of the photoisomer of DODCI has been obtained, and the establishment of equilibrium concentrations for the two forms of the dye in mode-locked rhodamine dye lasers has been confirmed.
46 citations
TL;DR: In this article, the case of a Doppler-broadened gas laser with a saturable intracavity absorber gas was discussed and the exact steady-state solution in single-mode operation was obtained.
Abstract: This paper discusses the case of a Doppler-broadened gas laser with a saturable intracavity absorber gas. The semiclassical equations governing the field intensities and the atomic density-matrix elements are set up. The latter are written as Fourier series, the components of which are shown to obey coupled difference equations. In this paper the exact steady-state solution in single-mode operation is obtained. The lowest approximation (rate-equation approximation) is used to compute detailed characteristics of the system. In particular, the influence of the pumping rates in the two cells are investigated and displayed in the figures. The regions of bistable operation are determined and conditions for the occurrence of an inverted Lamb dip are given. The effect of a slow modulation of the pumping rates is discussed. The range of validity of the lowest approximation is investigated both analytically and numerically. Finally, there is a brief discussion of the influence of pressure on the parameters of the theory.
42 citations
TL;DR: In this paper, the recovery time of a new saturable absorber suitable for mode locking of neodymium lasers has been measured and compared with the recovery of two commonly used saturable dyes (Eastman 9740 and 9860).
Abstract: The recovery time of a new saturable absorber suitable for mode locking of neodymium lasers has been measured and compared with the recovery of two commonly used saturable dyes (Eastman 9740 and 9860).
33 citations
TL;DR: In this article, a joint experimental-theoretical study of time delays and Q-switching effects in homostructure and heterostructure lasers is presented, and the experimental results are interpreted on the basis of a theoretical model involving saturable absorption of the lasing emission.
Abstract: Preliminary results are reported of a joint experimental-theoretical study of time delays and Q -switching effects in homostructure and heterostructure lasers. Spectral measurements of the normal lasing and Q -switching pulses indicate a broadening of the spectrum during the delay, with a high-energy emission during the Q -switched output. These experimental results are interpreted on the basis of a theoretical model involving saturable absorption of the lasing emission via states in the conduction band "tail," while the emission itself results from transitions associated with states in the parabolic part of the conduction band for temperatures above a certain critical temperature T c .
29 citations
TL;DR: In this article, the statistical behavior of passive mode locking and the discrimination characteristics of the nonlinear absorber were examined, and the probability W of having a second ultrashort pulse of a certain intensity within the resonator roundtrip time 2tL was described.
Abstract: Following the Letokhov model for passive mode locking, which describes the buildup of ultrashort light pulses from noise, the statistical behavior of passive mode locking and the discrimination characteristics of the nonlinear absorber are examined. The probability W of having a second ultrashort pulse of a certain intensity within the resonator round-trip time 2t_{L} is described. This probability is essentially a function of the initial dye absorption coefficient x 0 and a pumping parameter t p that is a measure for the excitation rate of the optical pump. Experimental results are reported that confirm these theoretical considerations.
27 citations
TL;DR: In this paper, a Fabry-Perot interferometer was used in the cavity cavity of a mode-locked Nd-glass laser to reduce the spectral narrowing effect.
24 citations
TL;DR: In this paper, the two-photon absorption of an optical (laser) and an x-ray quantum is considered within the context of the Born approximation and a simple expression relating the twophoton and onephoton photoionization absorption coefficients is obtained.
14 citations
14 citations
TL;DR: In this paper, the authors proposed a new field of applications of dye laser quenching, where if a weak absorber is placed inside the broad band laser cavity, the absorption is enhanced and this results in the same absorption bands or lines observable in the spectrally resolved laser output.
