Theory of Pulse Propagation in a Laser Amplifier
01 Aug 1963-Journal of Applied Physics (American Institute of Physics)-Vol. 34, Iss: 8, pp 2346-2349
TL;DR: In this paper, the growth of a radiation pulse traversing a medium with an inverted population is described by nonlinear, time-dependent photon transport equations, which account for the effect of the radiation on the medium as well as vice versa.
Abstract: The growth of a radiation pulse traversing a medium with an inverted population is described by nonlinear, time‐dependent photon transport equations, which account for the effect of the radiation on the medium as well as vice versa. The equations are solved in closed form for an arbitrary input pulse and an arbitrary initial distribution of inverted population. The solutions are discussed in detail for the particular cases of a square pulse and a Lorentzian pulse, both with a uniform initial population inversion.
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TL;DR: In this paper, the effect of the shape and the initial frequency chirp of input pulses on shape and spectrum of amplified pulses is discussed in detail and the case in which the input pulsewidth is comparable to the carrier lifetime so that the saturated gain has time to recover partially before the trailing edge of the pulse arrives.
Abstract: Amplification of ultrashort optical pulses in semiconductor laser amplifiers is shown to result in considerable spectral broadening and distortion as a result of the nonlinear phenomenon of self-phase modulation (SPM). The physical mechanism behind SPM is gain saturation, which leads to intensity-dependent changes in the refractive index in response to variations in the carrier density. The effect of the shape and the initial frequency chirp of input pulses on the shape and the spectrum of amplified pulses is discussed in detail. Particular attention is paid to the case in which the input pulsewidth is comparable to the carrier lifetime so that the saturated gain has time to recover partially before the trailing edge of the pulse arrives. The experimental results, performed by using picosecond input pulses from a 1.52- mu m mode-locked semiconductor laser, are in agreement with the theory. When the amplified pulse is passed through a fiber, it is initially compressed because of the frequency chirp imposed on it by the amplifier. This feature can be used to compensate for fiber dispersion in optical communication systems. >
1,175 citations
TL;DR: In this article, the authors studied the effect of nonlinear optical effects on self-focusing beams in the field of self-focus and Parametric Amplification in a nonlinear medium.
Abstract: CONTENTS 1. Introduction 609 2. Geometrical Optics of a Nonlinear Medium (Equations, Focal Points, Nonlinear Aberrations, Nonstationary Processes) 617 3. Wave Optics of a Nonlinear Medium (Diffraction Corrections to the Self-focusing Length, Formation of Proper Optical Waveguide, Nonstationary Processes) 624 4. Nonlinear Optical Effects in the Field of Self-focusing Beams (Stimulated Scattering in Liquids, Experimental Data, Self-focusing and Parametric Amplification) 629 5. Conclusion (Unsolved Problems, Diffraction in Nonlinear Interactions) 632 Cited Literature 634
881 citations
TL;DR: In this paper, the transition between the regimes of cw mode locking and Q-switched mode locking was investigated, and an extended theory that took into account nonlinear soliton-shaping effects and gain filtering was developed.
Abstract: The use of a saturable absorber as a passive mode locker in a solid-state laser can introduce a tendency for Q-switched mode-locked operation. We have investigated the transition between the regimes of cw mode locking and Q-switched mode locking. Experimental data from Nd:YLF lasers in the picosecond domain and soliton mode-locked Nd:glass lasers in the femtosecond domain, both passively mode locked with semiconductor saturable absorber mirrors, were compared with predictions from an analytical model. The observed stability limits for the picosecond lasers agree well with a previously described model, while for soliton mode-locked femtosecond lasers we have developed an extended theory that takes into account nonlinear soliton-shaping effects and gain filtering. © 1999 Optical Society of America [S0740-3224(99)01001-2] OCIS codes: 140.3580, 140.4050, 140.3540, 140.7090.
809 citations
TL;DR: To the knowledge this result represents the highest peak power pulses yet produced in any Ti:sapphire chirped-pulse amplification system.
Abstract: We have successfully produced a laser pulse with a peak power of 0.85 PW for a pulse duration of 33 fs in a four-stage Ti:sapphire amplifier chain based on chirped-pulse amplification. To our knowledge this result represents the highest peak power pulses yet produced in any Ti:sapphire chirped-pulse amplification system.
253 citations
TL;DR: In this article, a review of spectroscopic properties of complex molecules is presented and used to show that a simple two-level scheme is inadequate to describe the optical bleaching of dye molecules.
Abstract: A review of spectroscopic properties of complex molecules is presented and used to show that a simple two-level scheme is inadequate to describe the optical bleaching of dye molecules. Experimental data are reported for the transmission of intense ruby laser radiation by several types of dyes. Rate equation analyses are carried out using steady-state solutions and iterative computer solutions; calculated bleaching curves are compared with our data for cryptocyanine. On these bases, we show that, in general, the optical bleaching process involves the removal of ground-state molecules to other states having smaller absorption cross sections at the exciting frequency, and that recovery of absorption at this frequency is characterized by a complex relaxation mechanism.
199 citations
References
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TL;DR: In this article, a peak power output of approximately 5 kw, total output energy of near 1 joule, beam collimation of less than 10 − 2 rad, and a spectral width of individual components in the output radiation of about 6
Abstract: Optical absorption cross sections and the fluorescent quantum efficiency in ruby have been determined. This data has been used to correlate calculations with the analysis of the preceding paper. Stimulated emission from ruby under pulsed excitation has been studied in some detail; the observations are found to depend strongly on the perfection of the particular crystal under study. A peak power output of approximately 5 kw, total output energy of near 1 joule, beam collimation of less than ${10}^{\ensuremath{-}2}$ rad, and a spectral width of individual components in the output radiation of about 6\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}4}$A at 6943 A have been measured. It is suggested that mode instabilities due to temperature shifts and a time-varying magnetic field are contributing to an oscillatory behavior of the output pulse.
285 citations
01 Jan 1963
TL;DR: In this paper, a method of laser modulation is described which produces fast, intense and controllable "giant" laser pulses by "Q-modulation" in experiments with ruby, pulses of peak power up to 15 MW and of duration less than 30 nsec have been studied.
Abstract: A method of laser modulation is described which produces fast, intense and controllable "giant" laser pulses by "Q-modulation." In experiments with ruby, pulses of peak power up to 15 MW and of duration less than 30 nsec have been studied. The principles of the technique are outlined and early experimental results reviewed. The temporal, spectral and spatial structure of giant pulses produced from ruby by a nitrobenzene Kerr cell modulator is reported. The pulse characteristics found to date yield information about the nature of various relaxation processes in ruby and point the way to further experiments to clarify many questions which are raised. The results a) set an upper limit of 10-7sec on the E-→2A-relaxation time, b) show a shortening of upper-state relaxation time by about seven times under heavy pumping, c) show relaxation of excitation taking place across the laser line in microseconds, d) show progressive spectral broadening for shorter pulses to encompass most of the fluorescent line, e) show increasing asymmetry of spectral output for faster, more intense pulses, and f) show little broadening of beam divergence over normal, but with added structure.
81 citations
01 Nov 1961
TL;DR: In this article, a pulsed ruby maser has been operated as a light amplifier using a Ruby maser oscillator as a source, and a net gain of a factor of two was observed.
Abstract: A pulsed ruby maser has been operated as a light amplifier using a ruby maser oscillator as a source. A net gain of a factor of two was observed. The dependence of the gain on temperature and pumping power agrees with theory within experimental limits.
28 citations