Abstract: The advent of organic dye lasers made possible many experiments in physics, chemistry and biology Most of these applications are based on the possibility to tune dye laser emission almost at any wavelength between 3400 A and 12000 AThis quality combined with high light power made feasible multiphotone absorption, selective absorption and fluorescence experiments Recently a group of authors published the papers: “Enhancement of absorption spectra by dye laser quenching I and II”1,2 which start a new field of applications of dye lasers Namely if a weak absorber is placed inside the broad band laser cavity the absorption is enhanced and this results in the same absorption bands or lines observable in the spectrally resolved laser output This effect can be used for detection of the traces of elements as a complementary method to the classical absorption spectroscopy but with much higher sensitivity Same method could be also very useful for detection of transient species with a very short lifetimes
TL;DR: In this paper, three possible models were considered in order to try to explain the delays: saturable absorption via conduction-band tail states in equilibrium with the band, with the lasing emission occurring via transitions from the band states.
Abstract: Calculations have been made of time delays in semiconductor lasers, using a rate-equation approach to describe the transient behavior of photon and electron populations. Three possible models were considered in order to try to explain the delays: a) saturable absorption via conduction-band tail states in equilibrium with the band, with the lasing emission occurring via transitions from the band states; b) saturable absorption via conduction-band tail states not in equilibrium with the band; and c) absorption due to loss of waveguiding as a result of hole injection into the n-type regions of diode lasers. It was found that only the model b) was capable of satisfactorily accounting for the known properties of time delays.
TL;DR: In this article, a substantial reduction of spontaneous emission intensity is observed at the onset of stimulated emission in some injection lasers, which is caused by the saturation of optically absorbing traps present in the active region.
Abstract: A substantial reduction of the spontaneous emission intensity is observed at the onset of stimulated emission in some injection lasers. It is shown that this effect is caused by the saturation of optically absorbing traps present in the active region. It is suggested that saturable optical absorption is also responsible for previously unexplained similar reduction observed by Nicoll in bulk semiconductor lasers.
TL;DR: In this paper, the saturation saturation of absorbing gases is used to alter the temporal development of pulses from an electron-beam CO2 laser and several pulse-shaping effects have been observed including ramp generation and elimination of the initial spike from a rectangular pulse.
Abstract: Time‐dependent saturation of absorbing gases is used to alter the temporal development of pulses from an electron‐beam CO2 laser The gases used are SF6, CF2Cl2, and BCl3 Several pulse‐shaping effects have been observed including ramp generation and elimination of the initial spike from a rectangular pulse
Patent•
16 May 1973
TL;DR: In this paper, a method and apparatus for the operation of a ring laser in a biased mode is described. Butler et al. showed that the biased mode of operation can be realized through the action of a saturable absorber internal to the ring laser cavity.
Abstract: A method and apparatus is disclosed for the operation of a ring laser in a biased mode. Two separate cavity resonances support the simultaneous oscillations of two counter-circulating traveling waves. In the preferred embodiment the biased mode of operation is realized through the action of a saturable absorber internal to the ring laser cavity. Stabilization may be achieved by monitoring the intensity of one of the two output waves and tuning the cavity in response thereto.
TL;DR: In this article, the coupled Maxwell-Schrodinger equations are used to describe propagation of a pulse in a nonlinear absorbing medium, where the absorber is assumed to be comprised of a homogeneously broadened system of two-level atoms that are exactly resonant with the field.
Abstract: The coupled Maxwell-Schrodinger equations are used to describe propagation of a pulse in a nonlinear absorbing medium. The absorber is assumed to be comprised of a homogeneously broadened system of two-level atoms that are exactly resonant with the field. Numerical calculations have been performed for incident pulses of hyperbolic-secant shape and of duration that is long compared to the atomic phase-memory time. Selected values of input intensity are considered. For intensities below a certain level the calculations nearly agree with rate-equation predictions, but as the incident intensity is increased we find that optical nutation comes into play. The nutation effect leads to pulse breakup as the packet penetrates into the medium. An analytical calculation, for the case of an applied optical field of step-function form, has been performed in order to provide additional insight about the intensity threshold for nutation.
TL;DR: In this article, the semi-classical equations for the electric field and population inversion in a two-level medium are simplified for the case of a saturable absorber cell which is shorter than the length of fluctuations in the optical-pulse envelope.
Abstract: The semi-classical equations for the electric field and population inversion in a two-level medium are simplified for the case of a saturable absorber cell which is shorter than the length of fluctuations in the optical-pulse envelope. The spatial coordinates in the cell are effectively lumped, and the integration is reduced to the one dimension of time. The pulse is passed through an amplifying medium and frequency selective elements by a fast Fourier transform into its spectral components. The case of pulse formation in a ruby laser, starting from a noise fluctuation is computed for the parameters of a recently reported accurate measurement of pulse duration. Good agreement is obtained with experiment. Finally, a pulse length is predicted for a cavity containing an etalon which cancels gain narrowing.
TL;DR: In this paper, the absorption characteristics of COF2 both internal and external to the optical resonator of a CO2 laser were investigated over pressure ranges 1 −26 Torr, and the strongest absorption was on the P(24) line yielding an absorption coefficient of 0.005 cm−1 Torr−1.
Abstract: The absorption characteristics of COF2 both internal and external to the optical resonator of a CO2 laser were investigated over pressure ranges 1–26 Torr. Injection of small amounts of COF2 into the flow of an operating transfer chemical laser resulted in significant reductions in laser power. The absorption coefficient for COF2 was obtained from experiments using a CO2 laser with a line selection capability. For pure COF2 in the pressure range 1–10 Torr, the strongest absorption was on the P(24) line yielding an absorption coefficient of — 0.005 cm−1 Torr−1. When the COF2 was diluted with N2, the absorption was found to decrease as the operating laser line moves away from the COF2 absorption band centered at 965 cm−1 (10.36 μm).
TL;DR: In this article, rate equations are used to study the influence of a two-photon absorber with a large relaxation time on the shape of picosecond output pulses, where the absorber is assumed to be placed in a laser resonator in addition to a one-photone saturable absorber.
Abstract: Rate equations are used to study the influence of a two-photon absorber with a large relaxation time on the shape of picosecond output pulses. This absorber is assumed to be placed in a laser resonator in addition to a one-photon saturable absorber. Numerical methods are used to demonstrate that a 30% reduction in pulse duration (relative to the duration in the absence of the two-photon absorber) can be achieved for selected values of parameters.
TL;DR: In this article, a pure Ne discharge was used as a saturable absorber to mode lock an He-Ne laser operating at 6118 A. The pure discharge was then used as an absorbent to a pure NE discharge.
Abstract: A pure Ne discharge has been used as a saturable absorber to mode lock an He-Ne laser operating at 6118 A.
01 Jan 1973
TL;DR: In this article, the emission spectra of fluorescent dyes are shown schematically in Figo 2 and the dye molecular energy levels are shown in Fig. 3. But it was not until 1966 that Sorokin and Lankard and Schafer, Schmidt and Volze achieved laser action in dyes pumped by giant pulse lasers.
Abstract: While capable of producing high powers ruby and neodymium lasers suffer from the serious defect of fixed frequencies, apart from the high intrinsic cost of the active materials. The emission spectra of fluorescent dyes are broad, and there is a large number of dyes with fluorescence covering the optical spectrum from 340 to 1170 nm (see Fig. l). While the fluorescence efficiency of these organic compounds is very high, it was not until 1966 that Sorokin and Lankard [l] and Schafer, Schmidt and Volze [2] achieved laser action in dyes pumped by giant pulse lasers. The dye molecular energy levels are shown schematically in Figo 2. Because of very fast radiationless internal conversion within the manifold of excited singlet states, the lasing transitions occur from the bottom vibrational level of the first excited electronic singlet state to the ground state vibrational levels, and the resulting broad band emission is homogeneously broadened. The short fluorescence lifetimes, of a few nanoseconds, severely restrict the storage of energy in the active media, and to this extent, pulsed dye lasers may be regarded as operating quasi-continuously. The design of highly efficient amplifiers for pulsed systems is correspondingly more difficult, requiring very fast optical pumping or multipass arrangements.